Low-intensity-pulsed-ultrasound-treated menstrual-blood-derived mesenchymal stem cells repair endometrial injury by PI3K/AKT pathway inhibition

Research question: What is the effect and underlying mechanism of low-intensity-pulsed-ultrasound (LIPUS)-treated menstrual-blood-derived mesenchymal stem cells (MenSC) on intrauterine adhesions (IUA)? Design: First, MenSC were identified and exposed to LIPUS. The proliferation, migration, invasion, cytokine secretion, and ability to differentiate into human endometrial epithelial cells (HEEC) of LIPUS-treated MenSC were characterized. In vitro, human endometrial stromal cells (HESC) were treated with 10 ng/ml transforming growth factor-$1 (TGF-$1) to simulate IUA, and then co-cultured indirectly with LIPUS-treated MenSC. In vivo, IUA rat models were constructed and LIPUS-treated MenSC were transplanted into the uterus. The morphology, structure, and levels of fibrosis and repair-related factors of the uterus were detected. In the mechanism study, insulin-like growth factor-1 (IGF-1) was applied to verify whether the PI3K/AKT pathway participated in the repair of endometrial injury by LIPUS-treated MenSC. Results: In vitro, LIPUS treatment showed beneficial effects on MenSC by promoting cell proliferation and migration; inhibiting apoptosis; and enhancing the expression of epidermal growth factor, hepatocyte growth factor and vascular endothelial growth factor. It also facilitated the differentiation of MenSC into HEEC while reducing the level of fibrosis in TGF-$1-treated HESC by decreasing the concentrations of p-PI3K and p-AKT. However, these effects were reversed with the use of IGF-1. In vivo, transplantation of LIPUS-treated MenSC resulted in increased uterine length, width and weight. The transplanted cells also improved completeness of the endometrial structure, reduced inflammatory infiltration, increased endometrial thickness and gland abundance, and decreased endometrial fibrosis. Additionally, increased concentations of endometrial-repair-related proteins and receptivity-related markers were observed after transplantation of LIPUS-treated MenSC. Conclusion: LIPUS-treated MenSC repaired endometrial injury by inhibiting the PI3K/AKT pathway.