“…Hematopoietic stem cell (HSC) engraftment, proliferation, and differentiation are critically regulated by niche microenvironments, which involve endothelial cells (ECs) and vessel-associated mesenchymal cells (Comazzetto et al, 2019;Crane et al, 2017;Ding et al, 2012;Doan et al, 2013a;Greenbaum et al, 2013;Himburg et al, 2018;Hoggatt et al, 2016;Mendelson and Frenette, 2014;Rafii et al, 2016;Ramasamy et al, 2016;Severe et al, 2019;Sugiyama et al, 2006;Zhao et al, 2014). Whereas it is proposed that lethal irradiation triggers acute loss of ECs, vessel dilation or swelling and changes in permeability have been also reported (Bowers et al, 2018;Doan et al, 2013b;Hassanshahi et al, 2017;Himburg et al, 2016;Hooper et al, 2009;Li et al, 2008;Slayton et al, 2007;Zhou et al, 2015). Thus, our understanding of irradiation and chemotherapyinduced vascular damage and the factors promoting regeneration remain insufficient.…”