Skin atrophy and delayed wound healing are observed in aged humans; however, the molecular mechanism are still elusive. The aim of this study was to analyze the molecular mechanisms of delayed wound healing by aging using alpha-Klotho-deficient (kl/kl) mice, which have phenotypes similar to those of aged humans. The kl/kl mice showed delayed wound healing and impaired granulation formation compared with those in wild-type (WT) mice. The skin graft experiments revealed that delayed wound healing depends on humoral factors, but not on kl/kl skin tissue. The mRNA expression levels of cytokines related to acute inflammation including IL-1 beta, IL-6 and TNF-alpha were higher in wound lesions of kl/kl mice compared with the levels in WT mice by RT-PCR analysis. LPS-induced TNF-alpha production model using spleen cells revealed that TNF-alpha production was significantly increased in the presence of FGF23. Thus, higher levels of FGF23 in kl/kl mouse may have a role to increase TNF-alpha production in would lesion independently of alpha-Klotho protein, and impair granulation formation and delay wound healing. (C) 2016 Elsevier Inc. All rights reserved.