A New Record for the Longest Lived Laboratory Rat, Resulting from Plasma Dilution

Many more life span studies are carried out in mice rather than rats, so it is not too surprising to see people pushing the record for longest lived rat. The longest lived mice are those in which growth hormone receptor signaling is inhibited, while the longest lived rats are the result of life-long calorie restriction. The group noted here is pursuing a strategy of processing the blood plasma from young animals and then introducing the processed plasma into old animals. A treatment starting in mid-life produced a modest gain in median life span in rats, while the one still surviving rat from the small study group has surpassed the existing record for calorie restricted mice. It is an interesting data point for the field of dilution of blood plasma to reduce harmful factors present in the bloodstream of old individuals, though as I understand it, this group favors explanations involving factors from the processed young plasma that are beneficial.

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.

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. The results from the 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.

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 found that infusions of young blood plasma wound back the biological clock on rat liver, blood, heart and a brain region called the hypothalamus. 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.

Link: https://www.theguardian.com/science/2023/feb/08/anti-ageing-scientists-extend-lifespan-of-oldest-living-lab-rat