Comparative Studies on the In Vitro: DISCUSSION(2)
Cytoskeletal proteins are important in mitosis, cell growth, and changes in cell shape and also for the regulation of protein secretion. Alpha SMA is an important filamentous protein associated with the cytoskeleton. In the baboon, aSMA is absent in the stromal fibroblasts of the endometrium throughout the menstrual cycle but becomes evident as early as Day 14 of pregnancy and Day 18 of simulated pregnancy. Between Days 32 and 40 of pregnancy, the number of positively stained stromal fibroblasts decreases, particularly around the implantation site, and by Days 50-60 this staining disappears. We have shown in our in vitro system that cells begin to produce aSMA shortly after they are put into culture. birth control pills
This may be due to factors present in the culture media or factors secreted by these cells to promote adhesion. It has been shown that transforming growth factor p induces aSMA expression in smooth muscle cells and human breast gland fibroblasts. It is also possible that the elongation of isolated stromal cells after plating involves a remodeling of the cy-toskeleton, requiring expression of certain cytoskeletal proteins. Chick fibroblasts, upon spreading, become elongated and form stress fibers characterized by actin bundles and vinculin streaks. These stress fibers are quite noticeable in human and baboon endometrial stromal cells grown in monolayer. Alternatively, cell-cell contact through cell surface adhesion proteins could trigger the polymerization of the actin cytoskeleton within the cell.