The significance of membrane type 1 metalloproteinase in structural involution of human corpora lutea

Abstract

The expression of membrane type 1 (MT1) matrix metalloproteinase (MMP), MMP-2, and tissue inhibitors of MMP-1 and -2 during structural involution of the human corpus luteum was examined using immunohistochemistry, Northern blotting, Western blotting, gelatin zymography and in-situ hybridization techniques. The corpora lutea of 20 patients were investigated at the time of total hysterectomy and were obtained from five patients each in the early, mid- and late luteal phases and during gestation. Immunohistochemistry for MT1-MMP in corpus luteum showed that the protein appeared in granulosa lutein cells in the late luteal phase. Both the expression of MT1-MMP mRNA and the amount of the protein increased in the late luteal phase. In-situ hybridization showed that MT1-MMP mRNA was localized mainly in the cytoplasm of granulosa lutein cells. These results suggest that increased expression of MT1-MMP may be a major factor in remodelling of the human corpus luteum during structural luteolysis.

Altered expression of Fas/Fas ligand/caspase 8 and membrane type 1-matrix metalloproteinase in atretic follicles within dehydroepiandrosterone-induced polycystic ovaries in rats

“…The results of the present study suggest that the under PCOSlike conditions induced by DHEA, the Fas/FasL/Caspase-8 death receptor pathway plays a pivotal role in the follicular atresia associated with apoptosis of granulosa cells, and are consistent with our earlier findings indicating the importance of MT1-MMP during tissue remodeling in structural luteolysis [29,30]. A well-known mediator of apoptosis is the transmembrane protein Fas receptor (or APO-1 or CD95); upon the binding of its ligand, FasL, Fas triggers a cascade leading to activation of activation of various caspases and cell death [36].…”

“…Consistent with this idea is the result we obtained using gelatin zymography, which showed significantly increased MT1-MMP activity in DHEA-7 rats, though expression of FasL did not significantly differ in DHEA-7 and Control-7 rats. We therefore suggest that MT1-MMP plays an important role in DHEA-induced follicular atresia, as it does during regression of the CL [29, 30]. Moreover, given that release of MT1-MMP is reportedly part of a shedding process mediated by degradation of membrane-bound proteins during apoptosis [42], and that coordinated apoptosis and MT1-MMP activity are reportedly associated with cartilage dissolution [43], we suggest that the follicular atresia seen in PCOS rats in the present study is the result of coordinated apoptotic and MT1-MMP activities.…”

“…Briefly, we used a Teflon glass tissue grinder to homogenize samples of ovarian tissue on ice in 2 ml of Tris buffer containing 0.25 mol/l sucrose, after which the homogenates were filtered through nylon mesh (42 µm) and centrifuged for 10 min at 120 g. The resultant supernatant was centrifuged at 10,000 g for 30 min at 4 • C, after which the pellets were stored at − 80 • C until used. We assessed MT1-MMP activity as a function of the processing of pro-MMP-2 in this fraction as previously described [29,30]. Samples of membrane fraction (20 µg) were mixed with 1 µl of FCS and incubated for 2 h at 37 • C. The reaction was terminated by the addition of non-reducing sample buffer, after which the mixture was analyzed using gelatin zymography.…”

“…Figure 9 shows that after incubating the plasma membrane fractions from rat ovaries with FCS as a source of procollagenase [29,30], there was significantly greater activation of pro-MMP-2 by MT1-MMP in the samples from DHEA-15 rats than in those from the other three groups. Similarly, there was significantly greater activation in the samples from DHEA-7 rats than in Control-7 rats.…”

“…Matrix metalloproteinases (MMPs) are also known to be involved in both the formation and regression of the CL and in follicular development, ovulation and atresia [25,26], and we previously reported that MMP-2 likely plays a central role in structural luteolysis [27]. In addition, MT1-MMP, which can activate the pro-form of MMP-2 in vitro, is constitutively expressed during the formation, function and regression of the CL [28], and we previously showed that in both rats [29] humans [30] MT1-MMP can mediate remodeling of the extracellular matrix of the CL during the process of structural luteolysis. Whether MT1-MMP plays a role in the apoptotic process during follicular atresia under PCOS-like conditions is not known, however.…”