The ontogeny of haemopoiesis during fetal life and the differentiation of blood cells in adult
life depend upon a fully competent microenvironment to provide appropriate signals via
production of soluble factors and cell contact interactions. The cellular constituents of the
microenvironment, also defined as the haemopoietic niche, largely derive from a common
progenitor of mesenchymal origin. Mesenchymal stem cells (MSC), initially identified in adult
bone marrow, have also been described in fetal haemopoietic tissues where they …