Localization of integrin heterodimer α9β1 on the surface of uterine endometrial stromal and epithelial cells in mice.

Previously, we reported that endometrial stromal (ES) and endometrial epithelial (EE) cells did not attach to tenascin C, indicating the absence of active integrin α9β1 on the surface of mouse ES and EE cells. However, that study used recombinant tenascin C without fibronectin (FN) type III repeats interacting with integrin heterodimers. Therefore, we re-evaluated the presence of integrin α9β1 actively functioning on the surface of mouse ES and EE cells using full-length native tenascin C with FN type III repeats. The functionality of integrin α9β1 was confirmed using attachment and antibody inhibition assays. Both mouse ES and EE cells showed significantly increased adhesion to native tenascin C, and functional blocking of integrin α9β1 significantly inhibited adhesion to native tenascin C. These results demonstrate that the integrin α9 and β1 subunits function as active heterodimers on the plasma membrane of mouse ES and EE cells, respectively.