The two layers of skin cells, the dermis and epidermis must grow together in a specific way in order for hair follicles to develop.

‘A single skin organoid unit developed in culture can give rise to both the epidermis and dermis layers of skin, which grow together in a process that allows hair follicles to form.’

Karl Koehler, an assistant professor of otolaryngology at the Indiana University School of Medicine, originally began using pluripotent stem cells from mice, which can develop into any type of cells in the body, to create organoids--miniature organs in vitro--that model the inner ear. But Koehler and his team discovered they were generating skin cells in addition to inner ear tissue, and their research shifted towards coaxing the cells into sprouting hair follicles. 




The team's recent research demonstrates that a single skin organoid unit developed in culture can give rise to both the epidermis (upper) and dermis (lower) layers of skin, which grow together in a process that allows hair follicles to form the same way as they would in a mouse's body.
"You can see the organoids with your naked eye," Koehler says. "It looks like a little ball of pocket lint that floats around in the culture medium. The skin develops as a spherical cyst, and then the hair follicles grow outward in all directions, like dandelion seeds."
While the researchers were unable to identify exactly which types of hairs developed on the surface of the organoid, they believe the skin grew a variety of hair follicle types similar to those present naturally on the coat of a mouse. The skin organoid itself consisted of three or four different types of dermal cells and four types of epidermal cells--a diverse combination that more closely mimics mouse skin than previously developed skin tissues.
By observing the development of this more lifelike skin organoid, the researchers learned that the two layers of skin cells must grow together in a specific way in order for hair follicles to develop. As the epidermis grew in the culture medium, it began to take the rounded shape of a cyst. The dermal cells then wrapped themselves around these cysts. When this process was disrupted, hair follicles never appeared.
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After discovering this recipe for lab-grown hair follicles, the researchers must now work to overcome a new roadblock in the study of in vitro hair development--physical limitations that prevent the hairs from shedding and regenerating. The shape of the tissue in culture causes the hair follicles to grow into the dermal cysts, leaving them with nowhere to shed.
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"It could be potentially a superior model for testing drugs, or looking at things like the development of skin cancers, within an environment that's more representative of the in vivo microenvironment," says Koehler. "And it would allow us to limit the number of animals we use for research."
Source-Eurekalert