Abstract 378: Bone Morphogenetic Protein 2 (BMP-2) and Wingless 3a (Wnt 3a) Promote Pulmonary Arterial Endothelial Cell (PAEC) Angiogenesis by Simultaneous Recruitment of Canonical and Noncanonical Wnt Pathways
Background: Idiopathic Pulmonary Arterial Hypertension (IPAH) is characterized by abnormal angiogenic responses following loss of small arteries. While studies have shown that functional loss of BMPRII promotes IPAH, its impact on PAEC activities related to vascular regeneration is unclear. We have shown that both BMP and Wnt signaling promote PAEC proliferation, migration and survival suggesting functional interactions between the 2 pathways. Thus, we proposed that BMPRII induces proliferation and survival by activating canonical Wnt/active β catenin (AβC) signaling while enhancing motility via a Disheveled (Dvl) dependent noncanonical Wnt/RhoA-Rac1 pathway.
Results: Knockdown of BMPRII and AβC by RNA interference significantly reduced BMP-2 and Wnt 3a induced PAEC proliferation and survival while enhancing their migration (P<0.001). Given the enhancement of motility with AβC knockdown, we sought evidence for BMP-2 and Wnt 3a induced noncanonical signaling in PAECs. Pulldown assays showed that BMP-2 and Wnt 3a produce activation of RhoA and Rac1 within 4 hours. The role of Dvl in this mechanism was studied by transfection of GFP tagged constructs including wild type (WT), two dominant negative (DN) mutants lacking critical domains known to interfere with Rho and Rac signaling and a dominant positive (DP) form. Compared to WT, DP-Dvl transfected cells exhibited higher BMP-2 induced migratory response associated with enhanced Rho-Rac activation (P<.001). In contrast, DN-Dvl transfected cells failed to show a migratory response to BMP-2 in association with failed Rho and Rac activation. Confocal microscopy confirmed that BMP2 induced PAEC motility was associated with WT-Dvl recruitment to sites of RhoA and Rac1 activation in lamellipodia. Using live cell imaging, we confirmed that BMP-2 promotes membrane redistribution of Dvl, an event that correlated with enhanced cell motility.
Conclusions: Loss of BMP-RII prevents BMP mediated proliferation and survival reducing angiogenic response after injury. However, non-canonical mediated motility may be preserved, perhaps accounting for the recruitment of apoptosis resistant progenitor cells to sites of injury thereby promoting abnormal vascular remodeling.