Abstract
Thrombospondin-1 (TSP-1)/CD47 signaling induces cell death and inhibits angiogenesis. Here, we investigated the possibility of improving donor engraftment by blocking the TSP-1/CD47 pathway in mouse models of total body irradiation (TBI)-conditioned syngeneic hematopoietic stem cell transplantation (HSCT). Our findings revealed that HSCT engraftment was improved in mice deficient in CD47 (Cd47 -/- ) or TSP-1 (Thbs1 -/- ) compared to wild-type (WT) mice. The lack of TSP-1 or CD47 enhanced the production of CXCL12 by megakaryocytes and platelets, promoting the seeding of donor hematopoietic stem cells (HSCs) in sinusoidal endothelial cell (SEC)/megakaryocyte niches. Both Cd47 -/- and Thbs1 -/- mice showed reduced platelet adhesion to sinusoidal vascular cells, attenuated endothelial injury, and enhanced BM vascular regeneration, preserving SEC niches. Antibody neutralization of TSP-1 significantly increased CXCL12 production, donor HSC engraftment, and vascular niche regeneration in WT mice. In summary, the TSP-1/CD47 pathway is a promising therapeutic target to enhance HSCT efficacy and reduce endothelial injury syndrome.