Altered growth responses of muscle cells from patients pulmonary artery smooth with primary pulmonary hypertension to transforming growth factor-beta(1) and bone morphogenetic proteins

Background-Mutations in the type II receptor for bone morphogenetic protein (BMPR-II), a receptor member of the transforming growth factor-beta (TGF-b eta) superfamily, underlie many cases of familial and sporadic primary pulm onary hypertension (PPH). We postulated that pulmonary artery smooth muscle cells (PASMCs) from patients with PPH might demonstrate abnormal growth re sponses to TGF-beta superfamily members. Methods and Results-For studies of H-3-thymidine incorporation or cell proliferation, P ASMCs (passages 4 to 8) were derived from main pulmonary arteries. In contr ol cells, 24-hour incubation with TGF-beta (1) (10 ng/mL) or bone morphogen etic protein (BMP)-2, -4, and -7 (100 ng/mL) inhibited basal and serum-stim ulated H-3-thymidine incorporation, and TGF-beta (1) and BMPs inhibited the proliferation of serum-stimulated PASMCs. In contrast, TGF-beta (1) stimul ated H-3-thymidine incorporation (200%; P <0.001) and cell proliferation in PASMCs from PPH but not from patients with secondary pulmonary hypertensio n. In addition, BMPs failed to suppress DNA synthesis and proliferation in PASMCs from PPH patients. Reverse transcription-polymerase chain reaction o f PASMC mRNA detected transcripts for type I (TGF-beta RI, Alk-1, ActRI, an d BMPRIB) and type II (TGF-beta RII, BMPR-II, ActRII, ActRIIB) receptors. R eceptor binding and cross-linking studies with I-125-TGF-beta (1), confirme d that the abnormal responses in PPH cells were not due to differences in T GF-beta receptor binding. Mutation analysis of PASMC DNA failed to detect m utations in TGF-beta RII and Alk-1 but confirmed the presence of a mutation in BMPR-II in 1 of 5 PPH isolates. Conclusions-We conclude that PASMCs from patients with PPH exhibit abnormal growth responses to TGF-beta (1) and BMPs and that altered integration of TGF-beta superfamily growth signals may contribute to the pathogenesis of P PH.