title: Impaired TGF-β signaling and a defect in resolution of inflammation contribute to delayed wound healing in a female rat model of type 2 diabetes.
abstract: Wound healing (WH) impairment is a well-documented phenomenon in clinical and experimental diabetes. Sex hormones, in addition to a number of signaling pathways including transforming growth factor-β1 (TGF-β1)/Smads and TNF-α/NF-κB in macrophages and fibroblasts, appear to play a cardinal role in determining the rate and nature of WH. We hypothesized that a defect in resolution of inflammation and an enhancement in TNF-α/NF-κB activity induced by estrogen deficiency contribute to the impairment of TGF-β signaling and delayed WH in diabetes models. Goto-Kakizaki (GK) rats and full thickness excisional wounds were used as models for type 2 diabetes (T2D) and WH, respectively. Parameters related to the various stages of WH were assessed using histomorphometry, western blotting, real-time PCR, immunofluorescence microscopy and ELISA-based assays. Retarded re-epithelialization, suppressed angiogenesis, delayed wound closure, reduced estrogen level and heightened states of oxidative stress were characteristic features of T2D wounds. These abnormalities were associated with a defect in resolution of inflammation, shifts in macrophage phenotypes, increased β3-integrin expression, impaired wound TGF-β1 signaling (↓p-Smad2/↑Smad7) and enhanced TNF-α/NFκB activity. Human/rat dermal fibroblasts of T2D, compared to corresponding control values, displayed resistance to TGF-β-mediated responses including cell migration, myofibroblast formation and p-Smad2 generation. A pegylated form of soluble TNF receptor-1 (PEG-sTNF-RI) or estrogen replacement therapy significantly improved re-epithelialization and wound contraction, enhanced TGFβ/Smad signaling, and polarized the differentiation of macrophages toward an M2 or "alternatively" activated phenotype, while limiting secondary inflammatory-mediated injury. Our data suggest that reduced estrogen levels and enhanced TNF-α/NF-κB activity delayed WH in T2D by attenuating TGFβ/Smad signaling and impairing the resolution of inflammation; most of these defects were ameliorated with estrogen and/or PEG-sTNF-RI therapy.
authors.affiliation: Department of Pathology, University of Kuwait, Faculty of Medicine, Health Sciences Center, 13110, Kuwait. fahd@al-mulla.org
authors.forename: Fahd
authors.initials: F
authors.lastname: Al-Mulla
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Leibovich
authors.forename: Issam M
authors.initials: IM
authors.lastname: Francis
authors.forename: Milad S
authors.initials: MS
authors.lastname: Bitar
mesh_terms: D000818:Animals; D002460:Cell Line; D002465:Cell Movement; D003924:Diabetes Mellitus, Type 2 / Q000276:immunology* / Q000378:metabolism / Q000503:physiopathology*; D004967:Estrogens / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000473:pathology / Q000502:physiology; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D008264:Macrophages / Q000473:pathology; D016328:NF-kappa B / Q000502:physiology; D018384:Oxidative Stress; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D012867:Skin / Q000166:cytology; D051899:Smad2 Protein / Q000378:metabolism; D051906:Smad7 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D014945:Wound Healing
chemical_list: D004967:Estrogens; D016328:NF-kappa B; D051899:Smad2 Protein; D051906:Smad7 Protein; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha