Identification and specific expression of matrix metalloproteinase-26 in rhesus monkey endometrium during early pregnancy

Matrix metalloproteinases (MMPs) and their tissue inhibitors may play important roles in tissue remodelling processes of the uterus. This study identified MMP-26 (endometase/matrilysin-2) in the endometrium of pregnant rhesus monkeys (Macaca mulatta) and monitored the spatial and temporal expression of the transcript and protein in the uteri on days 12, 18 and 26 of pregnancy. The partial monkey MMP-26 gene sequence of 289 nucleotides was 98% identical to that of its human homologue and its protein fragment contained a PHCGVPDGSD sequence in the prodomain identical to that in human MMP-26. RT–PCR analysis demonstrated that the average level of MMP-26 mRNA in the endometrium was high on day 12 of pregnancy, but significantly decreased on days 18 and 26 (P < 0.05). In-situ hybridization confirmed that MMP-26 mRNA is specifically localized in the endometrial compartments, with intense signals in the glandular epithelium on day 12 and in the walls of spiral arterioles adjacent to the implantation site on day 26. The hybridization signal for MMP-26 mRNA in the glandular epithelium decreased dramatically on day 18 and was undetectable on day 26. No MMP-26 mRNA transcripts were detected in the placental villi on days 18 and 26. Immunohistochemistry showed that the expression pattern of MMP-26 protein was similar to that of its mRNA. The restricted expression pattern of MMP-26 in the monkey uterus implies that this new MMP is involved in the highly regulated tissue remodelling processes of the glandular epithelium and spiral arteries during early pregnancy.