Micro-proteomics reveals distinct protein profiles and SPARC/FGF2/CDH1 regulation of human Sertoli cells between Sertoli cell-only syndrome and normal men

Sertoli cell-only syndrome (SCOS) is one of the most severe non-obstructive azoospermia (NOA) types, since only Sertoli cells with not any male germ cells exist with the seminiferous tubules. As such, it is of particular significance to elucidate molecular mechanisms underlying SCOS for improving the diagnosis and treatment strategies for this disease. Due to the difficulties in obtaining sufficient human testicular tissues and the limited availability of human cells, the traditional proteomics is inadequate for comparing the differences in large scale of protein expression patterns of human Sertoli cells between SCOS and normal men. To solve this issue on the requirement of large amount of cell numbers, we employed micro-proteomics to reveal distinct global protein expression profiles of human Sertoli cells between SCOS and obstructive azoospermia (OA) with normal spermatogenesis utilizing single human Sertoli cells. We found a significant downregulation of proteins involved in cell adhesion pathways in SCOS Sertoli cells, whereas proteins related to apoptosis were markedly upregulated. Interestingly, we identified the lower expression of SPARC (secreted protein acidic and rich in cysteine) and the higher expression of FGF2 (fibroblast growth factor 2) in human Sertoli cells of the SCOS compared to normal men. SPARC silencing led to upregulation of FGF2 in human Sertoli cells, and SPARC may be associated with the occurrence of SCOS and serves as a reliable marker for the diagnosis of this disease. This study thus comprehensively offers the proteomic landscape of human Sertoli cells in the testes of SCOS patients and it sheds a novel insight into the pathogenesis of SCOS.