Some observations on the distant collagen response to wound healing in young and old rats

Influence of physical exercise on aging rats: II. Life-long exercise delays aging of tail tendon collagen

Regular physical exercise has been shown to have a number of benefits compared with sedentary behaviour, such as delaying a number of aging changes and increasing the life expectancy but not the maximum lifespan. The purpose of this paper is to analyze the effects of physical exercise on the connective tissues of the body, especially systemic effects. We trained male Sprague-Dawley rats in a treadmill from the age of 5 months to 23 months. We analyzed the effects of training on tail tendons with respect to thermal stability of collagen and biomechanical properties of tendon bundles. Although tail tendons are attached to muscles, the are not weight-bearing as limb muscle tendons and can, therefore, be considered to be subjected mainly to systemic effects. The thermal stability of tail tendon collagen was significantly lower or "younger' for the trained group compared with the sedentary one. The biomechanical parameters were likewise "younger' with respect to maximum stress, although considerably stiffer compared with a 5-month-old base-line group. This suggests that there are several mechanisms, elicited by physical exercise, that act on the connective tissues. It can be concluded that life-long physical exercise has a beneficial influence on the connective tissues of the maturing and aging organism.

Effect of D-penicillamine on collagen, glycosaminoglycans, DNA and RNA of granulation tissue and connective tissue of skin, bone and aorta in rats

Granulation tissue was produced by subcutaneous implantation of viscose-cellulose sponges on rats. The effect of D-penicillamine 500 mg/kg/day for 10 days on granulation tissue and the connective tissue of skin, bone and aorta was studied ny comparison of treated animals with operated and unoperated controls. In addition, the effect of sponge implantation on intact tissues was studied by comparison between the control groups. The amount of granulation tissue was not affected by D-penicillamine, and the granulomas-DNA content even increased. D-penicillamine increased the amount of salt soluble collagen in all tissues consistent with an inhibition of collagen crosslinking as reflected by increased aldehyde content and alpha/beta chain ratio in soluble skin collagen. Skin appeared to be most sensitive. The content of free hydroxyproline and RNA and the RNA/DNA ratio in skin decreased suggesting a decreased collagen biosynthesis. The hydroxylation of proline and lysine was not affected by the treatment. The water percentage of aorta increased during D-penicillamine treatment, and the 35S-sulphate uptake in the sulphated glycosaminoglycans was stimulated in all tissues, in granulation tissue mainly in the chondroitin-4/6-sulphate fraction. No quantitative glycosaminoglycan changes occurred in granulation tissue. Sponge implantation caused an increase in the amount of salt soluble skin collagen without any change in alpha/beta chain ratio and aldehyde content of purified, soluble collagen. D-penicillamine plus operation reduced the collagen content of aorta. The effects of D-penicillamine on connective tissue compounds may be of importance for its antirheumatic efficacy, but the accompanying effect on normal tissues may imply side effects.

Healing of incisional wounds in stomach and duodenum. Collagen distribution and relation to mechanical strength

The present study was performed to determine the changes in and distribution of collagen concentration around a healing incision in rat stomach and duodenum. These concentrations were related to the mechanical properties presented previously. Wounds were made in the nonglandular (rumen) and the glandular oxyntic parts (corpus) of the stomach and in duodenum. Specimens were cut parallel to the incision line and hydroxyproline contents and dry defatted weight were measured. Wounds were investigated 50 to 40 days after operation. Of the intact tissues the nonglandular part of the stomach had twice the collagen concentration of the glandular oxyntic part and duodenum, which did not differ from each other. The healing wounds in the glandular oxyntic part of the stomach and duodenum showed the most rapid increase in collagen concentration in the incision line and 40 days postoperatively both had collagen concentrations significantly greater than those of intact tissues. Wounds in the nonglandular part of the stomach only reached the level of intact tissue after 40 days. The dimensions of the biochemically active zones around incisions in stomach and duodenum remain essentially unchanged for 40 days after operation. A relation between the development of collagen concentration and mechanical strength was shown. These findings indicate that would healing in stomach and duodenum is rapid, that collagen is the primary factor in the mechanical properties and that the highest activity is limited to a zone close to the incision line. The width of the biochemical zone remains constant.

Collagen development in granulation tissue as compared with collagen of skin and aorta from injured and non-injured rats

Granulation tissue in rats was produced by subcutaneous implantation of viscose cellulose sponges. Granulomas, aortae, and skin samples were taken 4, 8, 14, 22, 33, and 42 days after the sponge implantation and compared with age-matched non-operated rats. 14C-proline was given 4 hours before death to animals killed on day 0, 14, and 42. The 14C-OH-proline activity in salt insoluble collagen was higher in granulation tissue and aorta than in skin. This indicates a faster formation, or an increased stability of the intermolecular cross-links in granulation tissue and aorta, than in skin. The percentage of free OH-proline was than in skin, reflecting a relatively increased collagen degradation in granulation tissue. An increased collagen degradation may also, in part, explain a registered higher alpha/beta ratio in collagen from granulation tissue than from skin, as well as the increase in alpha/beta ratio in the older granulomas. The sponge implantation did not affect the collagen of aorta and skin, but caused a decrease in the dry weight of aorta and skin, and an increase in the number of granulocytes in the blood.