Histomorphometric and immunohistochemical changes in interstitial cells and ovarian follicles of rats treated with metformin during and after induction of permanent estrus

Objective: To evaluate the histomorphometric and immunohistochemical changes in interstitial cells and ovarian follicles of rats treated with metformin during and after induction of permanent estrus. Methods: Thirty-two adult-female rats with regular estrous cycle were equally divided into four groups: 1) GCtrl - at estrous phase. 2) GPCOS - at permanent-estrous phase. 3) GMet1 - rats and daily treated with metformin (12.5 mg/Kg) during 60 consecutive days, as preventive form and 4) GMet2 - PCOS rats, which remained exposed to 60 days of continuous illumination and treated with metformin. After that, the animals were euthanized, and the ovaries were removed and processed for paraffin embedding. Sections were stained with H.E. for histomorphometry or subjected to immunohistochemistry for Ki-67 and cleaved caspase-3 (Casp-3) detections. Results: The GPCOS showed lack of corpus luteum and several ovarian cysts, as well as interstitial-like cells. The presence of corpus luteum and a significant increase in primary and antral follicles were observed in Mel-treated groups, which also showed a decrease in the number of ovarian cysts and in the area occupied by interstitial-like cells. The presence of corpus luteum along with an increase in the number of primary follicles in the Met2 group were noticed (p<0,01). A significant reduction in number of cysts and in the area occupied by interstitial cells, as well as a decrease in nuclear volume of interstitial cells, were noticed in the Met-treated groups, mainly in the Met2 group. The percentage of cell proliferation was significantly higher in granulosa cells of the Met-treated groups than PCOS group, mainly in the GMet2 (p<0,01), which was similar to the GCtrl group. On the other hand, the percentage of apoptosis (cleaved-caspase-3- positive cells) was significantly higher in the granulosa cells of GPCOS and Met-treated groups than the GCtrl group, but without significant difference, which showed weak cleaved caspase-3 immunoreactivity in those cells. Conclusion: The ovaries of rats treated with metformin showed a decrease in nuclear volume and in the area occupied by interstitial cells, presence of corpus luteum, in addition to a decrease in the number of cysts.