Construction and functional evaluation of an autologous thymokidney model in the rat

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.

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.

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.

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.