What I want to talk about is hair. It’s something that’s on our mind a lot. It’s dispensable, but important. What I hope you’ll understand that it is an organ. And each hair is an organ which is like all other organs in the body. And it is a window into how we can regenerate other organs like the lung and the liver. It’s really a model for stem cell biology because the things you talk about for hair growth are the same things we talk about for trying to regenerate lung and liver, bone, cartilage, and that sort of thing.
Hair Biology :
A little bit about hair biology. What is normal hair aging? Soil and seed factors, hair color and then preventing the immune system from ruining your hair and give you a bad hair day. at first to start, is about hair growth. And hair growth really is a matter of seeds and soil. I think that’s really what we want you to think about. Every hair on your head, all thousands of them, come out of a group of stem cells that make a hair. So there’s basically groups of 10,000 of hairs, of little stem cell pockets on your scalp, that grow a hair out. And that’s the hair stem cell.
But around the stem cell are a whole micro environment called the soil. Its micro-environment, or stem cell niche, however you what to call it, but really it informs the stem cell when and where to grow. And there’s blood vessels and nerves and big fat adipocytes, fat cells, that secrete factors that cause the hair to grow in response to metabolic conditions in your body. And so really these little buggers, the groups of stem cells that make the hair grow, are bio-sensors for the body that sense what’s going on minute to minute and then read that out in terms of how the hair grows.
Because the hairs are just a bunch of protein that’s being excreted. And it’s a big energy drain on the body to put out 10,000 of these guys at a time. And so if the machine is not working, it doesn’t want to put it out. And so that’s really the issue. These little bio-sensors, these stem cells, read out the body and then make the hair grow. So it really is like little seeds and soil.
Stress And Emotional State :
we’ll talk about stress, our emotional state. There’s little peptides that are coming from the nerves that actually will affect the stem cells. These are big adipocytes. If you have a crash diet the factors here that make the hair grow will go away and then the hair won’t grow. And so these are bio sensors that make it grow.
Hair growth is a matter of seed and soil. The seeds are the things that make different types of hair. They code the instructions. On the left there you can see different kinds of hair color. The seeds are very similar to, for example, a peacock, feathers. Each one of the feather stem cells rather than making a hair makes feather. Those are also genetically encoded and actually we can spend a whole evening talking about feather biology. Which is very similar to hair biology and how birds fly. And they have to fly in a very perfect way. And different animals have different length hair.
So, for example, a mouse grows very similar to a human hair but only grows about an inch and a half because the growth cycle, the season I’ll talk about, is very short. And the bunny does the same thing. But there are mutants, there are rabbit mutants, called Angora where they’re just a big ball of fur because the hair doesn’t stop growing. So that’s really what we’re seeing today is we’re going to talk about the seeds and the soil.
Hair Conditions :
So the basic bottom line is this. There are different kinds of soil. And in different parts of the body there are different kinds of soil. And the seeds are different as well. So these are little green bean seeds and these are yellow ones. So they’re very similar. They make different kinds of hair. These would make different qualities of hair. And so if you put these seeds, and this is basically how hair development works, this is developmental biology right here, OK? Basically what they do is, during development, the stem cells are set apart. And the skin is actually pulled apart and the stem cells are put into the cell underneath the skin and they start to grow. But they’re encoded and make a different kind. So one kind makes this kind of hair and they’re encoded, the other kind are encoded, to make this kind of hair.
And so if you look on your scalp there’s terminal hairs, big thick Redwood trees. On your arm they’re different, they’re vellus hairs. They’re very tiny ones. So different parts, different soils. Different parts of the body have different kinds of hair. It’s genetically encoded. But how they grow and the quality where they grow and when they grow is determined by the soil that they’re growing in.
a human hair grows about that much a month, as you know, but the season is about four years. And that’s why it keeps growing and growing and growing. And then you go down to your waist. And then at that point, there’s a cycle, where the hair pops out this hair growth here and then it basically stops. And the real question that biologists are trying to figure out is why does it stop? But it actually knows how to tell time.
It stops and then basically rest and sits there. And the hair stops growing, it’s this long. And then basically it ejects the hair and then another one starts growing for four years. That’s the hair cycle. That happens and there’s a counter. The seeds have about 40 growth seasons in their DNA. And so if it’s two to four years and there’s like 40 cycles it’s around 80. And that’s your lifetime. So that’s hair biology. It’s 40 cycles of about two years, on average. And that’s why your hair is this long.
And then the new hair production facility has grown out. And the hair has grown out here and it’s going to basically kick that old one out. And this new one is going to come out this way and then make a new hair out of the same hole. 40 times in your lifetime out of the same hole. Now what you have to understand in terms of understanding hair biology and hair disease is this, that each hair on your head is in a different stage of that two year cycle.