As you might know, in recent years researchers have joined the circulatory systems of old and young mice and seen that this causes stem cells in the old mice to return to work in greater numbers, somewhat reversing a number of measures of aging. Stem cell function declines with age in response to damage, and this reduces the risk of cancer due to damaged cells running awry. Thus there is a strong possibility that forcing old tissues to behave as though young by changing the signaling environment - such as by using young blood - will result in a greatly raised risk of cancer. This risk remains to be quantified.
Researchers are beginning to isolate specific signaling changes that lead to stem cell decline in aging, and the protein GDF11 is a promising start - though no doubt far from the only important signal. Boosting levels of GDF11 in old mice has already been shown to improve heart function. Here researchers find other benefits:
Injections of a protein known as GDF11, which is found in humans as well as mice, improved the exercise capability of mice equivalent in age to that of about a 70-year-old human, and also improved the function of the olfactory region of the brains of the older mice - they could detect smell as younger mice do. Studies examined the effect of GDF11 in two ways. First, by using what is called a parabiotic system, in which two mice are surgically joined and the blood of the younger mouse circulates through the older mouse. And second, by injecting the older mice with GDF11, which in an earlier [study] was shown to be sufficient to reverse characteristics of aging in the heart.
GDF11 is naturally found in much higher concentrations in young mice than in older mice, and raising its levels in the older mice has improved the function of every organ system thus far studied. "From the previous work it could have seemed that GDF11 was heart specific, but this shows that it is active in multiple organs and cell types. Prior studies of skeletal muscle and the parabiotic effect really focused on regenerative biology. Muscle was damaged and assayed on how well it could recover."
"The additional piece is that while prior studies of young blood factors have shown that we achieve restoration of muscle stem cell function and they repair the muscle better, in this study, we also saw repair of DNA damage associated with aging, and we got it in association with recovery of function, and we saw improvements in unmanipulated muscle. Based on other studies, we think that the accumulation of DNA damage in muscle stem cells might reflect an inability of the cells to properly differentiate to make mature muscle cells, which is needed for adequate muscle repair."
"We think an effect of GDF11 is the improved vascularity and blood flow, which is associated with increased neurogenesis. However, the increased blood flow should have more widespread effects on brain function. We do think that, at least in principle, there will be a way to reverse some of the cognitive decline that takes place during aging, perhaps even with a single protein. It could be that a molecule like GDF11, or GDF11 itself, could reverse the damage of aging."
It is worth noting that these results are all over the news at the moment, which I imagine has nothing to do with the merits of the science and everything to do with the fact that a company has been formed and is presently raising venture funding to commercialize this treatment. There is a sort of alchemy underway behind the scenes where influence and money is turned into press attention so as to obtain a better valuation.