Regulation of TIMP-1, -2 and -3 in human endometrial stromal cells during decidualization and under the influence of hCG

Objective: Tissue inhibitors of matrix metalloproteinases (TIMPs) are secreted by the human endometrium. By regulating the activity of trophoblastic matrix metalloproteinases, TIMPs play an essential role during early implantation. The receptivity of the endometrium is determined by the decidualization of endometrial stromal cells (ESC). Human chorionic gonadotropin (hCG) is one of the first embryonic signals in the embryo-maternal cross-talk and has been shown to influence endometrial differentiation. We investigated the expression of TIMP-1, -2 and -3 in human ESC during decidualization in vitro and under the influence of hCG.

Methods: ESC were isolated from hysterectomy specimens. The purity of the cell culture was proven by immunofluorescence staining of vimentin. Decidualization in vitro was performed by the application of 1µM progesterone and 30 nM estradiol over 9 days and proven by the expression of prolactin. Decidualized ESC were incubated with recombinant hCG (0.01–100 IU/ml) for 24h. The mRNA of TIMP-1, -2 and -3 was measured by semiquantitative real-time RT-PCR. TIMP-1 and -2 proteins in cell-culture supernatants were determined by enzyme-linked immunosorbent assays (ELISA).

Results: During decidualization in vitro, TIMP-1 showed no significant changes, whereas TIMP-2 was significantly reduced over the time course. In contrast to this, TIMP-3 showed the most considerable changes, being sharply up-regulated on days 3 and 6 (1041%±116%, p<0.01, day 6 vs. day 0). When hCG was applicated for 24h on day 9, only a slight reduction of TIMP-1 and -2 was observed. The effect of hCG on TIMP-3 was more pronounced, showing a significant decrease after incubation with 0.1, 1, 10 and 100 IU/ml (1IU/ml: 49.8%±5.2%, p<0.01).

Conclusion: The different expression patterns of TIMP-1, -2 and -3 during decidualization in vitro underline the regulatory importance of these factors for the implantation process. We can show that hCG modulates TIMP-1, -2 and -3 in ESC, thereby giving the embryo the potency to modulate the endometrial milieu during early implantation.