Association of sperm protamine1 and protamine2 transcript content with paternal age: A cross-sectional study.

Background: Over the last decade, there has been a significant increase in average paternal age.

Objective: The present study investigated the effects of male age on sperm parameters, DNA fragmentation, andprotamine1 (PRM1) and protamine2(PRM2) transcript content in normozoospermic men.

Materials and methods: In this cross-sectional study, 106 semen samples from normozoospermic men were obtained. The objects were divided into 3 age groups: 20-25, 30-35, and 40-45 yr. Sperm parameters and DNA fragmentation were assessed, and transcript levels of PRM1 and PRM2 were analyzed in ejaculated spermatozoa.

Results: The highest levels of sperm concentration, motility, and normal morphology were observed in men aged between 20 and 25 yr. Significant declines were seen in sperm total motility (p = 0.006) and normal morphology (p = 0.015) after 40 yr compared to younger men. Significantly (p $<$ 0.001) higher levels of DNA damage were seen in 40-45-yr-old men. DNA fragmentation correlated significantly with sperm total motility (r = -0.242, p = 0.012) and normal morphology (r = -0.257, p = 0.008). The lowest levels of PRM1 and PRM2 transcripts were seen in 40-45-yr-old men. DNA damage was significantly associated with reduced transcript levelsof PRM1 (r = -0.453, p = 0.018) and PRM2 (r = -0.492, p = 0.009). Transcript levels of PRM1 and PRM2 in ejaculated spermatozoa were correlated significantly with the age of men.

Conclusion: Our findings demonstrate age-related changes in sperm PRM1 and PRM2 transcript content and their correlations with sperm parameters and DNA fragmentation.