Therapeutic Dose of Hydroxyurea-Induced Synaptic Abnormalities on the Mouse Spermatocyte.

Xiaobo Fan,Bing Zhang,Cui Zhang,Yanan Wang,Naixin Wang,Yunxia Zhu

doi:10.3389/fphys.2021.666339

Abstract

Hydroxyurea (HU) is a widely used pharmacological therapy for sickle cell disease (SCD). However, replication stress caused by HU has been shown to inhibit premeiotic S-phase DNA, leading to reproductive toxicity in germ cells. In this study, we administered the therapeutic doses of HU (i.e., 25 and 50 mg/kg) to male mice to explore whether replication stress by HU affects pachytene spermatocytes and causes the abnormalities of homologous chromosomes pairing and recombination during prophase I of meiosis. In comparison with the control group, the proportions of spermatocyte gaps were significantly different in the experimental groups injected with 25 mg/kg (p < 0.05) and 50 mg/kg of HU (p < 0.05). Moreover, the proportions of unrepaired double-stranded breaks (DSBs) observed by γH2AX staining also corresponded to a higher HU dose with a greater number of breaks. Additionally, a reduction in the counts of recombination foci on the autosomal SCs was observed in the pachytene spermatocytes. Our results reveal that HU has some effects on synaptonemal complex (SC) formation and DSB repair which suggest possible problems in fertility. Therefore, this study provides new evidence of the mechanisms underlying HU reproductive toxicity.

Highlights

Sickle cell disease (SCD) affects approximately 4.4 million people worldwide and is most prevalent in Asia and Africa
We examined whether the DNA damage caused by unrepaired double-stranded breaks (DSBs) occurred in pachytene spermatocytes after HU treatment. γH2AX was used as a marker of DNA damage located within unsynapsed regions and DSB regions (Figure 3A). γH2AX signals on autosomal synapsis were grouped into two types, namely, small γH2AX foci (S-foci) and larger γH2AX foci (Lfoci) as recently described (Crichton et al, 2018)
The results showed that the low dose (59.2%, n = 70; p < 0.05) and the high dose (75.7%, n = 70; p < 0.05) had greater percentages of pachytene nuclei with γH2AX foci of autosomal synaptonemal complex (SC) compared with controls (Figure 3B)

Summary

Introduction

Sickle cell disease (SCD) affects approximately 4.4 million people worldwide and is most prevalent in Asia and Africa. HbS alters the erythrocyte membrane causing vaso-occlusion and disrupting endothelial cell function. This situation places patients with SCD at increased risk of episodic ischemia, resulting in hypoxia to vital organs such as the brain, skeleton, and liver. Another symptom of SCD is chronic and episodic pain in patients. Since the middle of the 1980s, HU has been used as a clinically effective pharmacological therapy to Abbreviations: HU, hydroxyurea; SCD, sickle cell disease; DSBs, double-stranded breaks; SC, synaptonemal complex; CNV, copy number variants

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Conclusion