US scientists have developed a system to induce hair growth on skin-like structures grafted on to mice.
In laboratory trials at the Indiana University School of Medicine, more than 50 percent of the skin grafts created showed hair growth.
'This makes it possible to produce human hair for science without having to take it from a human,' explained Benjamin Woodruff, a contributing technician on the study and now first-year graduate student at Oregon Health and Science University. 'For the first time, we could have, more or less, an unlimited source of human hair follicles for research.'
Pluripotent stem cells were grown under specific conditions to create a skin organoid, a three-dimensional tissue culture. Skin consists of two separate components, the dermis and the epidermis, both of which were needed to create the skin organoid. Researchers incubated the pluripotent stem cells for growth, then sequentially added growth factors, proteins that stimulate cell growth, to induce the formation of both skin components. Initially, growth factor BMP4, along with an inhibitor of TGF-beta were added to cells to induce growth of the epidermis. Later additions included growth factor FGF2 and a bone morphogenetic proteins (BMP) inhibitor to ensure the dermis grew simultaneously.
The cells were incubated for 70 days before follicles began to appear, and the hairs present were pigmented showing melanocytes, melanin-producing cells, had also grown within the dermis as would occur in vivo. Tissues associated with hair follicles such as sebaceous glands, nerves and their receptors and muscle also developed. Immune cells usually found in the skin cells were not found to be present.
The organoids were grafted on to immunodeficient mice, to ensure the grafts were not rejected, and showed between two and five millimetres of hair growth in 55 percent of cases, suggesting this could be used as a treatment for hair loss.
'Direct comparison to fetal specimens suggests 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' said corresponding author Dr Karl Koehler, a plastic surgeon at Harvard Medical School in Boston.
Other uses for this technology have already been suggested, including the use of organoids to develop skin grafts using pluripotent stem cells. However, as the follicle development and grafts took 140 days to do, this would not currently be viable for burns victims in need of immediate treatment.
Dermatologists Dr Leo Wang and Dr George Cotsarelis, of Pennsylvania University, who were not involved in the study, described the findings 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.'