Researchers from Indiana University School of Medicine and Harvard Medical School have developed a method of growing human skin organoids that bear hairs entirely from human pluripotent stem cells.
The skin is a complex organ consisting of multiple layers that helps the body retain fluids, provides protection from the environment, helps regulate body temperature, and mediates the sensation of touch and pain. Creating such a complex organ in the lab represents a significant challenge and one that, until now, has not been met. Growing human skin in the lab has been the goal of skin biologists for decades and has profound implications for reconstructive surgery.
The researchers successfully created a cyst-like organoid in the lab entirely from stem cells over a period of around 4-5 months. “We use 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,” explained the researchers.
The skin organoid had a stratified epidermis, dermis, and pigmented hair follicles complete with sebaceous glands, and nerve-like bundles of sensory neurons and Schwann cells that mimicked the neural circuitry associated with the sensation of touch. The hair follicles appeared after about 70 days in culture.
The researchers used single-cell RNA sequencing alongside direct comparison and found the skin organoids were equivalent to human fetus facial skin at the second trimester of development. When the organoids were transplanted onto nude mice, the tissue integrated with the mouse skin and formed planar hair-bearing skin. More than half of the organoids grafted onto mice grew human hair follicles.
The research team was led by Karl Koehler, PhD, assistant professor of otolaryngology at Harvard Medical School and Boston Children’s Hospital.
Being able to grow almost complete skin in the lab in vitro entirely from stem cells could provide researchers with an unlimited supply of human skin for use in research and modelling skin diseases, rather than having to harvest skin for research from human patients. The tissue could also potentially be used in reconstructive surgery and at some point in the future it may be possible to grow skin organoids in the lab which could be used to reverse baldness.
You can read more about the research in the paper – Hair-bearing human skin generated entirely from pluripotent stem cells – which was recently published in the journal Nature. DOI: 10.1038/s41586-020-2352-3