Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 50, Issue 1 B40-B47, Copyright © 1995 by The Gerontological Society of America
Effects of aging and caloric restriction on extracellular matrix biosynthesis in a model of injury repair in rats
K Reiser, C McGee, R Rucker and R McDonald
Department of Internal Medicine, University of California, Davis.
This study was designed to investigate the effects of aging and caloric
restriction on collagen deposition in a model of wound healing. Polyvinyl
alcohol sponges were implanted in Fischer 344 rats aged 6, 10, or 24
months. Sponges were removed after 7, 10, or 14 days and analyzed for
hydroxyproline content and for enzymatic crosslinks. Aging was associated
with a decrease in collagen accumulation as well as a delay in reaching
peak rates of collagen accumulation. Levels of enzymatic crosslinks were
increased in granulation tissue from old animals relative to young animals.
Caloric restriction (60% of ad libitum intake) maintained only during the
2-week experimental period did not affect collagen accumulation, but did
result in decreased levels of the difunctional crosslink
dihydroxylysinonor-leucine (DHLNL) in sponges implanted for 10 days, but
not 14 days. Caloric restriction initiated 4 months before sponges were
implanted resulted in decreased collagen accumulation and decreases in
DHLNL at all implantation times. These studies suggest that: (1) aging
affects total collagen production as well as rate of collagen production in
response to injury; (2) aging is not associated with impaired crosslinking
in granulation tissue; (3) chronic caloric restriction is associated with
decreased collagen production and decreased levels of DHLNL; (4) the
adverse effects of chronic caloric restriction on wound healing may have a
greater impact on wound healing in old animals.
