Mechanosensitive mechanism of angiogenesis in the lung - Project Summary Angiogenesis plays important roles in organ regeneration. Compensatory lung growth is induced in the remaining lung tissues after unilateral pneumonectomy (PNX), while inhibition of angiogenesis attenuates the effects. Stretching forces associated with mechanical deformation and expansion of alveoli after resection of lung lobe are one of the driving factors for post-PNX lung growth. Stretching forces control angiogenesis. We have reported that proliferation of endothelial cells (ECs) is stimulated at the peripheral region of the post-PNX mouse lungs, where stretching forces are increased. The overall goal of this proposal is to investigate the mechanism by which mechanical stretching controls angiogenesis during regenerative lung growth. Stimulating the regenerative ability of the lungs would be one of the promising strategies for patients with lung diseases. Focal adhesion protein, paxillin senses mechanical forces and regulates angiogenesis. Angiogenic signaling, angiopoietins (Angs)-Tie2 mediates lung regeneration. The mechanosensitive mechanism of paxillin in spatial control of vascular formation at the peripheral region during regenerative lung growth remains unclear. Our preliminary data demonstrate that (1) Post-PNX lung growth and EC proliferation at the peripheral region are inhibited by silicone prosthesis insertion that replaces an excised lobe and suppresses mechanical expansion; (2) The levels of paxillin increase in alveolar epithelial type 2 (AT2) cells and ECs in the right lungs after left PNX, upregulating the levels of Ang1 and Ang2, respectively, while prosthesis insertion inhibits the effects; (3) Post-PNX lung growth is suppressed in the tamoxifen-induced Pxnfl/fl-Sftpc-CreERT2 or Pxnfl/fl-Cdh5(PAC)- CreERT2 mouse lungs, in which paxillin expression is knocked down in AT2 cells and ECs, respectively; (4) the levels of paxillin are lower and angiogenesis is inhibited in SU5416-induced mouse emphysema and human chronic obstructive pulmonary disease (COPD) lungs; and (5) Extracellular matrix (ECM) proteins that impact cell mechanical responses are differentially expressed at the peripheral vs. proximal region of post-PNX mouse lungs. We hypothesize that paxillin senses stretching forces induced after PNX and mediates spatial control of post-PNX vascular formation in the lungs. In Aim 1, we will determine whether paxillin mediates spatial control of angiogenesis during post-PNX lung growth. In Aim 2, we will investigate the mechanosensitive mechanism by which paxillin mediates angiogenic signaling under stretching in vitro. In Aim 3, we will examine the spatial changes in ECM proteins in the post-PNX mouse lungs and their effects on angiogenesis. Our focus on the mechanosensitive mechanism of spatial control of angiogenesis during regenerative lung growth using transgenic mice, transcriptome/proteome analysis, a large animal model, and lung ECM implantation is innovative. If this study proves the role of paxillin in spatial control of angiogenesis after PNX and inhibition of angiogenesis in human/mouse COPD lungs, this work will lead to the development of new strategies (e.g., injectable ECM) for lung regeneration/repair.
