Discrimination and characterization of Sertoli cell-only syndrome in non-obstructive azoospermia using cell-free seminal DDX4

Cell-free seminal mRNA (cfs-mRNA) contains testis-specific transcripts from bilateral testes. This study determined the presence of DEAD box polypeptide 4 (DDX4) in cfs-mRNA to identify and characterize the incidence of Sertoli cell-only (SCO) syndrome in men with non-obstructive azoospermia (NOA). DDX4 cfs-mRNA was determined in 315 men with NOA, and compared with testicular samples obtained by microdissection from 19 NOA patients. Karyotype and azoospermia factor microdeletion analysis were performed, and clinical features were evaluated. Negative DDX4 cfs-mRNA suggestive of SCO was found in 13.7% of NOA patients, with a similar incidence in NOA men with known genetic causes and those without known genetic causes. DDX4 cfs-mRNA was absent in 44% of SCO cases diagnosed by testicular histopathology, but present in all patients presenting with maturation arrest or hypospermatogenesis. Furthermore, 84.2% of NOA men with DDX4 cfs-positive mRNA had a DDX4-positive testicular sample. In NOA men without genetic causes, SCO patients discriminated by negative DDX4 cfs-mRNA showed different clinical features when compared with non-SCO cases. These results suggest that the evaluation of DDX4 cfs-mRNA is more accurate than testicular histopathology in discriminating SCO, and also permits the identification of a specific group of NOA men with distinct clinical features.