Hair follicles encourage scar remodelling

Thanks to evolution, injured tissues usually heal rapidly by necessity, although the payback for this fast fix is often the formation of a scar. But scar tissue, as well as being unsightly in some cases, doesn’t have the same functions as the original tissue it replaced, which means a scar can affect how well a healed body part can work subsequently. Recently, though, Imperial College’s Claire Higgins has made a surprising discovery: hair follicles implanted into scarred skin seem to trigger a repair process that reverses some of the scarring. If she can discover how, it might unlock the door to copying the trick to repair other organs that can scar, like the heart or liver. For Claire, this has meant a trip to the Canary Islands, as James found out…

Claire - We wanted to do an in human experiment as opposed to an experiment in the lab with cells or tissues. And so we contacted a hair transplant surgeon and flew over to Gran Canaria and Dr. Jimenez recruited three patients who had scars on the back of their scalp which were caused by surgeries several years prior. He took hair follicles from areas of the scalp that still contained hair and transplanted them into these scars. And then we isolated biopsies from these three patients prior to the hair follicles being transplanted into the scars, and then two, four and six months after the hair follicles were transplanted into the scar to see if the hair follicle or the presence of the hair follicle within the scar tissue was actively remodelling the scar itself.

James - So, to be clear, this procedure from the surgeon you were in touch with, they were going to go ahead anyway?

Claire - Yes. So the hair transplantation into scar tissue on the scalp is often used to camouflage scarring on the scalp.

James - Got you

Claire - But no one has then looked at whether you actually get changes to the scar tissue other than a cosmetic effect of introducing a hair follicle into the scar.

James - And what did you find?

Claire - So we found that the hair follicle seemed to be actively remodelling the surrounding tissue. We found a doubling in the number of blood vessels back to the levels that we would expect to see in healthy skin - the kind of bulk matrix that you get in scar tissue which is very characteristic and leads to differences in the mechanical properties of scars. We saw a decrease in this bulk connective tissue pushing it towards a phenotype that would be more characteristic of healthy skin.

James - Fantastic. So this treatment would work on other parts of the body as well, other than the head where it's got that cosmetic function as well?

Claire - Yeah. So in our work, as I said, we transplanted hair follicles into scars on the scalp, and so the presence of a hair follicle would be desirable; it helps camouflage the scar. But, of course, you don't want to be transplanting hair follicles into scars on every body site. You do get scars internally and externally, so we think about skin scars, but actually whenever you have tissue injury, you get a scar. So if you have a heart attack, you have fibrotic tissue or scar tissue on the heart, which then impairs the function of the heart. So just as scars in the skin impair functionality there, scarring has impacts elsewhere. So what we're doing now is trying to figure out how the hair follicle actually facilitated this scar remodelling, and then the idea is we will just isolate that component, or take that and try to use it to remodel scars in contexts where we don't want to introduce a hair follicle into the scar. Our work completely challenged this dogma that a scar is for life. We found that you actually can take scars and they can be remodelled, which is quite exciting, I think, for the future.