Telomere dysfunction induces alterations in the systemic environment, impairing thymic epithelial maintenance. (A-C) The thymi of 12-month-old G3mTerc^−/− or mTerc^+/+ mice were analyzed by FACS (n = 5 mice per group). (A) Bar graph showing the total number of epithelial cells. (B) Representative FACS profiles showing thymus epithelial cells (CD45⁻, G8.8⁺), in thymic cortex (CD45⁻, G8.8⁺, ly51⁺) and medulla (CD45⁻, G8.8⁺, ly51⁻). (C) The ratio of cortical to medullary epithelial cells (cTEC/mTEC) in thymi of 12-month-old G3mTerc^−/− or mTerc^+/+ mice. (D-E) Neonatal thymi from G3mTerc^−/− or mTerc^+/+ mice were transplanted side-by-side under the left and right kidney capsules of 2- to 3-month-old G3mTerc^−/− or mTerc^+/+ recipient mice (n = 5 per group). The grafted thymi were analyzed 9 months after transplantation. (D) Representative FACS profiles and (E) corresponding bar graph showing the ratio of cortical to medullary epithelial cells in the transplanted thymi. (F-G) Thymi from 12-month-old G3mTerc^−/− mice were transplanted under the kidney capsules of 2- to 3-month-old mTerc^+/+ recipient mice (n = 5 per group). Native nontransplanted thymi and grafted thymi were analyzed 2 to 3 months after transplantation. Bar graphs show (F) thymus weight and (G) percentage of CD4 and CD8 DP cells in total thymocytes of native nontransplanted G3mTerc^−/− thymi and grafted thymi 2 to 3 months after transplantation into mTerc^+/+ recipients. Error bars represent SD in all panels.