Editorial: Disruptors on Male Reproduction - Emerging Risk Factors

1 State Key Laboratory of Reproductive Medicine, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China, 2 Institute of Reproductive Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China, 3 Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy, 4 Centre for Reproductive Medicine, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels, Belgium, 5 Department of Obstetrics and Gynaecology, University of Alexandria, Alexandria, Egypt, 6 In Vitro Fertilisation (IVF) Athens, Athens, Greece, 7 Key Lab of Medical Protection for Electromagnetic Radiation, Ministry of Education of China, Institute of Toxicology, College of Preventive Medicine, Army Medical University (Third Military Medical University), Chongqing, China

we have accepted 18 articles and reviews, which provide interesting and exciting insights to this growing field with coverage of various potential risk factors.
Radiation is a ubiquitous environmental exposure in modern society. In the current Research Topic, Guo et al. investigated that the abscopal effects of C-irradiation on testis with regard to both structure and function and ultimately decreased sperm quality in mice. Chen et al. studied the motility, acrosomal integrity, and mitochondrial membrane potential (MMP), as well as proteomic change, of cynomolgus macaque sperm after cryopreservation. They hypothesized that AFP III may reduce the release of cytochrome C and thereby reduce sperm apoptosis by modulating the production of ROS in mitochondria. This may represent a novel molecular mechanism for cryoprotection. In addition, Jaffar et al. concluded that the long-term Wi-Fi exposure from pre-pubertal to adult age could reduce spermatogonia proliferation in the testis.
Another well celebrated example of risk factors was exposure to environmental chemicals. Although in vitro, Mancuso et al. Environmental factors mediate changes in expression patterns can be explained by a complex network of modifications to the DNA, histone proteins and degree of DNA packaging as well as changes in DNA structure such as mitochondrial DNA copy number and chromatin integrity. Throughout our lives, epigenetic processes shape our development and enable us to adapt to a constantly changing environment. Ma et al. integrated glufosinateammonium (GLA) induced alterations in sperm epigenome and embryo transcriptome, and further explored their concordance, thus providing a new strategy for gamete-to-embryo toxicity assessment. Intriguingly, this study also noted that paternal GLA exposure induced aberrant transcription in both paternal and maternal alleles of preimplantation embryos, which deserves further investigation. Wang et al. concluded that bivalent chromatin structure resulted in large differences in the methylation of autism genes between manually selected spermatozoa (MSS) and Zona pellucida (ZP)-bound spermatozoa (ZPBS). Intracytoplasmic sperm injection (ICSI) using MSS, which increased the risk of methylation changes compared with ZPBS, may lead to a higher risk of autism in offspring. Liu et al. contributed to the understanding of epigenetic regulation of tet methylcytosine dioxygenase 1-Sp1 transcription factor (TET1-SP1) during spermatogonia self-renewal and proliferation. Shi et al. focused on the associations between sperm mitochondrial DNA copy number (mtDNA-CN), DNA fragmentation index (DFI), and reactive oxygen species (ROS) and embryo development as well as pregnancy outcomes in assisted reproductive technology (ART).
COVID-19 is a serious challenge to the global health systems. It has been found that the hazardous effects of COVID-19 go far beyond respiratory system, and a body of studies explored the impact of COVID-19 on male reproduction from different aspects. Updated information about increasingly emerging environmental perpetrators, including physical, chemical, biological and behavioral/lifestyle risk factors can improve our understanding of male reproductive health. With the rapid evolvement of omics technologies in genomics, epigenomics, transcriptomics, proteomics and metabolomics, it is reasonable to expect that in the near future there will be plenty of studies to renew our knowledge on emerging risk factors and the attendant adverse effects on male reproductive health, as well as the underlying mechanisms. Hence, to keep the constant concern and to inspire new studies to this filed, the Volume II focusing on the same topic has started and we anticipate to receive high-quality submissions all over the world (https://www.frontiersin. org/research-topics/35111/).

AUTHOR CONTRIBUTIONS
All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication.