Date of Award
Program or Major
Doctor of Philosophy
Paul C W Tsang
Matrix metalloproteinases (MMPs) have been postulated to be important for angiogenesis and for tissue remodeling events associated with corpus luteum (CL) development. The MMPs are mainly regulated at three levels, transcription, activation, and inhibition by endogenous tissue inhibitors of metalloproteinases (TIMPs). Unlike most MMPs, pro-MMP-2 activation is accomplished on the cell surface rather than extracellularly. The objectives of the present study were to clone bovine cDNAs for MMP-2 and its activator, membrane type 1- (MT 1-)MMP, to investigate the expression and localization of MMP-2, MT1-MMP, TIMP-1, and TIMP-2 in three ages of CL, and to explore the regulation of MMP-2 expression in luteal and endothelial cells by cytokines. Molecular cloning and sequence analysis demonstrated that the bovine MMP-2 and MT1-MMP genes are highly similar to their homologs in other species. Although the levels of MMP-2 and MT1-MMP transcripts were constant in the early (day 4), mid (day 10), and late (day 16) stage CL, active MMP-2 and MT1-MMP proteins were significantly increased (p < 0.05) from the early to the mid and late stages. In addition, the patterns of TIMP-2 mRNA and protein expression were similar to MMP-2 and MT1-MMP, being expressed at higher (p < 0.05) levels in the mid and late stages than the early. Immunohistochemistry demonstrated that MMP-2, MT1-MMP, and TIMP-2 were localized in endothelial and large luteal cells. In contrast, TIMP-1 mRNA and protein were highly expressed in the early and mid cycle CL, but decreased in the late stage. TIMP-1 was detected in vascular smooth muscle cells and large luteal cells. In a luteal cell culture system, TNFalpha stimulated MMP-2 expression in a dose and time dependent manner. In luteal-derived endothelial cells, TNFalpha increased while IFNgamma inhibited MMP-2 expression. In the presence of both cytokines, IFNgamma attenuated the stimulatory effects of TNFalpha alone, bringing MMP-2 expression down to control levels. In conclusion, the coordinate expression of TIMP-2, and active MMP-2 and MT1-MMP suggests that the MT1-MMP/TIMP-2/pro-MMP-2 system may be spatially and temporally available for pro-MMP-2 activation in the bovine CL. Furthermore, cytokines regulate MMP-2 expression in luteal and endothelial cells.
Zhang, Bo, "Expression, activation, and regulation of matrix metalloproteinase 2 (MMP-2) in the bovine corpus luteum" (2002). Doctoral Dissertations. 86.