title: Smaller cardiac cell size and reduced extra-cellular collagen might be beneficial for hearts of Ames dwarf mice.
abstract: OBJECTIVE
  To test the hypothesis that cardiac morphologic differences between Ames dwarf and wild-type littermates might correlate with the increased longevity observed in the Ames dwarf mice.
  
  
  METHODS
  Hearts removed from young adult (5-7 mo) and old (24-28 mo) Ames dwarf and wild-type littermates underwent histological and morphometric analysis. Measurements of cell size, nuclear size, and collagen content were made using computerized color deconvolution and particle analysis methodology.
  
  
  RESULTS
  In the young mice at six months of age, mean cardiomyocyte area was 46% less in Ames dwarf than in wild-type mice (p<0.0001). Cardiomyocyte size increased with age by about 52% in the wild-type mice and 44% in the Ames dwarf mice (p<0.001). There was no difference in nuclear size of the cardiomyocytes between the young adult wild-type and Ames dwarf mice. There was an age-associated increase in the cardiomyocyte nuclear size by approximately 50% in both the Ames and wild-type mice (p<0.001). The older Ames dwarf mice had slightly larger cardiomyocyte nuclei compared to wild-type (2%, p<0.05). The collagen content of the hearts in young adult Ames dwarf mice was estimated to be 57% less compared to wild-type littermates (p<0.05). Although collagen content of both Ames dwarf and wild-type mouse hearts increased with age, there was no significant difference at 24 months.
  
  
  CONCLUSIONS
  In wild-type and Ames dwarf mice, nuclear size, cardiomyocyte size, and collagen content increased with advancing age. While cardiomyocyte size was much reduced in young and old Ames dwarf mice compared with wild-type, collagen content was reduced only in the young adult mice. Taken together, these findings suggest that Ames dwarf mice may receive some longevity benefit from the reduced cardiomyocyte cell size and a period of reduced collagen content in the heart during adulthood.
authors.affiliation: Donald W Reynolds Department of Geriatrics, The University of Arkansas for Medical Sciences and Geriatric Research, Education, and Clinical Center, Little Rock, AR, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Helms
authors.forename: Gohar
authors.initials: G
authors.lastname: Azhar
authors.forename: Chunlai
authors.initials: C
authors.lastname: Zuo
authors.forename: Sue A
authors.initials: SA
authors.lastname: Theus
authors.forename: Andrzej
authors.initials: A
authors.lastname: Bartke
authors.forename: Jeanne Y
authors.initials: JY
authors.lastname: Wei
mesh_terms: D000367:Age Factors; D000818:Animals; D002467:Cell Nucleus / Q000648:ultrastructure; D048429:Cell Size; D003094:Collagen / Q000378:metabolism*; D006321:Heart / Q000033:anatomy & histology; D008136:Longevity; D051379:Mice; D008815:Mice, Inbred Strains; D009206:Myocardium / Q000166:cytology* / Q000648:ultrastructure; D009929:Organ Size
chemical_list: D003094:Collagen
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