title: Mechanical Stress Changes the Complex Interplay Between HO-1, Inflammation and Fibrosis, During Excisional Wound Repair.
abstract: Mechanical stress following surgery or injury can promote pathological wound healing and fibrosis, and lead to functional loss and esthetic problems. Splinted excisional wounds can be used as a model for inducing mechanical stress. The cytoprotective enzyme heme oxygenase-1 (HO-1) is thought to orchestrate the defense against inflammatory and oxidative insults that drive fibrosis. Here, we investigated the activation of the HO-1 system in a splinted and non-splinted full-thickness excisional wound model using HO-1-luc transgenic mice. Effects of splinting on wound closure, HO-1 promoter activity, and markers of inflammation and fibrosis were assessed. After seven days, splinted wounds were more than three times larger than non-splinted wounds, demonstrating a delay in wound closure. HO-1 promoter activity rapidly decreased following removal of the (epi)dermis, but was induced in both splinted and non-splinted wounds during skin repair. Splinting induced more HO-1 gene expression in 7-day wounds; however, HO-1 protein expression remained lower in the epidermis, likely due to lower numbers of keratinocytes in the re-epithelialization tissue. Higher numbers of F4/80-positive macrophages, αSMA-positive myofibroblasts, and increased levels of the inflammatory genes IL-1β, TNF-α, and COX-2 were present in 7-day splinted wounds. Surprisingly, mRNA expression of newly formed collagen (type III) was lower in 7-day wounds after splinting, whereas, VEGF and MMP-9 were increased. In summary, these data demonstrate that splinting delays cutaneous wound closure and HO-1 protein induction. The pro-inflammatory environment following splinting may facilitate higher myofibroblast numbers and increase the risk of fibrosis and scar formation. Therefore, inducing HO-1 activity against mechanical stress-induced inflammation and fibrosis may be an interesting strategy to prevent negative effects of surgery on growth and function in patients with orofacial clefts or in patients with burns.
authors.affiliation: Department of Orthodontics and Craniofacial Biology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , Netherlands ; Experimental Rheumatology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , Netherlands.
authors.forename: Niels A J
authors.initials: NA
authors.lastname: Cremers
authors.affiliation: Department of Orthodontics and Craniofacial Biology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , Netherlands.
authors.forename: Maarten
authors.initials: M
authors.lastname: Suttorp
authors.affiliation: Department of Orthodontics and Craniofacial Biology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , Netherlands.
authors.forename: Marlous M
authors.initials: MM
authors.lastname: Gerritsen
authors.affiliation: Department of Pediatrics, Stanford University School of Medicine , Stanford, CA , USA.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Wong
authors.affiliation: Department of Orthodontics and Craniofacial Biology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , Netherlands.
authors.forename: Coby
authors.initials: C
authors.lastname: van Run-van Breda
authors.affiliation: Department of Surgery, University Medical Center Groningen , Groningen , Netherlands.
authors.forename: Gooitzen M
authors.initials: GM
authors.lastname: van Dam
authors.affiliation: Department of Plastic, Reconstructive and Hand Surgery, VU University Medical Center, MOVE Research Institute Amsterdam , Amsterdam , Netherlands ; Association of Dutch Burn Centers , Beverwijk , Netherlands.
authors.forename: Katrien M
authors.initials: KM
authors.lastname: Brouwer
authors.affiliation: Department of Orthodontics and Craniofacial Biology, Cleft Palate Craniofacial Center, Radboud University Medical Center , Nijmegen , Netherlands.
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Kuijpers-Jagtman
authors.affiliation: Department of Orthodontics and Craniofacial Biology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , Netherlands.
authors.forename: Carine E L
authors.initials: CE
authors.lastname: Carels
authors.affiliation: Department of Orthodontics and Craniofacial Biology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , Netherlands.
authors.forename: Ditte M S
authors.initials: DM
authors.lastname: Lundvig
authors.affiliation: Department of Orthodontics and Craniofacial Biology, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences , Nijmegen , Netherlands.
authors.forename: Frank A D T G
authors.initials: FA
authors.lastname: Wagener
keywords: burns; cleft palate; fibrosis; heme oxygenase-1; inflammation; mechanical stress; wound healing