Epigenetic repression of bone morphogenetic protein receptor II expression in scleroderma

Germline mutations in the bone morphogenetic protein type II receptor ( BMPRII ) gene play an essential role in the pathogenesis of familial pulmonary arterial hypertension ( FPAH ). In view of the histological similarities between scleroderma ( SS c) and FPAH arterial lesion, we examined the expression levels of BMPR II in SS c microvascular endothelial cells ( MVEC ). Oxidative stress and serum starvation were used to examine apoptotic responses of MVEC s. BMPR II expression levels were determined by RT ‐ PCR and by Western blot. Epigenetic regulation of BMPR II expression was examined by the addition of epigenetic inhibitors to MVEC s cultures, by methylation‐specific PCR , and by sequence analysis of DNA methylation pattern of the BMPR II promotor region. SS c‐ MVEC s were more sensitive to apoptotic signals than were normal‐ MVEC s. A significant decrease in BMPR II expression levels in SS c‐ MVEC s was noted, whereas no significant differences in the expression levels of BMPRIA and BMPRIB were observed. Similar reduction in expression levels was noted in SS c skin biopsies. The expression level of BMPR II in SS c‐ MVEC s was normalized by the addition of 2‐deoxy‐5‐azacytidine and trichostatin A to cell cultures. Extensive CpG sites methylation in the BMPR II promoter region was noted in SS c‐ MVEC s with no detectable site methylation in control‐ MVEC s. SS c‐ MVEC s are more sensitive to apoptotic triggers than are control‐ MVEC s. The enhanced apoptosis may be related to epigenetic repression of BMPR II expression as apoptosis of control‐ MVEC s can be augmented by knocking down BMPR II expression. The role of BMPR II underexpression in the pathogenesis of SS c vasculopathy is suggested and should be investigated further.