Recipient bone marrow assimilates the myeloid/lymphoid reconstitution of distinct fetal hematopoietic stem cells.

The fetal liver (FL) is a source of hematopoietic stem and progenitor cells (HSPCs) for transplantation. However, whether FL-HSPCs collected at distinct developmental stages reconstitute similarly or differently in the recipient bone marrow (BM) remains undetermined. We examined this problem in a congeneic mouse transplantation model. We first analyzed the lineage components of FL from 12.5 days post-fertilization (dpf) to 18.5 dpf. The myeloid and lymphoid cells were dynamic in absolute number and ratio. The largest difference was between 12.5 and 16.5 dpf. The FL-HSPCs (Lin- CD150+ CD48- ) at these two time points were then respectively transplanted into the recipients. The difference in lineage reconstitution was undetectable at week 4 or 6 post-transplantation and afterward, indicating that the BM environment assimilated the transplanted cells. Profiling lineage-regulation genes of input and output HSPCs showed that the expression levels were much different in the former and almost the same in the engrafted HSPCs. Therefore, the recipient BM microenvironment could determine the developmental lineage-trends of FL-HSPCs.