A Draft: Pathologic and Cardiovascular Calcification in Relation to Aging (2008-2010)

Some time ago, I was writing a review on this topic but had to stop due to health problems before finishing it. Here, I publish the draft from 2010 almost unmodified. I hope it is fine if I publish it for people to (possibly) learn from it. A big thank you to everyone who helped with the review, especially the SENS- and Methuselah Foundation.
Despite proof-reading, I am sure I made some mistakes, hopefully not too stupid ones. But, really, the reference to the then-controversial, now-disproven "nanobacteria" in the review makes me laugh already. (At least disproven as far as the bacteria part is concerned.) Even back then I only included it for for the sake of completeness, see if you can find it!

ABSTRACT: “In the first part of the review I am going to discuss vascular disorders involving calcification, how they relate to aging and their clinical implications. Second, I will provide a quick overview of mechanisms involved both in age-related calcification and vascular aging.
The remainder of the review is devoted to potential therapies. The third chapter shortly summarises nutritional and lifestyle influences on calcification. Thereafter, theoretical and practical concepts and problems relating to regression will be discussed, including the role of spontaneous, surgical and pharmacological regression. Lastly, in the fifth part, I will summarise the main points, identify specific targets for future research and introduce the reader to several promising “targeted” therapies in preclinical development.

The major conclusions of this review are that calcification is more dynamic than is appreciated. Calcification may regress spontaneously, albeit inefficiently, thus necessitating development of effective drugs. Therapeutic regression would likely alleviate the age-related decline of the cardiovascular system.”

WVK – model of calcification, which develops after warfarin & vitamin K administration
VDN – model of calcification, after vitamin D and nicotine administration
CVD – cardiovascular disease
VC – vascular calcification
MEC – medial elastocalcinosis, often synonymous with Mönckeberg’s sclerosis (see text)
CAC – coronary artery calcification, often measured as “Agatston score” or volumetric score, a marker of atherosclerotic disease burden, which may confer risk of its own.

1. Introduction
2. Mechanisms
3. Nutrition, lifestyle and calcification
4. Regression
General concepts, spontaneous and natural regression, Surgical regression, pharmacological regression
5. Summary and outlook

1. Introduction
The idea of postponing intrinsic aging is now considered a serious possibility among biogerontologists and is gaining acceptance.
Aging, together with lifestyle, are two major predisposing influences on the development of cardiovascular disease. Therefore vascular aging is central to any comprehensive approach to slow or reverse aging [de_grey2002] and calcification may importantly contribute to age-related vascular stiffening and loss of function.

At least three major age-related vascular disorders involve calcification. They can be distinguished according to their location and other characteristics: intimal (atherosclerotic), medial (Mönckeberg’s sclerosis) and valvular calcification [giachelli2009]. Additionally, there is a general rise in medial calcium content which could be unrelated to, or a precursor of, Mönckeberg’s sclerosis: “This elastic, tissue calcification is grossly invisible and impalpable, being revealed only by methods such as microincineration or direct chemical analysis.” [lansing1950]

The exact nature of pathologic calcification remains elusive, but complete understanding may not be necessary to develop treatments and for the purpose of this review a pragmatic definition will suffice. Herein, I consider VC and specifically MEC a kind of age-related molecular damage. As predicted by this view, deposition starts early, proceeds throughout life and eventually reaches a pathologic threshold (see for instance [shaw2006, newman2001, lansing1950, elliott1994]).
Other age-related changes in the vessel wall include glycation and lipid fixation as modifications of the extracellular matrix and alterations in cell quality as well as quantity [robert2008, dao2005]. Changes in the extracellular matrix, calcification and glycation likely play a predominant role, but the exact contribution of each to the cardiovascular decline remains unclear. And as we will see below, controversy often surrounds the impact of calcification per se (especially in atherosclerosis).

Clinical implications
It is hypothesised that cardiovascular (and -respiratory) aging ultimately limits human maximal life span to 100-120 years [robert2008] and atherosclerotic calcification has been proposed as a “measure of biologic age” even surpassing chronological age in predictive ability [shaw2006]. Indeed a meta-analysis found that presence of any vascular calcification is a powerful risk factor that predicts mortality [rennenberg2009].
Medial calcification is strongly implicated in worse outcomes in diabetes and renal disease [atkinson2008]. However, data from healthy populations is conflicting. One study found MEC not to influence mortality in the general population [everhart1988], but breast arterial calcification confers a modest risk [iribarren2004] and high ankle brachial index (an indirect measure of MEC) independently predicts mortality [resnick2004].
Similarly, valvular calcification is associated with worse outcomes independently of risk factors and atherosclerosis [fox2003].
Although, intimal calcification, as quantified by Agatston score (CAC) and variants thereof, strongly predicts mortality, it is not clear whether those effects are independent of other atherosclerotic changes. In fact atherosclerotic calcification has been suggested to aggravate and to stabilise atheroma. Perhaps, in the early phases increased interface area [abedin2004] and inflammation [spronk2006] destabilise lesions, while later calcification stabilises them. In vivo the relationship may be even more complex, and is thus an area needing further study.

[Idealised relationship, adapted from Abedin et al.]

Several other mechanisms may explain the detrimental effects of VC and especially MEC; 1) increased stiffness leading to reduced cardiorespiratory fitness [robert2008], 2) remodelling and end organ damage [dao2005], 3) isolated systolic hypertension and its sequelae [dao2005], 4) degraded vascular responsivity [atkinson2008, kitagawa1993] and 5) amplification of other pathologic processes [robert2008].

Resistance to calcification may offer valuable insights, as 10-20% of the elderly demonstrate no or only minimal CAC [shaw2006, newman2001] and after 16 years of hemodialysis some patients (~8%) still remain free from VC [goldsmith1997]. Only medial calcium deposition is universal among the elderly but absolute levels vary up to three-fold [elliott1994]. Apart from heritable factors [narayan1996], lifestyle choices may explain those differences. Some of which we will explore later in the review.

2. Mechanisms
Several mechanisms leading to vascular calcification have been proposed, but detailed discussion is beyond the scope of this paper (see [atkinson2008, giachelli2009] for a review).

Six major mechanisms have been described in the literature: lack of inhibition, stimulation, physiochemical promotion (calcium-phosphate product), apoptotic debris, circulating nucleational complexes and alterations of the elastic network. Angiogenesis and infections, though, likely of lesser significance, may also contribute to the pathology [hayden2005]. The latter includes but is not limited [Grahame-Clarke03] to the controversial “nanobacteria”. [maniscalco04]
(adapted from [giachelli2009])

Of particular interest are mechanisms lying at the crossroads between different age-related pathologies. Those include fragmentation and degradation of the protein elastin as well as glycation.
In fact virtually no de novo synthesis of functional elastin may occur in vivo [powell1992], making elastin prone to the above mentioned processes and explaining its central role in vascular aging. Mechanistically, degraded elastin fragments promote calcium deposition, may serve to nucleate hydroxyapatite, and can up-regulate elastolytic enzymes, perhaps, leading to a “vicious circle” [robert2008]. Additionally, fragmentation and degradation of the elastic network may directly contribute to stiffness [fonck2009].
Plasma advanced glycation endproducts correlate with vascular calcification in animals [bruel1996], stiffness in population studies [semba2008] and accelerate calcification in vitro.
“Catabolic insufficiency” is thought to contribute to atherosclerosis and several other age-related diseases [mathieu2009]. Impaired phagocytosis within atherosclerotic plaques leads to accumulation of apoptotic bodies [schrijvers2007] which can predispose to mineralisation by increasing the local calcium-phosphate product.
More hypothetically, similar mechanisms may underlie other forms of age-related calcification and/or senescence may contribute to decreased clearance.
Furthermore, cellular senescence is known to promote osteoblastic transdifferentiation and calcification as well as elastolysis in vitro [burton2009, robert2008].

3. Nutrition, lifestyle and calcification
In this chapter I will shortly summarise the emerging role of nutrition and “lifestyle” in the context of vascular calcification. Modifiable, sub-clinical deficiencies may contribute to VC throughout life. Most importantly in the elderly, because aging is associated with malnutrition and abnormal metabolism of many nutrients: decreased cutaneous vitamin D synthesis [holick2007], impaired absorption of B12, abnormal calcium homeostasis, alterations of magnesium metabolism and possibly increased need of vitamin K for effective γ-carboxylation [tsugawa2006].

Physiologic levels of phytate protect animals from age-related and many other types of calcification [grases2008]. Recent population studies have linked phytate to decreased incidence of kidney stones [curhan2004] and increased bone density [lopez2008], suggesting that it could beneficially modulate calcium metabolism in humans. Currently a trial exploring its influence on valvular calcification is underway (NCT01000233).
Another dietary component, taurine protects from calcification in the VDN model [yamauchi1986] and is generally antiatherogenic (e.g. [zulli2009]). Also, it has been found to reduce homocysteine levels [ahn2009] and decrease several markers of vascular stiffness [satoh2009], but its effects on pathologic calcification in man are unknown.

Administration of fish oil attenuates kidney calcification in animals [schlemmer1998], but data from population studies on fish intake has been inconsistent, albeit suggestive of modest benefits [heine-broring2010].
A combination of fish oil, statins, niacin, vitamin D and dietary intervention has shown promising results on CAC progression in a recent open-label study [davis2009]. It remains to be determined whether the results can be replicated and which of those interventions are most effective.

A question of balance? The discussion of calcium supplementation is complicated by recent studies. Neither serum nor dietary calcium intakes consistently associate with VC or mortality. However, Bolland et al. found increased event-rates in women supplemented with calcium [bolland2008] and similar trends in other trials. Suggestive but not conclusive data links use of calcium containing phosphate binders (leading to extremely high calcium intakes) to worse outcomes in renal disease as well [jamal2009].
Paradoxically, calcium supplementation reduces calcification in animal models (e.g. [hsu2006]), which may be explained by beneficial effects on lipids, bone resorption or other factors.
Vitamin K, Magnesium (vide infra)

Vitamin D has an undeservedly bad reputation due to often unjustified toxicity concerns [holick2007], including concerns over calcification.
To the contrary, the literature is largely consistent with a U-shaped dose-response curve, both in regards to mortality [melamed2008] and calcification [mathew2008], but optimal levels remain enigmatic.
Mechanistical evidence and data from observational studies is consistent with a protective effect. Evidence is often limited to cross-sectional studies, showing either null or beneficial associations of vitamin D metabolites and coronary calcification. Recently the first larger prospective study reported beneficial associations with incident CAC, but not other endpoints [de_boer2009].
Thyroid levels influence calcification in vitro and in vivo. In healthy rats hypothyroidism led to a moderate increase, while hyperthyroidism decreased calcium content below baseline levels [sato2005].
Consistently, hypothyroidism is associated with mildly elevated (cardiovascular) mortality in observational studies [ochs2008]. Although, aging increases the incidence of thyroid abnormalities, thyroid hormones, like vitamin D, have pleiotropic effects and more research is necessary to elucidate their clinical effects.

In theory vitamin B6, B12 and folic acid could exert modest effects via homocysteine metabolism [VanCampenhout2009]. While protein malnutrition has dramatic effects on experimental MEC [price2006], possibly mediated by hypoalbuminemia. Obesity is linked to increased rates of CAC [cassidy2005] and bona fide caloric restriction attenuates vascular aging in model organisms [castello2005]. Warfarin and glucocorticoid use has been linked to accelerated VC in observational studies [lerner2009, del_rincn2004].

Before we discuss regression in more detail it should be noted that despite several differences, similar principles may govern all types of biomineralisation [bonucci05, mccullough2008]. Therefore some non-vascular disorders involving calcification can (and due to lack of data sometimes must) serve as a proxy. For example, drugs used in the treatment of soft tissue calcification can work in models of VC and vice versa [palmieri1995, thompson1992]. Consequently, once developed, therapies may find broad application to various calcifying disorders with only slight modifications (e.g. in the mode of delivery).

Calcification can regress naturally or pharmacologically, but it is unknown whether all calcium deposits can regress completely and not rigorously proven that vascular calcification regresses in humans at all.
Putative mechanisms of in vivo regression involve phagocytosis [yamada2009, bas2006], acidification (presumably via carbonic anhydrase) and physiochemical dissolution [steitz2002, essalihi2005] or a combination thereof.

Some authors suggest that if a physiologic milieu and calcium homeostasis were restored, calcification might naturally regress [jahnen-dechent2008]. However, calcification starts in the 20s or 30s and thus a de facto physiologic milieu can sustain a certain level of calcification [lansing1950] and unfacilitated regression is often incomplete [bas2006, atkinson1994, essalihi2005].
Additionally, preventative interventions may provide only diminished benefits to patients with established pathology, thus justifying a research focus on the regression paradigm.

Conflicting data
Few high-quality, interventional studies have examined progression of calcification and most focused on the impact of statins on CAC. Although, monotherapy with statins can reduce the lipid core of atheroma as measured by ultrasound [klein2007], calcification usually remains. In fact slightly accelerated calcification may contribute to a plaque stabilising effect of statins [kadoglou2008].
While biologically plausible, evidence of regression is from low quality studies. In clinical practice, complete regression of calcification has been described in case-reports after treatments such as vinpocetine [ueyoshi1992], bisphosphonates and amlodipine [ramjan2009], sodium thiosulfate [subramaniam2008] and diltiazem [palmieri1995] but only bisphosphonate studies addressed VC.
Small pilot trials show impressive but extraordinarily heterogeneous responses to experimental therapies [nitta2004, maniscalco2004, davis2009]. Observational studies on the natural progression and medical therapy of calcification also demonstrated that regression is possible.
However, due to limited and contradictory interventional data there is dispute whether serial measurements of CAC are a clinically useful marker of atherosclerosis regression or
stabilisation [klein2007]. Spontaneous regression, chance or bias may explain findings in smaller studies, but it bears emphasizing that any considerable (even spontaneous) regression is incompatible with the view that calcification is a largely irreversible disease.

Several issues could contribute to lacklustre study results.
Transdifferentiated cells and damage to the elastic network may persist after regression and continue to diminish tissue function. Animal studies indicate that calcium regression partially restores function, but any effects of decalcification are difficult to isolate from structural improvements [schurgers2007, dao2002, essalihi2007, bouvet2008]. However, the situation in humans remains unclear. To this day “regression” studies mostly investigated calcification and vascular stiffness in isolation but not in relation to each other. More studies with a focus on diverse markers of tissue function are needed to provide definitive answers.
“Mature” calcification may regress poorly (e.g. as suggested by [bas2006]) or not at all. One reason is that hydroxyapatite is very insoluble compared to octacalcium phosphate and amorphous calcium phosphates [lomashvili2009, bonucci/demer], suggested to be precursors occurring during the mineralisation process.
This is supported by the observation that areas remaining calcified were not affected by treatment in the WVK model [essalihi2004]. Clinical evidence confirms that highly calcified atheromas are not easily amenable to therapy, perhaps due to lower levels of inflammation and lipids [nicholls2007] or frank inaccessibility. Indeed the least calcified plaques responded best to antihypertensive or lipid-lowering therapies [bruining2009, nicholls2007]. Conceivably, non-responders in other pilot trials could have had locally advanced calcification.
Additionally, there may be tissue-specific differences in the potential for regression. In the carotid only minimal or no regression was observed in response to darusentan and amlodipine [essalihi2005].

Spontaneous regression
The natural history of coronary calcification is not incompatible with regression.
For instance, in the MESA cohort (n=5756) regression was seen in ~13% of the sample population [kronmal2007], albeit it is unsure whether this resulted from interscan variation or not. In another study, a small cohort of paediatric kidney patients (n=52), regression was seen in four and one patient, with a baseline CAC score of 140, showed complete disappearance [civilibal2009].
Similarly, spontaneous regression has been documented in many cases of non-vascular calcification, e.g. tumoral calcinosis [okada2004], rheumatic calcification [weinberger1979], pseudoxanthoma elasticum [bryant1979] or heterotopic ossification of diverse origin [van_der_linden1984, sferopoulos1997]. Those cases may illustrate the body’s universal ability to resorb pathologic mineral deposits and the apparent overrepresentation of young patients is intriguing and consistent with calcification as a disease of old-age.
Study of such rare cases is difficult, but rigorous analysis of regression may help elucidate the mechanisms involved. Furthermore, it remains to be seen if therapies that facilitate the endogenous capacity for regression can be successfully developed.
Animal studies
Recently Bas et al. demonstrated macrophage-mediated regression of calcitriol-induced calcification suggesting that natural regression may occur once the causative factor is removed [bas2006].
In the aorta and stomach, however, regression was still incomplete after nine weeks and tissue function was not assessed. Additionally, the observed increase and absolute levels of calcium tended to be lower than those seen in human aging [elliott1994] and studies in the VDN and WVK model show modest or no regression [atkinson1994, essalihi2004]. Therefore the data is compatible with the view that calcification does not regress completely by itself.
Research in non-human primates lends further support to this hypothesis. Dietary induced intimal calcification does not regress in rhesus monkeys after a 3.5 year period of cholesterol lowering on a regular diet (and in some experiments seems to progress). Although, other plaque components may regress partly [stary2000].
Similar results were obtained in long term studies of other species. Regression of atherosclerotic calcifications in non-human primates, swine and other types of calcification in rabbits and cows is modest if it takes place at all [hnichen1990].

Surgical regression
For advanced valvular calcification insertion of bioprosthetic valves remains the only definitive treatment and surgical excision is an option for some types of extra-vascular calcification. For instance, complete resolution of tumoral calcinosis is possible after parathyroidectomy and/or excisional biopsy (n=25)[thakur1999].
A small study found that coronary calcification stabilises after kidney transplantation and may show non-significant regression from 6 to 12 months (n=31)[oschatz2006].
Select conditions may benefit from advances in tissue engineering and surgical techniques. Though, in general the invasive nature and lack of benefit for wide-spread or diffuse forms of calcification (e.g. MEC) limits the utility of surgical approaches.

Pharmacological regression
Countless modalities prevent or reduce calcification in animal models, for instance antihypertensive drugs [dao2002], pre-treatment with polyphenols, Al- or FeCl3 [atkinson2008], calcimimetics [lopez2009], chelators [herd1964], glitazones [gaillard2005], hydrogen sulfide [wu_hydrogen_2006], estrogen [manson2007], statins, pyrophosphate [schibler1968] or teriparatide [shao2003]. For most, their clinical impact on calcification and outcomes, if any, has not been firmly established.
This review summarises only some of the most promising approaches towards regression.
Pilot studies [davis2009, maniscalco2004] suggest that regression of intimal calcium deposits can be facilitated using a combined approach and can be as high as 63%.

Endothelin-A receptor antagonists
Darusentan, a selective endothelin-A receptor antagonist, has been shown to regress VC in the WVK model and bosentan to prevent VC in the VDN model [wu2003]. Regression partially restored function, reducing pulse pressure and the collagen/elastin ratio [dao2002]. The purported mechanism of action is a transient increase in carbonic anhydrase, acidification and resorption of calcium deposits.
Interestingly, bosentan has shown some promise as a treatment of digital ulcers in systemic sclerosis [dhillon2009], a disease often associated with extravascular calcification. Although preliminary results are encouraging, human studies are still lacking.

Numerous animal studies showed that bisphosphonates prevent vascular calcification approximately at therapeutic, anti-resorptive doses (see [toussaint2009] for a short review).  Pleiotropic effects beyond bone resorption including physiochemical inhibition of mineralisation and direct effects on the vasculature could contribute to their efficacy.
However, a recent study found that inhibition of calcification better correlated with suppression of bone formation than resorption. Therefore higher doses than expected may be necessary in humans [lomashvili2009].
Even though case-reports are mixed, some report considerable regression of calcinosis [ramjan2009] and several small studies in Japan found cyclical etidronate to be of benefit [toussaint2009]. However, larger studies of different bisphosphonates (ibandronate, alendronate) failed to show benefits. Among newer nitrogen-containing bisphosphonates risedronate is associated with reduced incidence of stroke [steinbuch2002] and improved arterial elasticity in a small open-label trial [luckish2008].
It is tempting to speculate that the conflicting results can be explained by differential effects of newer and older bisphosphonates and/or the mode of administration (cyclical vs. other).

Vitamin K
Vitamin K is thought to exert its beneficial effects by serving as a cofactor for γ-carboxylation of glutamate residues on a range of proteins, prominently, MGP and Gas6. High doses prevent and regress calcification in the VDN and WVK model, respectively [seyama1996, schurgers2007].
Vitamers may differ in their effects: At common dietary intakes the different menaquinones (vitamin K2), but not phylloquinone (vitamin K1), may protect from cardiovascular calcification and disease. Observational studies support this hypothesis, for instance the prospective Rotterdam study [geleijnse2004]. While cross-sectionally menaquinone intake was inversely associated with CAC [beulens2009] and breast artery calcification [maas07] (although, the latter became insignificant after adjustment).

Two preliminary interventional studies have been performed: In the first one, 1000 mcg/day of phylloquinone (and 400 IU/day of vitamin D) given over three years prevented the age-related decline in vascular elasticity [braam2004]. In the second, CAC progression was slowed by 6% in adherent subjects (500 mcg/day) [shea2009].
The amount of vitamin K1 needed to maximise vascular MGP-carboxylation is unknown, but at least 1000 mcg are necessary for maximal carboxylation of osteocalcin [binkley2002] and vitamin D is known to increase MGP expression [fraser1988]. Considering those two points, the latter study may underestimate the efficacy of a better dosing scheme. Several studies of vitamin K and VC are now underway.

Calcium channel blockers
Several drugs of this class can modulate pathologic calcification.
Diltiazem represents a promising treatment for various disorders involving ectopic calcification. The drug prevents calcification in some animal models [thompson1992], but human evidence is limited to case-series:
Diltiazem eliminated or drastically improved calcification in cases of scleroderma [palmieri1995, sharma09], dermatomyositis [oliveri1996] and other conditions. Although, one group found no clear benefit on subcutaneous calcification [vayssairat1998].
Verapamil is similarly effective in animal models [thompson1992], but may be clinically inferior [palmieri1995].
Dihydropyridines (e.g. amlodipine) can prevent and partly regress calcification in animal models [essalihi2007] and were shown to slow down progression of CAC [motro2001]. However, those modest benefits did not translate into better clinical outcomes as compared to diuretics [epstein2001].
Vinpocetine is claimed to have eliminated tumoral calcinosis in a small case-series (n=8)[ ueyoshi1992] and shows beneficial effects on calcification in a model of experimental atherosclerosis [yasui1989].

Phosphate homeostasis
Observational trials in the population at large suggest that serum phosphate, even within the reference range, may predispose to CVD and VC [kanbay2009]. The hypothesis is supported by recent data from NHANES III, which confirmed an additive risk of elevated serum alkaline phosphatase and makes a strong case for the importance of the phosphate/pyrophosphate ratio [tonelli2009].
Interestingly, a recent prospective study found phosphate binders to benefit survival of hemodialysis patients with normal phosphate levels (>3.7mg/dl) [isakova2009].
Different phosphate binders are used. Aluminium containing binders are relatively well-studied and have been historically also used to treat rheumatic calcification, often as adjuvant therapy. However, recently they have fallen into disfavour due to potential toxicity. Counterintuitively, calcium-free phosphate binders have not been proven superior to calcium salts, but a possible benefit cannot be excluded [jamal2009].
Magnesium carbonate is an emerging adjuvant phosphate binder and, at least in dialysis patients may decrease VC independently of phosphate metabolism [wei2006]. It is known that magnesium deficiency enhances CAC progression in swine [ito1990] and that the mineral may have important effects on cellular calcium homeostasis.
Probenecid, a drug known to increase phosphate excretion, has been used with some success in the treatment of calcification, further underlining the importance of phosphate metabolism.

Sodium thiosulfate (STS)
is effective in experimental uremia and other models. In humans STS has been used as an experimental treatment of tumoral calcinosis, urolithiasis, calciphylaxis [subramaniam2008] (even in a patient with normal renal function [hackett2009]) and may be able to slow CAC progression in hemodialysis patients [adirekkiat2010].
At least two trials in ESRD patients are exploring this treatment.

Doxycycline prevents calcification in animals, for instance in the WVK and VD model as well as after sub-dermal implantation (see [bouvet2008] for a recent discussion). Early human studies also documented benefits:
A treatment called “comET” consisting of tetracycline HCl, EDTA and a range of supplements was  investigated in an observational, open-label trial of questionable design. After four months “responders” (n=44) showed a 14% decrease in calcium score, but apparently there was no effect across the whole group (n=77) [maniscalco2004].
A small open label study using 50 to 100 mg minocycline as a treatment for cutaneous calcinosis reported modest decreases of calcium deposits [robertson2003].
Beneficial effects likely stem from non-selective MMP inhibition and in the case of atherosclerotic disease, perhaps strong anti-inflammatory effects. Alternative hypotheses attribute the effects to antibiotic and “nanobactericidal” activity, but as of yet they are not supported by strong evidence.

5. Summary and outlook
Systemic therapies
Countless case-reports detail the use of pharmacotherapy to treat and regress calcification, yet synergies of established treatments remain largely unexplored both in model organisms and in the clinic. Combined regimens of two or more compounds that have been shown to mitigate calcification and are unlikely to interact negatively are a possible avenue of research. Although, difficult to implement, this may be a necessary and appropriate step in the treatment of vascular calcification.
Diltiazem and a bisphosphonate [oliveri1996] or phosphate binder have been used together on at least one occasion [sharma09]. In fact phosphate binders are regularly combined with other drugs to treat chronic kidney disease and its sequelae.
To recap, phosphate has been suggested to be a neglected, important and modifiable risk factor [kanbay2009]. Although less certain, other dietary and lifestyle factors could play a similar role.
For example, wide-spread vitamin D insufficiency could predispose to a range of diseases [holick2007], including VC. Based on the available evidence vitamin D and K combination therapy seems a prudent avenue of research. However, those two vitamins should not be studied in isolation and interactions with vitamin A could merit further study [fu2008].

Bisphosphonates and pharmacologic doses of vitamin K2 are another interesting combination. Both are used in the treatment of osteoporosis, relatively safe and may modulate pathologic calcification. Furthermore, at clinically relevant doses, they show additive effects on calcification, as well as tropoelastin and MGP levels in vitro [saito2007].
In theory the above or other anti-osteoporotic drugs could synergise with therapies that reduce calcification at the cost of bone-loss (see below).
Another example, tetracyclines and low dose flurbiprofen show synergistic effects on proteinase inhibition [lee2004] and could be explored in models of calcification.

A link between bone loss and calcification has been known for a long time [warburton2007].
Several treatments that have shown promising efficacy in attenuating VC have unexpectedly neutral or beneficial effects on physiologic mineralisation, e.g. vitamin D, K, magnesium and anti-resorptive use of bisphosphonates. Those results imply that pathologic calcification might be treated without aggravating osteoporosis, another disease of old age.

Alternatively, if age-related osteoporosis could be controlled, more efficacious, anti-mineralising treatments which work at the cost of bone could be developed and used intermittently. Bone being by far the biggest reservoir of calcium would suffer considerably less from systemic calcium loss and recover faster than other calcium deposits.
For example, the induction of metabolic acidosis is an effective way to prevent calcification in vivo and is a powerful promoter of hydroxyapatite dissolution in vitro, but is associated with side-effects on bone [mendoza2008]. Interestingly, regression associated with the calcification-inhibitor osteopontin may also ocurr via acidification [steitz2002].
A negative calcium and, based on recent data, especially phosphate balance, should accelerate dissolution and resorption of mineral - partly via a decreased calcium-phosphate product. Phosphate binders are routinely used to that effect, especially in uremia, but any drugs that induce phosphaturia and hypophosphatemia are potential candidates.
Interestingly, STS may exert its effects both via acidosis and reduction of available calcium (while also being a strong antioxidant). Comprehensive studies of STS, metabolic acidosis and calcium-phosphate-balance in non-uremic calcification are lacking.

Possible targeted therapies include catheter based delivery of anti-calcifying agents, gene therapy, cell therapy, immunotherapy and selective stimulation of phagocytosis. Currently most ‘targeted’ approaches must be delivered to the vasculature directly via catheter [sharif2004].
Medial calcification is particularly inaccessible and some authors have suggested that the dense ECM is impermeable to vectors as small as 70-100nm [richter2000]. Which is a potential problem for cell, gene and immunotherapy. Another important issue is sparing vulnerable but long lived elastic tissue. It will be essential to minimise damage and if necessary to weigh harms against benefits from decalcification.

Catheters can be used to deliver various substances: First, physiochemical inhibitors e.g. acids, crystallisation inhibitors, chelators or a combination thereof. Likely, prolonged exposure would be necessary. Thus feasibility of this approach will depend on our ability to design vectors with certain characteristics. Optimally, a non-viral, biodegradable vector, with high affinity for hydroxyapatite allowing sustained-release of H+ ions could be employed.
Second, drugs, especially those with a strong affinity for calcium, should reach higher concentrations via this route (e.g. bisphosphonates, tetracyclines). Third, delivery of peptides or vectors carrying nucleic acids. If long term expression were possible, targeted peptides would become an extraordinarily promising option for delivery to the media [ogawa2009].

Gene therapy could be used to express inhibitors or suppress stimulators of calcification. Keeping with the regression paradigm, the endothelin-osteopontin-carbonic anhydrase triad is an attractive target. Alternatively, highly effective inhibitors like MGP or perhaps fetuin-A could be overexpressed locally, or, if feasible, stimulators like alkaline phosphatase inhibited.
Several animal studies have shown that downregulation of cbfa1/Runx2, an early master regulator of osteoblast differentiation, via siRNAs can prevent heterotopic ossification [xue2009].
For the treatment of advanced calcification additional or ‘downstream’ osteogenic transcription factors (and their effectors) may be preferable targets. Possible candidates include Smads [xue2009] and BMP–Msx2–Wnt signaling [shao2007] or perhaps the AP-1 or Sp family (including osterix) [jensen2010].
Fortunately, therapies targeting atherosclerotic calcification can indirectly benefit from advances in gene therapy being already developed for restenosis, atherosclerosis and other conditions. Among therapies currently in clinical development, expression of tissue inhibitors of metalloproteinases (TIMPs) holds promise for calcifying disorders.
However, depending on the combination of vector and delivery system several limitations need to be overcome: low transfection rates of the media, short-lived expression, tissue damage by the vector or delivery system and systemic dissemination. Interestingly, use of a “potent secretory transgene product“ could offset low transfection rates [sharif2004].
Nonetheless - and despite early promise - clinical development of vascular gene therapy has been arduous.

Cell therapy against VC aims to deliver or induce local osteoclast-like cells. Apart from delivery, induction and maintenance, matrix degradation via osteoclast proteases like MMP-9, is a possible stumbling block. A recent study, however, provides proof of concept that osteoclasts can limit calcification without apparent elastin degradation [simpson2007].

Immunotherapy includes tolerisation and vaccination approaches, i.e. conceivably immunisation against pro-calcifying factors, or calcium deposits [jahnen-dechent2008]. The difficulty of exploiting subtle differences between pathologic and physiologic calcification may explain why this idea has remained a theoretical proposal.
Regardless, immunotherapeutic approaches are already under investigation for atherosclerosis and their progress may benefit other fields. Immunotherapy may not be an ideal solution, though, as medial, in contrast to valvular and intimal, calcification is very inaccessible and thought to occur without extensive inflammation.

Enhancement of phagocytosis. The natural phagocytic ability of macrophages, VSMCs or other local cells could be promoted directly; by ameliorating phagocytic dysfunction (e.g. senescence); or indirectly by opsonisation of calcium deposits (via OPN, immunotherapy) or apoptotic bodies (via fetuin-A). Benefits and risks need to be investigated, because non-selective enhancement may aggravate atheroma [schrijvers2007] and inflammation as well as matrix degradation may be paradoxically enhanced [schrijvers2007, jahnen-dechent2008].
Macrophages have been associated with regression in vivo [bas2006] and although fibroblasts or chondrocytes do phagocytose mineral in vitro, it is unknown if the same applies to vascular cells, especially VSMCs. Different lines of evidence suggest this is indeed the case: VSMCs naturally phagocytose apoptotic bodies and it is the only plausible hypothesis to explain swift regression of medial calcification by vitamin K [schurgers2007].

To summarise, confirmation is needed whether atherosclerotic calcification is best treated pre-emptively, as long as it is better amenable to therapy and poses a higher risk of events. Anti-calcific therapy can potentially enhance the effects of anti-atherogenic treatments. The treatment of MEC and valvular calcification may be beneficial at all stages.
Vascular calcification most probably worsens tissue function and the totality of evidence suggests that the disease is not immutable and theoretically avoidable or reversible.
Calcification is more dynamic than generally accepted. Spontaneous regression occurs, but is rare and often incomplete, necessitating the development of effective treatments. Studies of different drugs or the natural disease progression sometimes detail considerable regression that cannot be attributed to variability. Altogether, regression seems within grasp of current or future therapies.

References, Introduction >25
()Ann N Y Acad Sci. 2002 Apr;959:452-62; discussion 463-5.
Time to talk SENS: critiquing the immutability of human aging.
() Olshansky still looking for a good ref
() Biogerontology. 2008 Apr;9(2):119-33. Epub 2008 Jan 4.
Rapid increase in human life expectancy: will it soon be limited by the aging of elastin?
Robert L, Robert AM, Fülöp T.
()Cardiovasc Res. 2005 May 1;66(2):307-17.
Evolution and modulation of age-related medial elastocalcinosis: impact on large artery stiffness and isolated systolic hypertension. Dao HH, Essalihi R, Bouvet C, Moreau P.

()Biological Calcification: Normal and Pathological Processes in the Early Stages. Ermanno Bonucci. 2005.
()Adv Chronic Kidney Dis. 2008 Oct;15(4):396-412. Review.
Amplification of atherosclerotic calcification and Mönckeberg's sclerosis: a spectrum of the same disease process. McCullough PA, Chinnaiyan KM, Agrawal V, Danielewicz E, Abela GS.
()Kidney Int. 2009 May;75(9):890-7. Epub 2009 Jan 14.
The emerging role of phosphate in vascular calcification.
Giachelli CM.
() J Gerontol. 1950 Apr;5(2):112-9.
Calcium and elastin in human arteriosclerosis.

()Circulation. 2001 Nov 27;104(22):2679-84.
Coronary artery calcification in older adults to age 99: prevalence and risk factors.
Newman AB, Naydeck BL, Sutton-Tyrrell K, Feldman A, Edmundowicz D, Kuller LH.
()Calcification of the human thoracic aorta during aging.
Elliott RJ, McGrath LT. Calcif Tissue Int. 1994 Apr;54(4):268-73.
() NEED FULL Nephron. 1997;77(1):37-43.
Vascular calcification in long-term haemodialysis patients in a single unit: a retrospective analysis. Goldsmith DJ, Covic A, Sambrook PA, Ackrill P.
()NEED FULL Diabetes Care. 1996 Sep;19(9):968-71.
Familial aggregation of medial arterial calcification in Pima Indians with and without diabetes. Narayan et al.

()J Appl Physiol. 2008 Nov;105(5):1643-51. Epub 2008 Sep 4.
Age-related medial elastocalcinosis in arteries: mechanisms, animal models, and physiological consequences. Atkinson J.

()Vasc Health Risk Manag. 2009;5(1):185-97. Epub 2009 Apr 8.
Vascular calcifications as a marker of increased cardiovascular risk: A meta-analysis.
Rennenberg RJ, Kessels AG, Schurgers LJ et al.
()Arterioscler Thromb Vasc Biol. 2004 Jul;24(7):1161-70. Epub 2004 May 20. Review. Vascular calcification: mechanisms and clinical ramifications.
Abedin M, Tintut Y, Demer LL.
()Vitamin K epoxide reductase complex and vascular calcification: is this the important link between vitamin K and the arterial vessel wall?
Spronk HM.
Circulation. 2006 Mar 28;113(12):1550-2. Review. No

()Jpn J Pharmacol. 1993 Apr;61(4):283-9.
Altered vasoconstrictor responsiveness in vitamin D-induced arteriosclerotic rat aortas.
Kitagawa et al.
()Nephrol Hypertens. 2005;14:525–531. 146. Lehto S, Niskanen L, Suhonen M, Ronnemaa T, Laakso M. Medial artery calcification. A neglected harbinger of cardiovascular complications in noninsulin-dependent diabetes mellitus. Arterioscler Thromb http://atvb.ahajournals.org/cgi/content/full/16/8/978
()Nephrol Dial Transplant. 2003 Sep;18(9):1731-40.
Arterial media calcification in end-stage renal disease: impact on all-cause and cardiovascular mortality. London GM, Guérin AP, Marchais SJ, Métivier F, Pannier B, Adda H.
()Diabetologia. 1988 Jan;31(1):16-23.
Medial arterial calcification and its association with mortality and complications of diabetes. Everhart JE, Pettitt DJ, Knowler WC, Rose FA, Bennett PH.
()H.E. Resnick, R.S. Lindsay and M.M. McDermott et al., Relationship of high and low ankle brachial index to all-cause mortality. The Strong Heart Study, Circulation 109 (2004), pp. 733–739.
()J Womens Health (Larchmt). 2004 May;13(4):381-9; discussion 390-2.
Breast vascular calcification and risk of coronary heart disease, stroke, and heart failure. Iribarren et al.

() Pathophysiology. 2004 Oct;11(2):95-101.
Calcification in coronary artery disease can be reversed by EDTA-tetracycline long-term chemotherapy. Maniscalco BS, Taylor KA.

Nutrition, Lifeystle: >30 refs
()Vitamin D deficiency.
Holick MF.
N Engl J Med. 2007 Jul 19;357(3):266-81.
()Am J Clin Nutr. 2006 Feb;83(2):380-6.
Vitamin K status of healthy Japanese women: age-related vitamin K requirement for gamma-carboxylation of osteocalcin.
Tsugawa N, Shiraki M, Suhara Y, Kamao M, Tanaka K, Okano T.

()J Med Food. 2008 Dec;11(4):747-52.
Phytate (myo-inositol hexaphosphate) and risk factors for osteoporosis.
López-González AA, Grases F, Roca P, Mari B, Vicente-Herrero MT, Costa-Bauzá A.
()Arch Intern Med. 2004 Apr 26;164(8):885-91.
Dietary factors and the risk of incident kidney stones in younger women: Nurses' Health Study II. Curhan GC, Willett WC, Knight EL, Stampfer MJ.
()Front Biosci. 2008 May 1;13:7115-22.
Phytate reduces age-related cardiovascular calcification.
Grases F, Sanchis P, Perello J, Isern B, Prieto RM, Fernandez-Palomeque C, Saus C.

()Biochem Biophys Res Commun. 1986 Oct 30;140(2):679-83.
Taurine protection against experimental arterial calcinosis in mice.
Yamauchi-Takihara K, Azuma J, Kishimoto S.
() Hypertension. 2009 Jun;53(6):1017-22. Epub 2009 Apr 27.
High dietary taurine reduces apoptosis and atherosclerosis in the left main coronary artery: association with reduced CCAAT/enhancer binding protein homologous protein and total plasma homocysteine but not lipidemia. Zulli et al.
() Adv Exp Med Biol. 2009;643:415-22.
Effect of taurine supplementation on plasma homocysteine levels of the middle-aged Korean women. Ahn CS.
() Adv Exp Med Biol. 2009;643:47-55.
Modulation by taurine of human arterial stiffness and wave reflection. Satoh H, Kang J.

() J Am Coll Cardiol. 2008 Aug 5;52(6):417-24.
Marine-derived n-3 fatty acids and atherosclerosis in Japanese, Japanese-American, and white men: a cross-sectional study. Sekikawa et al.
() Prostaglandins Leukot Essent Fatty Acids. 1998 Sep;59(3):221-7.
Ectopic calcification of rat aortas and kidneys is reduced with n-3 fatty acid supplementation. Schlemmer et al.
() Am J Ther. 2008 Dec 15. [Epub ahead of print]
Effect of a Combined Therapeutic Approach of Intensive Lipid Management, Omega-3 Fatty Acid Supplementation, and Increased Serum 25 (OH) Vitamin D on Coronary Calcium Scores in Asymptomatic Adults. Davis W, Rockway S, Kwasny M.

() Arch Intern Med. 2008 Aug 11;168(15):1629-37.
25-hydroxyvitamin D levels and the risk of mortality in the general population.
Melamed ML, Michos ED, Post W, Astor B.
() J Am Soc Nephrol. 2008 Aug;19(8):1509-19. Epub 2008 Apr 30.
Vitamin D receptor activators can protect against vascular calcification.
Mathew S, Lund RJ, Chaudhary LR, Geurs T, Hruska KA.
() J Am Soc Nephrol. 2009 May 14. [Epub ahead of print]
25-Hydroxyvitamin D Levels Inversely Associate with Risk for Developing Coronary Artery Calcification. de Boer IH, Kestenbaum B, Shoben AB, Michos ED, Sarnak MJ, Siscovick DS.

() BMJ. 2008 Feb 2;336(7638):262-6. Epub 2008 Jan 15.
Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial. Bolland et al.
() Nephrol Dial Transplant. 2009 Jul 21. [Epub ahead of print]
The effects of calcium-based versus non-calcium-based phosphate binders on mortality among patients with chronic kidney disease: a meta-analysis.
Jamal SA, Fitchett D, Lok CE, Mendelssohn DC, Tsuyuki RT.
() Lipids Health Dis. 2006 Jun 23;5:16. Effects of dietary calcium on atherosclerosis, aortic calcification, and icterus in rabbits fed a supplemental cholesterol diet.  Hsu HH, Culley NC. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1513571/?tool=pubmed

() Atherosclerosis. 2008 May 28. [Epub ahead of print]
Role of homocysteine in aortic calcification and osteogenic cell differentiation.
Van Campenhout A, Moran CS, Parr A, Clancy P, Rush C, Jakubowski H, Golledge J.
() Kidney Int. 2006 Nov;70(9):1577-83. Epub 2006 Sep 6.
Artery calcification in uremic rats is increased by a low protein diet and prevented by treatment with ibandronate. Price PA, Roublick AM, Williamson MK.
() Circulation. 2005 Apr 19;111(15):1877-82.
Progression of subclinical coronary atherosclerosis: does obesity make a difference?
Cassidy AE, Bielak LF, Zhou Y, Sheedy PF 2nd, Turner ST, Breen JF, Araoz PA, Kullo IJ, Lin X, Peyser PA.
() FASEB J. 2005 Nov;19(13):1863-5. Epub 2005 Sep 8.
Calorie restriction protects against age-related rat aorta sclerosis. Castello et al.
()Arthritis Rheum. 2004 Dec;50(12):3813-22.
Effect of glucocorticoids on the arteries in rheumatoid arthritis.
del Rincón I, O'Leary DH, Haas RW, Escalante A.
()J Thromb Haemost. 2009 Sep 28. [Epub ahead of print]
Warfarin use and the risk of valvular calcification. Lerner et al.

() Circ Res. 2005 Sep 16;97(6):550-7. Epub 2005 Aug 11.
Thyroid hormone targets matrix Gla protein gene associated with vascular smooth muscle calcification. Sato et al.
()Ann Intern Med. 2008 Jun 3;148(11):832-45. Epub 2008 May 19.
Meta-analysis: subclinical thyroid dysfunction and the risk for coronary heart disease and mortality. Ochs et al.

Regression ~25
() J Bone Miner Res. 2006 Mar;21(3):484-90. Epub 2005 Dec 19.
Reversibility of calcitriol-induced medial artery calcification in rats with intact renal function.
Bas A, Lopez I, Perez J, Rodriguez M, Aguilera-Tejero E.
() NDT Plus. 2009 Apr;2(2):155-157. Epub 2009 Feb 10.
Osteoclast-like multi-nucleated giant cells in uraemic tumoral calcinosis.
Yamada et al.
()Am J Pathol. 2002 Dec;161(6):2035-46.
Osteopontin inhibits mineral deposition and promotes regression of ectopic calcification.
Steitz SA, Speer MY, McKee MD, Liaw L, Almeida M, Yang H, Giachelli CM.
() Circulation. 2005 Sep 13;112(11):1628-35. Epub 2005 Sep 6.
Regression of medial elastocalcinosis in rat aorta: a new vascular function for carbonic anhydrase. Essalihi R, Dao HH, Gilbert LA, Bouvet C, Semerjian Y, McKee MD, Moreau P.

() J Mol Med. 2008 Apr;86(4):379-89. Epub 2007 Dec 15.
Mineral chaperones: a role for fetuin-A and osteopontin in the inhibition and regression of pathologic calcification. Jahnen-Dechent W, Schäfer C, Ketteler M, McKee MD.
()Am J Physiol. 1994 Feb;266(2 Pt 2):H540-7.
Vascular Ca overload produced by vitamin D3 plus nicotine diminishes arterial distensibility in rats. Atkinson J, Poitevin P, Chillon JM, Lartaud I, Levy B.

() Blood. 2007 Apr 1;109(7):2823-31.
Regression of warfarin-induced medial elastocalcinosis by high intake of vitamin K in rats. Schurgers et al.
() J Hypertens. 2002 Aug;20(8):1597-606.
Pharmacological prevention and regression of arterial remodeling in a rat model of isolated systolic hypertension.
Dao HH, Essalihi R, Graillon JF, Larivière R, De Champlain J, Moreau P.
() J Hypertens. 2007 Sep;25(9):1879-86.
Distinct effects of amlodipine treatment on vascular elastocalcinosis and stiffness in a rat model of isolated systolic hypertension.
Essalihi R, Zandvliet ML, Moreau S, Gilbert LA, Bouvet C, Lenoël C, Nekka F, McKee MD, Moreau P.
()Arterioscler Thromb Vasc Biol. 2008 May;28(5):856-62. Epub 2008 Feb 21.
Sequential activation of matrix metalloproteinase 9 and transforming growth factor beta in arterial elastocalcinosis.
Bouvet C, Moreau S, Blanchette J, de Blois D, Moreau P.

()Kidney Int. 2009 Mar;75(6):617-25. Epub 2009 Jan 7.
Effect of bisphosphonates on vascular calcification and bone metabolism in experimental renal failure.
Lomashvili KA, Monier-Faugere MC, Wang X, Malluche HH, O'Neill WC.
()J Cardiovasc Pharmacol. 2004 Nov;44 Suppl 1:S147-50.
Phenotypic modulation of vascular smooth muscle cells during medial arterial calcification: a role for endothelin?
Essalihi R, Ouellette V, Dao HH, McKee MD, Moreau P.
() J Am Coll Cardiol. 2007 Jan 16;49(2):263-70. Epub 2006 Nov 9.
Coronary artery calcification and changes in atheroma burden in response to established medical therapies. Nicholls et al.
() J Am Coll Cardiol. 2007 Jan 16;49(2):271-3. Epub 2006 Nov 9. Atherosclerosis regression, vascular remodeling, and plaque stabilization. Klein LW.
()Coron Artery Dis. 2009 Sep;20(6):409-14.
Coronary calcium significantly affects quantitative analysis of coronary ultrasound: importance for atherosclerosis progression/regression studies. Bruining et al.

() Am J Kidney Dis. 2004 Oct;44(4):680-8.
Effects of cyclic intermittent etidronate therapy on coronary artery calcification in patients receiving long-term hemodialysis.
Nitta K, Akiba T, Suzuki K, Uchida K, Watanabe R, Majima K, Aoki T, Nihei H.

() J Int Med Res. 1992 Sep;20(5):435-43.
NEED FULL Clinical appraisal of vinpocetine for the removal of intractable tumoral calcinosis in haemodialysis patients with renal failure.
Ueyoshi A, Ota K.
()Nat Clin Pract Endocrinol Metab. 2009 Mar;5(3):167-72.
Generalized arterial calcification of infancy: treatment with bisphosphonates.
Ramjan et al.
()Australas J Dermatol. 2008 Feb;49(1):30-4.
Complete resolution of recurrent calciphylaxis with long-term intravenous sodium thiosulfate.
Subramaniam K, Wallace H, Sinniah R, Saker B.
()Arterioscler Thromb Vasc Biol. 2001 Mar;21(3):421-6.
Natural history and topographic pattern of progression of coronary calcification in symptomatic patients: An electron-beam CT study. Schmermund et al.
() Pediatr Nephrol. 2009 Mar;24(3):555-63. Epub 2008 Nov 4.
Progression of coronary calcification in pediatric chronic kidney disease stage 5.
Civilibal et al.

() Eur J Dermatol. 2004 Nov-Dec;14(6):424-5.
Spontaneous regression of multiple tumoral calcinosis in a child. Okada et al.
()Ann Rheum Dis. 1979 Aug;38(4):384-6.
Extensive soft tissue calcification (calcinosis universalis) in systemic lupus erythematosus. Weinberger et al.
() Regression of pseudoxanthoma elasticum.
Bryant J.
Arch Pathol Lab Med. 1979 Jan;103(1):51-2
()Int Orthop. 1984;8(1):25-7.
Spontaneous regression of neurogenic heterotopic ossification.
van der Linden AJ.
()Int Orthop. 1997;21(6):412-4.
Ectopic bone formation in a child with a head injury: complete regression after immobilisation. Sferopoulos et al.

Animal studies
() Z Kardiol. 2000;89 Suppl 2:28-35.
Natural history of calcium deposits in atherosclerosis progression and regression. Stary HC.
()NEED FULL Dtsch Tierarztl Wochenschr. 1990 Nov;97(11):479-82.
[The question of reversibility of tissue calcification in enzootic calcinosis of cattle and in experimental hypervitaminosis D]
Hänichen T, Hermanns W.

Surgical regression
()Surgery. 1999 Jul;126(1):95-8.
Tumoral calcinosis regression after subtotal parathyroidectomy: a case presentation and review of the literature. Thakur A, Hines OJ, Thakur V, Gordon HE.
()Am J Kidney Dis. 2006 Aug;48(2):307-13.
Changes of coronary calcification after kidney transplantation.
Oschatz et al.

Pharmacological regression ~9
()NEED FULL Herd JK, Vaughan JH: Calcinosis universalis complicating dermatomyositis-its treatment with Na,EDTA: report of two cases in children. Arthritis Rheum 7:259-271, 1964
()Hypertension. 2005 Aug;46(2):372-9. Epub 2005 Jun 20.
Pioglitazone improves aortic wall elasticity in a rat model of elastocalcinotic arteriosclerosis. Gaillard et al.
()NEED FULL Clin Sci. 1968 Oct;35(2):363-72.
Inhibition by pyrophosphate and polyphosphate of aortic calcification induced by vitamin D3 in rats. Schibler D, Russell RG, Fleisch H.
()Am J Physiol Renal Physiol. 2009 Jun;296(6):F1376-85. Epub 2009 Mar 25.
The calcimimetic AMG 641 accelerates regression of extraosseous calcification in uremic rats. Lopez I, Mendoza FJ, Guerrero F, Almaden Y, Henley C, Aguilera-Tejero E, Rodriguez M. http://jasn.asnjournals.org/cgi/content/full/17/3/795
()N Engl J Med. 2007 Jun 21;356(25):2591-602.
Estrogen therapy and coronary-artery calcification.
Manson et al. WHI and WHI-CACS Investigators.
()J Biol Chem. 2003 Dec 12;278(50):50195-202. Epub 2003 Sep 22.
Teriparatide (human parathyroid hormone (1-34)) inhibits osteogenic vascular calcification in diabetic low density lipoprotein receptor-deficient mice.
Shao et al.
()Acta Pharmacol Sin. 2006 Mar;27(3):299-306.
Hydrogen sulfide ameliorates vascular calcification induced by vitamin D3 plus nicotine in rats. Wu SY, Pan CS, Geng B, Zhao J, Yu F, Pang YZ, Tang CS, Qi YF.

()Eur J Vasc Endovasc Surg. 2008 Jun;35(6):661-8. Epub 2008 Apr 18.
Intensive lipid-lowering therapy ameliorates novel calcification markers and GSM score in patients with carotid stenosis. Kadoglou et al.
()N Engl J Med. 1998 Dec 31;339(27):1972-8.
Effect of HMG-CoA reductase inhibitors on coronary artery disease as assessed by electron-beam computed tomography. Callister et al.

()  Peptides. 2003 Aug;24(8):1149-56.
Endothelin-1 is a potent regulator in vivo in vascular calcification and in vitro in calcification of vascular smooth muscle cells. Wu et al.
()Bosentan: a review of its use in the management of digital ulcers associated with systemic sclerosis. Dhillon S.
Drugs. 2009;69(14):2005-24. doi: 10.2165/10489160-000000000-00000.

Bisphosphonates ~7
() Clin J Am Soc Nephrol. 2009 Jan;4(1):221-33. Epub 2008 Nov 5.
Bisphosphonates in chronic kidney disease; balancing potential benefits and adverse effects on bone and soft tissue.
Toussaint ND, Elder GJ, Kerr PG.
Price PA, Faus SA, Williamson MK.
() Nat Clin Pract Endocrinol Metab. 2009 Mar;5(3):167-72.
Generalized arterial calcification of infancy: treatment with bisphosphonates.
Ramjan et al.

() Acad Radiol. 2002 Oct;9(10):1148-52.
NEED FULL Progression of coronary artery calcification in patients taking alendronate for osteoporosis. Hill et al.
() Osteoporos Int. 2005 Feb;16(2):184-90. Epub 2004 Jun 10.
Effective doses of ibandronate do not influence the 3-year progression of aortic calcification in elderly osteoporotic women.
Tankó LB, Qin G, Alexandersen P, Bagger YZ, Christiansen C.
() Bone. 2008 Aug;43(2):279-83. Epub 2008 Apr 22.
Effect of long-term treatment with risedronate on arterial compliance in osteoporotic patients with cardiovascular risk factors.
Luckish A, Cernes R, Boaz M, Gavish D, Matas Z, Fux A, Shargorodsky M.
()Regul Toxicol Pharmacol. 2002 Jun;35(3):320-6.
Assessment of mortality in patients enrolled in a risedronate clinical trial program: a retrospective cohort study. 
Steinbuch et al.

Vitamin K ~9
()NEED FULL Int J Vitam Nutr Res. 1996;66(1):36-8.
Effect of vitamin K2 on experimental calcinosis induced by vitamin D2 in rat soft tissue.
Seyama Y, Horiuch M, Hayashi M, Kanke Y.
()Atherosclerosis. 1995 Jul;116(1):117-23.
Vitamin K intake and osteocalcin levels in women with and without aortic atherosclerosis: a population-based study. Jie KS, Bots ML, Vermeer C, Witteman JC, Grobbee DE.
()J Nutr. 2004 Nov;134(11):3100-5.
Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study.
Geleijnse JM, Vermeer C, Grobbee DE, Schurgers LJ, Knapen MH, van der Meer IM, Hofman A, Witteman JC http://jn.nutrition.org/cgi/content/full/134/11/3100
()Atherosclerosis. 2009 Apr;203(2):489-93. Epub 2008 Jul 19.
High dietary menaquinone intake is associated with reduced coronary calcification.
Beulens et al.
() Maturitas. 2007 Mar 20;56(3):273-9. Epub 2006 Sep 28.  Vitamin K intake and calcifications in breast arteries.  Maas AH, van der Schouw YT, Beijerinck D, Deurenberg JJ, Mali WP, Grobbee DE, van der Graaf Y.

()Am J Clin Nutr. 2009 Jun;89(6):1799-807. Epub 2009 Apr 22.
Vitamin K supplementation and progression of coronary artery calcium in older men and women. Shea et al.
()Thromb Haemost. 2004 Feb;91(2):373-80.
Beneficial effects of vitamins D and K on the elastic properties of the vessel wall in postmenopausal women: a follow-up study.
Braam LA, Hoeks AP, Brouns F, Hamulyák K, Gerichhausen MJ, Vermeer C.
()Am J Clin Nutr. 2002 Nov;76(5):1055-60.
A high phylloquinone intake is required to achieve maximal osteocalcin gamma-carboxylation.
Binkley NC, Krueger DC, Kawahara TN, Engelke JA, Chappell RJ, Suttie JW.
()J Biol Chem. 1988 Jan 15;263(2):911-6.
1,25-Dihydroxyvitamin D3 stimulates the synthesis of matrix gamma-carboxyglutamic acid protein by osteosarcoma cells. Mutually exclusive expression of vitamin K-dependent bone proteins by clonal osteoblastic cell lines. Fraser JD, Otawara Y, Price PA. http://www.jbc.org/cgi/pmidlookup?view=long&pmid=3257212

Calcium-channel blockers
()Clin Rheumatol. 2009 Oct 17. [Epub ahead of print]
Systemic sclerosis sine scleroderma and calcinosis cutis: report of a rare case.
Sharma NL, Mahajan VK, Ranjan N, Sharma VC, Gupta M.
()NEED FULL J Rheumatol. 1996 Dec;23(12):2152-5.
Regression of calcinosis during diltiazem treatment in juvenile dermatomyositis.
Oliveri MB, Palermo R, Mautalen C, Hübscher O.
() Arthritis Rheum.
1995 Nov;38(11):1646-54.
NEED FULL Treatment of calcinosis with diltiazem.
Palmieri GM, Sebes JI, Aelion JA, Moinuddin M, Ray MW, Wood GC, Leventhal MR.
()Ann Rheum Dis. 1998 Apr;57(4):252-4.
Clinical significance of subcutaneous calcinosis in patients with systemic sclerosis. Does diltiazem induce its regression? Vayssairat M, Hidouche D, Abdoucheli-Baudot N, Gaitz JP. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9709184
() Circulation. 1992 Dec;86(6):1973-6.
Effects of calcium channel blockers on calcium uptake in rat aortic valve allografts.
Thompson SA, Smith GB, Cobb SM, Walters KS, Behrendt DM.

()Motro M, Shemesh J: Calcium channel blocker nifedipine slows down progression of coronary calcification in hypertensive patients compared with diuretics.
Hypertension 37: 1410–1413, 2001
()Hypertension. 2001 Jun;37(6):1414-5.
Arterial calcification and calcium antagonists: what does it mean?
Epstein M, Black HR.

()NEED FULL Acta Neurol Scand. 1989 Mar;79(3):239-42.
Preventive effect of vinpocetine on calcifications: atherosclerosis in experimental rabbits.
Yasui M, Yano I, Ota K, Oshima A.

Phosphate and binders ~6
() Blood Purif. 2009;27(2):220-30. Epub 2009 Jan 29.
Phosphate - the silent stealthy cardiorenal culprit in all stages of chronic kidney disease: a systematic review. Kanbay M, Goldsmith D, Akcay A, Covic A.
()Circulation. 2009 Nov 3;120(18):1784-92. Epub 2009 Oct 19.
Relation between alkaline phosphatase, serum phosphate, and all-cause or cardiovascular mortality. Tonelli et al.
()J Am Soc Nephrol. 2009 Feb;20(2):388-96. Epub 2008 Dec 17.
Phosphorus binders and survival on hemodialysis. Isakova et al.
()Nephrol Dial Transplant. 2009 Jul 21. [Epub ahead of print]
The effects of calcium-based versus non-calcium-based phosphate binders on mortality among patients with chronic kidney disease: a meta-analysis.
Jamal SA, Fitchett D, Lok CE, Mendelssohn DC, Tsuyuki RT.
() Perit Dial Int. 2006 May-Jun;26(3):366-73.
Relationship between serum magnesium, parathyroid hormone, and vascular calcification in patients on dialysis: a literature review.
Wei M, Esbaei K, Bargman J, Oreopoulos DG
()Ito M, Cho BH, Kummerow FA: Effects of a dietary magnesium deficiency and excess vitamin D3 on swine coronary arteries. J Am Coll Nutr 9: 155–163, 1990

()Australas J Dermatol. 2008 Feb;49(1):30-4.
Complete resolution of recurrent calciphylaxis with long-term intravenous sodium thiosulfate.
Subramaniam K, Wallace H, Sinniah R, Saker B.
()Clin Exp Dermatol. 2009 Jan;34(1):39-42. Epub 2008 Jul 4.
Calciphylaxis in a patient with normal renal function: response to treatment with sodium thiosulfate. Hackett BC, McAleer MA, Sheehan G, Powell FC, O'Donnell BF.
()Nephrol Dial Transplant. 2010 Jan 18. [Epub ahead of print]
Sodium thiosulfate delays the progression of coronary artery calcification in haemodialysis patients. Adirekkiat et al.

()Arterioscler Thromb Vasc Biol. 2008 May;28(5):856-62. Epub 2008 Feb 21.
Sequential activation of matrix metalloproteinase 9 and transforming growth factor beta in arterial elastocalcinosis.
Bouvet C, Moreau S, Blanchette J, de Blois D, Moreau P.
()J Periodontol. 2004 Mar;75(3):453-63.
Subantimicrobial dose doxycycline efficacy as a matrix metalloproteinase inhibitor in chronic periodontitis patients is enhanced when combined with a non-steroidal anti-inflammatory drug. Lee HM, Ciancio SG, Tüter G, Ryan ME, Komaroff E, Golub LM.
()Ann Rheum Dis. 2003 Mar;62(3):267-9.
Treatment of cutaneous calcinosis in limited systemic sclerosis with minocycline.
Robertson LP, Marshall RW, Hickling P.

Summary and outlook ~13
()J Atheroscler Thromb. 2007 Dec;14(6):317-24. Epub 2007 Dec 17.
Treatment with vitamin k(2) combined with bisphosphonates synergistically inhibits calcification in cultured smooth muscle cells. Saito E, Wachi H, Sato F, Sugitani H, Seyama Y.
()J Nutr. 2008 Dec;138(12):2337-41.
9-Cis retinoic acid reduces 1alpha,25-dihydroxycholecalciferol-induced renal calcification by altering vitamin K-dependent gamma-carboxylation of matrix gamma-carboxyglutamic acid protein in A/J male mice. Fu X, Wang XD, Mernitz H, Wallin R, Shea MK, Booth SL.

() Cardiovascular disease and osteoporosis: balancing risk management.
Warburton DE, Nicol CW, Gatto SN, Bredin SS.
Vasc Health Risk Manag. 2007;3(5):673-89. Review.

()Kidney Int. 2008 Feb;73(4):407-14. Epub 2007 Nov 7.
Metabolic acidosis inhibits soft tissue calcification in uremic rats.
Mendoza FJ, Lopez I, Montes de Oca A, Perez J, Rodriguez M, Aguilera-Tejero E.

()Am J Physiol. 1994 Feb;266(2 Pt 2):H540-7.
Vascular Ca overload produced by vitamin D3 plus nicotine diminishes arterial distensibility in rats. Atkinson J, Poitevin P, Chillon JM, Lartaud I, Levy B.

()Protein transduction method for cerebrovascular disorders.Ogawa T et al. Acta Med Okayama. (2009)
()Gene Ther. 2009 Nov 26. [Epub ahead of print]
Non-virus-mediated transfer of siRNAs against Runx2 and Smad4 inhibit heterotopic ossification in rats. Xue et al.
()Ann N Y Acad Sci. 2007 Nov;1117:40-50.
Vascular Bmp Msx2 Wnt signaling and oxidative stress in arterial calcification.
Shao et al.
()Biofactors. 2010 Jan 19;36(1):25-32. [Epub ahead of print]
Regulation of gene expression in osteoblasts.
Jensen ED, Gopalakrishnan R, Westendorf JJ.
()Cardiovasc Res. 2004 Nov 1;64(2):208-16. Current status of catheter- and stent-based gene therapy. Sharif et al.
()Cardiovasc Pathol. 2007 Jan-Feb;16(1):29-37.
Toward cell therapy for vascular calcification: osteoclast-mediated demineralization of calcified elastin. Simpson CL, Lindley S, Eisenberg C, Basalyga DM, Starcher BC, Simionescu DT, Vyavahare NR
()Cardiovasc Res. 2007 Feb 1;73(3):470-80. Epub 2006 Sep 16.
Phagocytosis in atherosclerosis: Molecular mechanisms and implications for plaque progression and stability. Schrijvers et al.
()Physiol Genomics. 2000 Apr 27;2(3):117-27.
Adeno-associated virus vector transduction of vascular smooth muscle cells in vivo.
Richter et al.