Vascular remodeling in patients with rare genetic disorders

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Monogenetic disorders grant the unique prospect to understand complex diseases due to a single defined genetic defect. Advanced sequencing technology accelerates the discovery of possible gene candidates, but this progress is hampered by the inability to distinguish between functional disease related and numerous non-disease related mutations. Patient-specific in-vitro disease modeling systems are used in combination with genetic tools to identify disease related mutation. Furthermore, these systems provide the unique possibility to study gene related disease mechanism and to perform drug screening on an individual level. Arterial calcifications contribute to morbidity and are predictors of premature death. Vascular calcification is presented as a secondary complication to diseases such as atherosclerosis, diabetes mellitus type II, and chronic kidney disease. The mechanism of this pathology is poorly understood, however some components seem to mimic bone formation. We have recently identified a novel genetic disease in which de novo vascular calcifications form in the lower extremity arteries of affected adult individuals in a consanginous family. This vascular phenotype shares calcification pathologies seen in diabetes mellitus and end-stage renal failure. A single nucleotide polymorphism array revealed a shared 22.4 MB region of homozygosity on chromosome 6 in all affected members. Direct sequencing identified a homozygous nonsense mutation (c662C>A; pS221X) in NT5E, encoding CD73. CD73 is an enzyme involved in the extracellular purine metabolic pathway. CD73 converts extracellular AMP to adenosine and inorganic phosphate. Cultured fibroblasts isolated from affected individuals show complete loss of CD73 enzyme activity. Our preliminary data shows that these cells display increased tissue non-specific alkaline phosphatase (TNAP) activity, a key enzyme necessary for calcification, and were found to calcify in vitro. Genetic rescue and treatment with adenosine reduced both TNAP activity and in vitro calcification in the patient fibroblasts, suggesting that adenosine signaling in normal tissue inhibits ectopic vessel calcification. Adenosine signaling has been shown to be protective during harmful events in the cardiovascular system, however the link between adenosine and protection from calcification is unprecedented. We are currently investigating if adenosine or other members of the extracellular purine metabolic pathways modulates heterotopic calcifications in probably related disorders like, Pseudoxanthoma elastic, Fahr Syndrome, Pseudohypoparathyreodism type1a. Prolidase deficiency (PD) is a rare autosomal recessive disorder characterized by recurrent lower extremity ulcerations, recurrent infections, telangiectasias, and mild developmental delays. Prolidase, the defected peptidase, is responsible for the breakdown of proline and hydroxyproline dipeptides, thus playing a major role in collagen degradation and recycling of proline. The pathogenesis is not well understood, therapy is mainly supportive, and prognosis is poor. There are case reports of prolidase deficiency as a cause of Hyper IgE syndrome (HIES), as similarities exist between PD and autosomal dominant Hyper-IgE syndrome (HIES; Jobs Syndrome) caused by mutations in STAT3. PD shares with HIES elevated serum IgE, pulmonary infections often resulting in parenchymal damage such as bronchiectasis, hyperextensibility, and some similar facial features. Like PD, the pathogenesis of many HIES features remain poorly understood. Both PD and HIES appear to have abnormalities with wound healing, manifest primarily by the pronounced skin ulcerations in PD, and by the abnormal lung healing after pneumonias and lung surgeries in HIES. Our preliminary studies show defects in extracellular matrix degrading enzymes MMP 1,3, 9, 12 and proangiogenic factors like FLK1, VEGF, and Endothelin in PD and HIES fibroblasts after stimulation with TNF-alpha. These abnormalities are thought to involve dysregulated HIF signaling. In addition, in vitro, the MMP and angiogenic defects in PD and HIES fibroblasts improve after supplementation with hydroxyproline. Further studies with more patient samples are needed to define the mechanism and patient-patient variability and to further explore hydroxyproline as a potential therapy for these individuals. A clinical trial will be planned with hydroxyproline supplementation with monitoring of immunologic changes (such as Th17 cell differentiation, serum IgE), and MMP fibroblast activity and plasma levels. Improvement of the wound healing abnormalities would significantly improve the quality of life and long-term prognosis for both diseases. Turner syndrome (TS) is the most common genetic disorder affecting females and encompasses a broad spectrum of features, most notably short stature and loss of ovarian function. TS is a disorder resulting from the loss of all or part of one sex chromosome. Individual genetic mutations can alter different metabolic pathways ultimately affecting multiple tissue and or cellular functions. A cardiovascular phenotype is well established in the TS population. Cardiac valve abnormalities are classical findings in TS patients. Recently, advanced imaging has revealed of additional set of structural cardiovascular abnormalities. This includes specifically the aortic arch and is associated with high incidence of aortic dissection. Furthermore, some of the pathological changes in the aortic arch resemble Marfan syndrome which is caused by a mutation in fibrillin1 and associated with increased TGF-b activity. We already recruited 2 TS patients and successful generated patient specific cell lines for further functional studies.