Comparative study of bone marrow mesenchymal stromal cells at different stages of ontogeny

The aim of this study was to analyze the changes that occur in the population of bone marrow mesenchymal stromal cells (MSCs) during the individual development of an organism. For this purpose, the basic characteristics of MSCs (the content of clonogenic cells, immunophenotype, and potencies to differentiate in vitro and in vivo) in the prenatal, early postnatal, and late postnatal ontogeny of the rat were compared. It is shown that the cloning efficiency of bone marrow MSCs in 10-day-old and adult rats is comparable and hundreds of times smaller than that of bone cells of 20-day-old fetuses with a bone marrow rudiment. The activity of alkaline phosphatase, a marker of osteogenic cells, was found in the majority of colonies formed by MSCs of postnatal bone marrow but not by the fetal bone. By the CD90 expression and potencies for in vitro adipogenesis, the stromal cells from the fetal bone and bone marrow of 9- to 10-day-old rats were comparable with those of the mature bone marrow MSCs but differed from them by the small number of CD73-bearing cells and a weaker ability to osteogenesis in an inductive environment. The analysis of the fate of MSCs from the studied sources after their transplantation to adult rats showed that their ectopic transplantation as part of tissue fragments into the kidney results in the formation of bone tissues and hematopoietic stroma. In diffusion chambers with MSCs that were precultured in vitro, transplantation into the peritoneal cavity led to osteogenesis and chondrogenesis. However, no significant differences in the potencies of bone marrow MSCs for differentiation in vivo depending on the developmental stage have been found. Thus, during ontogeny, bone marrow MSCs enhance the expression of CD73 and the ability to osteogenesis in vitro, whereas the expression of CD90 and the potencies for adipogenesis in induction medium and differentiation in different directions in vivo do not change significantly.