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Explants from rabbit anterior cruciate ligaments (ACL) and medial collateral ligaments (MCL) were utilized to compare the relative rates that fibroblasts migrate onto glass and plastic culture surfaces in vitro. During the first two weeks in culture, a monolayer of cells appeared on the periphery of all the ACL and MCL explants. From 45 to 134 hrs in culture, the mean total MCL cell count per explant was 6-12 times greater than that for the ACL on the plastic culture dishes, and this difference was even greater for the cells attached to the glass cover slides over the explants. These differences were significant at the p < .005 level. The rates of cell proliferation were quite similar for primary cultures of ACL and MCL grown in the same medium as that used for the migration assay. The large difference in cell number at early times of culture is thus due to the more rapid MCL cell migration out of the explants, and not to a difference in the rate of cell proliferation. These data support the hypothesis that differences in cell migration rate play a role in the greater healing capacity of the MCL as compared with the ACL. The assay described in this work may then be useful in assessing factors that promote wound healing.

Positive effects on the tensile characteristics of swine digital extensors were found following twelve months of exercise training. Compared to sedentary controls, the tendons from the exercised animals became stronger as a material and exhibited hypertrophy. These biomechanical results were supported by biochemical analyses of tendon composition. Exercise increased the concentration of collagen as well as the total weights of the tendons. For determining stress and strain in tendon material, we used specially designed instruments to measure the tendon cross-sectional area, and a video dimensional analyzer system to measure accurately its "non-contact" tensile strain. With these newly developed apparatus, the mechanical properties of the tendons were accurately determined so that the effects of exercise training could be compared.

Rabbits immobilized with one leg pinned in a fully flexed position, were treated with 60 mg of D-penicillamine/kg three times a week for 9 weeks. After this period of immobilization the animals were sacrificed and the periarticular connective tissue collagen reduced with [3H] NaBH4 for determination of collagen cross-links. There was a significant decrease in the formation of cross-links in the control and immobilized knee in the treated animals as compared to the untreated animals. Penicillamine also blocked the increase in DHLNL, HLNL and HHMD previously demonstrated in immobilized rabbit knees. This is the first demonstration that in vivo administration of penicillamine directly inhibits cross-linking reactions in collagen.

A significant increase in the NaBH4 reducible intermolecular cross-links in the 9 week immobilized rabbit periarticular connective tissue was found. Dihydroxylysinonorleucine, hydroxylysinonorleucine, and histidinohydroxymerodesmosine were the major cross-links which increased during the period of immobilization. No change in the hydroxlysine/lysine ratio between the immobilized and control periarticular connective tissue collagen was detected during the 9 weeks of enforced immobilization of the rabbit knee. Since the collagen mass in the immobilized periarticular connective tissue does not change, or at most is reduced 10%, we suggest that there is an increase in collagen cross-links expressed both in per unit weight of collagen and on the basis of collagen mass per knee due to the lack of physical stress and motion.

The purpose of this study was to evaluate changes over time in surgically ruptured medial collateral ligament (MCL) with respect to collagen synthesis, collagen degradation and collagen type. Our method involved prelabeling collagen in growing rabbits using 3H-proline followed by surgical injury to the MCL. Animals were sacrificed at intervals up to 40 weeks post-injury. At each time point total hydroxyproline, changes in collagen mass, and collagen synthesis and degradation were determined and related to the unruptured control MCL. A separate semiquantitative determination of collagen type was also performed on the midsubstance of each healing and control ligament. Results showed an increase in total collagen mass and a decrease in collagen concentration in all healing ligaments. Concommitantly, an increase in the collagen turnover rate was observed. Relative turnover was greatest at 3 to 6 weeks after injury and returned toward the normal rate by 40 weeks. Type I collagen was partially replaced by type III, probably as a result of increased synthesis during scar formation. The mechanism for collagen remodeling (replacement of mass and concentration in an organized fashion) in untreated rabbit MCL scar appears functional by virtue of its chronicity but, due to a shift in collagen type, it may also be qualitatively inadequate.

The distribution of collagen types was studied in control and immobilized periarticular connective tissue to test the hypothesis that inflammatory tissue is the basis of the contracture process. The hypothesis derives from the fact that Type III collagen is prominent in inflammatory processes. The content of Type I and Type III collagen was determined by standard differential salt precipitation of the pepsin solubilized collagen, followed by resolution of the subunits on CM-cellulose. Analysis of the peptide fragments produced by cyanogen bromide was performed and their distribution determined by SDS gel electrophoresis. The collagen of control and immobilized periarticular connective tissue proved to be entirely Type I. Type III was not present. The periarticular connective tissue contracture process, therefore, is different from the intraarticular process in which fibrofatty connective tissue proliferation is prominent.