Testis cell pyroptosis mediated by CASP1 and CASP4: possible sertoli cell-only syndrome pathogenesis.

BACKGROUND: Sertoli cell-only syndrome (SCOS) is the most serious pathological type of non-obstructive azoospermia. Recently, several genes related to SCOS have been identified, including FANCM, TEX14, NR5A1, NANOS2, PLK4, WNK3, and FANCA, but they cannot fully explain the pathogenesis of SCOS. This study attempted to explain spermatogenesis dysfunction in SCOS through testicular tissue RNA sequencing and to provide new targets for SCOS diagnosis and therapy. METHODS: We analyzed differentially expressed genes (DEGs) based on RNA sequencing of nine patients with SCOS and three patients with obstructive azoospermia and normal spermatogenesis. We further explored the identified genes using ELISA and immunohistochemistry. RESULTS: In total, 9406 DEGs were expressed (Log2|FC|≥ 1; adjusted P value < 0.05) in SCOS samples, and 21 hub genes were identified. Three upregulated core genes were found, including CASP4, CASP1, and PLA2G4A. Thus, we hypothesized that testis cell pyroptosis mediated by CASP1 and CASP4 might be involved in SCOS occurrence and development. ELISA verified that CASP1 and CASP4 activities in the testes of patients with SCOS were significantly higher than those in patients with normal spermatogenesis. Immunohistochemical results showed that CASP1 and CASP4 in the normal spermatogenesis group were mainly expressed in the nuclei of spermatogenic, Sertoli, and interstitial cells. CASP1 and CASP4 in the SCOS group were mainly expressed in the nuclei of Sertoli and interstitial cells because of the loss of spermatogonia and spermatocytes. CASP1 and CASP4 expression levels in the testes of patients with SCOS were significantly higher than those in patients with normal spermatogenisis. Furthermore, the pyroptosis-related proteins GSDMD and GSDME in the testes of patients with SCOS were also significantly higher than those in control patients. ELISA also showed that inflammatory factors (IL-1 ß, IL-18, LDH, and ROS) were significantly increased in the SCOS group. CONCLUSIONS: For the first time, we found that cell pyroptosis-related genes and key markers were significantly increased in the testes of patients with SCOS. We also observed many inflammatory and oxidative stress reactions in SCOS. Thus, we propose that testis cell pyroptosis mediated by CASP1 and CASP4 could participate in SCOS occurrence and development.

Identification of PDCL2 as a candidate marker in Sertoli cell-only syndrome by chromatin immunoprecipitation-sequencing and bioinformatics analysis.

Background: Sertoli cell-only syndrome (SCOS) or germ cell aplasia is one of the most serious histopathological subtypes within the scope of non-obstructive azoospermia (NOA). Understanding the molecular mechanism of SCOS and identifying new non-invasive markers for clinical application is crucial to guide proper sperm procurement and avoid unnecessary interventions. This study sought to identify the differentially expressed genes (DEGs) of SCOS by using gene sequencing identity and verify the key marker genes to provide basic data for subsequent research on SCOS. Methods: A total of 50 testicular samples were collected in this study from 25 patients with SCOS and 25 patients with normal spermatogenesis. In total, 5 pairs of testis samples were used for the RNA-sequencing (RNA-seq). We identified the DEGs between the SCOS and normal spermatogenesis patients and conducted a Gene Ontology (GO) analysis and a Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. The expression of the main target gene phosducin-like 2 (PDCL2) was examined by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC). Results: In total, 3,133 upregulated DEGs and 1,406 downregulated DEGs were identified by the RNA-seq. The highly enriched processes involved in spermatogenesis included the mitotic cell cycle, cell cycle, and oocyte maturation. The expression of PDCL2 was verified as a downregulation marker in SCOS by qRT-PCR and IHC. Conclusions: This study identified the DEGs of SCOS, and the bioinformatics analysis results identified the potential target key genes and pathways for SCOS. PDCL2 is a key gene involved in SCOS and may serve as a non-invasive downregulation marker of SCOS.

Discoidin domain receptor 2 expression increases phagocytotic capacity in sertoli cells of sertoli cell-only syndrome testes.

Discoidin domain receptor 2 (DDR2) belongs to the receptor tyrosine kinase (RTK) family, other RTKs have been reported to regulate phagocytic function of Sertoli cells (SCs), yet little is known about the function of DDR2 in Sertoli cells. In the present study, we aim to explore the function and mechanism of ectopic discoidin domain receptor 2 (DDR2) expression in Sertoli cells of Sertoli cell-only syndrome (SCOS) testes. We found that discoidin domain receptor 2 (DDR2) was absent in Sertoli cells of normal testis but was expressed in Sertoli cells of SCOS testes. This Sertoli cell DDR2 expression was induced by impaired androgen receptor (AR) signaling, but was inhibited by increased AR signaling from testosterone administration. The Sertoli cell DDR2 expression led to an increase in phagocytosis through up-regulation of Scavenger receptor class B member 1 (SR-BI) levels. However, loss of DDR2 by knock-out or knock-down weakened the phagocytotic capacity of Sertoli cells. Furthermore, the expression of DDR2 in Sertoli cells activated matrix metallopeptidase 9 (MMP-9) to consume abnormal collagen increase in seminiferous tubules which was responsible for the block of testosterone transportation and AR loss and to compensate for the impaired blood-testis-barrier (BTB). Our data suggest that the AR/DDR2 cascade may serve as a negative feedback mechanism to help compensate for the homeostasis of seminiferous epithelium in SCOS testis.

Sertoli cell only syndrome induced by a varicocele.

A case is reported which describes the severity of testicular histological damage that can be induced by a high-grade varicocele in a male with secondary infertility. A chart review of a patient's case was performed. A 34-year-old male with a three-and-a-half-year-old son who was conceived spontaneously with timed intercourse, with a grade three left varicocele, who's semen parameters progressed to non-obstructive azoospermia (NOA). He did not regain sperm in the ejaculate three or six months post left subinguinal microsurgical varicocele repair. He underwent bilateral microdissection testicular sperm extraction (microTESE) without identification of sperm in the testicular samples. A testicular biopsy from the time of microTESE revealed a Sertoli cell only pattern. A high-grade varicocele has the potential to induce sufficient testicular damage to result in the most severe testicular histological architecture associated with non-obstructive azoospermia (NOA), Sertoli cell only syndrome (SCOS).