Direct selection of human bone marrow mesenchymal stem cells using an anti‐CD49a antibody reveals their CD45^med,low phenotype

Abstract

Summary. Human bone marrow mesenchymal stem cells (MSC) generate, via a fibroblast colony-forming unit (CFU-F), osteo-chondroblastic cells as well as adipocytes and stromacytes. To date, these stem cells are isolated indirectly using a cell culture method and phenotyped as CD45 negative while the in vivo counterparts are undetermined. Our aim was to develop a direct selection method and to determine the phenotype of the MSC isolated in this way. Mesenchymal cells were selected with anti-CD49a and/or anti-CD45 antibodies using either flow cytometry or a magnetic beads method. All CFU-F were always detected in the small population of CD49a-positive cells. These CFU retained their differentiation potential and gave rise to osteochondroblastic cells, adipocytes and stromacytes. Phenotypic studies on uncultured cells revealed a CD45 med,low , CD34 low , HLA-II -cell population. Flow cytometry cell sorting showed that MSC with CFU-F potential were obtained only from a CD49a + /CD45 med,low population. In addition, when cultured, they clearly became CD45 -, CD34 -, HLA-II -, CD49a + . These results confirmed that MSC can be directly selected easily from human bone marrow using magnetic beads without altering their differentiation potential. These cells expressed mildly the haematopoietic marker CD45, which was dramatically downregulated by in vitro culture. The expression of CD45 coupled to CD49a thus enabled direct selection of the MSC.

Marrow-isolated adult multilineage inducible (MIAMI) cells, a unique population of postnatal young and old human cells with extensive expansion and differentiation potential

“…The data suggests that MIAMI, RS-1 and MAP cells are not identical but that they are potentially linked developmentally within the heterogeneous mesenchymal compartment. Since the expression of a particular immunophenotype depends more on the culture conditions than on the developmental status of a cell (Deschaseaux et al, 2003) it is hard to establish at this point how these different cells are positioned within a developmental hierarchy based on their molecular profile. However, based on their differentiation properties it would be reasonable to assume that MIAMI and MAP cells represent a more primitive developmental stage than RS-1 cells.…”

Role of bone marrow cell trafficking in replenishing skeletal muscle SP and MP cell populations

“…Previous reports have demonstrated that a proportion of BM cells trafficking to the skeletal muscle might lose expression of CD45 (Issarachai et al, 2002b;Issarachai et al, 2002a). In addition, CD45 -mesenchymal BM cells could also contribute to muscle (Deschaseaux et al, 2003). These observations urged us to use markers other than CD45 to monitor cellular contribution from the BM to skeletal muscle SP cells.…”

Potential of mesenchymal stem cells in gene therapy approaches for inherited and acquired diseases

“…The stem cell for the haematopoietic and mesenchymal systems remains elusive, as there is no known marker that identifies exclusively either the HSC, haematopoietic progenitor cells, or the MSC; yet the biology of the HSC has served to identify its presence among a heterogeneous population of CD34 + progenitor cells and other cells that also express CD34, such as endothelial cells and mast cells. Similarly, studies utilising antibodies to known MSC-associated markers, such as nerve growth factor receptor, CD49a or STRO-1 [106][107][108], have shown that progenitors, CFU-F, to MSCs can be enriched. Further discovery of novel surrogate markers, may serve in a similar fashion as the CD34 antigen has as the surrogate marker for the haematopoietic stem cell.…”