Skip to main content

'Tis only a flesh wound!



We have all witnessed first-hand the magical power of healing that our skin possesses. Even a deep cut can fix itself up with almost no help from special medical procedures. My favorite personal example involves my fourth toe being half torn from my foot after a freak accident at a friend’s sleepover. Cringe-worthy stories aside, I learned a lot more about the mysterious workings of our largest organ at a talk by Elaine Fuchs during UCLA’s Mautner Lecture Series earlier this year.

Part of what makes skin special is the pool of stem cells that hang out down inside our hair follicles. “Ooooh, stem cells!” you say. I couldn’t agree more! And for good reason: stem cells are powerful. They are different from the other cells in your body in a couple of ways. Most tissues in your body are made up of cells that can essentially clone themselves. These cells undergo mitosis – an exact copy of the genetic material of the cell is made, then it splits itself in half, forming two completely identical cells. This means that a muscle cell can only divide into more muscle cells and a fat cell can only make more fat cells. Stem cells on the other hand, have the power of multipotency. That is, when a stem cell divides it has the capacity to specialize, becoming a cell of any number of tissue types. If stem cells divide to become other types of cells, wouldn’t we run out of stem cells pretty fast? Yes however, the solution to this problem lies in the stem cells’ second power – self-renewal. Some of a stem cell’s progeny are more stem cells. So when a stem cell divides, it can divide into 2 new stem cells or one stem cell and one “fated” cell. The “fated” cell then goes on to become a new fat cell, or a muscle cell. There are lots of factors that govern when a stem cell divides and where the “fated” cells end up – this is where the hair follicle comes in.

Stem cells exist in what are termed “niches”. The niche basically refers to the area where the stem cells hang out and the immediate environment. In this case, the hair follicle acts as a niche for a specific type of stem cell that is found there. The most important thing for us to know is that the “decision” a stem cell makes about dividing is a direct result of changes in the niche environment. Now, when I say changes in the niche environment, I don’t mean global-niche-warming or emissions of greenhouse niche gases. The types of signals that stem cells care about are for example, the presence or lack of a certain protein in the area or the switching-on of a chemical pathway within the cell itself.

Dr. Fuchs describes one of these types of signals in her hair follicle research. The pathway is known as the Wnt-signalling pathway and it is known to play a role in stem cell differentiation in mammals (along with some other important cell responses). When a Wnt-protein bumps into a cell with a special receptor molecule that recognizes Wnt-proteins, a chemical chain reaction starts inside that cell. In the case of stem cells, the message that the chain reaction sends to the cell is “differentiate!” The cool thing about this type of cell-cell communication is that it is directional. In the hair follicle niche, if a Wnt-signal comes from below a stem cell, it will trigger the growth of a new hair. However, if a Wnt-signal comes from above a stem cell, it will know that it needs to focus on repairing a wound to the skin. That just blows my mind.

This is only the tip of the hair follicle iceberg, and if you’re keen to see what else Dr. Fuchs and colleagues have discovered about our largest organ, you should check out a few of the papers listed below. I would also like to acknowledge my grandmother, Dr. Emily F Maverick who made it possible for me to attend Dr. Fuchs’ lecture at UCLA. Thanks!



Sources and further reading:


Fuchs E, Chen T (2013) A matter of life and death: self-renewal in stem cells. EMBO Reports 14: 39-48.

Hsu Y, Pasolli HA, Fuchs E (2011) Dynamics between Stem Cells, Niche, and Progeny in the Hair Follicle. Cell 144: 92-105.

Tumbar T, et al. (2004) Defining the Epithelial Stem Cell Niche in Skin. Science 303: 359-363.
Labels:

Comments

  1. Anne MMay 17, 2013 at 6:00 PM

    So, no hair, no healing? Anne M.

    ReplyDelete
  2. AnonymousMay 22, 2013 at 9:30 PM

    Or, one may ask, is it the follicle or the hair that counts? Some of us have more hair than others; do some of us have better healing of skin wounds than others? Emily says the stem cells react to signals from "above" the follicle. So maybe it's having enough follicles that is important.

    ReplyDelete

Post a Comment

Popular posts from this blog

Winter is here

Frigid temperatures in Arkansas this weekend have inspired an icy topic.   If you’ve ever wondered why your lettuce wilts when it accidentally freezes in the refrigerator, or your basil dies after the first frost then this post is for you.  Contrary to what I believed and maybe what some of you do to, plant cells themselves rarely freeze. The water in between cells freezes much more readily than the cells themselves; this is the start of the plant’s problems.  Dehydration is the most common culprit for cell death at cold temperatures. It seems counter intuitive that dehydration would occur as a result of freezing water , but it makes sense when you begin to think like a plant cell. All living cells exist in a state of equilibrium with their surroundings. Ions, gases, small molecules and water are constantly moving around the plant, going in and out of cells as needed. The concentrations of these species inside and outside of the cell are carefully regulated b...
4 comments
Read more

Chemically combating chemical combat

As we have witnessed all too recently, chemical warfare is a very tangible concern for many people of the world. The latest large scale attack occurred in Syria only a few months ago with the use of Sarin gas. The news from Syria makes it all the more urgent that scientists find ways to combat the use of chemical weapons. A group of engineers at UC San Diego have done just that using a new kind of structure called “micromachines”. Many chemical weapon agents used in warfare belong to a class of chemicals broadly labeled “organophosphates”. This label is given to molecules that have a generically organic part and a phosphate part. Here is the molecule sarin, with its organic and phosphate parts highlighted: Nerve gasses like sarin are dangerous because of the way the molecules interact with our nervous system. This interaction is highly dependent on the shape, or conformation of the molecule. That is, if we could somehow break up the atoms in the sarin molecule, they w...
Post a Comment
Read more

Thrills and Chills -- and Dopaminergic Spills?

Scenario: You’re listening to one of your favorite pieces.   Suddenly some cue in the music makes your heart feel like it might beat out of your chest and your skin start to tingle. Within seconds your arm hairs are standing straight up, a wave of chills runs down your spine and you are covered in goose bumps. The first time this happened to me I think I was about 12 singing along to a hymn from the pew of my church. I thought for sure what I was feeling was the Holy Spirit coursing through my veins! Not to write off any divine experience my 12-year old self was having, but it turns out that there were some other things going on – mostly in my brain. It’s been known for a while now that lots of human behavior is reinforced by activity in our brains that makes us feel good. For the most part these feelings of pleasure are meant to encourage us to keep doing things that tend to help our species survive, i.e. having sex or eating delicious food (although highly addictiv...
4 comments
Read more