The MRL mouse repairs both cryogenic and ischemic myocardial infarcts with scar.
OBJECTIVE
The MRL mouse strain shows extraordinary wound healing capacities. Some years ago, Leferovich et al. (Proc Natl Acad Sci U S A 2001;98:9830-35) have reported the absence of scar formation after cryogenically-induced right ventricular myocardial infarcts in adult MRL mice. An independent group (Oh et al., Cardiovasc Pathol 2004;13:203-6) found that MRL mice repair left ventricular ischemic infarcts after coronary artery ligation with regular scar formation. Given the divergent outcomes in infarct healing in MRL mice reported by those two studies, we have investigated whether MRL mice heal myocardial infarcts without scar both in the cryoinjury and in the coronary ligation model.


RESULTS
Four different protocols of cryogenically induced right and left ventricular injury, as well as permanent ligation of the left anterior descending coronary artery, were tested in adult MRL and control C57Bl/6 mice. At 60 days after experimental infarction, MRL mice showed pronounced scarring of the affected right and left ventricular areas, with no significant differences in infarct size and thickness between MRL and C57Bl/6 mice using any of the five experimental protocols. Analysis of cell proliferation by 5-bromo-2'-deoxyuridine (BrdU) incorporation into the DNA did not show any difference between the two strains of mice after infarction. Histological analysis of infarct areas using picrosirius red staining did not show differences in extent of collagen and distribution between the two mouse strains.


CONCLUSIONS
MRL mice heal myocardial infarcts with scar formation in response to ischemic as well as to cryogenic injuries.
Grisel
Philippe
P
Department of Cardiology, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne 1011, Switzerland.
Meinhardt
Andrea
A
Lehr
Hans-Anton
HA
Kappenberger
Lukas
L
Barrandon
Yann
Y
Vassalli
Giuseppe
G
D000818:Animals; D049109:Cell Proliferation; D002921:Cicatrix / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D003080:Cold Temperature / Q000009:adverse effects; D003094:Collagen / Q000378:metabolism; D003331:Coronary Vessels / Q000601:surgery; D004261:DNA Replication; D004195:Disease Models, Animal; D005260:Female; D006335:Heart Injuries / Q000209:etiology / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D006352:Heart Ventricles / Q000473:pathology; D008026:Ligation; D051379:Mice; D008810:Mice, Inbred C57BL; D009203:Myocardial Infarction / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000473:pathology; D012038:Regeneration; D013997:Time Factors; D014945:Wound Healing
D003094:Collagen