title: Unexpected regeneration in middle-aged mice.
abstract: Complete regeneration of damaged extremities, including both the epithelium and the underlying tissues, is thought to occur mainly in embryos, fetuses, and juvenile mammals, but only very rarely in adult mammals. Surprisingly, we found that common strains of mice are able to regenerate all of the tissues necessary to completely fill experimentally punched ear holes, but only if punched at middle age. Although young postweaning mice regrew the epithelium without typical pre-scar granulation tissue, they showed only minimal regeneration of connective tissues. In contrast, mice punched at 5-11 months of age showed true amphibian-like blastema formation and regrowth of cartilage, fat, and dermis, with blood vessels, sebaceous glands, hair follicles, and, in black mice, melanocytes. These data suggest that at least partial appendage regeneration may be more common in adult mammals than previously thought and call into question the common view that regenerative ability is lost with age. The data suggest that the age at which various inbred mouse strains become capable of epimorphic regeneration may be correlated with adult body weight.
authors.affiliation: Ghost Lab, T Cell Tolerance and Memory Section, Laboratory of Cellular and Molecular Immunology, Twinbrook III, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA. BReines@niaid.nih.gov
authors.forename: Brandon
authors.initials: B
authors.lastname: Reines
authors.forename: Lily I
authors.initials: LI
authors.lastname: Cheng
authors.forename: Polly
authors.initials: P
authors.lastname: Matzinger
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D020405:Dermis / Q000502:physiology; D004423:Ear / Q000293:injuries / Q000502:physiology; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D012038:Regeneration / Q000502:physiology*; D012879:Skin Physiological Phenomena; D014945:Wound Healing / Q000502:physiology