Objective: Since sperm abnormalities are known to be a major reason for recurrent pregnancy loss (RPL), any defects in DNA structure and chromatin condensation can place embryos at risk in the early stage of development and implantation. As antioxidants such as vitamin C may play a protective role against the destruction of protamine genes in sperm chromatin, this study was conducted to evaluate the effects of vitamin C on chromatin and the expression of protamine genes in the male partners of couples with RPL. Methods: Twenty male partners of couples with RPL were selected as the intervention group and received vitamin C supplementation (250 mg daily for 3 months). Healthy fertile men (n = 20) were included as controls. Sperm chromatin, DNA integrity, and the expression levels of protamine genes were evaluated before and after treatment. Results: Significant differences were found in sperm morphology, protamine deficiency, and apoptosis between the two groups and before and after vitamin C administration. A significant change was found in mRNA levels of PRM1, PRM2, and the PRM1/PRM2 ratio after treatment. Conclusion: Daily oral administration of vitamin C may improve human sperm parameters and DNA integrity by increasing protamine gene expression levels in the male partners of couples with RPL. The beneficial effects of vitamin C supplementation as an antioxidant for the male partners of couples with RPL could lead to improved pregnancy outcomes in these cases. This is an Open Access article distributed under the terms of the Creative Commons AttributionNon-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. www.eCERM.org S Hamidian et al. The effect of vitamin C on sperm gene expression

Immune system disorders and increased inflammation in the male reproductive system can lead to fetal risk in the early stages of development and implantation. Antioxidants such as vitamin C can play a protective role against sperm inflammatory reactions. This study aimed to evaluate the effect of vitamin C on the expression of inflammatory and anti-inflammatory cytokine genes in the male partners of couples with recurrent pregnancy loss. In this randomized clinical trial, twenty male partners of couples with RPL were examined for sperm parameters and expression profile of some inflammatory and anti-inflammatory cytokine genes before and after treatment with vitamin C. There was a statistically significant higher rate of normal morphology and sperm concentration in each patient before and after treatment with vitamin C p ≤ 0.05 . The mRNA levels of interleukin 6 and tumor necrosis factor-alpha were significantly decreased in the sperm of patients after treatment with vitamin C compared to before treatment. In contrast, the gene expression levels of interleukin 4 and transforming growth factor-beta showed a significant increase in the sperm of patients after treatment with vitamin C. Oral daily administration of vitamin C may be effective in the fertility potential of male partners of couples with RPL not only through the improvement of the sperm parameters but also by modulating the expression profile of inflammatory and anti-inflammatory genes. Further studies on protein levels are needed to clarify the role of TNF-⍺ and IFN-γ as a prognostic value in evaluating the recurrent abortion risk in infertile male partners. This trial is registered with IRCT20180312039059N1.