Multi-Omics Perspectives on Testicular Aging: Unraveling Germline Dysregulation, Niche Dysfunction, and Epigenetic Remodeling.

Male reproductive aging proceeds gradually and involves complex alterations across germ cells, somatic cells, and the testicular niche. Multi-omics analyses highlight shifts in spermatogonial stem cell dynamics, diminished sperm quantity and quality, and reconfigured support from Sertoli and Leydig cells. These somatic cells show numerical declines and exhibit senescence-associated changes that amplify inflammatory signals and compromise blood-testis barrier integrity. Concurrently, fibrosis and heightened immune cell infiltration disrupt intercellular communication, contributing to further deterioration of spermatogenesis. Epigenetic remodeling-including DNA methylation drift, histone modification imbalances, and altered small non-coding RNA profiles-adds another dimension, reducing sperm integrity and potentially exerting transgenerational effects on offspring health. Observed hormonal changes, such as reduced testosterone and INSL3 production by aging Leydig cells, reflect the additional weakening of testicular function. These multifactorial processes collectively underlie the drop in male fertility and the increased incidence of adverse outcomes, such as miscarriages and developmental anomalies in the offspring of older fathers. Research into mitigation strategies, including interventions targeting senescent cells, oxidative stress, and inflammatory pathways, may slow or reverse key mechanisms of testicular aging. These findings underscore the importance of understanding the molecular hallmarks of male reproductive aging for preserving fertility and safeguarding offspring well-being.