ИСТИНА

Question. Regeneration and tissue repair is a complicated process and tissue revascularization is a crucial stage of regeneration. Mesenchymal stem cells (MSCs) possess a great capacity for tissue regeneration (repair) and angiogenesis. Recent studies have shown that Sca-1 is one of the key stem cell markers. In this study we investigated involvement of Sca-1+population of MSC in vascularization of implant. We suggested two different hypotheses: either Sca-1+ cells include endothelial precursors or Sca-1 provide essential tissue support for endothelial progenitors. Methods. We used mouse model of angiogenesis in Matrigel plug to follow the dynamics of Matrigel vascularization and evaluate Sca-1+cells contribution to this process. We also used in vitro tubes-formation assay on Matrigel to assess angiogenic properties of Sca-1-depleted and Sca-1-enriched adipose derived mouse MSC. Results. We found that Sca-1+ cells formed a capsular layer at day 3 and showed invasion into Matrigel during next week. Yet capillary or small blood vessels were discovered only from day 10 or 14 after Matrigel injection. It seems that de novo formed vascular structures were associated with previously formed Sca-1+cords. To test our hypothesis whether Sca-1+population contains endothelial precursors we isolated Sca-1 cells from total population and cultured it on Matrigel under pro-angiogenic conditions (MyeloCult medium). It was found that Sca-1-enriched population of cells was unable to form tube-like vessels. However Sca-1-depleted MSC population does not form vessel-like structures either. Conclusions. Taken together our data indicates that Sca-1 positive population is necessary for new vessel formation in implants. We suggest that Sca-1 cells form microenvironmental niche for attachment and differentiation of endothelial progenitors.