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

Interspecies chimera through blastocyst complementation could be an alternative approach to create human organs in animals by using human pluripotent stem cells.A mismatch of the major histocompatibility complex of vascular endothelial cells between the 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 humans within the organ is necessary.In this study,to explore whether donor xeno-pluripotent stem cells 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 cell 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-1^EGFP/ECFP 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 the YS.Our results suggested that rat vascular endothelial cells could undergo proliferation,migration,and self-assembly to form blood vasculature and that hematopoietic cells could differentiate into B cells,T cells,and myeloid cells in rat-mouse chimeras,which was able to rescue early embryonic lethality caused by Flk-1 deficiency in mouse.

Generation of functional organs from stem cells

We are now well entering the exciting era of stem cells.Potential stem cell therapy holds great promise for the treatment of many diseases such as stroke,traumatic brain injury,Alzheimer’s disease,Parkinson’s disease,amyotrophic lateral-sclerosis,myocardial infarction,muscular dystrophy,diabetes,and etc..It is generally believed that transplantation of specific stem cells into the injured tissue to replace the lost cells is an effective way to repair the tissue.In fact,organ transplantation has been successfully practiced in clinics for liver or kidney failure.However,the severe shortage of donor organs has been a major obstacle for the expansion of organ transplantation programs.Toward that direction,generation of transplantable organs using stem cells is a desirable approach for organ replacement and would be of great interest for both basic and clinical scientists.Here we review recent progress in the field of organ generation using various methods including single adult tissue stem cells,a blastocyst complementation system,tissue decellularization/recellularization and a combination of stem cells and tissue engineering.