Calcium Deposition and Associated Chronic Diseases (Atherosclerosis, Diffuse Idiopathic Skeletal Hyperostosis, and Others)

Bone Marrow-Derived ABCC6 Is an Essential Regulator of Ectopic Calcification In Pseudoxanthoma Elasticum

Physiological calcification of soft tissues is a common occurrence in aging and various acquired and inherited disorders. ABCC6 sequence variations cause the calcification phenotype of pseudoxanthoma elasticum (PXE) as well as some cases of generalized arterial calcification of infancy, which is otherwise caused by defective ENPP1. ABCC6 is primarily expressed in the liver, which has given the impression that the liver is central to the pathophysiology of PXE/generalized arterial calcification of infancy. The emergence of inflammation as a contributor to the calcification in PXE suggested that peripheral tissues play a larger role than expected. In this study, we investigated whether bone marrow-derived ABCC6 contributes to the calcification in PXE. In Abcc6‒/‒ mice, we observed prevalent mineralization in several lymph nodes and surrounding connective tissues and an extensive network of lymphatic vessels within vibrissae, a calcified tissue in Abcc6‒/‒ mice. Furthermore, we found evidence of lymphangiogenesis in patients with PXE and mouse skin, suggesting an inflammatory process. Finally, restoring wild-type bone marrow in Abcc6‒/‒ mice produced a significant reduction of calcification, suggesting that the liver alone is not sufficient to fully inhibit mineralization. With evidence that ABCC6 is expressed in lymphocytes, we suggest that the adaptative immune system and inflammation largely contribute to the calcification in PXE/generalized arterial calcification of infancy.

Diffuse Idiopathic Skeletal Hyperostosis Prevalence, Characteristics, and Associated Comorbidities: A Cross-Sectional Study of 1815 Whole Spine CT Scans

STUDY DESIGN

A Retrospective Study.

OBJECTIVE

To determine the prevalence and characteristics of DISH using whole spine CT scans and to evaluate the association of DISH with co-morbidities and other ossified lesions.

METHOD

A retrospective study of whole-spine CT scans of polytrauma patients from 2018-2021 above the age of 20 years. The screening was done using modified Resnick criteria. Overall and age-specific prevalence, characteristics, and associations with obesity, diabetes mellitus (DM), ischemic heart disease (IHD), aortic calcification (AC), ossified posterior longitudinal ligament (OPLL), and ossified ligamentum flavum (OLF) were evaluated.

RESULTS

Out of 1815 patients, 347 had DISH, with a prevalence rate of 19.1% and a mean age of 61.7 years. The highest prevalence of DISH was seen in individuals over 80 years of age (45.5%). The prevalence among males (20.2%) was higher than for females (14.9%). The most commonly involved level was T8-T9 (95.4%), followed by T9-T10 (91.9%), and the most common vertebra involved was T9 (96%). All the cases involving T9 had ossification on the right anterior aspect of the vertebral body. The presence of DM, high BMI, and IHD was found to be significantly higher in patients with DISH (P value < .001). The incidence of aortic calcification was 22.5%, OPLL was 13.3%, and OLF was 4.9% in patients with DISH.

CONCLUSION

This study reports a prevalence rate of 19.1% for DISH, with the highest prevalence among individuals above 80 years of age (45.5%). DISH has a higher propensity to affect the right anterior aspect of the vertebral body in the thoracic spine and is strongly associated with obesity, DM, IHD, and AC.

Inorganic Pyrophosphate at Serum Concentration May Not Be Able to Inhibit Mineralization: A Study in Aqueous Solutions and Serum

The constituent ions of calcium phosphate in body fluids are in the supersaturated state and tend to form minerals physiologically or pathologically. Inorganic pyrophosphate (PPi) has been considered as one of the most important inhibitors against the formation of calcium phosphate minerals. However, serum PPi concentrations in humans are maintained at a level of several μmol/L, and its effectiveness and mechanism for mineralization inhibition remain ambiguous. Therefore, this work studied the mineralization process in an aqueous solution, explored the effective inhibitory concentration of PPi by titration, and characterized the species during the reactions. We find that PPi at a normal serum concentration does not inhibit mineralization significantly. Such a conclusion was further confirmed in the PPi-added serum. This work indicates that PPi may not be a major direct inhibitor of mineralization in serum and possibly functions via alternative mechanisms.

The Purinergic Nature of Pseudoxanthoma Elasticum

Pseudoxanthoma Elasticum (PXE) is an inherited disease characterized by elastic fiber calcification in the eyes, the skin and the cardiovascular system. PXE results from mutations in ABCC6 that encodes an ABC transporter primarily expressed in the liver and kidneys. It took nearly 15 years after identifying the gene to better understand the etiology of PXE. ABCC6 function facilitates the efflux of ATP, which is sequentially hydrolyzed by the ectonucleotidases ENPP1 and CD73 into pyrophosphate (PPi) and adenosine, both inhibitors of calcification. PXE, together with General Arterial Calcification of Infancy (GACI caused by ENPP1 mutations) as well as Calcification of Joints and Arteries (CALJA caused by NT5E/CD73 mutations), forms a disease continuum with overlapping phenotypes and shares steps of the same molecular pathway. The explanation of these phenotypes place ABCC6 as an upstream regulator of a purinergic pathway (ABCC6 → ENPP1 → CD73 → TNAP) that notably inhibits mineralization by maintaining a physiological Pi/PPi ratio in connective tissues. Based on a review of the literature and our recent experimental data, we suggest that PXE (and GACI/CALJA) be considered as an authentic "purinergic disease". In this article, we recapitulate the pathobiology of PXE and review molecular and physiological data showing that, beyond PPi deficiency and ectopic calcification, PXE is associated with wide and complex alterations of purinergic systems. Finally, we speculate on the future prospects regarding purinergic signaling and other aspects of this disease.

Analysis of ABC Transporter Gene Expression in Atherosclerosis

ABC transporters are a large family of membrane proteins that transport chemically diverse substrates across the cell membrane. Disruption of transport mechanisms mediated by ABC transporters causes the development of various diseases, including atherosclerosis. Methods: A bioinformatic analysis of a dataset from Gene Expression Omnibus (GEO) was performed. A GEO dataset containing data on gene expression levels in samples of atherosclerotic lesions and control arteries without atherosclerotic lesions from carotid, femoral, and infrapopliteal arteries was used for analysis. To evaluate differentially expressed genes, a bioinformatic analysis was performed in comparison groups using the limma package in R (v. 4.0.2) and the GEO2R and Phantasus tools (v. 1.11.0). Results: The obtained data indicate the differential expression of many ABC transporters belonging to different subfamilies. The differential expressions of ABC transporter genes involved in lipid transport, mechanisms of multidrug resistance, and mechanisms of ion exchange are shown. Differences in the expression of transporters in tissue samples from different arteries are established. Conclusions: The expression of ABC transporter genes demonstrates differences in atherosclerotic samples and normal arteries, which may indicate the involvement of transporters in the pathogenesis of atherosclerosis.

Treatment of tophaceous pseudogout in the temporomandibular joint with resection and alloplastic reconstruction: a single-staged approach

Tophaceous pseudogout is a rare variant of the calcium pyrophosphate dihydrate (CPPD) disorder, with predilection for the TMJ. It is characterized by calcific deposits composed of rhomboid- or rectangular-shaped crystals that exhibit birefringence when examined under polarized light. We hereby present a case of a 65-year-old man with left pre-auricular tenderness and malocclusion. CT imaging was notable for a left TMJ mineralized mass with erosion of the condylar head. Treatment involved excision of the mass with eminectomy, condylectomy, and a stock total TMJ reconstruction. In this report, important considerations for diagnosis, biopsy, and surgical treatment with emphasis on reconstruction for tophaceous pseudogout of the TMJ have been highlighted by the authors.

G protein-coupled receptor 39 activation alleviates oxidized low-density lipoprotein-induced macrophage inflammatory response, lipid accumulation and apoptosis by inducing A20 expression

G protein-coupled receptor 39 (GPR39) agonist weakens oxidized low-density lipoprotein (ox-LDL)-induced attachment of monocytes to vascular endothelial cells and thus alleviates atherosclerosis. This study looks at whether GPR39 protects macrophages against ox-LDL-induced inflammation and apoptosis and ameliorates lipid accumulation in atherosclerosis and investigates its mechanism. Following inducement of ox-LDL, the expression of GPR39 and tumor necrosis factor alpha-induced protein 3 (TNFAIP3, also known as A20) in Raw 264.7 cells was detected by RT-qPCR and western blotting. The viability of macrophages treated with GPR39 agonist was detected by a cell counting kit 8 kit. GPR39 and A20 expression in ox-LDL-challenged macrophages was assayed by RT-qPCR and western blot with or without GPR30 agonist. After transfection of small interfering RNA (siRNA)-A20, the expression of pro-inflammatory cytokine tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 and anti-inflammatory cytokine IL-10 as well as NF-κB p65 and COX2 was detected. Lipid accumulation was observed through Oil Red O Staining. Total cholesterol (TC) and free cholesterol (FC) in macrophages were detected by commercial kits. Lastly, macrophage apoptosis was observed through TUNEL, and apoptosis-related proteins were detected by western blotting . Results indicated that decreased expression of GPR39 and A20 was observed in ox-LDL-induced macrophages. GPR39 agonist significantly increased A20 expression in ox-LDL-treated macrophages. Furthermore, A20 interference reversed the inhibitory effect of GPR39 agonist on ox-LDL-induced inflammation, lipid accumulation, TC and FC overexpression as well as cell apoptosis. In conclusion, activating GPR39 alleviates ox-LDL-induced macrophage inflammation, lipid accumulation and apoptosis in an A20-dependent manner.

ABCC6, Pyrophosphate and Ectopic Calcification: Therapeutic Solutions

Pathological (ectopic) mineralization of soft tissues occurs during aging, in several common conditions such as diabetes, hypercholesterolemia, and renal failure and in certain genetic disorders. Pseudoxanthoma elasticum (PXE), a multi-organ disease affecting dermal, ocular, and cardiovascular tissues, is a model for ectopic mineralization disorders. ABCC6 dysfunction is the primary cause of PXE, but also some cases of generalized arterial calcification of infancy (GACI). ABCC6 deficiency in mice underlies an inducible dystrophic cardiac calcification phenotype (DCC). These calcification diseases are part of a spectrum of mineralization disorders that also includes Calcification of Joints and Arteries (CALJA). Since the identification of ABCC6 as the “PXE gene” and the development of several animal models (mice, rat, and zebrafish), there has been significant progress in our understanding of the molecular genetics, the clinical phenotypes, and pathogenesis of these diseases, which share similarities with more common conditions with abnormal calcification. ABCC6 facilitates the cellular efflux of ATP, which is rapidly converted into inorganic pyrophosphate (PPi) and adenosine by the ectonucleotidases NPP1 and CD73 (NT5E). PPi is a potent endogenous inhibitor of calcification, whereas adenosine indirectly contributes to calcification inhibition by suppressing the synthesis of tissue non-specific alkaline phosphatase (TNAP). At present, therapies only exist to alleviate symptoms for both PXE and GACI; however, extensive studies have resulted in several novel approaches to treating PXE and GACI. This review seeks to summarize the role of ABCC6 in ectopic calcification in PXE and other calcification disorders, and discuss therapeutic strategies targeting various proteins in the pathway (ABCC6, NPP1, and TNAP) and direct inhibition of calcification via supplementation by various compounds.

Dietary Pyrophosphate Modulates Calcification in a Mouse Model of Pseudoxanthoma Elasticum: Implication for Treatment of Patients

Pseudoxanthoma elasticum is a heritable disease caused by ABCC6 deficiency. Patients develop ectopic calcification in skin, eyes, and vascular tissues. ABCC6, primarily found in liver and kidneys, mediates the cellular efflux of ATP, which is rapidly converted into inorganic pyrophosphate (PPi), a potent inhibitor of calcification. Pseudoxanthoma elasticum patients and Abcc6^-/- mice display reduced PPi levels in plasma and peripheral tissues. Pseudoxanthoma elasticum is currently incurable, although some palliative treatments exist. In recent years, we have successfully developed therapeutic methodologies to compensate the PPi deficit in animal models and humans. Here, we inadvertently discovered that modulating dietary PPi can also be an effective approach to reducing calcification in Abcc6^-/- mice. Our findings were prompted by a change in institutional rodent diet. The new chow was enriched in PPi, which increased plasma PPi, and significantly reduced mineralization in Abcc6^-/- mice. We also found that dietary PPi is readily absorbed in humans. Our results suggest that the consumption of food naturally or artificially enriched in PPi represents a possible intervention to mitigate calcification progression in pseudoxanthoma elasticum, that dietary preferences of patients may explain pseudoxanthoma elasticum heterogeneous manifestations, and that animal chow has the potential to influence data reproducibility.

Numerical characterization of regenerative axons growing along a spherical multifunctional scaffold after spinal cord injury

Spinal cord injury (SCI) followed by extensive cell loss, inflammation, and scarring, often permanently damages neurological function. Biomaterial scaffolds are promising but currently have limited applicability in SCI because after entering the scaffold, regenerating axons tend to become trapped and rarelyre-enter the host tissue, the reasons for which remain to be completely explored. Here, we propose a mathematical model and computer simulation for characterizing regenerative axons growing along a scaffold following SCI, and how their growth may be guided. The model assumed a solid, spherical, multifunctional, biomaterial scaffold, that would bridge the rostral and caudal stumps of a completely transected spinal cord in a rat model and would guide the rostral regenerative axons toward the caudal tissue. Other assumptions include the whole scaffold being coated with extracellular matrix components, and the caudal area being additionally seeded with chemoattractants. The chemical factors on and around the scaffold were formulated to several coupled variables, and the parameter values were derived fromexisting experimental data. Special attention was given to the effects of coating strength, seeding location, and seeding density, as well as the ramp slope of the scaffold, on axonal regeneration. In numerical simulations, a slimmer scaffold provided a small slope at the entry "on-ramp" area that improved the success rate of axonal regeneration. If success rates are high, an increased number of regenerative axons traverse through the narrow channels, causing congestion and lowering the growth rate. An increase in the number of severed axons (300-12000) did not significantly affect the growth rate, but it reduced the success rate of axonal regeneration. However, an increase in the seeding densities of the complexes on the whole scaffold, and that in the seeding densities of the chemoattractants on the caudal area, improved both the success and growth rates. However, an increase in the density of thecomplexes on the whole scaffold risks an over-eutrophic surface that harms axonal regeneration.Although theoretical predictions are yet to be validated directly by experiments, this theoretical tool can advance the treatment of SCI, and is also applicable to scaffolds with other architectures.

Prevalence of diffuse idiopathic skeletal hyperostosis among elderly subjects referred for radiological investigation in tertiary hospital at Oman

Diffuse idiopathic skeletal hyperostosis (DISH) is characterized by calcification of different entheseal sites including the anterior longitudinal ligament of the spine. There is no documented information about DISH in Oman. This study determined the prevalence of DISH and associated factors among elderly subjects in a national tertiary care referral hospital in Oman. This retrospective study reviewed chest X-rays of all patients aged more than 50 years, referred to the radiology department of Sultan Qaboos University Hospital in the year 2016, based on the Resnick's criteria. The prevalence was expressed as proportions across age groups and sex. Chi-square test and logistic regression analysis was done to determine the association of the age and sex with DISH. A total of 1305 chest X-rays of patients were reviewed. The overall prevalence of DISH was 10%, with male to female ratio of 1.56:1. The odds ratio for males and increasing age were 1.63 (95% confidence interval [CI], 1.12–2.3; P<0.05) and 1.34 (95% CI, 1.14–1.58; P<0.001) respectively. The prevalence increased with age to maximum of 13% in the age group of ≤80. The pre-stage DISH prevalence was 9.3% and more frequently observed among males. Prevalence of DISH in the national tertiary care referral center in Oman is lower than in Jewish population, almost similar to Japanese, but higher than in Koreans. DISH prevalence is positively associated with age and sex. It is necessary to take appropriate precautionary measures to target the ageing population in Oman, especially elderly males.

Thoracic aortic aneurysm is an independent factor associated with diffuse idiopathic skeletal hyperostosis

Aims

Although we often encounter patients with an aortic aneurysm who also have diffuse idiopathic skeletal hyperostosis (DISH), there are no reports to date of an association between these two conditions and the pathogenesis of DISH remains unknown. This study therefore evaluated the prevalence of DISH in patients with a thoracic aortic aneurysm (AA).

Patients and Methods

The medical records of 298 patients who underwent CT scans for a diagnosis of an AA or following high-energy trauma were retrospectively examined. A total of 204 patients underwent surgery for an AA and 94 had a high-energy injury and formed the non-AA group. The prevalence of DISH was assessed on CT scans of the chest and abdomen and the relationship between DISH and AA by comparison between the AA and non-AA groups.

Results

The prevalence of DISH in the AA group (114/204; 55.9%) was higher than that in the non-AA group (31/94; 33.0%). On multivariate analysis, the factors of AA, male gender, and ageing were independent predictors of the existence of DISH, with odds ratios of 2.9, 1.9, and 1.03, respectively.

Conclusion

This study revealed that the prevalence of DISH is higher in patients with an AA than in those without an AA, and that the presence of an AA significantly influenced the prevalence of DISH. Cite this article: Bone Joint J 2018;100-B:617-21.

Severe hip joint motion restriction in a patient with diffuse idiopathic skeletal hyperostosis: A case report

RATIONALE

Severe limitation of motion (LOM) in the spine occasionally occurs in patients with diffuse idiopathic skeletal hyperostosis (DISH). However, in extraspinal areas, significant LOM has rarely been reported. In this study, we report a patient with DISH who had severe motion restriction within both hip joints.

PATIENT CONCERNS

A 57-year-old man presented with a 10-year history of LOM of bilateral hip joints. He had gait difficulty due to shortened stride length induced by LOM. Also, he had mild bilateral hip pain [numeric rating scale (NRS): 2].

DIAGNOSES

Hip joint range of motion was 60.3% of normal. The patient had bridging ossification along the anterolateral borders of 7 contiguous vertebrae (T10 to L4) without the findings of ankylosing spondylitis or degenerative disc disease. In addition, severe hyperostosis was diffusely formed around bilateral hip joints. He was diagnosed with DISH.

INTERVENTIONS

No specific treatment was performed for controlling LOM of bilateral hip joints. Meloxicam 15 mg was administered to the patient for the management of mild bilateral hip pain.

OUTCOMES

At 2-month follow-up visit, the degree of LOM in the bilateral hip joints was not changed. However, the patient's pain severity was reduced from NRS 2 to 1.

LESSONS

We showed that DISH can cause significant motion restriction due to severe hyperostosis in the bilateral hip joints.

Neurological heterotopic ossification: Current understanding and future directions

Neurological heterotopic ossification (NHO) involves the formation of bone in soft tissue following a neurological condition, of which the most common are brain and spinal cord injuries. NHO often forms around the hip, knee and shoulder joints, causing severe pain and joint deformation which is associated with significant morbidity and reduced quality of life. The cellular and molecular events that initiate NHO have been the focus of an increasing number of human and animal studies over the past decade, with this work largely driven by the need to unearth potential therapeutic interventions to prevent the formation of NHO. This review provides an overview of the present understanding of NHO pathogenesis and pathobiology, current treatments, novel therapeutic targets, potential biomarkers and future directions.

Pyrophosphate Supplementation Prevents Chronic and Acute Calcification in ABCC6-Deficient Mice

Soft tissue calcification occurs in several common acquired pathologies, such as diabetes and hypercholesterolemia, or can result from genetic disorders. ABCC6, a transmembrane transporter primarily expressed in liver and kidneys, initiates a molecular pathway inhibiting ectopic calcification. ABCC6 facilitates the cellular efflux of ATP, which is rapidly converted into pyrophosphate (PPi), a major calcification inhibitor. Heritable mutations in ABCC6 underlie the incurable calcification disorder pseudoxanthoma elasticum and some cases of generalized arterial calcification of infancy. Herein, we determined that the administration of PPi and the bisphosphonate etidronate to Abcc6^-/- mice fully inhibited the acute dystrophic cardiac calcification phenotype, whereas alendronate had no significant effect. We also found that daily injection of PPi to Abcc6^-/- mice over several months prevented the development of pseudoxanthoma elasticum-like spontaneous calcification, but failed to reverse already established lesions. Furthermore, we found that the expression of low amounts of the human ABCC6 in liver of transgenic Abcc6^-/- mice, resulting in only a 27% increase in plasma PPi levels, led to a major reduction in acute and chronic calcification phenotypes. This proof-of-concept study shows that the development of both acute and chronic calcification associated with ABCC6 deficiency can be prevented by compensating PPi deficits, even partially. Our work indicates that PPi substitution represents a promising strategy to treat ABCC6-dependent calcification disorders.

ABC Transport Proteins in Cardiovascular Disease-A Brief Summary

Adenosine triphosphate (ATP)-binding cassette (ABC) transporters may play an important role in the pathogenesis of atherosclerotic vascular diseases due to their involvement in cholesterol homeostasis, blood pressure regulation, endothelial function, vascular inflammation, as well as platelet production and aggregation. In this regard, ABC transporters, such as ABCA1, ABCG5 and ABCG8, were initially found to be responsible for genetically-inherited syndromes like Tangier diseases and sitosterolemia. These findings led to the understanding of those transporter’s function in cellular cholesterol efflux and thereby also linked them to atherosclerosis and cardiovascular diseases (CVD). Subsequently, further ABC transporters, i.e., ABCG1, ABCG4, ABCB6, ABCC1, ABCC6 or ABCC9, have been shown to directly or indirectly affect cellular cholesterol efflux, the inflammatory response in macrophages, megakaryocyte proliferation and thrombus formation, as well as vascular function and blood pressure, and may thereby contribute to the pathogenesis of CVD and its complications. Furthermore, ABC transporters, such as ABCB1, ABCC2 or ABCG2, may affect the safety and efficacy of several drug classes currently in use for CVD treatment. This review will give a brief overview of ABC transporters involved in the process of atherogenesis and CVD pathology. It also aims to briefly summarize the role of ABC transporters in the pharmacokinetics and disposition of drugs frequently used to treat CVD and CVD-related complications.

Identifying the Cellular Mechanisms Leading to Heterotopic Ossification

Heterotopic ossification (HO) is a debilitating condition defined by the de novo development of bone within non-osseous soft tissues, and can be either hereditary or acquired. The hereditary condition, fibrodysplasia ossificans progressiva is rare but life threatening. Acquired HO is more common and results from a severe trauma that produces an environment conducive for the formation of ectopic endochondral bone. Despite continued efforts to identify the cellular and molecular events that lead to HO, the mechanisms of pathogenesis remain elusive. It has been proposed that the formation of ectopic bone requires an osteochondrogenic cell type, the presence of inductive agent(s) and a permissive local environment. To date several lineage-tracing studies have identified potential contributory populations. However, difficulties identifying cells in vivo based on the limitations of phenotypic markers, along with the absence of established in vitro HO models have made the results difficult to interpret. The purpose of this review is to critically evaluate current literature within the field in an attempt identify the cellular mechanisms required for ectopic bone formation. The major aim is to collate all current data on cell populations that have been shown to possess an osteochondrogenic potential and identify environmental conditions that may contribute to a permissive local environment. This review outlines the pathology of endochondral ossification, which is important for the development of potential HO therapies and to further our understanding of the mechanisms governing bone formation.

Hyperphosphatemic familial tumoral calcinosis: odontostomatologic management and pathological features

BACKGROUND

Hyperphosphatemic familial tumoral calcinosis (HFTC) is to a rare autosomal recessive disorder characterized by cutaneous and sub-cutaneous calcified masses, usually adjacent to large joints. The aim of the current study was to report on the clinico-pathological features of a patient with HFCT, with emphasis on alterations in the jawbones and teeth and the subsequent therapeutic interventions.

CASE REPORT

A 13-year-old male patient with HFTC diagnosis came to our attention for dental anomalies and maxillary and mandibular hypoplasia. OPT highlighted multiple impacted teeth, short and bulbous teeth, and pulp chamber and canal obliterations. Lateral cephalometric radiograms pointed out retrusion of both jaws, skeletal class II malocclusion, and deep-bite. He underwent orthopedic, orthodontic, conservative, and surgical treatments, allowing the correction of maxillo-facial and dental abnormalities and dysmorphisms without adverse effects. The surgical samples were sent for conventional and confocal laser scanning microscope (CLSM) histopathological examination, which highlighted several metaplastic micro- and macro-calcifications in the soft tissues, and typical islands of homogenous, non-tubular, dentino-osteoid calcified structures in dentinal tissues.

CONCLUSIONS

The management of maxillo-facial abnormalities in patients affected by HFTC is very difficult and, requires a combined therapeutic approach. To date, very few indications have been published in the literature.

Diffuse idiopathic skeletal hyperostosis: A review

Background:

Diffuse idiopathic skeletal hyperostosis (DISH) is a systemic noninflammatory disease characterized by ossification of the entheses.

Methods:

This paper reviews the etiopathogenesis, epidemiology, clinical features, differential diagnosis, and treatment of DISH, based on current available literature.

Results:

Exact prevalence and incidence of DISH remains undetermined. Many external and genetic factors have been reported as being contributors to the pathogenesis of DISH. Current theories focus on the pathologic calcification of the anterior longitudinal ligament of the spine as the main physiopathological mechanism of disease. Clinical features are variable from monoarticular sinovitis to airway obstruction, and can be associated to systemic conditions. Comorbidities include obesity, hypertension, diabetes mellitus, hyperinsulinemia, dyslipidemia, and hyperuricemia according to a number of reports.

Conclusions:

DISH is a disease which involves the calcification of the anterior longitudinal ligament of the spine and can be associated with numerous clinical presentations and comorbidities.

Biochemical and molecular aspects of spectral diagnosis in calcinosis cutis

Calcinosis cutis (CC) is a type of calcinosis wherein insoluble compounds or salts deposited on the skin. Clinical diagnosis of CC is usually achieved through time consuming histopathological or immunohistochemical procedures, but it can only be empirically identified by experienced practitioners. The use of advanced vibrational spectroscopy has been recently shown to have great potential as a diagnostic technique for various diseased tissues because it analyses the chemical composition of diseased tissue rather than its anatomy and predicts disease progression. This review article includes a summary of the application of Fourier transform infrared (FT-IR) and Raman spectroscopic or microspectroscopic analysis for the rapid diagnosis and identification of the chemical composition of skin calcified deposits in patients with various CC symptoms. Both advanced techniques not only can detect the types of insoluble salts such as calcium phosphate, calcium carbonate, and monosodium urate, and β-carotene in the calcified deposits of human skin tissue but also can directly differentiate the carbonate substitution in the apatite structure of the skin calcified deposits. In particular, the combination of both vibrational techniques may provide complementary information to simultaneously assess the intact components of the calcified deposits. In the future, both FT-IR and Raman vibrational microspectroscopic techniques will become available tools to support the standard test techniques currently used in some clinical diagnoses. Molecular spectroscopy technique is rapidly changing disease diagnosis and management.

The level of hepatic ABCC6 expression determines the severity of calcification after cardiac injury

Because vascular or cardiac mineralization is inversely correlated with morbidity and long-term survival, we investigated the role of ABCC6 in the calcification response to cardiac injury in mice. By using two models of infarction, nonischemic cryoinjury and the pathologically relevant coronary artery ligation, we confirmed a large propensity to acute cardiac mineralization in Abcc6−/− mice. Furthermore, when the expression of ABCC6 was reduced to approximately 38% of wild-type levels in Abcc6+/− mice, no calcium deposits in injured cardiac tissue were observed. In addition, we used a gene therapy approach to deliver a functional human ABCC6 via hydrodynamic tail vein injection to approximately 13% of mouse hepatocytes, significantly reducing the calcification response to cardiac cryoinjury. We observed that the level and distribution of known regulators of mineralization, such as osteopontin and matrix Gla protein, but not osteocalcin, were concomitant to the level of hepatic expression of human and mouse ABCC6. We notably found that undercarboxylated matrix Gla protein precisely colocalized within areas of mineralization, whereas osteopontin was more diffusely distributed in the area of injury, suggesting a prominent association for matrix Gla protein and osteopontin in ABCC6-related dystrophic cardiac calcification. This study showed that the expression of ABCC6 in liver is an important determinant of calcification in cardiac tissues in response to injuries and is associated with changes in the expression patterns of regulators of mineralization.

The molecular and physiological roles of ABCC6: more than meets the eye

Abnormal mineralization occurs in the context of several common conditions, including advanced age, diabetes, hypercholesterolemia, chronic renal failure, and certain genetic conditions. Metabolic, mechanical, infectious, and inflammatory injuries promote ectopic mineralization through overlapping yet distinct molecular mechanisms of initiation and progression. The ABCC6 protein is an ATP-dependent transporter primarily found in the plasma membrane of hepatocytes. ABCC6 exports unknown substrates from the liver presumably for systemic circulation. ABCC6 deficiency is the primary cause for chronic and acute forms of ectopic mineralization described in diseases such as pseudoxanthoma elasticum (PXE), β-thalassemia, and generalized arterial calcification of infancy (GACI) in humans and dystrophic cardiac calcification (DCC) in mice. These pathologies are characterized by mineralization of cardiovascular, ocular, and dermal tissues. PXE and to an extent GACI are caused by inactivating ABCC6 mutations, whereas the mineralization associated with β-thalassemia patients derives from a liver-specific change in ABCC6 expression. DCC is an acquired phenotype resulting from cardiovascular insults (ischemic injury or hyperlipidemia) and secondary to ABCC6 insufficiency. Abcc6-deficient mice develop ectopic calcifications similar to both the human PXE and mouse DCC phenotypes. The precise molecular and cellular mechanism linking deficient hepatic ABCC6 function to distal ectopic mineral deposition is not understood and has captured the attention of many research groups. Our previously published work along with that of others show that ABCC6 influences other modulators of calcification and that it plays a much greater physiological role than originally thought.

An infant with pseudohyperkalemia, hemolysis, and seizures: cation-leaky GLUT1-deficiency syndrome due to a SLC2A1 mutation

CONTEXT

GLUT1 (glucose transporter 1) deficiency syndrome is a well-known presentation in pediatric practice. Very rare mutations not only disable carbohydrate transport but also cause the red cell membrane to be constitutively permeant to monovalent cations, namely sodium and potassium.

OBJECTIVE

The aim of this study was to describe the pediatric presentation of a patient with GLUT1 deficiency with such a cation-leaky state.

SUBJECT AND METHODS

The infant presented with erratic hyperkalemia, neonatal hyperbilirubinemia, anemia, hepatic dysfunction, and microcephaly. Later, seizures occurred and developmental milestones were delayed. Magnetic resonance imaging and computerized tomography scans of the brain showed multiple abnormalities including periventricular calcification. Visual impairment was present due to the presence of both cataracts and retinal dysfunction.

RESULTS

Measurements of red cell cation content showed extremely leaky red cells (causing the hemolysis) and temperature-dependent loss of potassium from red cells (explaining the hyperkalemia as pseudohyperkalemia). A trinucleotide deletion in SLC2A1, coding for the deletion of isoleucine 435 or 436 in GLUT1, was identified in the proband.

CONCLUSION

This is the fourth pedigree to be described with this most unusual syndrome. The multisystem pathology probably reflects a combination of glucose transport deficiency at the blood-brain barrier (as in typical GLUT1 deficiency) and the deleterious osmotic effects of a cation-leaky membrane protein in the cells where GLUT1 is expressed, notably the red cell. We hope that this detailed description will facilitate rapid diagnosis of this disease entity.

Diffuse idiopathic skeletal hyperostosis of the cervical spine: an underestimated cause of dysphagia and airway obstruction

BACKGROUND CONTEXT

Diffuse idiopathic skeletal hyperostosis (DISH) is a common but underdiagnosed condition relating to ossification of spinal ligaments that can cause compression of the esophagus and trachea. According to case reports, dysphagia or airway obstruction resulting from DISH is a rare occurrence.

PURPOSE

This study was intended to identify all published cases of dysphagia and/or airway obstruction resulting from DISH to increase the epidemiologic/clinical knowledge of these related conditions.

STUDY DESIGN

A systematic review of the literature was performed.

METHODS

The articles resulting from the systematic PubMed/EMBASE search of the literature were closely read, and predefined parameters were scored.

RESULTS

The search yielded a total of 118 articles (95 case reports and 23 case series) describing 204 patients with dysphagia and/or airway obstruction resulting from DISH. The number of cases demonstrated a steady increase from 1980 to 2009. This might be a real effect not ascribable to publication bias or expansion of the medical literature alone.

CONCLUSIONS

Diffuse idiopathic skeletal hyperostosis as a cause of dysphagia and/or airway obstruction may be an increasing and underappreciated phenomenon. Diffuse idiopathic skeletal hyperostosis should be included in the differential diagnosis of dysphagia and airway obstruction.

Animal models of typical heterotopic ossification

Heterotopic ossification (HO) is the formation of marrow-containing bone outside of the normal skeleton. Acquired HO following traumatic events is a common and costly clinical complication. In contrast, hereditary HO is rarer, progressive, and life-threatening. Substantial effort has been directed towards understanding the mechanisms underlying HO and finding efficient treatments. However, one crucial limiting factor has been the lack of relevant animal models. This article reviews the major currently available animal models, summarizes some of the insights gained from these studies, and discusses the potential future challenges and directions in HO research.

Vascular disease is associated with facet joint osteoarthritis

OBJECTIVE

Epidemiologic studies have demonstrated associations between vascular disease and spinal degeneration. We sought to examine whether vascular disease was associated with lumbar spine facet joint osteoarthritis (FJ OA) in a community-based population.

DESIGN

441 participants from the Framingham Heart Study multi-detector computed tomography (MDCT) Study were included in this ancillary study. We used a quantitative summary measure of abdominal aortic calcification (AAC) from the parent study as a marker for vascular disease. AAC was categorized into tertiles of 'no' (reference), 'low', and 'high' calcification. FJ OA was evaluated on computerised tomography (CT) scans using a four-grade scale. For analytic purposes, FJ OA was dichotomized as moderate FJ OA of at least one joint from L2-S1 vs no moderate FJ OA. We examined the association of AAC and FJ OA using logistic regression before and after adjusting for age, sex and body mass index (BMI). Furthermore, we examined the independent effect of AAC on FJ OA after including the known cardiovascular risk factors; diabetes, hypertension, hypercholesterolemia, and smoking.

RESULTS

Low AAC (OR 3.84 [2.33-6.34]; P<or=0.0001) and high AAC (9.84 [5.29-18.3]; <or=0.0001) were strongly associated with FJ OA, compared with the reference group. After adjusting for age, sex, and BMI, the association with FJ OA was attenuated for both low AAC (1.81 [1.01-3.27]; P=0.05) and high AAC (2.63 [0.99-5.23]; P=0.05). BMI and age were independently and significantly associated with FJ OA. The addition of cardiovascular risk factors to the model did not substantially change parameter estimates for either AAC tertile.

CONCLUSIONS

AACs were associated with FJ OA in this community-based population, when adjusting for epidemiologic factors associated with spinal degeneration, and cardiovascular risk factors. Potentially modifiable risk factors for facet degeneration unrelated to conventional biomechanical paradigms may exist. This study is limited by cross-sectional design; longitudinal studies are needed.

Normophosphatemic familial tumoral calcinosis is caused by deleterious mutations in SAMD9, encoding a TNF-alpha responsive protein

Normophosphatemic familial tumoral calcinosis (NFTC) is an autosomal recessive disorder characterized by calcium deposition in skin and mucosae and associated with unremitting pain and life-threatening skin infections. A homozygous missense mutation (p.K1495E), resulting in SAMD9 protein degradation, was recently shown to cause NFTC in five families of Jewish-Yemenite origin. In this study, we evaluated another Jewish-Yemenite NFTC kindred. All patients were compound heterozygous for two mutations in SAMD9: K1495E and a previously unreported nonsense mutation, R344X, predicted to result in a markedly truncated molecule. Screening of unaffected population-matched controls revealed heterozygosity for K1495E and R344X only in individuals of Jewish-Yemenite ancestry, but not in more than 700 control samples of other origins, including 93 non-Jewish Yemenite. These data may be suggestive of positive selection, considering the rarity of NFTC and the small size of the Jewish-Yemenite population; alternatively, they may reflect genetic drift or the effect of a population-specific modifier trait. Calcifications in NFTC generally develop over areas subjected to repeated trauma and are associated with marked inflammatory manifestations, indicating that SAMD9 may play a role in the inflammatory response to tissue injury. We therefore assessed the effect of cellular stress and tumor necrosis factor-alpha (TNF-alpha), a potent pro-inflammatory cytokine, on SAMD9 gene expression. Whereas exogenous hydrogen peroxide and heat shock did not affect SAMD9 transcription, osmotic shock was found to markedly upregulate SAMD9 expression. In addition, incubation of endothelial cells with TNF-alpha caused a dose-related, p38-dependant increase in SAMD9 expression. These data link NFTC and SAMD9 to the TNF-alpha signaling pathway, suggesting a role for this system in the regulation of extra-osseous calcification.

Tumoral calcinosis: new insights for the rheumatologist into a familial crystal deposition disease

A growing body of evidence points to extraosseous calcification (calcification occurring in nonosseous tissues) as a major cause of morbidity and mortality in humans. The term familial tumoral calcinosis encompasses a number of rare recessive diseases, often associated with increased reabsorption of phosphate through the renal proximal tubule, which manifests with periarticular or acral calcium deposition. Recently, the molecular pathogenesis of this group of disorders has been elucidated, leading to the identification of several proteins playing pivotal roles in the regulation of extraosseous calcification. This report reviews these advances as well as the potential implications of these discoveries for the management of acquired conditions associated with abnormal calcification.

Immune and nutrition status in elderly Koreans with hyperLDL-cholesterolemia

Although the effects of nutrition and immune status on disease development have been investigated, little attention has been given to changes in immune function in the elderly vulnerable to coronary artery disease (CAD). Our objective was to evaluate the association between immune variables and CAD risk factors, and nutritional factors related to immune and lipid profiles in elderly Koreans (n = 90). The subjects were divided into three groups based on serum low-density lipoprotein cholesterol (LDL-cholesterol) level: risk (> or = 160 mg/dL), borderline (130-160 mg/dL), and control groups (< 130 mg/dL). Concanavalin A-induced lymphocyte proliferation rate and interleukin (IL)-2 secretion were significantly lower in the risk group than the control group. The subjects in the risk group showed the highest serum concentrations of proinflammatory mediators such as complement 3 (C3), IL-1beta, and IL-1 receptor antagonist (IL-1RA). The nutrient intake status of the subjects was generally satisfactory without differences among groups. IL-1RA concentration was negatively associated with intake of vitamin E and C3 was positively related to intake of Ca and Fe in the subjects with LDL-cholesterol > or = 130 mg/dL. This study suggests that elderly individuals with high serum LDL-cholesterol are in a mild chronic inflammation state and micronutrient status such as vitamin E, Ca, and Fe may relate to this state.

Diffuse hepatocellular calcification developing in a patient on chronic hemodialysis after ischemic hepatitis

Diffuse hepatic calcification is a rare condition. Previous reports have described patients with end-stage renal disease who developed diffuse hepatic calcification after ischemic hepatitis caused by shock. We herein present a similar case. A 41-year-old man on chronic hemodialysis developed ischemic hepatitis due to shock induced by ventricular tachycardia, followed by progressive hepatic failure. Necropsy of the liver revealed diffuse hepatocellular calcification. Given the similarity by which our case and previously reported cases developed this rare condition, we postulate that chronic renal failure is involved in the pathogenesis of diffuse hepatic calcification.

The pulsewave reflections model: Exploring for a fundamental mechanism of cardiovascular calcification

Cardiovascular calcification occurs in a variety of location and structure in the heart and the vasculature. Many hypotheses exist in describing local phenomena, however, there is no known global and unifying mechanism to explain all types of cardiovascular soft tissue calcification. The observed calcific changes in the cardiovascular system, however, does have a general pattern of occurring at structurally altered sites either due to disease processes or surgical manipulations. Areas of structural alterations, in conjunction with the pulsatile environment of the cardiovascular system, have been shown to disrupt normal pulsewave transmission throughout the arterial tree and induce local junctional or interfacial stress gradients. As such, these induced stress gradients can potentially aggregate and deposit cellular products and ionic particles at local sites to initiate calcification. A fundamental mechanism influencing all cardiovascular calcification is proposed based on pathophysiologic pulsewave propagations and reflections at these sites of structural changes. Initial supporting results of the theoretical model and experimentations are discussed leading to a call for future research in this direction.

A deleterious mutation in SAMD9 causes normophosphatemic familial tumoral calcinosis

Familial tumoral calcinosis (FTC) is a rare autosomal recessive disorder characterized by the progressive deposition of calcified masses in cutaneous and subcutaneous tissues, which results in painful ulcerative lesions and severe skin and bone infections. Two major types of FTC have been recognized: hyperphosphatemic FTC (HFTC) and normophosphatemic FTC (NFTC). HFTC was recently shown to result from mutations in two different genes: GALNT3, which codes for a glycosyltransferase, and FGF23, which codes for a potent phosphaturic protein. To determine the molecular cause of NFTC, we performed homozygosity mapping in five affected families of Jewish Yemenite origin and mapped NFTC to 7q21-7q21.3. Mutation analysis revealed a homozygous mutation in the SAMD9 gene (K1495E), which was found to segregate with the disease in all families and to interfere with the protein expression. Our data suggest that SAMD9 is involved in the regulation of extraosseous calcification, a process of considerable importance in a wide range of diseases as common as atherosclerosis and autoimmune disorders.