Cellular expression of protamine 1 and 2 transcripts in testicular spermatids from azoospermic men submitted to TESE–ICSI

Abstract

Testicular sperm extraction (TESE) combined with ICSI is used to treat azoospermia. However, the factors that influence the outcome of ICSI in this situation are ill-defined. We sought to investigate the expression of protamine 1 (PRM1) and protamine 2 (PRM2) transcripts in testicular spermatids from obstructive and non-obstructive azoospermic men with impaired spermatogenesis. The relationship between PRM1 and PRM2 transcript levels and the TESE-ICSI outcome was evaluated. The cellular expression of PRM1 and PRM2 mRNAs in single testicular spermatids from 41 azoospermic patients (in whom testicular spermatozoa were subsequently recovered and submitted for TESE-ICSI) was determined by radioactive in situ hybridization. Group I contained seven men with congenital, obstructive azoospermia and whose testicular biopsies indicated quantitatively normal spermatogenesis. Group II consisted of 18 azoospermic men with moderately impaired spermatogenesis. Sixteen men with non-obstructive azoospermia and severely deranged spermatogenesis (i.e. mixed atrophy with small foci of spermatids and spermatozoa) constituted group III. The spermatids of men with severely deranged spermatogenesis exhibited significant lower PRM1 mRNA expression than in the other patient groups. There were no significant inter-group differences in PRM2 mRNA expression. Spermatid PRM1 expression was lower in non-pregnant couples than in pregnant couples. The low number of spermatids in cases of mixed atrophy with small spermatogenic foci is associated with significantly lower PRM1 expression and a lower pregnancy rate. These results emphasize the role of PRM1 as a potentially critical factor in post-ICSI embryonic development.