title: Differential expression of transforming growth factor-beta receptors I and II and activation of Smad 3 in keloid fibroblasts.
abstract: Keloids represent a dysregulated response to cutaneous wounding that results in an excessive deposition of extracellular matrix, especially collagen. However, the molecular mechanisms regulating this pathologic collagen deposition still remain to be elucidated. A previous study by this group demonstrated that transforming growth factor (TGF)-beta1 and -beta2 ligands were expressed at greater levels in keloid fibroblasts when compared with normal human dermal fibroblasts (NHDFs), suggesting that TGF-beta may play a fibrosis-promoting role in keloid pathogenesis.To explore the biomolecular mechanisms of TGF-beta in keloid formation, the authors first compared the expression levels of the type I and type II TGF-beta receptors in keloid fibroblasts and NHDFs. Next, they investigated the phosphorylation of Smad 3, an intracellular TGF-beta signaling molecule, in keloid fibroblasts and NHDFs. Finally, they examined the regulation of TGF-beta receptor II by TGF-beta1, TGF-beta2, and TGF-beta3 ligands. Our findings demonstrated an increased expression of TGF-beta receptors (types I and II) and increased phosphorylation of Smad 3 in keloid fibroblasts relative to NHDFs. These data support a possible role of TGF-beta and its receptors as fibrosis-inducing growth factors in keloids. In addition, all three isoforms of recombinant human TGF-beta proteins could further stimulate the expression of TGF-beta receptor II in both keloids and NHDFs. Taken together, these results substantiate the hypothesis that the elevated levels of TGF-beta ligands and receptors present in keloids may support increased signaling and a potential role for TGF-beta in keloid pathogenesis.
authors.affiliation: Children's Surgical Research Program, Department of Surgery, Stanford University School of Medicine, Stanford, CA 94305-5148, USA.
authors.forename: G S
authors.initials: GS
authors.lastname: Chin
authors.forename: W
authors.initials: W
authors.lastname: Liu
authors.forename: Z
authors.initials: Z
authors.lastname: Peled
authors.forename: T Y
authors.initials: TY
authors.lastname: Lee
authors.forename: D S
authors.initials: DS
authors.lastname: Steinbrech
authors.forename: M
authors.initials: M
authors.lastname: Hsu
authors.forename: M T
authors.initials: MT
authors.lastname: Longaker
mesh_terms: D030201:Activin Receptors, Type I; D000293:Adolescent; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D007627:Keloid / Q000378:metabolism* / Q000473:pathology; D008875:Middle Aged; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction; D012867:Skin / Q000166:cytology; D051900:Smad3 Protein; D015534:Trans-Activators / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D004268:DNA-Binding Proteins; D018125:Receptors, Transforming Growth Factor beta; D011994:Recombinant Proteins; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II