If you eschew hyperbole and hang in for the long haul, maintaining a discipline of understatement in the midst of a flashy neon world, you may be offered a modicum of credence when you make an extraordinary announcement. No one is entitled to this courtesy twice. If the news that you trumpet to the moon does not pan out, your readers will be justified in discounting everything you say thereafter.
I believe major rejuvenation has been achieved in a mammal, using a relatively benign intervention that shows promise of scaling up to humans. I’m going to stake my reputation on it.
Cartoon by Maddy Ballard
In the race to effect substantial, system-wide rejuvenation, Harold Katcher is a dark horse. He has the right academic credentials and a solid history of research. In fact, in earlier life he was part of a team that discovered the breast cancer gene, brca1. I asked Harold for a biographical sketch, and have printed it in a box at the end of this posting.
But Katcher has no research grants or university lab or venture capital funding, no team of grad students mining databases and screening chemicals in the back room.
One thing Katcher has going for him is the correct theory. Most of the explosion in aging research (and virtually all the venture capital startups) are looking to treat aging at the cellular level. Their paradigm is that aging is an accumulation of molecular damage, and they see their job as engineering of appropriate repair mechanisms.
The truth, as Katcher understands it, is that, to a large extent, aging is coordinated system-wide via signal molecules in the blood. It was our common realization of this vision that brought Katcher and me together more than a decade ago. Katcher briefly describes his 2009 epiphany below. It was the source of his 2013 essay (it took a few years to get it into print) on the significance of parabiosis experiments for the future of aging science.
Of course, Katcher was not the only one to get the message about the power of signal molecules in the blood to reprogram tissues to a younger state throughout the body. The problem is that there are thousands of constituents represented in tiny concentrations in blood plasma, but conveying messages that cells read. Which of these are responsible for aging? A small number of labs, including the Conboys at Berkeley, Amy Wager at Harvard, and Tony Wyss-Coray at Stanford have been searching for the answer over the last decade and more.
Katcher has been able to guess or intuit or experimentally determine the answer to this question. With seed funding from Akshay Sanghavi, he set up a lab in Mumbai two years ago, and tried to rejuvenate old lab rats, using a fraction extracted from the blood of younger rats. The first round of experiments were encouraging, published in this space a year ago. He obtained the next round of funding from a reader of this blog, and had enough rats to titrate dosages experimentally, and to see if treated rats who aged again over time could be re-treated successfully.
There is a hole in this story that awaits the resolution of intellectual property rights. Katcher and Sanghvi have not applied for patents and have not yet found a suitable partner to provide financing for human trials. They have not revealed any details of the treatment, besides the fact that it is in four intravenous doses, and that it is derived from a fraction of blood plasma. Katcher thinks that the molecules involved will not be difficult to manufacture, so that when a product is eventually commercialized, it will not require extraction from the blood of live subjects, rodent or human.
We’re still waiting for longevity curves of these treated rats. In the meantime, the best available surrogate measure of age comes from methylation clocks, as developed by Steve Horvath at UCLA, and other scientists as well. Crucially, Katcher found an ally in Horvath, who didn’t just test his rejuvenated rats, but did the needed statistical analysis to develop a set of six methylation clocks specialized to rats. FIve of the clocks are optimized for different tissues, and one is calibrated across species, so that it can measure age in humans as well as corresponding age in “rat years” (about 1/40 human year). The two-species clock was a significant innovation, a first bridge for translating results from an animal model into their probable equivalent in humans.
In a paper posted to BioRxiv on Friday, Katcher and Horvath report results of the methylation measurements in rejuvenated rats. “Crucially, plasma treatment of the old rats [109 weeks] reduced the epigenetic ages of blood, liver and heart by a very large and significant margin, to levels that are comparable with the young rats [30 weeks]….According to the final version of the epigenetic clocks, the average rejuvenation across four tissues was 54.2%. In other words, the treatment more than halved the epigenetic age.”
Human-rat clock measure of relative age defined as age/maximum species lifespan.
Besides the methylation clock, the paper presents evidence of rejuvenation by many other measures. For example:
- IL-6, a marker of inflammation, was restored to low youthful levels
- Glutathione (GSH), superoxide dismutase (SOD), and other anti-oxidants were restored to higher youthful levels
- In tests of cognitive function (Barnes maze), treated rats scored better than old rats, but not as well as young rats.
- Blood triglycerides were brought down to youthful levels
- HDL cholesterol rose to youthful levels
- Blood glucose fell toward youthful levels
A major question in blood plasma rejuvenation experiments has been how often the cure must be administered. Many of the components of blood plasma are short-lived, secreted into the blood and absorbed continuously throughout the day. The good news from Katcher’s results is that it seems only four injections are needed in order to achieve rejuvenation.
A second question which these experiments resolve is whether rejuvenation requires both adding and removing molecular species from the blood plasma. For example, pro-inflammatory cytokines are found in old blood at much higher levels. Irina and Mike Conboy, people who I regard as most credible in the field, have said that removing bad actors from the blood is probably more important than restoring youthful levels of beneficial signals. They were grad students at Stanford 15 years ago, when the modern wave of parabiosis science was initiated, and have pursued the subject continuously ever since. Katcher’s experiments have achieved their results only by adding blood components, not by removing or even neutralizing others. This suggests that he has found the necessary formula for re-programming epigenetics, so that lower levels of the bad actors occur as a result. But it remains to be seen whether even better results can be obtained if some plasma constituents are removed.
A question that remains unresolved concerns the location and mechanism of the aging clock. I have been undecided over the years between two models:
- There is a central aging clock, perhaps in the hypothalamus, which keeps its own time and transmits signals throughout the body that coordinate methylation state of dispersed tissues
- Information about epigenetic age is dispersed through the body, and the body’s clock is a feedback loop that is continually updating methylation age locally in response to signals received about the methylation age globally.
There is a suggestion in the data that the hypothalamus may be more difficult to rejuvenate than other tissues. Does it play a more important role than other tissues in coordinating the age of the entire body? Horvath (personal communication) counsels caution in drawing this inference until measurements are corroborated and more experiments are done.
The Bottom Line
These results bring together three threads that have been gaining credibility over the last decade. Mutually reinforcing, the three have a strength that none of them could offer separately.
- The root cause of aging is epigenetic progression = changes in gene expression over a lifetime.
- Methylation patterns in nuclear DNA are not merely a marker of aging, but its primary source. Thus aging can be reversed by reprogramming DNA methylation.
- Information about the body’s age state is transmitted system-wide via signal molecules in the blood. Locally, tissues respond to these signals and adopt a young or an old cellular phenotype as they are directed.
Harold Katcher, Biographical Sketch
So, you might consider me a late bloomer. While I have thousands of citations in the literature, with publications ranging from the discovery of the human ‘breast cancer gene’, to protein structure, bacteriology, biotechnology, bioinformatics, and biochemistry, there was no center or direction to my work as I had given up my personal goal of solving/curing aging when I learned that ‘wear and tear’ was the cause of it. Yet something happened in year 1985 when I was in California working with Michael Waterman and Temple Smith (fathers of bioinformatics) that is inexplicable: I found myself in Intensive Care with a tube inserted into my trachea and the knowledge that I might not live. And then I had a dream: I dreamed that somehow in the far future (and on another world), I was being feted for ‘bringing immortality to mankind’. Clearly, I survived that incident (started with an infected tooth). I lived a wonderful life – becoming a computer programmer (which I loved), leaving that for the University of Maryland’s Asian division, becoming a full professor and then the Academic Director for the Sciences, in Tokyo, Japan. By the time I left Japan in 2004, (my daughter Sasha was a fourth-grader, (yonensei), in the Japanese school system), I was teaching for U of M online – somewhat retired, and looking forwards to writing computer programs for fun and profit. Yet I never ever forgot that dream. It was clearly impossible; I had no lab – and really, there was no way to repair all damaged cells – it’d be like sweeping back the ocean. And then, in 2009, I read an old paper from 2005, a paper written by the Conboys, (Michael and Irina), Tom Rando and others, coming from Irv Weisman’s lab, that completely changed my life; that showed me that everything I believed about aging was wrong – that aging occurred at the organismic level, not at the cellular level and could be reversed. Well, the rest of the story is about persistence and the blessed intervention of Akshay Sanghvi who too saw there was another way and provided the structural, monetary, and emotional support (and some good ideas) that had me start a new career at age 72 in Mumbai, India. I feel twenty years younger than I did three years ago, I guess that’s another hint about aging. Now the ‘mystical’ dream? It wouldn’t be the first time in history that that happened – take that as a datum.