A new, hair-sprouting dollop of human skin created in the lab might one day help prevent hair loss.

Organoids are small, lab-grown cell groupings are designed to model real-world organs -in this case, skin. A paper published in Nature describes the hairy creation as the first hair-baring human skin organoid made with pluripotent stem cells, or the master cells present during early stages of embryonic development that later turn into specific cell types.

The authors used stepwise modulation of the transforming growth factor β (TGFβ) and fibroblast growth factor (FGF) signalling pathways to co-induce cranial epithelial cells and neural crest cells within a spherical cell aggregate.

During an incubation period of 4–5 months, they observed the emergence of a cyst-like skin organoid composed of stratified epidermis, fat-rich dermis and pigmented hair follicles that are equipped with sebaceous glands. A network of sensory neurons and Schwann cells form nerve-like bundles that target Merkel cells in organoid hair follicles, mimicking the neural circuitry associated with human touch.

Single-cell RNA sequencing and direct comparison to fetal specimens suggest that the skin organoids are equivalent to the facial skin of human fetuses in the second trimester of development. Moreover, the researchers show that skin organoids form planar hair-bearing skin when grafted onto nude mice. 

"This makes it possible to produce human hair for science without having to take it from a human," explained graduate student. "For the first time, we could have, more or less, an unlimited source of human hair follicles for research."

Having access to more hair-growing skin can help researchers better understand hair growth and development - and maybe even provide clues needed to reverse a retreating hair line.

https://www.nature.com/articles/s41586-020-2352-3