A single-cell transcriptomic landscape of mouse testicular aging

Introduction: Advanced paternal age of reproduction is an increasing trend, especially in developed coun-tries and areas. This trend results in elevated risks of adverse reproductive outcomes such as reduced fer-tility rates, increased pregnancy loss, and poor childhood health. Yet, a systematic profiling of aging -associated molecular and cellular alterations in testicular tissue is still missing. Objectives: We aimed to dissect aging-associated molecular characteristics in testes of mice. Methods: Single-cell transcriptomic sequencing and analysis were conducted in testes of young (2 months old) and old mice (24 months old). Immunofluorescences and immunochemistry were used to character-ize aging-associated phenotypes and verify single cell sequence results. Results: Here, we constructed the first single-cell transcriptomic atlases of testes of young and old mice. In-depth dissection of aging-dependent transcriptional alterations in specific cell types revealed multiple dysregulated biological processes such as increased 'senescence-associated secretory phenotype' and 'in-flammation', which were major aging-associated characteristics. Further analysis of aging-related differ-entially expressed genes uncovered a disrupted balance of undifferentiated and differentiated spermatogonia stem cells in spermatogonia, indicative of a potential role of spermatogonia stem cells in aging-associated subfertility. Importantly, for the first time, our results identified an increased subtype of aging-specific macrophages, which may contribute to a hostile proinflammatory microenvironment during testicular aging. Conclusion: Taken together, our findings depict the distinct single-cell transcriptional features of the aged mouse testes and provide enormous resources for a comprehensive understanding of the cell-type -specific molecular mechanisms underlying mouse testicular aging, which may shed light on developing novel potential diagnostic biomarkers and therapeutic targets for age-associated male subfertility. (c) 2023 The Authors. Published by Elsevier B.V. on behalf of Cairo University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).