Generation of rat blood vasculature and hematopoietic cells in rat-mouse chimeras by blastocyst complementation

Abstract Interspecies chimera through blastocyst complementation could be an alternative approach to create human organs in animals by using human pluripotent stem cells (hPSCs). A mismatch of the major histocompatibility complex (MHC) of vascular endothelial cells between human and host animal will cause graft rejection in the transplanted organs. Therefore, to achieve a transplantable organ in animals without rejection, creation of vascular endothelial cells derived from human within the organ is necessary. In this study, to explore whether donor xeno-PSCs can compensate for blood vasculature in host animals, we generated rat-mouse chimeras by injection of rat embryonic stem cells (rESCs) into mouse blastocysts with deficiency of Flk-1 protein, which is associated with endothelial and hematopoietic cells development. We found that rESCs could differentiate into vascular endothelial and hematopoietic cells in the rat-mouse chimeras. The whole yolk sac (YS) of Flk-1EGFP/EGFP rat-mouse chimera was full of rat blood vasculature. Rat genes related to vascular endothelial cells, arteries and veins, blood vessels formation process, as well as hematopoietic cells, were highly expressed in YS. Our results suggested that rat vascular endothelial cells can undergo proliferation, migration, and self-assembly to form blood vasculature; and that hematopoietic cells could differentiate into B cell, T cell and myeloid cells in rat-mouse chimeras, which was able to rescue early embryonic lethality caused by Flk-1 deficiency in mouse.