Scientists working on an experimental anti-ageing therapy claim to have broken a record by extending the lifespan of a lab rat called Sima. Named after the Hindi word for “limit” or “boundary”, Sima is the last remaining survivor from a group of rodents that received infusions of blood plasma taken from young animals to see if the treatment prolonged their lives. Sima, who was born on 28 February 2019, has lived for 47 months, surpassing the 45.5 months believed to be the oldest age recorded in scientific literature for a female Sprague-Dawley rat, the researchers say. So far, Sima has outlived her closest rival in the study by nearly six months. “We have the oldest living female Sprague Dawley rat,” said Dr Harold Katcher, a former biology professor at the University of Maryland, now chief scientific officer at Yuvan Research, a California-based startup. Researchers have rushed to produce and trial therapies based on young blood plasma after numerous experiments found that infusions could reinvigorate ageing organs and tissues. But while studies have found benefits for rodents, there is no evidence to date that the somewhat vampiric approach to youthfulness will help humans dodge the passage of time, despite the best wishes of Silicon Valley. The results from Katcher’s latest study will be written up when Sima dies, but data gathered so far suggests that eight rats that received placebo infusions of saline lived for 34 to 38 months, while eight that received a purified and concentrated form of blood plasma, called E5, lived for 38 to 47 months. They also had improved grip strength. Rats normally live for two to three years, though a contender for the oldest ever is a brown rat that survived on a restricted calorie diet for 4.6 years. “The real point of our experiments is not so much to extend lifespan, but to extend youthspan, to rejuvenate people, to make their golden years really potentially golden years, instead of years of pain and decrepitude,” Katcher said. “But the fact is, if you manage to do that, you also manage to lengthen life and that’s not a bad side-effect.” Results from such small studies are tentative at best, but some scientists believe the work, and similar efforts by others, has potential. A preliminary study from a collaboration between Katcher and experts at the University of California in Los Angeles found that infusions of young blood plasma wound back the biological clock on rat liver, blood, heart and a brain region called the hypothalamus. Commenting on the work in 2020, Prof David Sinclair, a leading expert on ageing at Harvard medical school, said if the finding held up, “rejuvenation of the body may become commonplace within our lifetimes”. Prof Steve Horvath, a senior author on the UCLA study, is now a principal investigator at Altos Labs in San Diego, which is not working with Yuvan. “I think the results are stunning,” he said. “Some people will criticise the results due to the low sample size. One swallow does not make a summer. But I believe the results because several complementary studies support them.” He anticipates safe and effective treatments will emerge from plasma research in the next 20 years. A patent filing on the potential therapy describes how plasma from young mammals is purified and concentrated before use. Some components, such as platelets, are removed, as they can trigger immune reactions. The patent names pigs, cows, goats, sheep and humans as possible donors. The amount of plasma needed to produce a single concentrated dose is at least as much as the recipient has in their entire body, it states. If the therapy ever shows promise in humans – large trials are needed in more animals first – Katcher believes the plasma could be collected from pigs at abbatoirs. “I don’t like the idea, but it’s no more unethical than eating a meat sandwich,” he said. “When those pigs are killed they still have a lot of life in them. We just use that extra life instead of throwing it away.” Prof Joao Pedro de Magalhaes, a molecular biogerontologist at the University of Birmingham, said young blood plasma was a “promising intervention”, but that he was yet to be persuaded that it can rejuvenate older animals or even delay ageing. “It’s very important we don’t confuse short-term benefits with rejuvenation,” he said.