Heterochronic islet transplants increase proliferation of old β-cells and decrease proliferation of young β-cells. A: Islet grafts were placed under the kidney capsule of young and old mice to create isochronic and heterochronic transplant
groups. After 2 weeks, mice were killed and proliferation was measured using Ki67. Heterochronic transplant succeeded in increasing
β-cell proliferation of old islets and in decreasing proliferation of young islets using Student t test (*P < 0.05) and ANOVA (P < 0.01). Post hoc Tukey honestly significant difference test also showed a significant difference in both heterochronic transplant
groups (P < 0.007; N = 4). B: A representative image of β-cells transplanted under the kidney capsule from four different groups of transplanted mice
stained for insulin (green), Nkx6.1 (red), and Ki67 (blue). Ins, insulin; NS, not significant; O, old; Y, young.