Fig. 2: Thymic epithelial specific FGF21 overexpression protects against thymic aging.
From: Enhanced paracrine action of FGF21 in stromal cells delays thymic aging

a, Strategy for generation of TEC-specific FGF21 transgenic mice (created with BioRender.com). b, Representative hematoxylin and eosin (H&E) histology images of thymus in 24-month-old mice. TEC-specific overexpression of FGF21 increases cortical cellularity and protects against thinning of cortex and expansion of medulla. Scale bars, 200 μm (left) or 20 μm (right). Notably, FoxnCre-iFGF21Tg mice show reduced ectopic lipid in thymus and adipocytes. m, medulla; c, cortex. c, Expression of FGF21 in TECs of control and Foxn1Cre-FGF21Tg-overexpressing mice. Quantitative polymerase chain reaction (Q-PCR) analysis for FGF21 gene expression in various cell types and serum FGF21 levels in 12- and 24-month-old wilt-type and FoxN1Cre:iFGF21 mice (12 months, n = 8–9, 24 m, wild-type n = 25, 24 months Tg n = 19). The median, 25th and 75th percentiles (boundaries of boxes), and 5th and 95th percentiles (whiskers above and below boxplots) are indicated in the boxplots (P = 0.030). d–g, Characterization of thymic involution of aged mice. Shown are thymic mass (P = 0.014), body weight (P = 0.035), and cellularity (P = 0.009) (n = 6–13/group). h, FACS quantification, frequencies and numbers of naive (CD62L+CD44−) (P = 0.022) and E/M (CD62L−CD44+) (P = 0.039) T cells in spleen of 24-month-old control and iFGF21-FoxN1Cre mice (n = 6–7/group). Data are presented as means ± s.e.m. Two-tailed paired and unpaired t-tests were performed for statistical analysis (*P < 0.05, ** P < 0.01).