Scientists have grown hair on mice using human stem cells in a possible step towards curing baldness.
US scientists said they’ve created skin organoids – tiny tissue cultures – from stem cells in a lab dish.
These can generate into multi-layered skin tissue with hair follicles, sebaceous glands and neural circuitry when cultured for four to five months, they said.
In lab trials, when the nearly complete skin was grafted onto mice, more than half of the grafts went on to sprout hair in a promising development for bald men.
Currently, transplanting hair follicles from one part of the head to the other is the only option for male-pattern baldness.
The research could also lead to treatments for alopecia, the condition that causes hair to fall out, as well as burns, genetic skin disorders and cancers.
Human skin is a complex, multi-layered organ involved in diverse processes from temperature regulation and bodily fluid retention to the sensing of touch and pain. Reconstructing skin with hair follicles and sebaceous glands has been a major biomedical challenge
‘Reconstructing appendage-bearing skin in cultures and in bio-engineered grafts is a challenge that has yet to be met,’ said corresponding author Professor Karl Koehler, a plastic surgeon at Harvard Medical School in Boston.
‘Here we report an organoid culture system that generates complex skin from human pluripotent stem cells.
‘Direct comparison to foetal specimens suggest the skin organoids are equivalent to the facial skin of humans in the second trimester of development.
‘This shows the organoids are capable of integrating with the mouse epidermis and forming human hair-bearing skin.’
Human skin is a complex, multi-layered organ involved in diverse processes from temperature regulation and bodily fluid retention to the sensing of touch and pain, the team said.
Therefore, reconstructing skin with its associated structures – such as hair follicles and sebaceous glands – has been a major biomedical challenge.
Taking pluripotent stem cells, the US team created tiny skin buds, or organoids, in a petri dish.
The skin origanoids expressed genes characteristic of the chin, cheek, ear and scalp – suggesting it will work for hair transplants.
The buds were incubated in a cocktail of growth factors and other chemicals for four to five months.
This gave rise to both the upper and lower layers of skin – known as the epidermis and dermis, respectively.
Follicles with specific glands that lubricate hair with an oily substance called sebum also appeared – along with interwoven nerves, muscles and fat.
When the skin was implanted onto the backs of immuno-compromised bald mice, hair loss was reversed.
Human style strands 2 to 5 millimetres in length sprouted on more than half – 55 per cent – of the grafts.
What’s more, the creation supports a network of sensory neurons and nerve cells form nerve-like bundles that target Merkel cells – oval-shaped receptors essential for light touch sensation in organoid hair follicles.
A mouse in the lan. When implanted onto the back skin of mice, 2–5 mm hairs (right) sprouted on 55 per cent of the grafts
‘This mimics mimicking the neural circuitry associated with human touch,’ the researchers write in their study, published in Nature.
The skin could also lead to the development of better drugs for diseases – including cancer.
‘Our study establishes a model for investigating the cellular dynamics of developing human skin and its appendages – including sweat glands,’ Professor Koehler said.
‘A range of genetic skin disorders and cancers could be modelled with skin organoids to accelerate drug discovery.
Top, hair follicles stained with haematoxylin. Transmission electron microscopy image (bottom) of the region marked in the top dashed box, showing hair follicle layers
‘Moreover, they could be used to reconstitute appendage-bearing skin in patients with skin burns or wounds.’
Dermatologists Dr Leo Wang and Dr George Cotsarelis, who were not involved in the study, described it as a ‘major step towards a cure for baldness’.
‘This achievement places us closer to generating a limitless supply of hair follicles that can be transplanted to the scalps of people who have thinning or no hair.
‘Moreover, if the approach reaches the clinic, individuals who have wounds, scars and genetic skin diseases will have access to revolutionary treatments.’
‘The work holds great promise of clinical translation – we are confident that research will eventually see this promise realised.’
Several questions remain before this therapeutic approach can become a reality, according to Wang and Cotsarelis.