The role of the Vv seems crucial to the development of VOC and its resultant alteration regarding bone formation within the osteoid tissue of the fibrocalcific plaques of atherosclerosis. The medial and intima Vv are derived primarily from the adventitial layer of the artery. The Vv acts as a custom delivery system to supply the media and intimal layers with oxygen and nutrients as the atherosclerotic artery undergoes the positive outward remodeling. These angiogenic vessels also serve as a conduit delivering systemic hormones, cytokines and inflammatory cells to the remodeling media and the atherosclerotic intimal disease of atherosclerosis including ossification. Of particular importance is vital role of the Vv capillary endothelium and its guardian, multipotential, stem cell-like, supportive, mesenchymal cell the pericyte 1517 (table 2) (figure 1, 5). The location of VOC in these arteries is both in the medial and intimal layers. It is important to note that in health the Vv normally penetrates the media but not the intima. In disease the Vv invade excessively not only the media but also the intima and this may help to explain the detrimental process of intimal ossification.

Bone siloprotein synthesized by the osteoblast-like VSMC has recently been shown to be an angiogenic protein capable of inducing neovascularization by interacting with the alpha v beta 3 integrin 18. Even more exciting is the finding that the endothelial pericyte is capable of synthesizing this non-collagenous angiogenic factor as well as being related to ossification of atherosclerotic plaques.

Long before the development of overt T2DM there exists a pro-atherosclerotic process within the arterial vessel wall (AVW) 1516. The metS is associated with multiple metabolic toxicities referred to as the A-FLIGHT-U toxicities, which result in the production of ROS (table 3). Each of these excess toxic substrates is capable of generating ROS but in the metS they may act synergistically to result in perturbations of the AVW and contribute to a premature atherosclerosis, which has been termed atheroscleropathy (ASO) 1920. This is why many patients with overt T2DM often present with acute coronary syndromes and why T2DM should be considered a coronary heart disease (CHD) risk equivalent according to the National Cholesterol Educational Program Adult Treatment Panel III (NCEP ATP III) guidelines.

Insulin, IGF-1, and amylin are known to be elevated in the insulin resistance (IR) and metS patient 21. Insulin has been long known be a growth factor and is a stimulus for hepatic synthesis of IGF-1, which may be implicated in the accelerated ossification in ASO. There is a human gene polymorphism with a phenotype described as the Benardinelle lipoatrophic syndrome more commonly referred to as lipoatrophic diabetes and this syndrome is associated with manifestations of acanthosis nigricans, generalized lipoatrophy, hirsutism, muscle hypertrophy, intellectual impairment, IR diabetes mellitus with major diet-dependent type V hypertriglyceridemia, and an increase in bone density, thus implying osteogenesis 22.

In addition to insulin and IGF-1, there is another beta cell derived islet hormone that is elevated in IR, metS, prediabetes, and early T2DM termed amylin or islet amyloid polypeptide. Amylin may be considered to be the fraternal twin of insulin and has recently been shown to be a physiologic regulator of bone remodeling through favoring bone formation, while inhibiting bone resorption and thus is osteogenic 23 (table 3).

Htn is the second leading cause of ESRD after diabetes. Hypertension plays an important role in the ASO associated with metS and T2DM, as atherosclerosis is non-existent in the pulmonary arterial tree and the venous system, due to a lower systemic intravascular pressure. Htn may be considered toxic to the AVW and is known to be associated with VOC (table 3) 192024. Mehrotra R and colleagues have recently demonstrated that hypertension plays a more putative role in the association of coronary artery calcification than do levels of serum calcium, phosphorus, parathyroid hormone, and 1,25 di-hydroxy vitamin D levels in T2DM patients not requiring dialysis 25

The lipid triad of the metS and T2DM consists of an elevation in VLDL-C or triglycerides, small dense atherogenic LDL-C, and a decrease in HDL-C. Once these lipids become modified through oxidation in a milieu of increased ROS from the synergistic effect of the associated A-FLIGHT-U metabolic toxicities, they are a predictive determinate of osteogenesis within the media and intima of the AVW. The earliest changes associated of osteogenesis occur at the base of the lipid core in areas of necrotic-apoptotic macrophages and are associated with ROS and inflamation (figure 3). 119202627.

Elevated glucose levels (glucotoxicity) have been shown to be a direct sensitizer for osteogenesis 2829. In vitro studies with VSMCs and high glucose have been shown to induce cell proliferation and expression of osteopontin, while hypoxia seemed to have an additive effect 2829. Even though it is clinically known that diabetes is associated with an increase in medial VOC, the pathogenesis is not completely understood. Glucotoxicity seems to play an important role by transforming VSMCs and possibly pericytes into osteoblast-like cells (figure 6) 192829.

Ishimura E et al have nicely demonstrated the importance of controlling HbA1c levels. They were able to demonstrate that for every 1 percent increase in HbA1c there was a 2.1 fold increase in the risk of VOC 30. Poor glycemic control seemed to be of greater importance than calcium and phosphate concentrations.

VOC in T2DM involves primarily the media of the AVW, however depending on the degree of underlying ASO; it may frequently involve the intima in those arteries where there is a more extensive involvement of atherosclerosis due to a deeper penetration of the adventitial Vv 1. Medial artery calcification has been shown to be a strong independent predictor of cardiovascular mortality in patients with newly diagnosed T2DM 31.

In a clinical longitudinal study of 4,553 Pima Indians the risk factors for medial artery calcification in T2DM were impaired vibration perception, long duration of diabetes, and high glucose concentrations as compared to non-diabetic matched controls, whose risk factors for VOC were age, male gender, and high serum cholesterol 32.

Serum uric acid (SUA) has long been known for its association with the metS and also it's role in T2DM has recently been discussed in length 33. SUA is an important substrate in the A-FLIGHT-U multiple metabolic toxicities and contributes to the production of ROS with resultant modification of lipoproteins as well as interfering with the normal function of the eNOS enzyme resulting in an uncoupling phenomenon discussed later (table 3).

Elevated SUA reflects the activity of the xanthine oxidase enzyme and its production of ROS, which subsequently has a positive effect on VOC. Tseng CH has been able to show that SUA is an independent risk factor for the development of peripheral arterial disease in T2DM 34.

Each of these novel risk factors plays a significant role in metS – T2DM and contributes to the calcification of the AVW through their association with the multiple metabolic toxicities and production of ROS while contributing to the inflammatory process (table 3).

Hcy is known to be toxic to the AVW resulting in a host of fibrotic remodeling changes as a result of autoxidation, VSMC activation, and proliferation, as well as the production of ROS 35. Li J. et al. have been recently able to demonstrate that Hcy potentiates calcification of cultured rat VSMCs 36.

Mediators of inflammation such as oxidation, carbonyl stress, C-reactive protein (CRP), and cytokines may directly stimulate vascular calcification. Also, inflammation reduces fetuin-A, a naturally occurring inhibitor of vascular calcification, which binds excess mineral in serum 37.

Increased levels of CRP are significantly associated with the presence of vascular calcification (including atheromatous and medial calcification) in both aorta and hand arteries, which may indicate a relationship between inflammation and vascular calcification in hemodialysis patients 38. It is of interest to note that IL-10 plays an important role as an anti-inflammatory cytokine and is known to be decreased in CKD and ESRD. Low monocyte IL-10 synthesis may contribute to a chronic inflammatory state in these patients by defective feedback inhibition of proinflammatory cytokine production 39. While inflammation plays a very important role, it is important to note that ROS occurs upstream from inflammation and that ROS are an important mediator of the nuclear factor kappa B 3334.

Microalbuminuria is recognized as a surrogate marker for systemic endothelial dysfunction 40. Recently, microalbuminuria has been shown to be a strong predicting factor of medial arterial calcification independent of nephropathy in patients with diabetes 41.

Selye's initial experiments in rats set the stage for the description of this clinical entity in humans 64. He hypothesized that sensitizers such as PTH or vitamin D might condition the vasculature to VOC. After providing the sensitization he then challenged the rats with known provoking factors including metal salts, albumin, and trauma, which induced calcium deposition and subsequent inflammatory necrosis of the skin and subcutaneous tissue. Over time other studies suggested alternate contributing factors, such as those listed in table 5. The name originated from the combination of calcium and anaphylaxis, thus calciphylaxis, however this model does not involve IgE mechanisms.

Byrant and White (1898) are credited as having described the first clinical presentation in a six-month-old infant, in which there was VOC and what they termed endarteritis obliterans, indicating involvement of the intima 65. It was not until 1969 that Rees and Coles used the terminology calciphylaxis to describe this clinical and pathologic syndrome in man 66.

Coates (1998) coined the term calcific uremic arteriolopathy (CUA) as a replacement term for CPLX, since in many instances elevations of Ca++, Pi or PTH levels are absent 67. Over time CUA may become the preferred term, as this newer terminology is only six years old. The term calciphylaxis is almost entrenched in the medical literature at this point in time; however Selye's animal model more closely parallels the dystrophic tumorous soft tissue calcifications of uremic CPLX. His model did not exhibit the histology consistently described with uremic CPLX, i.e. small vessel calcifications and intimal hypertrophy in association with panniculitis (lobular fat necrosis, and inflammatory changes with neurtrophils, lymphocytes and macrophages, and small vessel thrombosis or involve IgE mechanisms 54676869. We favor the term: obliterative calcific vasculopathy.

VOC in the syndrome of CPLX – CUA is an important topic for discussion, as it is being reported at an exponential rate and especially over the past two years. The devastating complication of medial vascular calcification of small arterioles with resulting skin necrosis is rapidly becoming a morbid complication in both the non-diabetic and especially the large numbers of diabetic patients (T2DM > T1DM) undergoing renal replacement therapy (figure 7).

The skin lesions of CPLX present as painful violacous (livedo reticularis) areas in the extremities, proximal medial thighs, anterior abdomen and lateral flank areas, the breast in females, and frequently overlie or are adjacent to subcutaneous tumorous calcifications in areas of increased adipose tissue. They then progress to a blackened eschar, which later reveals itself on a granulating bed and enlarges at the periphery of the ulcer. They have a tendency to develop in sites of prior skin trauma, such as abdominal scars from previous surgical incisions and may even develop from the trauma of simple scratching of extremities due to ESRD-associated pruritis.

It is important to recognize the clinical presentation of the skin color changes and the neuropathic type of pain before ulceration has developed. If we wait until skin ulceration develops we place the CPLX patient at an increased risk of sepsis and premature death. We should carefully assess any palpable calcific tumorous masses in the subcutaneous tissue in patients at high risk for CPLX.

Not all skin ulcerations are due to CPLX and therefore we should utilize our differential diagnostic skills in evaluating ulcers in these high-risk patients with CKD, T2DM, and ESRD. A reasonable differential diagnosis might include the following (table 6). Even though a skin biopsy may show medial arteriolar calcification and atrophy of medial muscle layers in the arteriole, we should keep in mind that these changes although quite specific are not pathognomonic for CPLX.

The recent emergence of a newer skin pathology termed: neprogenic fibrosing dermopathy may appear co-morbidly with CPLX and recently it has been reported that transforming growth factor beta-1 (TGF beta-1) may to be related to both disorders 55. By making an accurate and earlier diagnosis of CPLX, a greater effort may be given by the primary care provider and the nephrology team as well as other specialties (dermatology and plastic surgery) to improve the multiple A-FLIGHT-U toxicities in each patient (table 3). Earlier treatment of each altered abnormality of the associated multiple metabolic derangements may prevent or delay the progression of this morbid mortal clinical syndrome (table 4,5).

The endothelium is an elegant symphony responsible for the synthesis and secretion of several biologically active molecules. It is responsible for regulation of vascular tone, inflammation, lipid metabolism, vessel growth (angiogenesis – arteriogenesis), arterial vessel wall – capillary sub endothelial matrix remodeling, and modulation of coagulation and fibrinolysis. One particular enzyme system seems to act as the maestro: The endothelial nitric oxide synthase (eNOS) enzyme and its omnipotent metabolic product: endothelial nitric oxide (eNO) (figure 2,8).

The eNOS enzyme reaction is of utmost importance to the normal functioning of the endothelial cell and the AVW. When this enzyme system uncouples, the endothelium becomes a net producer of superoxide and ROS instead of the net production of the protective antioxidant properties of endothelial derived nitric oxide (table 7) (figure 8). There are multiple causes for eNOS enzyme uncoupling: The A-FLIGHT -U multiple metabolic toxicities, oxidative – redox stress, ROS, metS, insulin resistance, prediabetes, T2DM and T1DM, Htn, endothelin, and asymmetrical dimethyl arginine (ADMA) 1192027283445.

The endothelial cell is important in controlling the function of small arterioles and how they may become a net producer of ROS. This endothelial dysfunction may precede the vascular narrowing – closure, prothrombotic state, thrombosis with resulting ischemia of the surrounding subcapillary interstitium, ischemic necrosis of the subcutaneous adipose tissue, and skin changes of livedo reticularis with transformation to painful necrosis, eschar formation, and skin ulceration.

In addition to correcting the underlying multiple metabolic A-FLIGHT toxicities and positive regulators of VOC (table 3,5), a strong consideration to newer therapies should be entertained in order to prevent, slow, and alter the morbid – mortal natural history of the dreaded complications associated with CPLX – CUA.

STS is an effective antibrowning, reducing, and antioxidant agent and therefore readily donates electrons to re-pair unpaired damaging electrons to be an effective antioxidant in addition to it use as a chelator of cations such as the calcium excess in CPLX – CUA (figure 9). The following is one of many possible antioxidant reactions as it scavenges ROS and may be responsible for producing glutathione:

STS is known to be a chelator of cations and has been used for over a century as an antidote for cyanide toxicity, topical treatments of acne and versicolor, and recently as a chemoprotectant against carboplatin and cisplatin toxicity. Its use in the treatment of calciphylaxis has only recently been described and its future use may become a standard of care in the treatment of the dreaded complications 70. Its dual role as an antioxidant and chelator makes STS an excellent choice for the treatment of calciphylaxis and it will be interesting to follow future clinical trials regarding it use.

Clinically, STS seems to have a rather intriguing rapid response in the relief of the pain associated with CLPX and it frequently reduces pain within the very first few treatments (personal experience). Additionally, it seems to promote healing of skin ulcerations especially when used in conjunction with hyperbaeric oxygen treatments 70.

STS may restore endothelial cell dysfunction in CPLX through its antioxidant actions and have a positive effect on eNOS uncoupling and eNO generation. We have formed a hypothesis that the rapid reduction in pain may be due to a restoration of endothelial dysfunction associated with this syndrome. The anitoxidant effect of STS, given in the intravenous dosage of 12.5–25 grams intravenous at the end of dialysis may help to restore the dysfunctional endothelial cell and begin restoring the endothelium's natural tendency (in health) to produce eNO (promoting vasodilation) instead of the dysfunctional super oxide and the resultant peroxynitrite (promoting vasoconstriction) (figure 8) 1192027283445.

STS could be working in two different vascular beds in the vulnerable subcutaneous tissue, as the peripheral neuronal unit is also involved with dystrophic ossification – calcification (figure 10): The vasa nervorum and the endoneurium of the peripheral neuronal unit 71 and the distal small pre-capillary arterioles. These changes would help to explain the rapid improvement of this morbid neuritic (breathtaking, stinging, burning, and knife-like) type of pain, as the chelation properties of STS would take much longer (months compared to hours or days) to restore the capabilities of the neuro-circulatory vascular beds.

Diabetic and peripheral arterial disease patients may be slower to respond as they are plagued with a much more intense endothelial cell dysfunction and endothelial nitric oxide enzyme uncoupling due to the advanced atherosclerotic process and medial calcifications and associated ischemic changes.

Undoubtedly the essential cofactor tetrahydrobiopterin (BH₄) becomes depleted during this chronic ischemia in the subcutaneous tissue from the multiple metabolic toxicities. STS may have a "folate-like redox shuttle effect" similar to the pleiotropic effects of folic acid supplementation 34 by allowing the oxidized cofactor BH₃ and BH₂ to undergo a restoration by the antioxidant effects of STS to the requisite completely reduced form BH₄. This may ameliorate the underlying oxidative stress within the pre-capillary and capillary beds of the interstitium and the endoneurium of the peripheral neuronal units involved. While this is only a hypothesis it seems to be clinically relevant due to the clinical observation of a rapid relief of the pain associated with CPLX.

Currently, the multiple roles of nanotechnology and nanobacteria are rapidly emerging and with new findings come new ideas, which may have a significant impact regarding the future of medicine. Nanobacteria may be a causative agent of diseases related to the biomineralization processes. As clinicians and scientists we must be careful as newer hypothesis and treatments emerge. For example even though nanobacteria have been found in multiple disease states associated with calcium deposition, we have yet to fulfill Koch's postulates regarding VOC. Because this information has just evolved it is important to review some of the background in this field of study.

We have witnessed the exciting story of H. pylori and its causative role in ulcer disease and followed the C. pneumonia story in atherosclerosis finding it to be one of the burdensome infectious injurious stimuli to the endothelium that results in remodeling and atheromatous changes in the AVW. Likewise, the new information regarding nanobacteria being associated with VOC is exciting and could play a very important role in the causation of the atheromatous process and VOC (figure 2).

Nanobacteria belong to the family of gram-negative rods (approximately 100 fold smaller in size) and have been recently localized in cardiovascular tissue. Miller VM et al. have found nanometer-scale particles (ranging in size from 30 to 100 nm) similar to those described as nanobacteria isolated from geological specimens and human kidney stones. These ultra small microbes can be visualized in and stained immunohistologically from calcified human cardiovascular tissue 72. Jelic et al. have demonstrated the presence of nanobacteria in a mitral valve associated with a localized calciphylaxis within mitral vegetations from a patient with T2DM 73.

Maniscalco BS et al., have been able to demonstrate a statistically significant improvement in coronary calcium scores (inferring a reversal of VOC) and a reduction in angina in a group of patients with CAD and coronary artery calcifications using thecombination of EDTA by rectal suppository and a combination of multiple known antioxidants with 500 mg tetracycline (nanobacteriocidal) given daily by mouth. The treatment duration was 4 months 74.

Recently the literature has been replete with the association of periodontal disease and its relation to cardiovascular disease and events. Whether this condition is responsible for the activation of the chronic inflammatory disease response driving the atherosclerotic process or not remains to be seen. The recent isolation of nanobacterium with periodontal disease has fueled the fire of this being a putative microorganism in the development and progression of atherosclerotic disease and VOC 75.

The coexistence of osteoporosis, CVD, and VOC with the aging process in humans and the concept of a shift of calcium from the osseous skeleton towards the AVW have been suggested as one of the explanations for their simultaneous existence 7677.

Accumulating evidence indicates that there are similar pathophysiological mechanisms underlying both diseases. The A-FLIGHT-U multiple metabolic toxicities and resultant ROS, oxidative stress, endothelial cell dysfunction, endotheliopathy, and inflammation have been central issues in this paper regarding VOC. Each of these is associated with a modulation of vascular and osteogenic cells but in an opposite manner and may act in a synergistic manner. The finding of oxidative stress promoting VOC while promoting osteoporosis may help to explain the paradoxical parallel buildup of VOC and the concurrent loss of bone mineralization in the osseous skeleton 787980. The current evidence linking both of these diseases is far from conclusive and additional research is necessary to further characterize the relationship between these two common illnesses as our population of baby (senior) boomers are aging in large numbers.

One such exciting and current emerging area in vascular biology involves the RANKL/RANK/OPG system, which belong to the tumor necrosis factor-related family recently discovered to be critical regulators of the immune system and skeletal biology. RANK(L) (receptor activator of nuclear factor kappaB (ligand) may promote and osteoprotegerin (OPG) may protect against vascular calcification (table 5). The mouse OPG knockout model displays osteroporosis and increased vascular calcification and human gene polymorphisms of OPG are currently being defined and how they may confer an increased risk of CAD in Caucasian men while interacting with VOC and osteoporosis 81. The finding that OPG levels may reflect endothelial cell dysfunction is certainly an area under serious consideration 7682.

The diabetic patient is already plagued with an underlying accelerated atherosclerosis (atheroscleropathy (ASO)), as well as, medial fibrosis and VOC (even if they do not develop CKD or ESRD requiring dialysis). With the current epidemic of obesity, metS, insulin resistance related T2DM (diabesity) in all age groups and particularly the aged and adolescent youth, a closer examination of this morbid – mortal complication is in order 8384858687.

If these T2DM patients do develop CKD and/or ESRD requiring dialysis they could be at a much higher risk of developing an even more severe form of VOC. This dual effect of having not only T2DM related medial calcification but also having the increased risk for the development of medial remodeling and VOC from CKD and/or ESRD requiring dialysis would place these individuals at an extremely high risk for the development of excessive medial arterial remodeling and VOC, as well as arteriole remodeling and VOC, which could possibly increase the risk of developing CPLX (figure 2, 7). Many T2DM patients may have medial arteriolar calcification that could be contributing to anunderlying skin necrosis currently being attributed singularly to peripheral arterial disease and ischemic necrosis or gangrene, when if fact they might have coexisting arteriolar calcification contributing to their skin changes of gangrene. This dual mechanism of VOC in the arterioles and conduit arteries could be playing an important role in development of CPLX.

The treatments to date have largely consisted of careful wound management, hyperbaric oxygen therapy 88, and specific treatment of wound infections, which frequently become systemic and result in deadly sepsis, organ failure, and patient demise. These open ulcerations of the skin are extremely difficult to heal and while they remain open they place the patient at an extreme risk of infection, as this patient population is known to have an impaired immune system from the combination of dialysis and T2DM 89. If STS does emerge as a treatment option for those with CPLX then a careful evaluation of the T2DM patient with skin ulceration should be explored and consideration given to the use of STS provided there is evidence of an associated arteriolar calcification in addition too medial calcification of the conduit arteries. The dual effect of STS being an antioxidant and a chelator of calcium could have a positive outcome in promoting healing of skin ulcerations, thus reducing the possibility of systemic infection and furthermore result in limb salvage of these high risk patients who seem to be presenting to dialysis clinics more and more as the obesity – T2DM epidemic continues to progress. Additionally, the use of STS may be considered in the treatment of VOC associated with CHD and peripheral arterial disease independent of CKD and dialysis.