Human umbilical cord mesenchymal stem cells restores mTOR-mediated autophagy homeostasis to alleviate placental injury and improve pregnancy outcomes in preeclampsia

Background Preeclampsia is a hypertensive disorder during pregnancy, which seriously threatens both maternal and infant health. Currently, the only treatment available is to induce infant and placenta delivery, resulting in interest in potential fetal-safe treatment strategies. One such strategy is cell therapy with human umbilical cord mesenchymal stem cells (hUC-MSCs), which possesses immunomodulatory, anti-inflammatory and angiogenic functions that could alleviate pre-eclamptic symptoms. However, the precise effects and underlying mechanisms behind their activities are still largely unknown. In this study, we aimed to elucidate the effect of hUC-MSCs, as well as the pathways involved, on placental function in preeclampsia, thereby highlighting potential novel avenue for stem cell therapy. Methods Both an in vivo rat model, involving N-nitro-L-arginine methyl ester (L-NAME) injections in pregnant rats, and an in vitro model, entailing HTR8 trophoblasts/human umbilical cord vein endothelial cells (HUVECs) being stimulated with lipopolysaccharide (LPS), were established to simulate pre-eclampsia. In vivo , maternal blood pressure, renal function, as well as placental and fetal weights, were measured. ELISA was used to measure maternal serum levels of angiogenic, inflammatory, and oxidative stress factors. Placental mitochondrial morphology was evaluated using transmission electron microscopy, while autophagic pathways were analyzed by Western blots. With the in vitro model, cell proliferation, invasion, oxidative stress, and apoptosis were evaluated in a Transwell co-cultured with hUC-MSCs. Results hUC-MSC administration was found in the in vivo model to increase fetal weights, along with alleviating hypertension and proteinuria, which are owed to those cells promoting placental angiogenesis and blood perfusion, as well as lowering inflammation, oxidative stress, and apoptosis. These findings were further supported by the in vitro model, where hUC-MSC co-culture with LPS-treated HTR8/HUVECs resulted in increased cell proliferation and invasion, along with lowered apoptosis and reactive oxygen species generation. All of these effects are owed to hUC-MSCs improving placental mitochondrial function by lowering autophagy; this is through activating Akt/mTOR and inhibiting AMPK/mTOR pathways, leading to pro-autophagic LC3 and Beclin1 downregulation, as well as anti-autophagic P62 upregulation. Conclusion hUC-MSCs are able to alleviate pre-eclampsia by restoring physiological placental autophagic homeostasis, which could serve as a promising therapeutic strategy for the disease.