scRNA-seq Profiling of Human Testes Reveals the Presence of the ACE2 Receptor, A Target for SARS-CoV-2 Infection in Spermatogonia, Leydig and Sertoli Cells

Abstract

In December 2019, a novel coronavirus (SARS-CoV-2) was identified in COVID-19 patients in Wuhan, Hubei Province, China. SARS-CoV-2 shares both high sequence similarity and the use of the same cell entry receptor, angiotensin-converting enzyme 2 (ACE2), with severe acute respiratory syndrome coronavirus (SARS-CoV). Several studies have provided bioinformatic evidence of potential routes of SARS-CoV-2 infection in respiratory, cardiovascular, digestive and urinary systems. However, whether the reproductive system is a potential target of SARS-CoV-2 infection has not yet been determined. Here, we investigate the expression pattern of ACE2 in adult human testes at the level of single-cell transcriptomes. The results indicate that ACE2 is predominantly enriched in spermatogonia and Leydig and Sertoli cells. Gene Set Enrichment Analysis (GSEA) indicates that Gene Ontology (GO) categories associated with viral reproduction and transmission are highly enriched in ACE2-positive spermatogonia, while male gamete generation related terms are downregulated. Cell-cell junction and immunity-related GO terms are increased in ACE2-positive Leydig and Sertoli cells, but mitochondria and reproduction-related GO terms are decreased. These findings provide evidence that the human testis is a potential target of SARS-CoV-2 infection, which may have significant impact on our understanding of the pathophysiology of this rapidly spreading disease.

Keywords: ACE2; SARS-CoV-2; infection; scRNA-seq; spermatogonia.

Figure 1

Single-cell transcriptome profiling from published adult human testes. (A) Uniform manifold approximation and projection (UMAP) clustering of combined adult human testicular cells from three individual samples. Nine major cell clusters were identified across a total of 16,632 cells. (B) Dot plot of proportion of cells in the respective cluster expressing selected marker genes (dot size), and average expression (color scale). SPG, spermatogonia; Early S’cytes, early spermatocytes; Late S’cytes, late spermatocytes; Early Round S’tids, early round spermatids; Later Round S’tids, later round spermatids; Elongating S’tids, elongating spermatids; Immuno, immune cells.

Figure 2

Angiotensin-converting enzyme 2 (ACE2) expression pattern in adult human testes. (A) Per-cell expression level of ACE2 of human testicular cells visualized on the UMAP plot. (B) UMAP plot of transmembrane serine protease 2 (TMPRSS2) expression across all cell clusters. (C) Violin plots of ACE2 expression in all identified cell types. (D) Violin plots of TMPRSS2 expression across all cell types. SPG—spermatogonia.

Figure 3

Composition of ACE2-positive cells and pseudotime analysis of human testicular cells. (A) ACE2-expression cells in each identified cell type. SPG—spermatogonia. (B) Trajectory of male germ cell development by pseudotime time analysis of human testicular cells.

Figure 4

Characteristics of ACE2-positive spermatogonia. (A) Gene ontology enrichment analysis of biological process categories of ACE2-positive spermatogonia compared with ACE2-negative spermatogonia. (B) Examples of the enrichment plot for terms of viral gene expression and male gamete generation.

Figure 5

Characteristics of ACE2-positive Leydig and Sertoli cells. (A) Gene ontology enrichment analysis of biological process categories of ACE2-positive Leydig and Sertoli cells compared with ACE2-negative cells. (B) Examples of the enrichment plot for terms of cell–cell junction organization and mitochondrial matrix.