However, ovariectomized mice that mimic osteoporosis exhibited reduced PDGF-BB secretion and Type-H vessels, while the phenotype was rescued by increasing PDGF-BB via local or systemic cathepsin K inhibition.147 In agreement with this finding, the number of Nestin+ arterioles and Type-H vessels was found to decrease with aging,14,148,149 and this change was accompanied by marked decreases in endothelial Notch signaling,149 the numbers of perivascular MSPCs, pericytes, and SCF/KITL, all of which are crucial to HSC maintenance. Here, KITLG is linked to osteoporosis.