Chromosome loss and heart health
While women have two X chromosomes, men have an X and a Y. But many men begin to lose their Y chromosome in a fraction of their cells as they age. This appears to be particularly true for smokers.
The loss occurs predominantly in cells that undergo rapid turnover, such as blood cells. (Loss of the Y chromosome does not occur in male reproductive cells, so it is not inherited by the children of men who exhibit Y chromosome loss.)
Scientists previously observed that men who suffer Y chromosome loss are more likely to die at a younger age and suffer age-associated maladies such as Alzheimer's disease. Walsh's new research, however, is believed to be the first hard evidence that chromosome loss directly causes harmful effects on men's health.
Walsh, of UVA's Division of Cardiovascular Medicine and the Robert M. Berne Cardiovascular Research Center, and his team used cutting-edge CRISPR gene-editing technology to develop a special mouse model to better understand the effects of Y chromosome loss in the blood. They found that the loss accelerated age-related diseases, made the mice more prone to heart scarring and led to earlier death.
This wasn't the result of just inflammation, the scientists determined. Instead, the mice suffered a complex series of responses in the immune system, leading to a process referred to as fibrosis throughout the body. This tug-of-war within the immune system, the researchers believe, may accelerate disease development.
The scientists also looked at the effects of Y chromosome loss in human men. They conducted three analyses of data compiled from the UK Biobank, a massive biomedical database, and found that Y chromosome loss was associated with cardiovascular disease and heart failure. As chromosome loss increased, the scientists found, so did the risk of death.
The findings suggest that targeting the effects of Y chromosome loss could help men live longer, healthier lives. Walsh notes that one potential treatment option might be a drug, pirfenidone, that has already been approved by the federal Food and Drug Administration for the treatment of idiopathic pulmonary fibrosis, a form of lung scarring.
The drug is also being tested for the treatment of heart failure and chronic kidney disease, two conditions for which tissue scarring is a hallmark. Based on his research, Walsh believes that men with Y chromosome loss could respond particularly well to this drug, and other classes of antifibrotic drugs that are being developed, though more research will be needed to determine that.
At the moment, doctors have no easy way to determine which men suffer Y chromosome loss. Walsh's collaborator Lars A. Forsberg, of Uppsala University in Sweden, has developed an inexpensive polymerase chain reaction (PCR) test, like those used for Covid-19 testing, that can detect Y chromosome loss, but the test is largely confined to his and Walsh's labs.
Walsh, however, can foresee that changing: "If interest in this continues and it's shown to have utility in terms of being prognostic for men's disease and can lead to personalized therapy, maybe this becomes a routine diagnostic test," he said.