A novel subpopulation of peripheral blood mononuclear cells presents in major burn patients.

Hypertrophic scars (HTS) are generally believed to result from proliferation and activation of resident connective tissue fibroblasts after burns. To demonstrate a potential role of blood-borne cells, the peripheral blood mononuclear cells (PBMCs) and the effect of PBMCs on dermal fibroblast behavior was investigated. Flow cytometry was used to analyze the surface and intracellular protein expression of PBMCs and fibroblasts. Transwell migration assay, enzyme-linked immunosorbent assay and real-time reverse transcription polymerase chain reaction was performed to assess fibroblast functions. We identified a novel subpopulation of PBMCs in burn patients in vivo that appears at an early stage following major thermal injuries, which primarily express procollagen 1, leukocyte specific protein 1, CD204, toll-like receptor 4 and stromal cell-derived factor 1 (SDF-1) receptor CXCR4. In vitro, the conditioned media from burn patient PBMCs up-regulated the expression of fibrotic growth factors and extracellular matrix molecules, down-regulated antifibrotic factor decorin, enhanced cell chemotaxis and promoted cell differentiation into contractile myofibroblasts in dermal fibroblasts. After thermal injury, this novel subpopulation of PBMCs is systemically triggered and attracted to the wounds under SDF-1/CXCR4 signaling where they appear to modulate the functions of resident connective tissue cells and thus contribute to the development of HTS.

The therapeutic potential of a C-X-C chemokine receptor type 4 (CXCR-4) antagonist on hypertrophic scarring in vivo.

Effective prevention and treatment of hypertrophic scars (HTSs), a dermal form of fibrosis that frequently occurs following thermal injury to deep dermis, are unsolved significant clinical problems. Previously, we have found that stromal cell-derived factor 1/CXCR4 signaling is up-regulated during wound healing in burn patients and HTS tissue after thermal injury. We hypothesize that blood-borne mononuclear cells are recruited into wound sites after burn injury through the chemokine pathway of stromal cell-derived factor 1 and its receptor CXCR4. Deep dermal injuries to the skin are often accompanied by prolonged inflammation, which leads to chemotaxis of mononuclear cells into the wounds by chemokine signaling where fibroblast activation occurs and ultimately HTS are formed. Blocking mononuclear cell recruitment and fibroblast activation, CXCR4 antagonism is expected to reduce or minimize scar formation. In this study, the inhibitory effect of CXCR4 antagonist CTCE-9908 on dermal fibrosis was determined in vivo using a human HTS-like nude mouse model, in which split-thickness human skin is transplanted into full-thickness dorsal excisional wounds in athymic mice, where these wounds subsequently develop fibrotic scars that resemble human HTS as previously described. CTCE-9908 significantly attenuated scar formation and contraction, reduced the accumulation of macrophages and myofibroblasts, enhanced the remodeling of collagen fibers, and down-regulated the gene and protein expression of fibrotic growth factors in the human skin tissues. These findings support the potential therapeutic value of CXCR4 antagonist in dermal fibrosis and possibly other fibroproliferative disorders.

Characterization of heterotopic ossification in burn patients.

Heterotopic ossification (HO) is a clinical condition of ectopic bone formation in soft tissue. This clinical entity has been associated with genetic disorders, traumatic injuries, and musculoskeletal surgeries. In this regard, functional impairments secondary to scar contractures seen in burn injuries may be exacerbated with underlying HO. The appropriate prevention or management of this complication is crucial to optimize outcome in burn patients. This clinical study reviews the incidence of HO in our burned patients, diagnostic methods, therapeutic approaches including surgical timing and techniques.

Deep dermal fibroblast profibrotic characteristics are enhanced by bone marrow-derived mesenchymal stem cells.

Hypertrophic scars are a significant fibroproliferative disorder complicating deep injuries to the skin. We hypothesize that activated deep dermal fibroblasts are subject to regulation by bone marrow-derived mesenchymal stem cells (BM-MSCs), which leads to the development of excessive fibrosis following deep dermal injury. We found that the expression of fibrotic factors was higher in deep burn wounds compared with superficial burn wounds collected from burn patients with varying depth of skin injury. We characterized deep and superficial dermal fibroblasts, which were cultured from the deep and superficial dermal layers of normal uninjured skin obtained from abdominoplasty patients, and examined the paracrine effects of BM-MSCs on the fibrotic activities of the cells. In vitro, deep dermal fibroblasts were found higher in the messenger RNA (mRNA) levels of type 1 collagen, alpha smooth muscle actin, transforming growth factor beta, stromal cell-derived factor 1, and tissue inhibitor of metalloproteinase 1, an inhibitor of collagenase (matrix metalloproteinase 1). As well, deep dermal fibroblasts had low matrix metalloproteinase 1 mRNA, produced more collagen, and contracted collagen lattices significantly greater than superficial fibroblasts. By co-culturing layered fibroblasts with BM-MSCs in a transwell insert system, BM-MSCs enhanced the fibrotic behavior of deep dermal fibroblasts, which suggests a possible involvement of BM-MSCs in the pathogenesis of hypertrophic scarring.

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-ß (TGF-ß) 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-ß, 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-ß1 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.

Human hypertrophic scar-like nude mouse model: characterization of the molecular and cellular biology of the scar process.

Hypertrophic scar (HTS) following thermal injury and other forms of trauma is a dermal fibroproliferative disorder that leads to considerable morbidity. Because of the lack of an ideal animal model, research is difficult. We have established an HTS model that involves transplanting human split-thickness skin graft (STSG) or full-thickness skin graft (FTSG) onto the backs of nude mice. The animals developed raised, firm, and reddish scars 2 months following transplantation. Histology and micromeasurement indicate raised, thickened engrafted skin with STSG and FTSG. In contrast, thickening was not observed with full-thickness rat skin grafts used as controls. Masson's trichrome staining demonstrates increased accumulations of collagen fibrils in the dermis in both scars grafted with STSG and FTSG. Staining cells with toludine blue and an antibody for F4/80 showed an increase in the infiltration of mast cells and macrophages. Quantification of fibrocytes reveals increased fibrocytes. Moreover, STSG grafted skin had significantly more macrophages, mast cells, and fibrocytes than FTSG. Real-time polymerase chain reaction analysis showed significantly elevated mRNA levels for type I collagen, transforming growth factor-ß, connective tissue growth factor and heat shock protein 47 in both types of engrafted skin. These data demonstrate that human skin grafted onto nude mice develops red raised and thickened scars having intrinsic properties that closely resemble HTS formation as seen in humans. Interestingly, STSG developed more scar than FTSG. Furthermore, inflammatory cells and bone marrow-derived fibrocytes may play a critical role in HTS development in this animal model.

Improved scar in postburn patients following interferon-alpha2b treatment is associated with decreased angiogenesis mediated by vascular endothelial cell growth factor.

Hypertrophic scar (HTS) after thermal injury is a dermal fibroproliferative disorder, which leads to considerable morbidity. Previous clinical studies from our laboratory have suggested that interferon-alpha2b (IFN-alpha2b) improves scar quality as a result of the suppression of fibroblast function. More recently, our work has demonstrated that the improvement of scar in patients with HTS after IFN-alpha2b treatment may be associated with a decreased number of fibrocytes and/or altered fibrocyte function. In this study, we report that the improvement of HTS after IFNalpha-2b treatment may be associated with a decrease in angiogenesis. Using immunohistochemistry, we demonstrate an increase in angiogenesis in HTS compared to normal skin, and also show an increase in the expression of vascular endothelial cell growth factor (VEGF) in HTS. Subsequently, we demonstrate a significant reduction in angiogenesis in HTS tissue from patients after treatment with systemic IFN-alpha2b. By using a [3H] thymidine incorporation assay, we demonstrate that IFN-alpha2b suppresses the proliferation of human umbilical vein endothelial cells (HUVECs) in a dose-dependent manner. In addition, IFN-alpha2b inhibits VEGF-induced proliferation and tube formation by using HUVECs. All these effects may be a result of the blocking of VEGF receptor expression on endothelial cells by IFN-alpha2b. Taken together with previous results, the present study suggests that the improvement of scar quality in HTS patients after IFN-alpha2b treatment may also be associated with decreased angiogenesis in HTS. The current in vitro results may provide some insights into the scar improvement that is seen with systemic IFN-alpha2b treatment.

Increased severity of bleomycin-induced skin fibrosis in mice with leukocyte-specific protein 1 deficiency.

Fibrosis is a complex process resulting from persistent inflammation following tissue damage. It involves the interaction of numerous cell types, soluble mediators, and extracellular matrix. Recently, a newly identified cell type, the fibrocyte, has been reported to contribute to wound healing and to fibrotic conditions such as hypertrophic scarring. Previously, we established leukocyte-specific protein 1 (LSP1) as a new marker for fibrocytes. In the present study, we examined the biological role of LSP1 in the development of skin fibrosis using bleomycin in an Lsp1(-/-) mice. These animals showed a significant increase in fibrosis, with increased thickness of the skin and collagen content. The skin in Lsp1(-/-) mice injected with bleomycin had higher densities of neutrophils, macrophages, and fibrocytes. In accordance with the increased leukocyte infiltration, the expression levels of macrophage-derived chemokines, transforming growth factor-beta1, and connective tissue growth factor were all upregulated in Lsp1(-/-) mice. These results demonstrate that the absence of LSP1 promotes fibrosis in the skin. The most likely mechanism for this effect seems to be through an increase in leukocyte infiltration, leading to locally elevated synthesis and the release of chemokines and growth factors.

Accelerated wound healing in leukocyte-specific, protein 1-deficient mouse is associated with increased infiltration of leukocytes and fibrocytes.

Wound healing is a complex process involving the integrated actions of numerous cell types, soluble mediators, and ECM. Recently, a newly identified cell type, the fibrocyte, has been reported to contribute to wound healing and fibrotic conditions such as hypertrophic scarring. We previously established leukocyte-specific protein 1 (LSP1) as a marker for fibrocytes. LSP1 is an F-actin binding protein and substrate of p38 mitogen-activated protein kinase and protein kinase C, and has been reported to be important in leukocyte chemotaxis. We examine the biological roles of LSP1 in skin wound healing using Lsp1(-/-) null mice. These animals showed accelerated healing of full-thickness skin wounds, with increased re-epithelialization rates, collagen synthesis, and angiogenesis. Healing wounds in Lsp1(-/-) mice had higher densities of neutrophiles, macrophages, and fibrocytes. Along with increased leukocyte infiltration, levels of macrophage-derived chemokine expression, TGF-beta1, and VEGF were all up-regulated. These results demonstrate that the absence of LSP1 promotes healing of skin wounds. The primary mechanism seems to be an increase in leukocyte infiltration, leading to locally elevated synthesis and release of chemokines and growth factors. Further analysis of Lsp1(-/-) mice may suggest ways to improve wound healing and/or treat fibrotic conditions of skin and other tissue.

Quality-of-life and outcome predictors following massive burn injury.

BACKGROUND: Quality of life is a major criterion when decisions regarding resuscitation, reconstruction, and rehabilitation of patients with massive burn injuries are being considered. There has been little research focusing on quality of life following burn injuries involving more than 50 percent total body surface area in the adult population. The authors' goals were to describe quality of life and identify specific clinical and functional indices that predict good quality of life following massive burn injuries. METHODS: Using a prospective study design, 47 patients who survived a massive burn between 1980 and 2001 were recruited from a single burn unit. Clinical data were collected from hospital records, function was assessed using the Abbreviated Burn-Specific Health Scale, and quality of life was assessed using the Short Form-36 survey. The Short Form-36 scores were compared with population norms. Univariate and multivariate regression analyses were used to identify factors predicting Short Form-36 scores. RESULTS: Overall, the mean age was 28 +/- 1.8 years, 96 percent (45 of 47) were men, and the mean burn size was 64 +/- 2.1 percent total body surface area. Compared with Canadian population norms, burn patients had significantly lower Short Form-36 scores in the domains of role physical (69.1 versus 82.1, p = 0.0067) and general health perception (67.2 versus 77.0, p = 0.00014). At the time of injury, the amount of total full-thickness burn predicted follow-up Short Form-36 physical summary scores (R2 = 15 percent, p < 0.001). At the time of follow-up, addition of the patient's hand function significantly contributed to the prediction of Short Form-36 physical summary scores (R2 = 44 percent, p < 0.001). At the time of injury, the age of the patient predicted follow-up Short Form-36 mental summary scores (R2 = 25 percent, p < 0.001). At the time of follow-up, addition of the patient's perceived level of social support significantly contributed to the prediction of Short Form-36 mental summary scores (R2 = 44 percent, p < 0.001). CONCLUSIONS: Survivors of massive burn injury reported a good quality of life in most Short Form-36 domains. The authors identified the size of the total full-thickness injury and the age of the patient as factors available at the time of injury that predict quality of life. The addition of hand function and the patient's perceived level of social support at the time of follow-up improved prediction of quality of life. Accordingly, this information on quality of life after massive burn injury could aid in decision making at the time of resuscitation, reconstruction, and rehabilitation.