The super super-healing MRL mouse strain.

The Murphy Roths Large (MRL/MpJ) mice provide unique insights into wound repair and regeneration. These mice and the closely related MRL/MpJ-Faslpr /J and Large strains heal wounds made in multiple tissues without production of a fibrotic scar. The precise mechanism of this remarkable ability still eludes researchers, but some data has been generated and insights are being revealed. For example, MRL cells reepithelialize over dermal wound sites faster than cells of other mouse strains. This allows a blastema to develop beneath the protective layer. The MRL mice also have an altered basal immune system and an altered immune response to injury. In addition, MRL mice have differences in their tissue resident progenitor cells and certain cell cycle regulatory proteins. The difficulty often lies in separating the causative differences from the corollary differences. Remarkably, not every tissue in these mice heals scarlessly, and the specific type of wound and priming affect regeneration ability as well. The MRL/MpJ, MRL/MpJ-Faslpr /J, and Large mouse strains are also being investigated for their autoimmune characteristic. Whether the two phenotypes of regeneration and autoimmunity are related remains an enigma.