Heat shock pretreatment of mesenchymal stem cells for inhibiting the apoptosis of ovarian granulosa cells enhanced the repair effect on chemotherapy-induced premature ovarian failure

Background: Premature ovarian failure (POF) is a severe complication associated with chemotherapy for female patients of childbearing age. A previous study has shown that bone marrow-derived mesenchymal stem cells (MSCs) can partially repair the damaged ovarian structure and function following chemotherapy. Heat shock (HS) is a pretreatment to enhance cell survival. The present study aimed to demonstrate the repair effect and potential working mechanism of HS MSCs on chemotherapy-induced POF. Methods: Rat MSCs were isolated, cultured and identified. At 24 h, 48 h and 72 h after different strengths of HS pretreatment for 30 min, 1 h, 2 h and 3 h, apoptosis of MSCs was detected to determine the optimal conditions. Apoptosis and cell proliferation changes of MSCs were detected under the optimal conditions of HS. Apoptosis of HS preconditioned MSCs was detected after adding phosphamide mustard (PM) to mimic the microenvironment under chemotherapy. Rat granulosa cells (GCs) were isolated and cultured. PM was added and apoptosis of GCs was detected after coculture with the pretreated MSCs. The rat model of chemotherapy-induced POF was established and the pretreated MSCs were injected into bilateral ovaries. Ovarian structure and endocrine function were evaluated by ovary weight, follicle count, estrous cycle and sex hormone levels. Apoptosis of GCs was detected by TUNEL assay. Results: The apoptosis rate of MSCs with 1 h of HS pretreatment decreased significantly, so 1 h was considered the optimal duration. Under this condition, the reduction in the apoptosis rate persisted until 120 h after the pretreatment and cell proliferation was accelerated. After HS pretreatment, MSCs displayed an increased tolerance to microenvironment under chemotherapy. After coculture with the HS-pretreated MSCs, PM-induced apoptosis of GCs decreased. Injection of the pretreated MSCs into the rat ovaries caused an increase in ovary weight and the number of follicles at different stages of estradiol levels, and a decrease in follicle stimulating hormone levels and apoptosis of GCs in the POF model. Conclusion: HS pretreatment enhanced the repair effect of MSCs on chemotherapy-induced POF. The reason for this may be the further vitality enhancement of MSCs, which led to a greater inhibition of apoptosis of GCs.