Keijiro Hori

Toll-like receptors expressed by dermal fibroblasts contribute to hypertrophic scarring.

Hypertrophic scar (HTS), a fibroproliferative disorder (FPD), complicates burn wound healing. Although the pathogenesis is not understood, prolonged inflammation is a known contributing factor. Emerging evidence suggests that fibroblasts regulate immune/inflammatory responses through toll‐like receptor 4 (TLR4) activated by lipopolysaccharide (LPS) through adaptor molecules, leading to nuclear factor kappa‐light‐chain‐enhancer of activated B cells and mitogen‐activated protein kinases activation, cytokine gene transcription and co‐stimulatory molecule expression resulting in inflammation. This study explored the possible role of TLR4 in HTS formation. Paired normal and HTS tissue from burn patients was collected and dermal fibroblasts isolated and cultured. Immunohistochemical analysis of tissues demonstrated increased TLR4 staining in HTS tissue. Quantitative RT‐PCR of three pairs of fibroblasts demonstrated mRNA levels for TLR4 and its legend myeloid differentiation factor 88 (MyD88) in HTS fibroblasts were increased significantly compared with normal fibroblasts. Flow cytometry showed increased TLR4 expression in HTS fibroblasts compared with normal. ELISA demonstrated protein levels for prostaglandin E2, interleukin (IL)‐6, IL‐8 and monocyte chemotactic protein‐1 (MCP‐1) were significantly increased in HTS fibroblasts compared to normal. When paired normal and HTS fibroblasts were stimulated with LPS, significant increases in mRNA and protein levels for MyD88, IL‐6, IL‐8, and MCP‐1 were detected. However, when transfected with MyD88 small interfering RNA (siRNA), then stimulated with LPS, a significant decrease in mRNA and protein levels for these molecules compared to only LPS‐stimulated fibroblasts was detected. In comparison, a scramble siRNA transfection did not affect mRNA or protein levels for these molecules. Results demonstrate LPS stimulates proinflammatory cytokine expression in dermal fibroblasts and MyD88 siRNA eliminates the expression. Therefore, controlling inflammation and manipulating TLR signaling in skin cells may result in novel treatment strategies for HTS and other FPD. J. Cell. Physiol. 226: 1265–1273, 2011.

Bladder outlet obstruction: progression from inflammation to fibrosis

Study Type – Aetiology (case control)
Level of Evidence 3b

Scar and Contracture: Biological Principles

Dysregulated wound healing and pathologic fibrosis cause abnormal scarring, leading to poor functional and aesthetic results in hand burns. Understanding the underlying biologic mechanisms involved allows the hand surgeon to better address these issues, and suggests new avenues of research to improve patient outcomes. In this article, the authors review the biology of scar and contracture by focusing on potential causes of abnormal wound healing, including depth of injury, cytokines, cells, the immune system, and extracellular matrix, and explore therapeutic measures designed to target the various biologic causes of poor scar.

Small leucine-rich proteoglycans, decorin and fibromodulin, are reduced in postburn hypertrophic scar.

Small leucine‐rich proteoglycans (SLRPs) are extracellular matrix molecules that regulate collagen fibrillogenesis and inhibit transforming growth factor‐β activity; thus, they may play a critical role in wound healing and scar formation. Hypertrophic scarring is a dermal form of fibroproliferative disorders, which occurs in over 70% of burn patients and leads to disfigurement and limitations in function. By understanding the cellular and molecular mechanisms that lead to scarring after injury, new clinical therapeutic approaches can by developed to minimize abnormal scar formation in hypertrophic scarring and other fibroproliferative disorders. To study the expression and localization of SLRPs with connective tissue cells in tissue immunohistochemistry, immunofluorescence staining, immunoblotting, and reverse‐transcription polymerase chain reaction were used in normal skin and hypertrophic scar (HTS). In normal skin, there was more decorin and fibromodulin accumulation in the superficial layers than in the deeper dermal layers. The levels of decorin and fibromodulin were significantly lower in HTS, whereas biglycan was increased when compared with normal skin. There was an increased expression of biglycan, fibromodulin, and lumican in the basement membrane and around basal epithelial cells. In contrast, these proteoglycans were absent or weakly expressed in HTS. The findings suggest that down‐regulation of SLRPs after wound healing in deep injuries to the skin plays an important role in the development of fibrosis and HTS.

Stromal cell-derived factor 1 (SDF-1) and its receptor CXCR4 in the formation of postburn hypertrophic scar (HTS).

Recent data support the involvement of stromal cell‐derived factor 1 (SDF‐1) in the homing of bone marrow‐derived stem cells to wound sites during skeletal, myocardial, vascular, lung, and skin wound repair as well as some fibrotic disorders via its receptor CXCR4. In this study, the role of SDF‐1/CXCR4 signaling in the formation of hypertrophic scar (HTS) following burn injury and after treatment with systemic interferon α2b (IFNα2b) is investigated. Studies show SDF‐1/CXCR4 signaling was up‐regulated in burn patients, including SDF‐1 level in HTS tissue and serum as well as CD14+CXCR4+ cells in the peripheral blood mononuclear cells. In vitro, dermal fibroblasts constitutively expressed SDF‐1 and deep dermal fibroblasts expressed more SDF‐1 than superficial fibroblasts. Lipopolysaccharide increased SDF‐1 gene expression in fibroblasts. Also, recombinant SDF‐1 and lipopolysaccharide stimulated fibroblast‐conditioned medium up‐regulated peripheral blood mononuclear cell mobility. In the burn patients with HTS who received subcutaneous IFNα2b treatment, increased SDF‐1/CXCR4 signaling was found prior to treatment which was down‐regulated after IFNα2b administration, coincident with enhanced remodeling of their HTS. Our results suggest that SDF‐1/CXCR4 signaling is involved in the development of HTS by promoting migration of activated CD14+CXCR4+ cells from the bloodstream to wound sites, where they may differentiate into fibrocyte and myofibroblasts and contribute to the development of HTS.

The use of laser Doppler imaging as a predictor of burn depth and hypertrophic scar postburn injury.

Hypertrophic scarring (HTS) is a fibroproliferative disorder that commonly develops after severe burn injuries. Overexpression of transforming growth factor-&bgr; (TGF-&bgr;) by an increased number of fibrocytes has been associated with increased extracellular matrix molecule expression leading to HTS. The most widely accepted adjuvant to clinical assessment of burn depth is laser Doppler imaging (LDI) and may predict injury to the dermis that corresponds to cellular and molecular changes associated with HTS. A prospective, blinded, control trial was performed comparing LDI and clinical assessment for the decision to operate. Immunohistochemistry and real-time reverse transcription polymerase chain reaction was performed to determine whether there is a correlation between histological assessment of burn depth and LDI, and the presence of fibrocytes was detected using confocal microscopy. The positive predictive value for a burn requiring a graft was calculated to be >90%. Immunohistochemistry on biopsy samples revealed an increased expression of TGF-&bgr;, connective tissue growth factor, heat shock protein 47, and collagen type I in deep burn wounds compared to superficial burns. Using the fibrocyte-specific markers procollagen type I and lymphocyte-specific protein-1, there was an increased number of fibrocytes in deep burn areas compared to superficial burn. In deep burn injuries, increased infiltration of fibrocytes occurs leading to an overexpression of TGF-&bgr;1 and connective tissue growth factor. More importantly, LDI was >90% accurate at predicting the need for excision and grafting. The accuracy of the decision to debride deep dermal burns to avoid HTS using both clinical parameters and LDI was supported by histological and biochemical measurements.

Impaired cutaneous wound healing in transforming growth factor‐β inducible early gene1 knockout mice

Transforming growth factor‐β inducible early gene (TIEG) is induced by transforming growth factor‐β (TGF‐β) and acts as the primary response gene in the TGF‐β/Smad pathway. TGF‐β is a multifunctional growth factor that affects dermal wound healing; however, the mechanism of how TGF‐β affects wound healing is still not well understood because of the complexity of its function and signaling pathways. We hypothesize that TIEG may play a role in dermal wound healing, with involvement in wound closure, contraction, and reepithelialization. In this study, we have shown that TIEG1 knockout (TIEG1–/–) mice have a delay in wound closure related to an impairment in wound contraction, granulation tissue formation, collagen synthesis, and reepithelialization. We also found that Smad7 was increased in the wounds and appeared to play a role in this wound healing model in TIEG1–/– mice.

Treatment of facial angiofibroma of tuberous sclerosis using cultured epithelial autografts

Treatment of facial angiofibroma of tuberous sclerosis is problematic, because the skin lesions involve entire dermis. Five patients aged from 14 to 33 (mean: 23.6) years old with angiofibroma of tuberous sclerosis were treated with cultured epithelial autografts between 1995 and 2004. The entire area of the facial lesions was excised using a razor to remove large nodules, and then the remaining lesions were further abraded to a rather deep layer of the dermis to smooth the skin and remove small nodules. Then a cultured autologous epithelium was grafted onto the wound. In all patients, epithelization was complete within 10 (mean: 9) days after the surgery. All patients were followed up for more than 6 months and showed neither depigmentation due to scar formation nor hypertrophic scars. In some patients, some pebbly regrowth had occurred at 5 years postoperatively, but the appearance was quite acceptable.

Comparison of contraction among three dermal substitutes: Morphological differences in scaffolds

Various kinds of synthetic dermal substitutes are produced and used in clinical application and contribute to wound bed preparation for subsequent skin grafting. Although their appearance and outcomes are different, the criteria for the selection of proper synthetic dermal substitutes is not well defined yet. In this study, we focused on the contraction of dermal substitutes and compared the morphological differences in scaffolds. A marked contraction was observed with Pelnac® compared to Integra® and Terudermis® in vitro. We also showed that the pore size of Pelnac® was smaller than that of Integra® and Terudermis®. The shape of the pore was oval in Pelnac®, whereas those in Integra® and Terudermis® were more circular. Differences in the morphological structure may have affected the contraction of the synthetic dermal substitutes.