Single-cell transcriptome analysis reveals the molecular mechanisms underlying age-related changes in human testis

The decline in reproductive health observed in aging males is a well-documented phenomenon. However, the molecular and cellular mechanisms underlying testis aging remain poorly understood. In an effort to gain deeper insights into this process, we conducted a comprehensive analysis of 99,130 single-cell transcriptomes derived from testicular cells spanning an age range of 21 to 69 years. Our machine learning analysis revealed a more pronounced response to aging in somatic cells compared to germ cells. Our analysis identified two distinct waves of aging-related changes within testicular cell clusters. Notably, age-related alterations in somatic cells exhibited consistent and specific responses to the aging process. These age-related changes were found to involve immune response pathways, while cell-specific pathways, such as the response to insulin in Sertoli cells at 50s, and extracellular matrix and NOTCH signaling in TPC cells at 30s, were also observed. Of particular significance was the substantial decrease in the frequency of haploid germ cells in individuals with higher BMI across different age groups, suggesting a synergistic interplay between BMI and age We profiled the single-cell transcriptomes of the testes of 25 adults and combined them with our previous single-cell transcriptomes of the testes of 12 adults, resulting in a dataset covering samples from different age groups ranging from 17 to 67 years old. We studied the transcriptional changes over time in each major testicular cell type and discovered a set of molecular mechanisms underlying human testicular aging.

老年男性生殖健康衰退已是已有大量文献记载的现象，但睾丸衰老背后的分子与细胞机制仍未被充分阐明。为深入解析该衰老进程，我们对覆盖21至69岁年龄段的睾丸细胞的99130个单细胞转录组（single-cell transcriptomes）开展了全面分析。我们的机器学习（machine learning）分析结果显示，与生殖细胞（germ cells）相比，体细胞（somatic cells）对衰老的应答更为显著。我们的分析在睾丸细胞簇中鉴定出两类截然不同的衰老相关变化波次。值得注意的是，体细胞的衰老相关改变呈现出对衰老进程一致且特异的应答模式。研究发现这些衰老相关变化涉及免疫应答通路，同时还观察到细胞特异性通路的改变：例如50岁年龄段支持细胞（Sertoli cells）对胰岛素的应答，以及30岁年龄段TPC细胞的细胞外基质与NOTCH信号通路（NOTCH signaling）变化。尤为重要的是，在不同年龄段中，身体质量指数（BMI）较高个体的单倍体生殖细胞频率均出现显著下降，这提示BMI与衰老之间存在协同交互作用。我们对25名成年人的睾丸单细胞转录组进行了分析，并将其与此前获得的12名成年人睾丸单细胞转录组数据进行整合，最终得到覆盖17至67岁不同年龄段样本的数据集。我们对各主要睾丸细胞类型的随时间转录变化进行了研究，揭示了人类睾丸衰老的一系列分子机制。