Background: We constructed a rat model of stable autologous thymokidney to observe the time required for revascularization and to examine functional recovery of the transplanted tissue and the reconstruction of T-cell reservoirs in peripheral blood mononuclear cells.
Materials and methods: Male adult Sprague-Dawley rats were divided into groups. Group I (n=12, 150 to 250 g) underwent thymectomy, group II (n=15, 150 to 250 g) received an autologous thymokidney in which thymic tissue was transplanted under the renal capsule, group III (n=5, 50 to 100 g) received sham surgery, and group IV (n=5) consisted of rats selected from group 1 to undergo splenectomy 8 weeks after thymectomy. Revascularization and functional recovery of the transplanted thymuses were evaluated with flow cytometry and histomorphologic examination.
Results: Two weeks after surgery, blood vessels grew into the renal capsules in group II, the transplanted thymic tissue thickened at 8 weeks, and thymic structure was normal. At 6 weeks, numbers of CD4-CD8- T lymphocytes increased in group I and especially in group IV. A gradual decrease was noted in group II. Numbers of CD4+ and CD8+ T lymphocytes fluctuated at low levels in group I but stayed constant in group II. The transplanted thymuses began to gradually degenerate 12 to 16 weeks after surgery.
Conclusions: Thymuses transplanted under the renal capsules adequately revascularized 2 weeks after surgery, and the autografts began functional recovery at 6 weeks. Proliferation of peripheral mature T lymphocytes is important in maintaining the number of mature T lymphocytes in peripheral blood mononuclear cells.