Persistent vascular defects in lung allografts attributed to defective endogenous endothelial progenitors

(a) Neovascularization or host-graft vascular development occurs in both normal and hypoplastic lung allografts. (b) Development and maturation of implanted normal and hypoplastic lungs follow the establishment of the vascular connections between the host and grafts. (c) The host-graft vascular connections do not improve the growth of normal or hypoplastic lungs. (d) Neovascularization failed to overcome the embryonic defects in vascular formation and the pulmonary vasculogenesis remained defective in hypoplastic lung allografts, which may be attributed to the defective endogenous endothelial progenitor cells.