[Expression of matrix metalloproteinases-9 and tissue inhibitor of metalloproteinases-1 mRNA in the endometrium during mid- luteal phase in women with unexplained infertility]

OBJECTIVE: To investigate the expression of matrix metalloproteinases-9 (MMP-9) and tissue inhibitor of metalloproteinases-1 (TIMP-1) mRNA in the endometrium during mid-luteal phase in women with unexplained infertility and its steroidal regulation. METHODS: In situ hybridization method was utilized to detect the location of MMP-9 and TIMP-1 mRNA. Reverse transcription polymerase chain reaction (RT-PCR) method was utilized to detect and quantitate MMP-9 and TIMP-1 mRNA expression levels in the endometrium during mid-luteal phase. Serum concentration of estradiol (E(2)) and progesterone (P) were measured by radioimmunoassay. Thirty-eight patients with unexplained infertility were included as study group, and 20 women with male factor infertility or normal volunteers were selected as control group. RESULTS: MMP-9 and TIMP-1 mRNA were diffusely distributed in the cytoplasm and nuclei of glandular and stromal cells. Their staining in control group were more abundant than those in study group. Endometrial MMP-9 and TIMP-1 mRNA expression during mid-luteal phase showed by RT-PCR in the study group were significantly lower than those in the control group (0.42 +/- 0.19 Vs 0.57 +/- 0.19, P < 0.05; 0.59 +/- 0.19 Vs 0.81 +/- 0.20, P < 0.01 respectively). Serum P of the study group was significantly lower than that of control group [(34 +/- 15) nmol/L Vs (53 +/- 17) nmol/L, P < 0.01]. Serum P level was positively correlated with MMP-9 mRNA only in control groups. CONCLUSIONS: MMP-9 and TIMP-1 mRNA might play an important role in the process of implantation. The decreased expression of their gene related to P level might be one of the major causes in unexplained infertility.