Sca-1 is involved in the adhesion of myosphere cells to αVβ3 integrin.

Amyosphere cell is a unique type of muscle stemcell that is able to maintain its pre-myogenic state in culture over time. These cells are propagated in culture as free-floating, non-adherent spheres. We believe that the 3-dimensional adhesive cell-cell interactions involved in maintaining the sphere-like myosphere structures are also involved in maintaining their longevity in culture. We found that Sca-1, which is highly expressed by myosphere cells, plays a role in the growth and the formation of the myospheres. In comparing adhesion molecules expressed by 3-dimensionally grown myosphere cells to those expressed by 2-dimensionally grown primary myoblasts, we found that there was a distinct difference in the expression of beta 3 integrin. Upon further investigation we discovered that there is an adhesive interaction between Sca-1(+) cells and alpha V beta 3 integrin. Here we show that Sca-1(+) cells (myosphere cells and NIH3T3 cells) adhere to alpha V beta 3 integrin and that Sca-1 2 cells (primary myoblasts) do not adhere. The interaction between Sca-1 and alpha V beta 3 integrin was confirmed using antibody blocking, shRNA knockdown of Sca-1 in Sca-1(+) cells, and by expressing Sca-1 cDNA in Sca-1 2 cells, which demonstrated that the level of adhesion of these cells to alpha V beta 3 integrin was dependent on the presence of Sca-1. Additionally, we found that the co-expression of Sca-1 and beta 3 resulted in significantly greater adhesion of Sca1(+) cells to alpha V beta 3 integrin. In conclusion, our data indicate that Sca-1 is involved in maintaining the 3-dimensional myosphere cell-cell contacts and that Sca-1 is involved in the binding of cells to aVb3 integrin. (C) 2012. Published by The Company of Biologists Ltd.