Every scar tells a story, but that story may soon be coming to a close, as new research from Stanford University reveals clues to why scars form—and offers clues on how scarring could become a thing of the past.
Reported last week in the journal Science, the research team pinpointed the type of skin cell responsible for scarring and, importantly, also identified a molecule that, when activated, can actually prevent the skin cells from forming a scar. As one of the study’s senior authors Michael Longaker explained in a press release, the biomedical burden of scarring is vast.
“About 80 million incisions a year in this country heal with a scar, and that’s just on the skin alone,” said Longaker, who also co-directs Stanford’s Institute for Stem Cell Biology and Regenerative Medicine. “Internal scarring is responsible for many medical conditions, including liver cirrhosis, pulmonary fibrosis, intestinal adhesions and even the damage left behind after a heart attack.”
Scars are normally formed when a type of skin cell called a fibroblast secretes a protein called collagen at the injury site. Collagen acts like a biological Band-Aid that supports and stabilizes the damaged skin.
In this study, which was funded in part by a grant from CIRM, Longaker, along with co-first authors Yuval Rinkevich and Graham Walmsley, as well as co-senior author and Institute Director Irving Weissman, focused their efforts on a type of fibroblast that appeared to play a role in the earliest stages of wound healing.
This type of fibroblast stands out because it secretes a particular protein called engrailed, which initial experiments revealed was responsible for laying down layers of collagen during healing. In laboratory experiments in mouse embryos, the researchers labeled these so-called ‘engrailed-positive fibroblast cells,’ or EPF cells, with a green fluorescent dye. This helped the team track how the cells behaved as the mouse embryo developed.
Interestingly, these cells were also engineered to self-destruct—activated with the application of diphtheria toxin—so the team could monitor what would happen in the absence of EPF cells entirely.
Their results revealed strong evidence that EPF cells were critical for scar formation. The scarring process was so tied to these EPF cells that when the team administered the toxin to shut them down, scarring reduced significantly.
Six days later the team found continued differences between mice with deactivated EPF cells, and a group of controls. Indeed, the experimental group had repaired skin that more closely resembled uninjured skin, rather than the distinctive scarring pattern that normally occurs.
Further examination of EPF cells’ precise function revealed a protein called CD26 and that blocking EPF’s production of CD26 had the same effect as shutting off EPF cells entirely. Wounds treated with a CD26 inhibitor had scars that covered only 5% of the original injury site, as opposed to 30%.
Pharmaceutical companies Merck and Novartis have already manufactured two types of CD26 inhibitor, originally developed to treat Type II diabetes, which could be modified to block CD26 production during wound healing—a prospect that the research team is examining more closely.