Chimerism levels after stem cell transplantation are primarily determined by the ratio of donor to host stem cells.

摘要

Ever since the concept of the hematopoietic stem cell (HSC) niche was first proposed in 1978, there has been debate whether toxic ablative conditioning is required before transplantation for creating HSC niche space, or whether engraftment is merely determined by stem cell competition between donor and host stem cells. Two recent studies describe low chimerism levels after transplanting high doses of purified HSCs in unconditioned hosts and attribute this poor engraftment to limited HSC niche spaces. This shows that in more than 30 years of research, the issue of HSC niche availability as a prerequisite for substantial chimerism has not been settled.