Here are some interesting articles (it might be something in this):
Cloning Stem Cells. 2004;6(4):352-63
The MRL mouse heart healing response shows donor dominance in allogeneic fetal liver chimeric mice.
Bedelbaeva K, Gourevitch D, Clark L, Chen P, Leferovich JM, Heber-Katz E.
The Wistar Institute, 3400 Spruce St., Philadelphia, PA 19104, USA.
We previously demonstrated that after a severe cryoinjury to the right ventricle of the heart, adult MRL mice display structural and functional recovery with myocardial tissue replacement resembling that seen in amphibians. The control non-regenerating adult C57BL/6 (B6) mouse shows a predominant scar response. In the present study, radiation chimeras reconstituted with fetal liver cells from either healer MRL or nonhealer B6 mice were generated to test for a transfer of phenotype. Allogeneic MRL fetal liver cells were injected into x-irradiated (9 Gy) B6 mice and B6 fetal liver cells were injected into x-irradiated MRL mice. In these allogeneic chimeras, the healing response to cardiac cryoinjury was predominantly of the donor phenotype. Thus, MRL fetal liver cells transferred the healing phenotype to the B6 nonhealer with the appearance of Y-chromosome positive, donor-derived cardiomyocytes in the injury site and MRL-like healing with little scar. Similarly, B6 fetal liver cells transferred the nonhealing phenotype to the MRL with little cardiomyocyte growth and an acellular B6-like scar. These results are in contrast to the ear hole closure response which was of the recipient phenotype.
We conclude that, in the case of the heart, fetal liver-derived stem cells regulate regenerative healing.
and another one:
Philos Trans R Soc Lond B Biol Sci. 2004 May 29;359(1445):785-93.
The scarless heart and the MRL mouse.
Heber-Katz E, Leferovich J, Bedelbaeva K, Gourevitch D, Clark L.
The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA.
heberkatz@wistar.upenn.edu
The ability to regenerate tissues and limbs in its most robust form is seen in many non-mammalian species. The serendipitous discovery that the MRL mouse has a profound capacity for regeneration in some ways rivalling the classic newt and axolotl species raises the possibility that humans, too, may have an innate regenerative ability.
The adult MRL mouse regrows cartilage, skin, hair follicles and myocardium with near perfect fidelity and without scarring. This is seen in the ability to close through-and-through ear holes, which are generally used for lifelong identification of mice, and the anatomic and functional recovery of myocardium after a severe cryo-injury. We present histological, biochemical and genetic data
indicating that the enhanced breakdown of scar-like tissue may be an underlying factor in the MRL regenerative response. Studies as to the source of the cells in the regenerating MRL tissue are discussed. Such studies appear to support multiple mechanisms for cell replacement.
and another
Cell Tissue Res. 2005 Jun;320(3):417-26. Epub 2005 Apr 23
Prior injury accelerates subsequent wound closure in a mouse model of regeneration.
Davis TA, Longcor JD, Hicok KC, Lennon GG.
Endogeny Bio Corporation, 9700 Great Seneca Highway, Rockville, MD 20850, USA.
davist@nmrc.navy.mil
Tissue regeneration and scarless healing involves the complete replacement and functional restoration of damaged organs and tissues. In this study of the "scarless healing" MRL mouse model, we demonstrate that 2-mm diameter through-and-through holes made in the cartilaginous part of previously injured MRL mouse ears are closed more efficiently, and that the regenerative repair response is significantly accelerated compared with unprimed MRL and control "nonhealer" strains of mice. Accelerated healing was detected both locally and distally from the original site of injury indicating the involvement of systemic components such as circulating cell types or soluble factors. Histologically, we observed early differences during the wound repair process (before Day 4 post injury) with accelerated formation of blastema-like structures, epidermal downgrowths, and enhanced epithelium thickening in wound border zones in primed MRL mice versus unprimed MRL mice. Although the mechanism of tissue regeneration remains unclear, the results from this study justify the use of the MRL model for further experimentation directed toward the identification of proteins and cell types capable of stimulating scarless tissue regeneration.
..and this Biochem Biophys Res Commun. 2005 Apr 29;330(1):117-22.
Isolation of wound healing/regeneration genes using restrictive fragment differential display-PCR in MRL/MPJ and C57BL/6 mice.
Masinde G, Li X, Baylink DJ, Nguyen B, Mohan S. Musculoskeletal Disease Center, JL Pettis VA Medical Center, Loma Linda, CA 92357, USA.
Wound healing in mammals can take several weeks to months and the process is always accompanied by scar formation. Wound healing mechanisms that mimic regeneration are not found in most mature mammalian tissues. However, the MRL/MPJ (MRL) mouse has the unique capacity to regenerate ear hole wound completely in less than a month. To identify genes involved in wound healing without a scar, we chose to use restriction fragment differential display-PCR to isolate genes differentially expressed in the MRL (good healer) mouse and the C57BL/6 (poor healer) mouse at different stages of wound healing. We identified 36 genes that were differentially expressed in the regenerating tissue of good and poor healer strains of which several genes are also genetically linked to wound healing and thus are potential candidate genes for scarless wound healing.