Megakaryocyte and platelet thrombospondin-1 regulates matrix remodeling by stabilizing basement membrane COL6A1 in lung injury.

An early event after lung injury is extracellular matrix (ECM) remodeling and the formation of a provisional matrix. While megakaryocytes and platelets (Mgk/plt) play important roles in hemostasis, their impact on the matrix in lung injury is not fully understood. Using lung intravital microscopy, 3D large area scanning with multiphoton confocal hybrid imaging, and label-free quantitative proteomics, the matricellular protein thrombospondin-1 (TSP1) arising from Mgk/plt protects the lung from alveolar injury. Mgk/plt cell-specific Thbs1 knockout (cKO) mice show increased alveolar barrier disruption with exaggerated neutrophil-mediated injury. The cKO mice exhibit striking extracellular matrix re-organization with reduction in basement membrane matrix protein COL6A1 after injury. Moreover, cKO mice increase Mgk numbers to regions of fibrillar collagen deposition and alveolar leak. Our findings indicate Mgk/plt-derived TSP1 represents a key mechanism of matrix stabilization by protecting the basement membrane from neutrophil-mediated proteolytic damage, regulating injury severity and Mgk numbers at the alveolar interface.