Researchers have been testing telomerase gene therapies in mice for more than a decade now, demonstrating extension of life, improved stem cell and tissue function, reduced cancer incidence, and so forth. The research results here, treating neurodegeneration in mice, are a representative example of the sort of work that has emerged in recent years. Telomerase primarily acts to lengthen telomeres, the repeated DNA sequences at the ends of chromosomes. Telomeres shorten with each cell division, a part of the mechanism determining the Hayflick limit to cell replication. Thus the general upregulation of telomerase should result in greater cell activity.
Telomerase upregulation was also widely expected to raise the risk of cancer, by putting damaged cells back to work, but so far that hasn’t emerged in animal studies. If anything, the risk is reduced, perhaps due to increased activity in those parts of the immune system responsible for destroying cancerous and precancerous cells. One challenge in translating this work to human medicine is that telomere and telomerase dynamics are very different in mice and humans, and thus the balance of cancer risk versus improved regeneration may be quite different – though clearly clinical