AKT2/mTOR/VEGF Signaling Attenuates Aging-Related Male Infertility by Suppressing Epididymal Autophagy and Apoptosis via Extracellular Vesicle-Mediated Sperm Rescue.

Abstract

Aging-related decline in male fertility is closely associated with impaired sperm quality and dysregulated autophagy/apoptosis in reproductive tissues. This study elucidates the protective role of the AKT2/mTOR/VEGF axis in mitigating age-induced epididymal dysfunction and sperm deterioration. Utilizing iTRAQ proteomics and transcriptome sequencing in young (6-month) versus aged (18-month) rat models, we identified AKT2 and VEGF as key regulators of reproductive aging. Functional validation revealed that AKT2/mTOR/VEGF activation suppressed oxidative stress, preserved mitochondrial membrane potential, and inhibited autophagy/apoptosis in rat epididymal epithelial cells (REECs, cells lining the epididymis involved in sperm maturation and transport) through downstream targets including Bcl-2, Bax, and LC3-II. Notably, extracellular vesicles (EVs) derived from AKT2-activated REECs enhanced sperm motility and reduced sperm DNA fragmentation through reactive oxygen species (ROS) scavenging and autophagy modulation. Pharmacological inhibition of VEGF or AKT2 exacerbated cellular stress responses, while lentivirus-mediated AKT2 overexpression reversed age-related epididymal damage in vivo. Mechanistically, the pathway crosstalk between mTOR-driven VEGF secretion and EV-mediated intercellular communication emerged as a critical mechanism for maintaining sperm viability. These findings establish AKT2/mTOR/VEGF signaling as a central coordinator of epididymal homeostasis and propose EV-based therapies as promising strategies to counteract male reproductive aging.