The role of heat shock protein 70 (Hsp 70) in male infertility:: is it a line of defense against sperm DNA fragmentation?

Objective: To clarify the role of heat shock protein 70 (Hsp 70) and its relation with DNA damage in male infer tility. Design: Prospective study. Setting: Andrology laboratory of Istanbul Medical Faculty. Patient(s): Semen samples from 37 infertile men and 13 fertile men (as controls). Intervention(S): The percentage of DNA fragmentation was assayed with the use of terminal deoxynucleotidyl transferase- mediated dUTP nick end-labeling (TUNEL). Sperm Hsp 70 expression was determined by using Western blot analysis. Main Outcome Measure(s): Both the percentages of sperm DNA fragmentation and Hsp 70 expression were correlated with semen analysis parameters. Results: TUNEL-positive spermatozoa in the infertile group (18.7% for asthenospermics and 13.0% for oligoasthenospermics) were higher than the fertile group (4.9%). Significant inverse correlations were detected between percentage of TUNEL-positive cells and both concentration (r = -0.487) and motility (r = -0.377) of spermatozoa. No expression of Hsp 70 was observed in azospermic group, whereas Hsp 70 levels were found increased significantly in infertile group (U = 62 for asthenospermics and U = 38 for oligoasthenospermics) compared to fertile group as analyzed by using Mann-Whitney U Wilcoxon rank surn test. Furthermore, significant positive correlation was found between percentage of TUNEL-positive cells and Hsp 70 expression (r = 0.357). Conclusion(s): Hsp 70 expression may have been increased as a protective mechanism against apoptosis in spermatozoa of infertile men.