Researchers at the Washington School of Medicine detected that youthful skin heals better than old skin. They did further research in a mouse model, because human and mouse skin are very similar in behavior. They found a transcription factor Lef1 that heals skin wounds without a scar.
Right underneath the epidermis is a skin layer with the name papillary dermis. It is there that special fibroblasts produce transcription factor Lef1. In newborn children and youth, the function of this layer is still in order and skin lacerations do not leave an ugly scar in the long term. But in adult skin this function is lost. This is why adult skin injuries can result in ugly looking scars.
Mouse experiments showing that youthful skin heals better than old skin
The authors of the above link demonstrated that neonatal skin in mice can develop small hair follicles 7 days after wounding the skin. In contrast, adult mouse skin heals with scarring. The researchers further analyzed what cell clusters in tissue culture were responsible for hair follicle regeneration. They found that developing fibroblasts had the ability to regenerate skin so that scar formation was avoided. In neonatal skin this required Lef1 expression as other mouse experiments showed.
Next the researchers investigated whether adult mouse skin could regain the capacity to heal without a scar. Adult skin was capable of healing wounds with invisible scars and hair follicle regeneration when adult dermis induced Lef1 expression.
Human observations with surgery on embryos
Clinicians observed for some time that surgeries done in the womb healed without any sign of skin scars by the time the baby was born.
The mouse experiments suggest that the developing fibroblasts with the ability to regenerate severed skin healed the fetal skin wounds.
Skin mucosa in the oral cavity has the capacity to heal with very little scarring or no scarring similar to fetal wound healing. The difference in healing between a mucosal skin tear in the mouth and a skin wound of the body elsewhere needs to be investigated further.
Youthful Skin Heals Better than Old Skin
Conclusion
The observation that youthful skin heals better than old skin has led to mouse experiments, which revealed the following: Right underneath the epidermis is a skin layer with the name papillary dermis. It is there that special fibroblasts produce transcription factor Lef1. In newborn and youth, the function of this layer is still in order and skin lacerations do not leave an ugly scar in the long term. But adult skin has lost this function.
Wounds in the mouth heal better than on body skin
The researchers found that the developing fibroblasts had the ability to regenerate skin healing without a scar. The mucosal skin in the oral cavity is a location where developing fibroblasts preserve the youthful expression. As a result ugly scars are rare in the oral cavity. Unfortunately, wounds in the rest of human skin on the body still tends to heal with scars. Future research needs to determine whether it is possible to somehow reactivate developing fibroblasts to heal body wounds without a scar.
