EFFECTS OF AGING AND CALORIC RESTRICTION ON EXTRACELLULAR-MATRIX BIOSYNTHESIS IN A MODEL OF INJURY REPAIR IN RATS

This study was designed to investigate the effects of aging and calori c restriction on collagen deposition in a model of wound healing. Poly vinyl alcohol sponges were implanted ill Fischer 344 rats aged 6, 10, or 24 months. Sponges were removed after 7, 10, or 14 days and analyze d for hydroxyproline contest and for enzymatic, crosslinks. Aging was associated,with a decrease in collagen accumulation as,veil as a delay in reaching peak rates of collagen accumulation. Levels of enzymatic crosslinks were increased in granulation tissue from old animals relat ive to young animals. Caloric restriction (60% of ad libitum intake) m aintained only during the 2-week experimental period did not affect co llagen accumulation, but did result in decreased levels of the difunct ional crosslink dihydroxylysinonor-leucine (DHLNL) in sponges implante d for ID days, but not 14 days. Caloric restriction initiated 4 months before sponges were implanted resulted in decreased collagen accumula tion and decreases in DHLNL at all implantation times. These studies s uggest that: (I) aging affects total collagen production as well as ra te of collagen production in response to injury; (2) aging is not asso ciated with impaired crosslinking in granulation tissue; (3) chronic c aloric restriction is associated with decreased collagen production an d decreased levels of DHLNL; (4) the adverse effects of chronic calori c restriction on wound healing may have a greater impact on wound heal ing in old animals.