Exposure to cigarette smoke could affect reproductive health in both men and women, identifying changes in biological processes involved in ovarian function and sperm production.
This is according to a study that was led by researchers from the Universities of Nottingham and Sheffield, and published in Frontiers, which provides new insight into potential mechanisms linking smoking with reproductive health.
Infertility affects a significant proportion of people of reproductive age worldwide. According to the World Health Organization, approximately one in six people globally experience infertility at some point during their reproductive years.
In this study, researchers used a mouse model to examine the effects of different levels of cigarette-smoke exposure on the ovaries and testes, focusing on changes to reproductive tissues and the activity of genes involved in their normal function. The findings provide insight into biological processes that could help explain how smoking may affect reproductive health in humans.
In females, the number and structure of ovarian follicles — the structures in which eggs develop — showed relatively little change following exposure, even at higher levels. However, researchers identified clear changes in the activity of numerous genes.
Genes involved in cell division and metabolism became less active, while genes associated with protein production became more active. The pattern of gene activity showed similarities with biological processes previously associated with ovarian ageing and reduced ovarian function.
In males, higher levels of smoke exposure were associated with changes to structures within the testes, including enlargement of the seminiferous tubules, where sperm develop. Researchers also identified changes in the activity of genes involved in sperm production, immune responses and cell signalling.
Some genes associated with sperm production became more active, while others involved in immune function became less active. The findings suggest that cigarette-smoke exposure may alter biological processes important for normal testicular function and sperm development.
Professor Lucy Fairclough, from the School of Life Sciences at the University of Nottingham and co-author of the study, said: “Our study has identified potential biological mechanisms that could help explain the link between smoking and reproductive health in both men and women.
“In females, we identified changes in gene activity associated with biological processes that have previously been linked to ovarian ageing and reduced ovarian function. In males, we found changes in genes involved in sperm production and testicular function.
“These findings are important because they help us understand how exposure to cigarette smoke could affect reproductive health. Further research will be needed to establish how these biological changes relate to fertility in humans.”
The researchers say the findings add to existing evidence about the potential impact of smoking on reproductive health and highlight the need to better understand the biological mechanisms involved.
Dr Adam Watkins, from the University of Sheffield, said: ‘While it is well-established that smoking is harmful for your reproductive health, the exact mechanisms are not fully understood. Our mouse study has enabled us to explore how the ovaries and testes respond following exposure to cigarette smoke. Interestingly, our study shows that the ovary and testis respond differently to the cigarette smoke. We observed that while the structure of the ovary was unaltered, the testis showed measurable changes in its morphology. Within the ovary, we identified changes in genes that regulate cell proliferation and the synthesis of proteins, while in the testis, genes regulating sperm production were altered.
“While our study only assessed the effects of cigarette smoke on the ovaries and testes, it does provide new mechanistic insight into how parental smoking shapes their reproductive health.”
