Formation of haematopoietic microenvironment and haematopoietic stem cells from single human bone marrow stem cells.

Haematopoietic stem cells are a population of cells capable both of self renewal and of differentiation into a variety of haematopoietic lineages. Enrichment techniques of human haematopoietic stem cells have used the expression of CD34, present on bone marrow progenitor cells. But most CD34+ bone marrow cells are committed to their lineage, and more recent efforts have focused on the precise characterization of the pluripotent subset of CD34+ cells. Here we report the characterization of two distinct subsets of pluripotent stem cells from human fetal bone marrow, a CD34+, HLA-DR+, CD38- subset that can differentiate into all haematopoietic lineages, and a distinct more primitive subset, that is CD34+, HLA-DR-, CD38-, that can differentiate into haematopoietic precursors and stromal cells capable of supporting the differentiation of these precursors. These data represent, to our knowledge, the first identification of a single cell capable of reconstituting the haematopoietic cells and their associated bone marrow microenvironment.