Human native bone marrow CD200 positive mesenchymal stromal cells exhibit characteristics of cells forming the hematopoietic stem cell niche

Bone marrow (BM) mesenchymal stem/stromal cells are non-hematopoietic (CD45-), non-endothelial (CD31-) multipotential cells capable to differentiate into osteoblastes, chondrocytes and adipocytes. In addition, different subpopulations of MSCs and some of their derivatives (early osteoblastic lineage cells) were shown to form HSC-niche. This makes a complex picture of the relationship between MSCs and HSCs. Despite growing data in mice model, few describe the human counterpart. The BM CD200+ and CD271+ fractions were previously shown to be enriched in native MSCs in human. Herein, we found heterogeneity in expression of CD200 within CD45-/CD31-/CD271+ human BM fraction. We thus selected CD200+ and CD200- cells from CD45-/CD31-/CD271+ BM samples and we analyzed their transcriptome. The differential display of gene expression between these two types of BM fractions will give new insights in the identification of native human MSCs. Several human BM samples (n=6) were performed in order to specifically select CD271positive non-hematopoietic (CD45negative)/non-endothelial (CD31negative) cells expressing CD200 molecule and compared to those which were negative for CD200. This was perfomed through the use of flow cytometer. Then, the whole mRNA transcriptome of CD45neg/CD31neg/CD271pos/CD200pos was determined. Included patients were named in the protocol as (13_14) ; (17_18) ; (21_22) ; (23_24) ; (25_26 ); (27_28).