Expression of gelatinases and their tissue inhibitors in rat corpus luteum during pregnancy and postpartum

Extensive tissue remodeling occurs in the corpus luteum (CL) during both formation and luteolysis. Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are believed to play pivotal roles in these processes. In the present study, to evaluate the potential roles of matrix degrading proteases in luteal development and regression, we examined gelatinases and TIMP‐1, ‐2, ‐3 mRNA expressions, as well as gelatinase activity in rat CL during pregnancy and postpartum using Northern blot, in situ hybridization, and gelatin zymography, respectively. The results showed that MMP‐2 mRNA was only expressed at the early stages of pregnancy; TIMP‐2 mRNA was highly expressed at the early and late pregnancy and day 1 postpartum, but could not be detected during the mid‐phase of pregnancy; TIMP‐3 mRNA expression was abundant during early pregnancy and peaked at day 7, but was absent from other time points examined. MMP‐9 and TIMP‐1 mRNAs in rat CL were below detectable level in the current study. Furthermore, the active MMP‐2 was only present during the early stages of pregnancy, and no MMP‐9 activity was observed in the zymogram. Taken together, our results suggest that MMP‐2 and TIMP‐3 may have functional roles in rat luteal formation, while TIMP‐2 may be implicated in both formation and regression of the pregnant CL. Mol. Reprod. Dev. 63: 273–281, 2002. © 2002 Wiley‐Liss, Inc.