Venki Ramakrishnan

And then they have to be replaced by stem cells. And also those tissues can't be any other kind of cell, okay? So cellular reprogramming would be taking one of these final tissue cells, like a skin cell or an epithelial cell from your gut, and programming it to go backwards in that development process. And that means changing which genes it's expressing.

And then they have to be replaced by stem cells. And also those tissues can't be any other kind of cell, okay? So cellular reprogramming would be taking one of these final tissue cells, like a skin cell or an epithelial cell from your gut, and programming it to go backwards in that development process. And that means changing which genes it's expressing.

And what's amazing is that it, and this is why Yamanaka won the Nobel Prize, is that it only takes four factors to to take a final cell all the way back to that early pluripotent cell, which could create any type of cell, okay? The downside is that if you do that, you often end up getting cancers.

And what's amazing is that it, and this is why Yamanaka won the Nobel Prize, is that it only takes four factors to to take a final cell all the way back to that early pluripotent cell, which could create any type of cell, okay? The downside is that if you do that, you often end up getting cancers.

If you start developing those cells in a tissue culture, they often will develop tumor-like growths and so on. So I think, you know, That's both a promising and a challenging approach. And it's the one thing that actually reverses the process. And one reason that I am perhaps somewhat optimistic is, remember Dolly the Sheep? I do. Dolly the Sheep was cloned from something like a skin cell, okay?

If you start developing those cells in a tissue culture, they often will develop tumor-like growths and so on. So I think, you know, That's both a promising and a challenging approach. And it's the one thing that actually reverses the process. And one reason that I am perhaps somewhat optimistic is, remember Dolly the Sheep? I do. Dolly the Sheep was cloned from something like a skin cell, okay?

And It was a sick sheep and it had all sorts of problems. It had shorter telomeres than normal, and it died at about half the age of a normal sheep. And everybody went, aha, that's because you started with an adult cell, which is already old and damaged. And then you tried to grow a new animal out of it. And so of course you haven't reset the clock.

And It was a sick sheep and it had all sorts of problems. It had shorter telomeres than normal, and it died at about half the age of a normal sheep. And everybody went, aha, that's because you started with an adult cell, which is already old and damaged. And then you tried to grow a new animal out of it. And so of course you haven't reset the clock.

Well, it turns out Dolly was only one of a cohort. There were other sheep like Dorothy and Daisy and Debbie. They gave them all D names for some reason. Anyway, it turns out most of these sheep were normal. Of course, you have to realize that the frequency of success in a cloning experiment is very small. most of those experiments fail and don't grow into adult animals.

Well, it turns out Dolly was only one of a cohort. There were other sheep like Dorothy and Daisy and Debbie. They gave them all D names for some reason. Anyway, it turns out most of these sheep were normal. Of course, you have to realize that the frequency of success in a cloning experiment is very small. most of those experiments fail and don't grow into adult animals.

But of the ones that actually made it into adult animals, a number of them had normal lifespan and apparently normal health. So at least in those cases, and of course there was ruthless selection involved because as I said, most of these embryos failed to take. But nevertheless, it is possible, at least in theory, to reset the aging clock, just as we naturally do every generation.

But of the ones that actually made it into adult animals, a number of them had normal lifespan and apparently normal health. So at least in those cases, and of course there was ruthless selection involved because as I said, most of these embryos failed to take. But nevertheless, it is possible, at least in theory, to reset the aging clock, just as we naturally do every generation.

And that involved wiping out the signals, the programs of which genes are expressed, back to an early embryonic state. And that program is different from, the skin cell makes only a subset of genes, that we have. And it's a different subset from a brain cell or a heart cell or a blood cell. But you could take it all the way back.

And that involved wiping out the signals, the programs of which genes are expressed, back to an early embryonic state. And that program is different from, the skin cell makes only a subset of genes, that we have. And it's a different subset from a brain cell or a heart cell or a blood cell. But you could take it all the way back.

that you need tissue regeneration. And it turns out that, and you need to recycle bad products. You need a number of things that have to happen that become dysfunctional as we get older. And it turns out one of the things that allow us to be healthier in old age is caloric restriction. Again, there's a big debate about that because they're always comparing

that you need tissue regeneration. And it turns out that, and you need to recycle bad products. You need a number of things that have to happen that become dysfunctional as we get older. And it turns out one of the things that allow us to be healthier in old age is caloric restriction. Again, there's a big debate about that because they're always comparing

animal that gets just the bare number of calories it needs to live without starving. The animal is not losing weight and becoming lethargic. It's getting the bare minimum, though, to live. And they're comparing that with Animals that can eat all they want, an ad libitum diet. And there's always a difference.

animal that gets just the bare number of calories it needs to live without starving. The animal is not losing weight and becoming lethargic. It's getting the bare minimum, though, to live. And they're comparing that with Animals that can eat all they want, an ad libitum diet. And there's always a difference.

Now, some people have argued, including Leonard Hayflick, who was the first person to discover that cells can only divide a certain number of times, which eventually was explained by telomere loss and so on. But that guy died, by the way, Leonard Hayflick died in his 90s, only about a month or two ago. Anyway, he was a skeptic.

Now, some people have argued, including Leonard Hayflick, who was the first person to discover that cells can only divide a certain number of times, which eventually was explained by telomere loss and so on. But that guy died, by the way, Leonard Hayflick died in his 90s, only about a month or two ago. Anyway, he was a skeptic.