BIOTECHNOLOGY
Stem Cells Can Provide a Cure for Baldness
A new study published in Nature shows how appendage-bearing skin can be generated entirely from stem cells
Skin is the largest organ in the human body, and without it, we wouldn’t be able to survive. Now, scientists show that stem cells can be directed to transform into the almost complete skin tissue.
Why skin is a vital organ of the human body?
Skin is a complex tissue composed of many different types of cells with multiple functions. It protects our bodies from the outside world and helps to maintain homeostasis. It acts as a barrier to sunlight and harmful substances. It actively defends us from infections by secreting antibacterial substances, keeps our body temperature, and produces vitamin D, required for incorporating calcium into our bones. On top of that, it is through the nerves endings stationed in the skin of our fingers, that we can experience the world by touch.
It is because of how vital this tissue is for us, regenerating damaged skin has become an ultimate goal of regenerative medicine.
Broad and deep skin burns, genetic diseases, or acute severe injuries can compromise the protective role of the skin. If not treated efficiently, simple infections can become life-threatening. Currently, the primary treatment involves skin grafting. In this technique, the skin is removed from one area of the body and transplanted to the damaged area.
The most significant limitation of skin grafting is the limited source of healthy skin. Donor skin must originate from the same person, to avoid immune rejections. In the case of extensive burns, there might just not be enough healthy skin left.
Currently, scientists are racing to harness the power of stem cells to replace skin grafting with skin regeneration.
Stem cells give hope for skin regeneration
Stem cells have the remarkable ability to form all the cell types of the human body if given the right cues. Lee and colleagues leveraged this property to generate almost complete skin organoids-3D structures grown in the laboratory that resemble real skin. As authors say:
“Here we report an organoid culture system that generates complex skin from human pluripotent stem cells.”
How are skin organoids created?
First, individual human embryonic stem cells are aggregated to form 3-dimensional clusters.
Next, these cell clusters are transferred to another dish containing a cocktail called a ‘differentiation medium.’ Differentiation medium consists of precisely optimized doses of molecules that push stem cells to transform into a different, specialized cell type. In this case, into skin cells.
The big challenge is to make a faithful reproduction of human skin tissue, which consists of all cell types that are present in real skin. To achieve induction of different cell types, Lee and colleagues designed a protocol in which they add differentiation factors sequentially, at specific times of 70 days long protocol.
Finally, after over two months, what was initially a clump of identical stem cells, turned into a cyst-like sphere with main skin cell types organized in the same way as in real skin.
How similar is stem cell-derived skin to the real one?
Very. Skin organoids have the capacity to develop all cell types present in the real skin, except for one.
In the experiments conducted by researchers from Harvard Medical School, skin organoids grew the layer of the epidermis, fat-rich dermis, and importantly, pigmented hair follicles. This might be a piece of excellent news for those awaiting effective treatment for hair loss. After grafting onto mice, in vitro skin grew pigmented hair.
In vitro grown skin also developed muscles and neuron-like structures that are similar to those associated with human touch.
And when analyzing every single cell in the skin organoid, scientists found that skin they made in the laboratory is equivalent to the facial skin of human fetuses in the second trimester of development.
The only cells lacking in stem-cell-derived skin were immune cells that normally sit next to hair follicles.
Can in vitro-grown skin replace real skin?
Using skin organoids for skin regeneration is only one of the ways in which this work could be clinically relevant.
- Growing skin tissue from stem cells can serve as a model of skin development. Researchers can use this to investigate processes that underlie skin formation.
- Skin organoids can also be used as a powerful tool to simulate genetic diseases and test the effects of drugs for these disorders. What makes it possible is the ability to introduce in stem cells the same mutation that causes the disease. Such stem cells will then simulate skin growth with the same genetic aberration.
- There is an exciting possibility that skin organoids can be used to reconstitute skin in patients with burns or wounds. Such therapies would encourage healing, prevent scarring, and overcome limitations of traditional skin grafting.
- Finally, stem-cells-grown skin may, in the future, be used for transplantation into areas lacking hair and provide a ‘cure’ for baldness.
The applications of skin organoids hold great promise for regenerative medicine, and the work from Lee and colleagues brings us yet another step closer to realizing this promise.
