Identification, isolation and characterisation of scavenging endothelial cells in placenta

Abstract

Haemopoiesis occurs in the BM, where haemopoietic stem cells (HSC) reside in a three-dimensional “niche” and give rise to the millions of circulating blood cells required everyday of life. The precise regulation of this immense task occurs by interaction of HSC with other BM cells and extracellular matrix molecules. In addition, the BM vasculature has also now been identified as a key HSC regulator. The most common use of HSC is in clinical transplantation for patients with haematological malignancies, immunologic diseases and other blood disorders. Recently, murine bone marrow (BM) scavenging endothelial cells (BMSEC) were identified, isolated and characterised. These cells were demonstrated to have transplant potential; homing to the BM and contributing to new blood vessel formation in irradiated recipients. In order to potentially use endothelial cells to improve HSC transplants a clinically applicable source of human endothelial cells needs to be identified and characterised. Human placenta is a readily available tissue and human placental endothelial cells can be easily and non-invasively isolated. As human samples are extremely precious, a study of murine placental endothelial cells was used as a surrogate. For the first time, this study has identified, isolated and characterised placental scavenging endothelial cells (PSEC). These findings, together with functional assays, including homing and transplantation, provide evidence suggesting placenta SEC have the potential to home and engraft in a transplant recipient.