Autophagy activated by GR/miR-421-3p/mTOR pathway as a compensatory mechanism participates in chondrodysplasia induced by prenatal caffeine exposure in male fetal rats.

Autophagy has been implicated in the developmental toxicity of multiple organs in offspring caused by adverse environmental conditions during pregnancy. We have previously found that prenatal caffeine exposure (PCE) can cause fetal overexposure to maternal glucocorticoids, leading to chondrodysplasia. However, whether autophagy is involved and what role it plays has not been reported. In this study, a PCE rat model was established by gavage of caffeine (120 mg/kg.d) on gestational day 9-20. The results showed that reduced cartilage matrix synthesis in male fetal rats in the PCE group was accompanied by increased autophagy compared to the control group. Furthermore, the expression of mTOR, miR-421-3p, and glucocorticoid receptor (GR) in male fetal rat cartilage of PCE group was increased. At the cellular level, we confirmed that corticosterone inhibited matrix synthesis in fetal chondrocytes while increasing autophagic flux. However, administration of autophagy enhancer (rapamycin) or inhibitor (bafilomycin A1 or 3-methyladenine) partially increased or further decreased aggrecan expression respectively. At the same time, we found that corticosterone could increase the expression of miR-421-3p through GR and target to inhibit the expression of mTOR, thereby enhancing autophagy. In conclusion, PCE can cause chondrodysplasia and autophagy enhancement in male fetal rats. Intrauterine high corticosterone activates GR/miR-421-3p signaling and down-regulates mTOR signaling in fetal chondrocytes, resulting in enhanced autophagy, which can partially compensate for corticosterone-induced fetal chondrodysplasia. This study confirmed the compensatory protective effect of autophagy on the developmental toxicity of fetal cartilage induced by PCE and its epigenetic mechanism, providing novel insights for exploring the early intervention and therapeutic target of fetal-originated osteoarthritis.