Thymic inhibition of wound healing: Abrogation by adult thymectomy

It has been previously observed that the thymus and wound respond in a similar manner, i.e., agents that enhance thymic function increase wound healing, while factors which decrease thymic function impair healing. In order to elucidate if the thymus has a direct influence on wounds, we have studied wound healing in adult rats who have undergone thymectomy at 4–8 weeks of age. In three separate experiments we found that thymectomized rats had fresh wound breaking strengths significantly greater than sham-thymectomized rats. There were no differences noted in the amount of reparative collagen accumulated in subcutaneously implanted polyvinyl alcohol sponges or in the breaking strength of wound strips fixed in 10% formalin, which maximally cross-links the collagen present; the ratios of fixed to fresh wound breaking strengths were significantly greater in sham-thymectomized rats. Rats who had undergone thymectomy with immediate intraperitoneal placement of Millipore chambers containing autologous thymic fragments had wound breaking strengths similar to sham-thymectomized or intact animals. We conclude that thymectomy at 4–8 weeks of age increases wound maturation and collagen cross-linking. This suggests that the thymus normally has an inhibitory effect on wound healing and a role of T-suppressor cells on this process is postulated.