Neuronal PAS Domain 2 (Npas2)-Deficient Fibroblasts Accelerate Skin Wound Healing and Dermal Collagen Reconstruction.

The circadian clock, which consists of endogenous self-sustained and cell-autonomous oscillations in mammalian cells, is known to regulate a wide range of peripheral tissues. The unique upregulation of a clock gene, neuronal PAS domain protein2 (Npas2), observed along with fibroblast aging prompted us to investigate the role of Npas2 in the homeostasis of dermal structure using in vivo and in vitro wound healing models. Time-course healing of a full-thickness punched wound was monitored in C57Bl6J (WT) and Npas2 KO mice. Fibroblasts were isolated from mouse dorsal skin with each genotype. Core clock gene expression was determined by RT-PCR. Fibroblast behaviors were characterized in vitro for cell proliferation, cell migration and cell contraction (collagen gel contraction and single-cell force contraction). Collagen synthesis in vitro was demonstrated by RT-PCR and picrosirius red staining. Dermal collagen architecture in the wound healing area was characterized by confocal laser scanning microscopy. Npas2-/- mice demonstrated faster skin wound closure than the other groups (p<0.01). There was no difference in core clock gene expression among the three genotypes except for Npas2 and Per2. Cell proliferation, cell migration and cell contraction of Npas2-/- fibroblasts were greater than those for WT fibroblasts (p<0.01). An increased expression of type XII and XIV FAICT collagens and dermis-like collagen fiber formation was found in Npas2 KO fibroblasts in vitro (p<0.01). The collagen fiber structure in the granulation tissue area was better reconstructed in Npas2-/- mice. This study suggests that Npas2 may be a novel therapeutic target for skin homeostasis and wound healing. This article is protected by copyright. All rights reserved.