KGF treatment normalized intrathymic IL-7 expression, thymic architecture, and TEC organization in aged mice. TEC organization in aged mice was compared 8 days or 1 month after initiation of a single 3-day course of PBS or KGF treatment. (A) Total RNA from whole thymus on day 8 after initiation of PBS or KGF treatment was analyzed for the epithelium-specific transcript EVA and IL-7 by quantitative RT-PCR (n = 5 per group). Each transcript level was normalized to β-actin expression. *P < .05; NS indicates not significant. (B) H&E staining of thymic sections from normal young PBS- or KGF-treated aged mice. (C) Immunofluorescence staining for K5 and K8, and DAPI nuclear staining. The thymus in aged mice displayed indistinct corticomedullary junctions and decreased TEC populations with areas that were completely devoid of keratin-positive TECs (asterisk). KGF treatment normalized TEC organization in aged mice. The magnification was 200 ×.