Comparative Studies on the In Vitro: DISCUSSION(3)
One possible role for the appearance of aSMA, other than initiating changes in cell shape, may be to decrease the proliferation process in these cells in preparation for differentiation. It has been shown that induction of aSMA by transforming growth factor p in smooth muscle inhibits proliferation, thus maintaining the cell in its contractile state. Also, changes in actin or actin-binding proteins appear to be important for cellular differentiation of granulosa cells. It would be interesting to determine whether the expression of aSMA is necessary in order for stromal cells to decidualize or whether this process is an independent phenomenon unrelated to the decidualization process. buy diabetes drugs
It has been shown in vivo that baboon stromal cells expressing aSMA protein do not coexpress IGFBP-1 protein. We have demonstrated in this study that when cells express high levels of IGFBP-1 after long-term dbcAMP and hormone treatment, the levels of aSMA mRNA expression decrease. It is possible that the expression of aSMA or other cytoskeletal proteins is inhibitory to the expression of IGFBP-1 and that prolonged treatment with dbcAMP and hormones causes the disappearance or breakdown of cytoskeletal elements. Alternatively, it is possible that the cells must attain a critical level of IGFBP-1 in order to repress the expression of aSMA. In cases in which aSMA and IGFBP-1 mRNA were expressed simultaneously (Fig. 4A), it is probable that individual stromal cells in culture were at different stages of decidualization, with some cells producing only IGFBP-1 and others expressing only aSMA. Further studies are required to clarify the relationship between IGFBP-1 and aSMA expression.