Ponce de León may have been born 500 years too soon if some of the recent research in mice is confirmed and holds true for humans as well. Three studies indicate there is a protein in the blood of young mice that when given to old mice leads to significant improvement in cardiac and skeletal muscle functioning as well as significant improvement in brain functioning. Two closely connected groups of researchers have been involved in this work. Most members of both groups were associated with Harvard’s Department of Stem Cell and Regenerative Biology. Scientists from the University of California and the Howard Hughes Medical Institute also participated. In all, there were 26 different scientists involved in the most recent two of these peer-reviewed papers, and four of them participated in both research efforts.
The first group showed that there were factors in the blood of young mice that when allowed to circulate in the blood of old mice for five weeks led to improved blood circulation in the brain and enhanced formation of new brain cells both of which normally decline significantly as a mouse ages. Initially, the Harvard scientists actually connected the blood circulations of an old mouse and a young mouse in a process known as parabiosis, much as happens naturally in many cases of Siamese twins born to humans. With these experiments they found the neural stem cells in a few regions of the brain began to proliferate in the old mouse and blood flow throughout much of the brain was increased. Additionally, the scientists reported evidence that these old mice experienced an improved sense of smell. In parallel studies they showed that blood from an old mouse did not have any observed negative effects on young mice. When they went looking to see if these results were caused by a single blood compound or required a complex mixture of blood chemicals from young mice, they found the result could be induced by a single factor called GDF 11 which stands for “growth differentiation factor 11.” This chemical is naturally present in the blood of young mice but declines with age; it is also a member of a large group of transforming growth factors whose various functions have been a great interest to research biologists.
The second group, which had previously shown that blood from young mice could correct age-induced heart muscle enlargement in old mice, focused on skeletal muscle functioning. As in the brain, there are stem cells in muscles that become active in the repair of muscle damage. These stem cells (called satellite cells) normally age and become genetically damaged with time decreasing their ability to respond to injury. Using mouse GDF 11 made by genetically engineered bacteria they injected it daily for four weeks into the abdomen of old mice, from where it is absorbed into the blood stream. They found this treatment allowed the satellite muscle cells in the old mice to repair their genomes and go on to heal injured muscle, restoring its functioning. Furthermore, following this treatment old mice showed evidence of increased strength and improved endurance when exercising.
Given that it is rare for the physiology of mice to be radically different from that of humans, I’m wondering how many humans might volunteer to become subjects for research of this nature. Any bets?