Round spermatids from infertile men exhibit decreased protamine-1 and-2 mRNA

During spermiogenesis, histone-to-protamine exchange causes chromatin conde nsation. Spermatozoa from infertile men are known to exhibit an increased p rotamine-1 (PRM1) to protamine-2 (PRM2) protein ratio. Since patients under going testicular sperm extraction (TESE) followed by intracytoplasmic sperm injection (ICSI) reveal low fertilization rates, whether the outcome of IC SI could be related to the percentage of round spermatids expressing PRM1-m RNA and PRM2-mRNA was investigated. Applying in-situ hybridization, 55 test icular biopsies from men undergoing TESE/ICSI were investigated. The percen tage of PRM1-mRNA and PRM2-mRNA positive spermatids was significantly (P < 0.0001) decreased in men with at least qualitatively normal spermatogenesis (PRM1-mRNA: 58.4 +/- 13.8%; PRM2-mRNA: 56.4 +/- 11.3%) and impaired sperma togenesis (PRM1-mRNA: 32.6 +/- 10.8%; PRM2-mRNA: 31.7 +/- 11.1%) compared w ith men with obstructive azoospermia and quantitatively normal spermatogene sis (PRM1-mRNA: 79.9 +/- 4.6%; PRM2-mRNA: 78.1 +/- 5.7%). A positive correl ation (r(PRM1) = 0.733; r(PRM2) = 0.784; P < 0.001) was demonstrated betwee n the score and the percentage of PRM1-mRNA and PRM2-mRNA positive spermati ds, While successful fertilization was neither related to the score, nor to the percentage of PRM1-mRNA and PRM2-mRNA positive spermatids, a significa nt (P < 0.05) relationship was demonstrated between successful fertilizatio n and the PRM1-mRNA to PRM2-mRNA ratio. Therefore, the PRM1-mRNA to PRM2-mR NA ratio in round spermatids may serve as a possible predictive factor for the outcome of ICSI.