Matrix metalloproteinases and their inhibitors in human cumulus and granulosa cells as biomarkers for oocyte quality estimation

Objective: To study the molecular profile of metalloproteinases and their tissue inhibitors in granulosa and cumulus cells in a subset of fertile and infertile women. Design: Molecular study with granulosa and cumulus cells. Setting: University hospital. Patient(s): Forty-four women undergoing assisted reproductive techniques for female infertility factor, with partners having a normal spermiogram and 15 normally fertile women with male partner affected by severe oligoasthenoteratozoospermia or nonobstructive azoospermia. Intervention(s): In vitro fertilization. Main Outcome Measurement(s): We investigated gene expression level of metalloproteinases (MMP2, MMP9, MMP11) and their tissue inhibitors (TIMP1, TIMP2) by means of quantitative reverse-transcription polymerase chain reaction, protein quantification by means of Western blot, and localization by means of immunofluorescence. Result(s): We firstly validated HPRT1 as the most reliable housekeeping gene enabling correct gene expression analysis in both granulosa and cumulus cells. Gene expression, Western blot, and immunofluorescence analysis of MMP2, MMP9, and MMP11 and their tissue inhibitors TIMP1 and TIMP2 demonstrated that these enzymes are finely tuned in these cells. MMP9 is specifically expressed only in granulosa, whereas MMP2 is more expressed in cumulus and granulosa cells in cases of reduced ovarian response and decreased fertilization rate. Conclusion(s): This study sheds light on MMP and TIMP expression in granulosa and cumulus cells, and it may help in understanding the fine regulation of oocyte maturation inside the follicle. Although further studies are needed to fully understand the molecular mechanisms involved in these processes, our findings may be useful in the identification of biomarkers of oocyte maturation, competence acquiring, and fertilization.