Characterization Of The Hematopoiesis In Umbilical Arteries Of Mid-gestation Mouse Embryos

Objective. the definitive hematopoiesis, is predominantly characterized by emergenceof bona fide hematopoietic stem cells (HSCs) within various locations, including theaorta-gonad-mesonephros (AGM) region, umbilical/vitelline arteries, placenta and YS.umbilical arteries (UA) are major arteries that link the plecanta and AGM. Thehemangioblast represents a unique type of hematopoietic precursor cells that possess bothblood-forming and vascular capacities. AGM region contained canonical BL-CFCs.Nevertheless, whether BL-CFCs is the ancestor of definitive hematopoiesis in the umbilicalarteries cannot be excluded. Here, The aim of our study is to get at the Characterization ofall types of hematopoietic stem progenitor cells in umbilical ateries.Methods. Our study apply the BL-CFC assay, OP9-based hematopoietic andendothelial progenitor potential assay, Hematopoietic CFC assay, Matrigel-based in vitrotube formation assay, Flow cytometry and LDL uptake assay,cell transplantation, andOrgan Cultures of Embryonic Tissues.Results. We find that the UA cells of E11.5mouse embryos were capable ofgenerating typical blast colonies. Flow cytometry showed that the blast colonies derivedfrom UA cells were composed of F4/80+, Ter119+, CD31+, c-Kit+, Sca-1+, and CD45+.Particularly, the CD31+c-Kit+, CD45+Sca-1+, and CD31+CD45+subsets were abundant inthe blast colony cells.On replating,these colonies produced erythroid/myeloid progenitorsand B220+B lymphocytes in vitro, corroborating their definitive hematopoietic nature.They also generated CD31+or Endomucin+tube-like structures on OP9stromal cells,showing their endothelial potential. The proximal and distal regions of UA had equalnumbers of BL-CFCs. UA-derived BL-CFC was predominantly included in the Tie2+andPDGFRβ-populations, indicating the endothelial layer as the main niche for hemangioblastdevelopment in the UA. To evaluate whether BL-CFCs can be autonomously maintained or expanded in UA or AGM, in vitro organ culture was performed. Interestingly, the BL-CFCpool in the AGM was significantly amplified, in striking contrast to a decrease in the UA. inaddition, our study find that in vitro organ culture of UA can retain but not amplify all typesof hematopoietic stem progenitor cells.Conclusion. Our data collectively supported the UA contained typical BL-CFC withboth definitive blood-forming and endothelial potential. The proximal and distal regions ofUA had equal numbers of BL-CFCs. UA-derived BL-CFC was predominantly included inthe Tie2+and PDGFRβ-populations. UA can retain but not amplify all types ofhematopoietic stem progenitor cells with in vitro organ culture.