Placenta as a source of hematopoietic stem cells.

The placenta is a large, highly vascularised hematopoietic tissue that functions during the embryonic and foetal development of eutherian mammals. Although recognised as the interface tissue important in the exchange of oxygen, nutrients and waste products between the foetus and mother, the placenta has increasingly become a focus of research concerning the ontogeny of the blood system. Here, we describe recent data showing the intrinsic hematopoietic potential and appearance of hematopoietic cells in the mouse and human placenta and probe the biological rationale behind its hematopoietic function. As a rest tissue that contains potent hematopoietic stem cells (HSCs), the human placenta could represent (in addition to umbilical cord blood cells) an accessible supplemental source of cells for therapeutic strategies.