In vivo haematopoietic cell production by bone marrow-derived hemogenic endothelium

By tracing the VE-cadherin expression in the newborn bone marrow hematopoietic LSK (lineage minus/Sca-positive/Kit-positive) cells, we demonstrated that the late foetal/newborn BM hemogenic endothelial cells produce a small cohort of hematopoietic stem and progenitor cells (HSPCs) capable of circulating and colonizing the secondary haematopoietic organs. Phenotypic and functional analyses disclosed that BM endothelium-derived HSPCs are mainly Multipotent Progenitors (MPPs) and a few Hematopoietic Stem Cells. We used microarrays to detail the global programme of gene expression underlying the endothelial origin of LSK cells in the newborn bone marrow. Six samples were analyzed including YFP positive cells (3 replicates) and YFP negative cells (3 replicates). We used the tamoxifen inducible Tg(Cdh5-Cre/ERT2) mice crossed to Rosa 26 YFP mice. Tamoxifen induction was performed at 1, 2 and 3 days after birth. At day 26 after day 1 induction, LSK cells were FACS-sorted and separated into YFP-positive and YFP-negative cells. YFP reports the expression of VE-Cadherin