Human blood enables vampires to remain physically attractive and mentally sharp according to ancient lore. But the anti-aging properties of blood may be more than a legend. Researchers at the biomedical startup Alkahest in California are actually running a small clinical trial that involves injecting human blood plasma from young people into dementia patients. The hope is that factors in the blood of young people will repair and rejuvenate ailing brains. It worked in mice, so maybe it will work in people.
Researchers associated with University of California, Berkeley, biologist Irina Conboy jumpstarted the hunt for youthful factors in blood with their work with mice involving heterochronic parabiosis. Heterochronic means differently aged and parabiosis means next to life. In their experiments the researchers basically sewed together young mice and old mice to see what would happen as their circulatory systems melded. They discovered that tissues in geezer mice were rejuvenated. Apparently, something in the blood of young mice stimulates the worn-out stem cells in old mice to start proliferating again to repair damaged tissues.
Stem cells are surrounded and supported by cells that regulate their activities and also respond to biochemical signals transported through the circulatory system. The support cells accumulate damage over time and lose their ability to nourish and protect the stem cells, which, in turn, lose their capacity for repair and replenishment of damaged tissues. In addition, factors found in the bloodstream also diminish the regenerative capacity of the stem cells.
Experiments on mice by researchers at Harvard, Stanford, and the Universities of California at Berkeley and San Francisco all find that young blood rejuvenates tissues and organs including muscles, liver, heart, and brain. Neurologist Tony Wyss-Coray heads up the Stanford Brain Rejuvenation Project and is the founder of Alkahest. In May, 2014, Wyss-Coray and his team reported in Nature Medicine that "exposure of an aged animal to young blood can counteract and reverse pre-existing effects of brain aging at the molecular, structural, functional and cognitive level." Specifically, they found that factors in young blood restored function in the hippocampus, the area of the brain where memories are consolidated. On the other hand, exposing young mice to old blood speeds up their decline. The researchers also found that it was not necessary to stitch old and young mice together. Injecting them with blood plasma was sufficient to elicit the effects.
The finding that exposure to young blood improves brain function is what is behind Alkahest's clinical trial to see if infusing blood plasma from young people into patients suffering from mild to moderate Alzheimer's disease will improve their cognition. The company expects to enroll 18 patients in the coming trial, half of whom will receive infusions of human blood plasma donated by men under age 30 once weekly for four weeks. The other half will receive saline. The trial will chiefly focus on the safety of the treatment and compliance by participants. Additionally, researchers will compare both groups to see if those treated with blood plasma perform better on a number of tests for Alzheimer's disease and if changes suggestive of cognitive improvement can be identified in their brains. The trial ends in October 2015.
What factors in young blood are responsible for its rejuvenating effects? As it happens, Harvard University researchers Amy Wagers and Lee Rubin in May 2014 reported in two studies in Science that the protein growth differentiation factor 11 (GDF 11) alone rejuvenated the vascular systems, muscles, and brains of old mice. They injected GDF 11 into the brains of geezer mice and found the protein improved blood flow and jumpstarted the growth of neurons. It is an open question if GDF 11 fixes damaged stem cells or enables them to overcome biochemical stop signals after which they then proceed to repair aging damage.
In September 2014, Science noted that University of California, San Francisco's Peter Ganz and his colleagues have followed nearly 2,000 elderly heart patients for nine years. Their so far unpublished data indicates that lower levels of GDF11 in the blood predicted higher rates of heart attack, stroke, congestive heart failure, and overall mortality. The Harvard researchers expect to have GDF 11 in initial human clinical trials in three to five years.
The good news is that if GDF 11 and other anti-aging factors can be isolated from young blood and synthesized, we baby boomers can then avoid having to siphon blood plasma from Millennials in order to maintain our position as the most (self-)important generation in history.