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

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

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

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.

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.

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