Formation of stromal microenvironment and formation of hematopoiesis in fetal spongy bone

The endosteal-vascular structuresof the bone marrow stroma that form hematopoietic niches regulate the self-maintenanceand development of hematopoietic stem cells(HSCs). The ontogenesis of hematopoiesis hasbeen studied in a series of experimental studies,while the works characterizing the formation ofhematopoietic niches structures in relation to thedevelopment of ancestral hematopoietic cells inthe human fetal spongy bone practically do notoccur. Our work is devoted to the morphologicalstudy of the stromal microenvironment of thebone marrow and the formation of hematopoiesis in the fetal spongy bone of human fetuses at9-27 gestational weeks. The presented data indicate that the development of bone and hematopoietic tissues in thefetal period passes through a number of succes-sive stages and by the 27th gestational week theformation of structures forming vascular andendosteal niches, which are able to regulate theactivity of the ancestral hematopoietic cells, iscompleted.