Gene Cell Tissue. 2021 October; 8(4):e114727. Published online 2021 August 10. doi: 10.5812/gct.114727. Research Article Sperm DNA Damage and Protamine Transcripts Content in Iranian Men with Unexplained Infertility Mehran Dorostghoal 1, 2, * , Hamid Galehdari 1 , Masoud Hemadi 3 and Saba Abdi 1 1 Department of Biology, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran 2 Biotechnology and Bioscience Research Center, Shahid Chamran University of Ahvaz, Ahvaz, Iran 3 Fertility, Infertility and Perinatology Research Center, Ahvaz Jundishapur University of Medical Science, Ahvaz, Iran * Corresponding author: Department of Biology, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran. Tel: +98-6133331045, Fax: +98-6133331045, Email: dorostghoal@gmail.com Received 2021 March 19; Revised 2021 May 03; Accepted 2021 May 19. Abstract Background: Incomplete chromatin condensation caused by altered amount of sperm protamines results in DNA fragmentation, which in turn leads to a lack of success in the development of the human embryo. Objectives: This study evaluated the sperm DNA damage and protamine transcripts content in Iranian normozoospermic fertile and infertile men. Methods: DNA damage was analyzed using comet assay. Transcript levels of protamine-1 (PRM1) and protamine-2 (PRM2) in ejaculated spermatozoa were assessed by quantitative real-time polymerase chain reaction (PCR). Results: Significantly higher levels of DNA damage were observed in unexplained infertile men (P = 0.001). DNA fragmentation correlated significantly with sperm total motility (r = -0.413, P = 0.032) and normal morphology (r = -0.424, P = 0.028). PRM1 and PRM2 transcripts contents were significantly lower in normozoospermic infertile men than healthy controls. Sperm PRM1 and PRM2 mRNA ratios were significantly higher (P = 0.035) in unexplained infertile patients than fertile men. Higher DNA damage was found to be significantly associated with reduced transcript levels of PRM1 (r = -0.453, P = 0.018) and PRM2 (r = -0.492, P = 0.009). Protamine transcripts ratios were significantly correlated with sperm normal morphology (r = -0.421, P = 0.029). Conclusions: Our findings showed the prognostic value and clinical utility of the sperm DNA damage and protamine transcripts contents for the discrimination between healthy fertile and unexplained infertile men. Keywords: Male Infertility, Spermatozoa, DNA Damage, Protamine 1. Background The sperm chromatin compaction occurs during the fi- nal post-meiotic phases of spermatogenesis, which plays an important role in protecting the male genome and is required for normal male fertility (1). Potential damage to development of normal embryo by sperm DNA fragmen- tation has emerged, which is associated with poor fertil- ization in vivo and in vitro, recurrent pregnancy loss, and anomalies and cancer in the offspring (2, 3). Higher levels of sperm with damaged DNA have been shown in infertile men (4). During the DNA packaging process, majority of hi- stones are replaced firstly by transition proteins and then by protamine. Histone changes during spermatogenesis are related to the sperm protamine contents. Protamine- 1 (PRM1) and protamine-2 (PRM2) are the abundant basic nuclear sperm proteins involved in condensation of the nucleus and in the integrity stability and repair of DNA. There is evidence that an altered amount of protamine may result in an incomplete chromatin condensation, and in turn, an increased susceptibility to sperm DNA damage (5). Relatively equal levels (1: 1 ratio) of PRM1 and PRM2 are expressed in fertile individuals (6). An altered amount of protamine has been shown in infertile and subfertile men that is associated with reduced embryo quality (7). A significant correlation was found between changes in pro- tamine protein ratio and protamine mRNA ratio in sperm cells (6). Alterations in mRNA content of PRM1 and PRM2 are associated with male infertility, and abnormal PRM1: PRM2 mRNA ratios have been reported in subfertile men (8). 2. Objectives The present study aimed to investigate DNA integrity and protamine transcripts contents in ejaculated sperma- tozoa of Iranian men with unexplained infertility. Copyright © 2021, Gene, Cell and Tissue. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.