Decreasing inflammatory response of injured patellar tendons results in increased collagen fibril diameters.

Tissue inflammation is essential in the healing process, but its effect on the quality of the healing tissue is not clear. This study determines the effect of decreasing early inflammation during wound healing in genetic deficient mice on collagen fibril diameter. Two strains of mice were used: three C3H/HeJ mice and three C3H/HeN mice for each of two time points (7 and 14 days postinjury). C3H/HeJ mice have a genetic deficiency in the production of tumor necrosis factor by macrophages and other cytokines in response to endotoxin, and C3H/HeN mice have no genetic deficiency. The right patellar tendon of both mouse strains was transversely transected, whereas the left patellar tendon was left intact for control. After 7 and 14 days, both right and left patellar tendons were harvested, and tendon samples were examined with transmission electron microscopy. We found that at 7 days, transected tendons of C3H/HeJ mice exhibited on average 1.6 times larger collagen fibril diameters than transected C3H/HeN tendons, whereas at 14 days, collagen fibril diameters of the C3H/HeJ mice were 1.3 times that of C3H/HeN mice. Also, at both 7 days and 14 days, collagen fibrils in C3H/HeJ mice appeared more organized than C3H/HeN mice. In addition, control tendons in both mouse strains showed no significant differences in collagen fibril diameter and organization. Therefore, these results suggest that decreasing the inflammatory response in the early stages of tendon wound healing enhances the quality of the healing tendon through increased collagen fiber diameter and better organization.