Memory Problems Common in Old Age Can Be Reversed

While immortality might forever be out of reach, a long, healthy retirement is the stuff dreams are made of. To that end, a recent study suggests that the kinds of memory problems common in old age can be reversed, and all it takes is some cerebrospinal fluid (CSF) harvested from the young. In mice, at least.

If this is sounding a little familiar, you might be thinking of a similar series of studies done back in the mid-2010s, which found that older mice could be generally ‘rejuvenated‘ with the blood of younger animals – both from humans and from mice. The FDA even had to warn people to stop doing it. This new study instead examined the links between memory and cerebrospinal fluid  (CSF), and the results show considerable promise, even providing a mechanism for how it works, and highlighting a potential growth factor that could mimic the results.

“We know that CSF composition changes with age, and, in fact, these changes are used routinely in the clinic to assess brain health and disease biomarkers,” Stanford University neurologist Tal Iram said. “However, we don’t know well how these changes affect the function of the cells in the aging brain.

To investigate, the researchers, led by Iram, took older mice (between 18–22 months old) and gave them light shocks on the foot, at the same time as a tone and flashing light were activated. The mice were then split into groups, and either given young mouse CSF (from animals 10 weeks old) or artificial CSF. In experiments like this, if the mice ‘freeze’ when they see the tone and light, it means they’re remembering the foot shock, and are preparing for it to happen again. In this study, three weeks after the foot shocks were conducted (which the team called “memory acquisition“), the researchers tested the mice, finding that the animals that had been given the CSF from young mice showed higher-than-average freezing rates, suggesting they had better memory. This was followed up by a battery of other experiments to test the theory, which revealed that certain genes (that are different in young-versus-old CSF) could be used to get the same response. In other words, without needing to extract someone’s brain fluid.

When we took a deeper look into gene changes that occurred in the hippocampus (a region associated with memory and aging-related cognitive decline), we found, to our surprise, a strong signature of genes that belong to oligodendrocytes,” Iram explained. “Oligodendrocytes are unique because their progenitors are still present in vast numbers in the aged brain, but they are very slow in responding to cues that promote their differentiation. We found that when they are re-exposed to young CSF, they proliferate and produce more myelin in the hippocampus.” Oligodendrocytes are particularly helpful because they produce myelin, a material that covers and insulates neuron fibers.

Rejuvenation by Controlled Reprogramming

On 19 January 2022, co-founders Rick Klausner and Hans Bishop publicly launched an aging research initiative called Altos Labs, with $3 billion in initial investment from backers including tech investor Yuri Milner and Amazon founder Jeff Bezos. This is the latest in a recent surge of investment in ventures seeking to build anti-aging interventions on the back of basic research programs looking at epigenetic reprogramming. In December, cryptocurrency company Coinbase’s cofounder Brian Armstrong and venture capitalist Blake Byers founded NewLimit, an aging-focused biotech backed by an initial $105 million investment, with the University of California, San Francisco’s Alex Marson and Stanford’s Mark Davis as advisors.

The discovery of the Yamanaka factors’ — four transcription factors (Oct3/4, Sox2, c-Myc and Klf4) that can reprogram a differentiated somatic cell into a pluripotent embryonic-like state — earned Kyoto University researcher Shinya Yamanaka a share of the Nobel prize in 2012. The finding, described in 2006, transformed stem cell research by providing a new source of embryonic stem cell (ESC)-like cells, induced pluripotent stem cell (iPSCs), that do not require human embryos for their derivation. But in recent years, Yamanaka factors have also become the focus for another burgeoning area: aging research.

So-called partial reprogramming consists in applying Yamanaka factors to cells for long enough to roll back cellular aging and repair tissues but without returning to pluripotency. Several groups, including those headed by Stanford University’s Vittorio Sebastiano, the Salk Institute’s Juan Carlos Izpisúa Belmonte and Harvard Medical School’s David Sinclair, have shown that partial reprogramming can dramatically reverse age-related phenotypes in the eye, muscle and other tissues in cultured mammalian cells and even rodent models by countering epigenetic changes associated with aging. These results have spurred interest in translating insights from animal models into anti-aging interventions. “This is a pursuit that has now become a race,” says Daniel Ives, CEO and founder of Cambridge, UK-based Shift Bioscience.

The Yamanaka factors that can reprogram cells into their embryonic-like state are at the heart of longevity research

We’re investing in this area [because] it is one of the few interventions we know of that can restore youthful function in a diverse set of cell types,” explains Jacob Kimmel, a principal investigator at Alphabet subsidiary Calico Life Sciences in South San Francisco, California. The zeal is shared by Joan Mannick, head of R&D at Life Biosciences, who says partial reprogramming could be potentially “transformative” when it comes to treating or even preventing age-related diseases. Life Biosciences, a startup co-founded by David Sinclair, is exploring the regenerative capacity of three Yamanaka factors (Oct4, Sox2 and Klf4).