Abstract 13678: Role of Protein Tyrosine Phosphatase 1B (PTP1B) in Stabilizing Endothelial Cell-Cell Junctions During Post-Ischemic Neovascularization
Neovascularization of ischemic tissues is sequential processes of vessel formation involving activation (loosening cell-cell adhesions and proliferation) and stabilization coordinated by inflammatory and VEGF signaling. We have shown that PTP1B negatively regulates VEGF-dependent endothelial cell (EC) proliferation and stabilizes cell-cell adhesions. However, its role in post-ischemic neovascularization in vivo remains unknown. In a femoral artery ligation model, here we show that PTP1B knockout (KO) mice exhibit reduced blood flow recovery (53%), capillary density (36%) and α-actin positive arterioles (51%) at day 14 in lower limb, which is followed by increased necrotic area (1.9-fold) at day 28, as compared to wild-type (WT) mice. WT-bone marrow (BM) transplantation into KO mice fails to rescue the impairment of KO mice, whereas KO-BM into WT mice show similar flow recovery to that of WT-BM into WT mice, suggesting the importance of PTP1B in non-hematopoietic cells during post-ischemic neovascularization. Detailed analysis of neoangiogenic niche reveal that a leaky microvasculature of varying size and irregular shape despite the increase in overall number of nascent vessel formation (28%) in KO mice. Mechanistically, depletion of PTP1B with siRNA increases EC permeability, as shown by reduced trans-endothelial resistance in EC monolayer (30% reduction) and in vivo Mile’s assay. In WT mice, PTP1B protein expression and its phosphatase activity are substantially increased after ischemia induction (82-fold and 10.4-fold, respectively), which would stabilize cell-cell junction. In line with this, adenovirus-mediated gene transfer of PTP1B in KO mice enhances blood flow recovery (35%) and reduced leaky vessels (48 %). Moreover, pro-angiogenic factor VEGF (2.8-fold) and proinflammatory cytokine TNFα (1.8-fold) markedly increase PTP1B gene expression in ECs. In summary, PTP1B activity induced by inflammatory signal is required for stabilization of activated ECs during inflammatory- and ischemia-initiated neovascularization. This may provide a compensatory mechanism of VEGF signaling regulation by inflammation. Thus, an appropriate control of PTP1B function may be a target for neovascularization of ischemic tissues.
- © 2011 by American Heart Association, Inc.