A new study by Imperial College London has found that skin scars could be mended by hair follicle transplants.
In three volunteers, skin scars began to behave more like uninjured skin following treatment with hair follicle transplants. The scarred skin harboured new cells and blood vessels, remodelled collagen to restore healthy patterns, and even expressed genes found in healthy unscarred skin.
Lead author Dr Claire Higgins of Imperial’s Department of Bioengineering said: “After scarring, the skin never truly regains its pre-wound functions, and until now, all efforts to remodel scars have yielded poor results. Our findings lay the foundation for exciting new therapies that can rejuvenate even mature scars and restore the function of healthy skin.”
The research is published today in Nature Regenerative Medicine.
New hope to repair skin scars
Scar tissue in the skin lacks hair, sweat glands, blood vessels and nerves, which are essential for regulating body temperature and detecting pain and other sensations. Scarring can also impair movement, causing discomfort and emotional distress.
Compared to scar tissue, healthy skin undergoes constant remodelling by the hair follicle. Hairy skin heals faster and scars less than non-hairy skin – and hair transplants have already shown they air wound healing. This led the researchers to look at whether transplanting growing hair follicles into scar tissue might induce scars to remodel themselves.
The team worked with Dr Francisco Jiménez, lead hair transplant surgeon at the Mediteknia Clinic and Associate Research Professor at University Fernando Pessoa Canarias in Gran Canaria, Spain. They transplanted hair follicles into the mature scars on the scalp of three participants in 2017. They used the most common skin scar, called normotrophic scars, which usually form after surgery.
They took microscope image 3mm-thick biopsies of the skin scars before transplantation and then again at two, four, and six months afterwards. They found that the follicles inspired profound architectural and genetic shifts in the scars towards a profile of healthy, uninjured skin.
Dr Jiménez said: “Around 100 million people per year acquire scars in high-income countries alone, primarily as a result of surgeries. The global incidence of scars is much higher and includes extensive scarring formed after burns and traumatic injuries. Our work opens new avenues for treating scars and could even change our approach to preventing them.”
Skin restoration following transplantation
After the transplant, the follicles produced hair and induced restoration across skin layers. Scarring causes the epidermis to thin out, leaving it more likely to scar. At six months post-transplant, the epidermis had doubled in thickness and increased cell growth, resulting in the skin becoming as thick as uninjured skin.
The dermis is populated with connective tissue, blood vessels, sweat glands, nerves and hair follicles. As the scar matured, it leaves the dermis with fewer cells and blood vessels; however, after transplantation, the number of cells doubled at six months, and the number of vessels had reached almost healthy-skin levels by four months. This showed the follicles lead to the growth of new cells and blood vessels in the scars, which are unable to do this unaided.
Furthermore, skin scars increase the density of collagen fibres, a protein in the skin, which causes scar tissue to become stiffer than healthy tissue. The hair transplants reduced the density of the fibres, which allowed them to form a healthier, weave pattern, which reduced stiffness.
The authors also found that after transplantation, the scars expressed 719 genes differently from before. Genes that promote cell and blood vessel growth were expressed more, while genes that promote scar-forming processes were expressed less.
Dr Higgins said: “This work has obvious applications in restoring people’s confidence, but our approach goes beyond the cosmetic as scar tissue can cause problems in all our organs.
“While current treatments for scars like growth factors focus on single contributors to scarring, our new approach tackles multiple aspects, as the hair follicle likely delivers multiple growth factors all at once that remodel scar tissue. This lends further support to the use of treatments like hair transplantation that alter the very architecture and genetic expression of scars to restore function.”