Abstract 3546: Enrichment for Stro-1 Enhances Paracine-mediated Cardiovascular Repair From Human Bone Marrow Mesenchymal Cells
Background: The cardiovascular therapeutic potential of bone marrow (BM) mesenchymal stromal/stem cells (MSC) is largely mediated by paracrine effects. Traditional preparation of MSC has involved plastic adherence-isolation. In contrast, prospective immunoselection aims to improve cell isolation by enriching for mesenchymal precursor cells (MPC) at higher purity. We set out to determine whether immunoselection using the antibody STRO-1 increases the cardiovascular paracrine properties of human mesenchymal cells.
Methods: Plastic adherence-isolated MSC (PA-MSC) and STRO-1-selected MPC were prepared from the same human BM donors and compared in biological assays. Conditioned medium (CM) from each population was assayed for its in vitro effects on rat cardiomyoblasts (CMC) and human umbilical vein endothelial cells (EC). Human MPC were then sorted into two subpopulations with discrepant STRO-1 expression (STRO-1Bright, STRO-1Dim), which were assessed for paracrine effects in vitro and in vivo, using a rat model of acute MI.
Results: Compared to PA-MSC, MPC displayed greater clonogenicity (10-fold) (P<0.0001), proliferative capacity (P<0.05) and multilineage differentiation potential, along with higher retention of STRO-1 and higher mRNA expression of stem cell-related transcripts (P<0.05). Although CM from both cell types induced mitogenic, migratory and anti-apoptotic responses in CMC and EC, these effects were greater for MPC, which also exhibited higher gene and protein expression for CXCL12 and HGF (P<0.01). Inhibition of these cytokines attenuated MPC-mediated angiogenesis and CMC responses respectively. In vitro paracrine responses were further augmented by STRO-1Bright CM and diminished with STRO-1Dim CM. Peri-infarct transplantation of STRO-1Bright MPC resulted in a higher presence of dividing cardiomyocytes (Ki67+) and greater vascular density (vWF+/SMA+) than injection of STRO-1Dim MSC or saline.
Conclusions: STRO-1-enriched MPC possess more stem-like properties than traditionally isolated MSC, along with enhanced cardiovascular paracrine capacity and increased expression of CXCL12 and HGF. Immunos-election provides a useful strategy for improving cardiovascular repair from mesenchymal cells.