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 infertility.

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 sum 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.