Epigenomic profiling of human testicular cells in aged males

• Applicant: Sara Di Persio, Ph.D.
• Subject Area: Reproductive Medicine, Urology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545924303

The number of couples delaying parenthood has progressively increased in most Western societies in recent decades. Importantly, both advanced maternal and paternal age have been associated with increased reproductive risks. While the effect of advanced maternal age on the female gamete has been more widely investigated, few studies have focused on the male side. Sperm of old men has been shown to present many hallmarks of aging as increased DNA fragmentation, higher mutation rate, and longer telomeres. However, new spermatozoa are generated every day from the testicular stem cells, therefore it has been suggested that aging does not directly affect the mature male gamete but rather the testicular stem cells. Indeed, alterations in this compartment have been identified in older men, and in particular changes in the proliferative status, DNA repair and chromatin structure. We hypothesize that the age-associated alterations observed in testicular stem cells are concurrent with specific changes in the histone modification profile, which controls chromatin structure as well as DNA repair, replication, and recombination. Furthermore, we suggest that in case of premature/altered recruitment of the stem cells, the aging process may be accelerated leading to stem cell exhaustion and impacting of sperm production. Capitalizing on our unique access to a wide range of human testicular tissues, we have established three groups (N=5 each) of testicular samples from differentially aged men to perform quantitative histomorphometrical analyses. We will screen all histone modifications that have been previously associated with transcriptional regulation and chromatin remodeling in quantitatively normal spermatogenesis (Group 1, 25-35 years). In this group we will also identify the cell type specific patterns enabling us to select up to 8 stem cell specific histone modifications for the subsequent analyses. We thereby generate a comprehensive testicular atlas of histone modifications. To unveil the changes in the stem cell histone modification profile during aging, we will quantify and compare the enrichment of these up to 8 selected stem cell-specific histone modifications in groups 1 and 2 ( >55 years). Finally we will investigate whether the changes are progressive. For this we have access to a unique and extremely rare cohort of infertile patients being biopsied twice at two time points being at least five years apart (Group 3) and in which altered recruitment of the stem cells has been shown. We will assess changes in stem cell numbers and stem cell specific histone modification patterns during the aging process. The identification of the age associated histone modification changes in human testicular stem cells will be the key achievement of this project. These insights will have a direct impact in unveiling the age-associated reproductive risks and will form the foundation for the subsequent 3 year project proposal.

• DFG Programme: Research Grants