The pathogenesis of hypertrophic/keloid scarring

Light emitting diode-red light for reduction of post-surgical scarring: Results from a dose-ranging, split-face, randomized controlled trial

Scarring has significant esthetic and functional consequences for patients. A need exists for anti-scarring therapeutics. Light emitting diode-red light (LED-RL) has been shown to modulate skin fibrosis. The aim of this study is to evaluate the safety and efficacy of LED-RL to reduce post-operative scarring. Cutaneous Understanding of Red-light Efficacy on Scarring was a randomized, mock-controlled, single-blind, dose-ranging, split-face phase II clinical trial. Starting 1 week post-surgery, patients received LED-RL irradiation and temperature-controlled mock therapy to incision sites at fluences of 160, 320 or 480 J/cm2 , triweekly for 3 weeks. Efficacy was assessed at 1, 3 and 6-12 months. The primary endpoint was difference in scar pliability between LED-RL-treated and control sites. Secondary outcomes included Patient and Observer Scar Assessment Scale, collagen and water concentration, and adverse events. There were no significant differences in scar pliability between treated and control scars. At certain fluences, treated scars showed greater improvements in observer rating and scar pliability, reflected by greater reductions in induration, from baseline to 6 months compared to control scars. Treatment-site adverse events included blistering (n = 2) and swelling (n = 1), which were mild and resolved without sequelae. LED-RL phototherapy is safe in the early postoperative period and may reduce scarring.

Hypertrophic scars and keloids: Overview of the evidence and practical guide for differentiating between these abnormal scars

Although hypertrophic scars and keloids both generate excessive scar tissue, keloids are characterized by their extensive growth beyond the borders of the original wound, which is not observed in hypertrophic scars. Whether or not hypertrophic scars and keloids are two sides of the same coin or in fact distinct entities remains a topic of much debate. However, proper comparison between the two ideally occurs within the same study, but this is the exception rather than the rule. For this reason, the goal of this review was to summarize and evaluate all publications in which both hypertrophic scars and keloids were studied and compared to one another within the same study. The presence of horizontal growth is the mainstay of the keloid diagnosis and remains the strongest argument in support of keloids and hypertrophic scars being distinct entities, and the histopathological distinction is less straightforward. Keloidal collagen remains the strongest keloid parameter, but dermal nodules and α-SMA immunoreactivity are not limited to hypertrophic scars alone. Ultimately, the current hypertrophic scars-keloid differences are mostly quantitative in nature rather than qualitative, and many similar abnormalities exist in both lesions. Nonetheless, the presence of similarities does not equate the absence of fundamental differences, some of which may not yet have been uncovered given how much we still have to learn about the processes involved in normal wound healing. It therefore seems pertinent to continue treating hypertrophic scars and keloids as separate entities, until such a time as new findings more decisively convinces us otherwise.

A dose-ranging, parallel group, split-face, single-blind phase II study of light emitting diode-red light (LED-RL) for skin scarring prevention: study protocol for a randomized controlled trial

BACKGROUND

Skin fibrosis is a significant global health problem that affects over 100 million people annually and has a profoundly negative impact on quality of life. Characterized by excessive fibroblast proliferation and collagen deposition, skin fibrosis underlies a wide spectrum of dermatologic conditions ranging from pathologic scars secondary to injury (e.g., burns, surgery, trauma) to immune-mediated diseases. Effective anti-scarring therapeutics remain an unmet need, underscoring the importance of developing novel approaches to treat and prevent skin fibrosis. Our in vitro data show that light emitting diode-red light (LED-RL) can modulate key cellular and molecular processes involved in skin fibrosis. In two phase I clinical trials (STARS 1 and STARS 2), we demonstrated the safety and tolerability of LED-RL at fluences of 160 J/cm² up to 480 J/cm² on normal human skin.

METHODS/DESIGN

CURES (Cutaneous Understanding of Red-light Efficacy on Scarring) is a dose-ranging, randomized, parallel group, split-face, single-blind, mock-controlled phase II study to evaluate the efficacy of LED-RL to limit post-surgical skin fibrosis in subjects undergoing elective mini-facelift surgery. Thirty subjects will be randomly allocated to three treatment groups to receive LED-RL phototherapy or temperature-matched mock irradiation (control) to either periauricular incision site at fluences of 160 J/cm², 320 J/cm², or 480 J/cm². Starting one week post-surgery (postoperative days 4-8), treatments will be administered three times weekly for three consecutive weeks, followed by efficacy assessments at 30 days, 3 months, and 6 months. The primary endpoint is the difference in scar pliability between LED-RL-treated and control sites as determined by skin elasticity and induration measurements. Secondary outcomes include clinical and photographic evaluations of scars, 3D skin imaging analysis, histological and molecular analyses, and adverse events.

DISCUSSION

LED-RL is a therapeutic modality of increasing importance in dermatology, and has the potential to limit skin fibrosis clinically by decreasing dermal fibroblast activity and collagen production. The administration of LED-RL phototherapy in the early postoperative period may optimize wound healing and prevent excessive scarring. The results from this study may change the current treatment paradigm for fibrotic skin diseases and help to pioneer LED-RL as a safe, non-invasive, cost-effective, portable, at-home therapy for scars.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03795116 . Registered on 20 December 2018.

Recombinant human endostatin reduces hypertrophic scar formation in rabbit ear model through down-regulation of VEGF and TIMP-1

BACKGROUND

Recombinant human endostatin (Endostar) has been widely used to suppress angiogenesis in carcinoma patients. Hypertrophic scar (HS) tissue, much like a carcinoma, is often associated with angiogenesis. However, there have been few studies conducted on the effects of Endostar on HS or its mechanism.

OBJECTIVE

This paper investigated the effects Endostar on the HS of rabbit ears and studied the effects of Endostar on VEGF and TIMP-1 expression.

METHODS

Sixteen New Zealand white rabbits were used to establish HS models. Then, rabbit ears containing HS were randomly assigned to either the Endostar group or the control group. The changes of appearance and histology were evaluated using the naked eye, hematoxylin eosin staining, and a scar elevation index. The VEGF and TIMP-1 expressions were detected by immunohistochemical staining, RT-PCR, and western blot.

RESULTS

The thickness of the connective tissue in the Endostar group were thinner, the numbers of micro vessels and fibroblasts were fewer, and the collagen fibers were smoother. Moreover, the mRNA and protein expressions of VEGF and TIMP-1 in the Endostar group were significantly lower than those in the control group.

CONCLUSION

The results suggested that Endostar reduced the formation of HS by down-regulation of VEGF and TIMP-1 expressions.

Endostatin inhibits hypertrophic scarring in a rabbit ear model

OBJECTIVE

The present study was designed to use an in vivo rabbit ear scar model to investigate the efficacy of systemic administration of endostatin in inhibiting scar formation.

METHODS

Eight male New Zealand white rabbits were randomly assigned to two groups. Scar model was established by making six full skin defect wounds in each ear. For the intervention group, intraperitoneal injection of endostatin was performed each day after the wound healed (about 15 d post wounding). For the control group, equal volume of saline was injected. Thickness of scars in each group was measured by sliding caliper and the scar microcirculatory perfusion was assessed by laser Doppler flowmetry on Days 15, 21, 28, and 35 post wounding. Rabbits were euthanatized and their scars were harvested for histological and proteomic analyses on Day 35 post wounding.

RESULTS

Macroscopically, scars of the control group were thicker than those of the intervention group. Significant differences between the two groups were observed on Days 21 and 35 (p<0.05). Scar thickness, measured by scar elevation index (SEI) at Day 35 post wounding, was significantly reduced in the intervention group (1.09±0.19) compared with the controls (1.36±0.28). Microvessel density (MVD) observed in the intervention group (1.73±0.94) was significantly lower than that of the control group (5.63±1.78) on Day 35. The distribution of collagen fibers in scars treated with endostatin was relatively regular, while collagen fibers in untreated controls were thicker and showed disordered alignment. Western blot analysis showed that the expressions of type I collagen and Bcl-2 were depressed by injection of endostatin.

CONCLUSIONS

Our results from the rabbit ear hypertrophic scar model indicate that systemic application of endostatin could inhibit local hypertrophic scar formation, possibly through reducing scar vascularization and angiogenesis. Our results indicated that endostatin may promote the apoptosis of endothelial cells and block their release of platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF), thereby controlling collagen production by fibroblasts. Blood vessel-targeted treatment may be a promising strategy for scar therapy.

Mechanosignaling pathways in cutaneous scarring

Mechanotransduction is the process by which physical forces are sensed and converted into biochemical signals that then result in cellular responses. The discovery and development of various molecular pathways involved in this process have revolutionized the fundamental and clinical understanding regarding the formation and progression of cutaneous scars. The aim of this review is to report the recent advances in scar mechanosignaling research. The mechanosignaling pathways that participate in the formation and growth of cutaneous scars can be divided into those whose role in mechanoresponsiveness has been proven (the TGF-β/Smad, integrin, and calcium ion pathways) and those who have a possible but as yet unproven role (such as MAPK and G protein, Wnt/β-catenin, TNF-α/NF-κB, and interleukins). During scar development, these cellular mechanosignaling pathways interact actively with the extracellular matrix. They also crosstalk extensively with the hypoxia, inflammation, and angiogenesis pathways. The elucidation of scar mechanosignaling pathways provides a new platform for understanding scar development. This better understanding will facilitate research into this promising field and may help to promote the development of pharmacological interventions that could ultimately prevent, reduce, or even reverse scar formation or progression.

Extracellular matrix molecules implicated in hypertrophic and keloid scarring

Tissue regeneration repairs the fabric of the skin to maintain homeostasis after injury. The expression and proliferation of extracellular matrix (ECM) molecules in the dermis, mediated by a range of growth factors and cytokines, is a fundamental element of wound repair. Previous work focused on how these complex molecular mechanisms relate to the formation of raised dermal scars, including keloid and hypertrophic scars, characterized by excessive deposition of ECM molecules. However, the mechanisms in the wound repair pathway which lead to the differential expression and organization of ECM molecules observed in different types of scar tissue are not fully understood. To summarize what is known about the expression and composition of ECM molecules in abnormal scarring, an extensive search of the literature was conducted, focusing on keywords connected to skin scarring, hypertrophic scars and keloid disease. The transcription and translation of collagen I and III, fibronectin, laminin, periostin and tenascin are all increased in raised dermal scar tissue. However, hyaluronic acid, dermatopontin and decorin are decreased, and the expression and localisation of fibrillin and elastin fibres in the dermis are altered compared with normal skin and scars. Recent whole genome profiling and proteomic studies have led to the identification of regulatory elements with different expression profiles in hypertrophic and keloid tissue. If the mechanisms of raised dermal scar formation are to be elucidated and effective therapeutic treatments developed, an integrated approach to research is required, focussing on the interactions between ECM molecules, regulatory elements and pathways.

The evidence for the role of transforming growth factor-beta in the formation of abnormal scarring

The complex biological and physiological mechanisms that result in poor quality scarring are still not fully understood. This review looks at current evidence of the role of transforming growth factor-beta (TGFβ) in this pathological process.

Suppression of TGF-β1/SMAD pathway and extracellular matrix production in primary keloid fibroblasts by curcuminoids: its potential therapeutic use in the chemoprevention of keloid

Keloid is a fibrotic disease characterized by abnormal accumulation of extracellular matrix (ECM) in the dermis. It is a late spreading skin overgrowth and may be considered a plastic surgeon's nightmare. In nature, curcuminoid is composed of curcumin, demethoxycurcumin (DMC) and bisdemethoxycurcumin (bDMC). Curcuminoids have been found to inhibit fibrosis. However, their role in the synthesis of ECM in the keloid fibroblasts (KFs) has remained unclear. In this series of studies, a total of seven primary KFs cultures were used as the KFs model for investigating the inhibitory effect of curcuminoids on the expression of ECM and TGF-β1. A sensitive and reproducible HPLC method was developed to provide a quantitative analysis on the cellular uptake of curcuminoids onto the KF cells. The level of ECM in the primary KFs was elevated. The elevation of ECM and TGF-β1/p-SMAD-2 level was substantially blocked by the cellular uptake of curcumin in a dose-dependent manner in all the seven primary KFs. The results have led to the conclusion that the excessive production of ECM in the KF cells could be blocked and/or rapidly decreased by curcumin.

Molecular dissection of abnormal wound healing processes resulting in keloid disease

Keloids are locally aggressive scars that typically invade into healthy surrounding skin and cause both physical and psychosocial distress to the patient. These pathological scars occur following minimal skin trauma after a variety of causes including burns and trauma. Although the pathogenesis of keloid disease is not well understood, it is considered to be the end product of an abnormal healing process. The aim of this review was to investigate the molecular and cellular pathobiology of keloid disease in relation to the normal wound healing process. The molecular aberrances in keloids that correlate with the molecular mechanisms in normal wound healing can be categorized into three groups: (1) extracellular matrix proteins and their degradation, (2) cytokines and growth factors, and (3) apoptotic pathways. With respect to cellular involvements, fibroblasts are the most well-studied cell population. However, it is unclear whether the fibroblast is the causative cell; they are modulated by other cell populations in wound repair, such as keratinocytes and macrophages. This review presents a detailed account of individual phases of the healing process and how they may potentially be implicated in aberrant raised scar formation, which may help in clarifying the mechanisms involved in keloid disease pathogenesis.

Adenovirus-mediated METH1 gene expression inhibits hypertrophic scarring in a rabbit ear model

Hypertrophic scarring remains a major problem for patients who have suffered from surgeries or burns. Vascularization plays an important role in the early phase of hypertrophic scarring. Therefore, the inhibition of angiogenesis might be used as a preventive strategy. In this study, we assessed the effect of anti-angiogenesis resulting from adenovirus-mediated METH1 (metalloprotease and thrombospondin1) gene expression on the hypertrophic scar formation in a rabbit ear model of hypertrophic scarring. We first investigated the number of microvessel and microcirculatory perfusion in untreated scars on days 10, 30, 60, and 90 after epithelialization. Then, we examined the effect of anti-angiogenesis by adenovirus-mediated METH1 expression on hypertrophic scar formation by calculating the scar elevation index, counting the microvessel and argyrophilic nucleolar organizer region particle, and detecting the amount of collagen on days 30 and 60 after treatment. We found that untreated scar tissues at the proliferative phase (days 10-60 after epithelialization) had a significantly higher density of microvessel and microcirculatory perfusion than those at the mature phase (day 90 after epithelization) (both p<0.05). On days 30 and 60 after treatment, the hypertrophic scar formation was significantly inhibited in the treatment group. There was significantly reduced scar elevation index, microvessel count, number of argyrophilic nucleolar organizer region, and total collagen content for treated scars. Our results demonstrate that METH1 has a markedly inhibitive effect on the formation of hypertrophic scar, and may thus have a promising application in the prevention of human hyperthropic scars.

Induction of TIMP-1 and HSP47 synthesis in primary keloid fibroblasts by exogenous nitric oxide

BACKGROUND

The excessive accumulation of extracellular matrix is a hallmark of many fibrotic diseases, including the hypertrophic scar and keloid. Recent reports from this research team had shown that exogenous nitric oxide (NO) participates in the keloid formation; however, its role on the synthesis of fibrotic factor (TGF-beta1, TIMP-1 and HSP47) in the keloid fibroblasts (KF) remained unclear.

OBJECTIVE

In this study, to better define the potential effect of exogenous NO on the expression of fibrotic factors in KF, the enhancing effect of exogenous NO, released from a NO donor, on the synthesis of fibrotic factors in KF was investigated.

METHODS

The seven primary KF cultures were set up to measure the effect of exogenous NO on enhancing the expression of fibrotic factor.

RESULTS

Elevation of cellular cGMP levels was observed to be induced by NO or blocked by the hydrolysis activity of phosphodiesterase (PDE) by the PDE inhibitor. The elevated levels of cellular cGMP were noted to enhance the expression of TIMP-1 and HSP47 in KF. Exogenous NO was found to significantly accelerate the production of TIMP-1 and HSP47 in the seven primary KFs with a corresponding increase in the production of TGF-beta1.

CONCLUSION

The results have led to a conclusion, that is: the excess collagen formations in the keloid lesion may be attributed to the NO/cGMP signal pathway by initiating a rapid increase in the expression of TGF-beta1, TIMP-1 and HSP47 in the KF cells.

Transforming growth factor beta (TGFbeta) and keloid disease

Keloids are benign fibroproliferative diseases of unknown aetiology. They occur as a result of derangement of the normal wound healing process in susceptible individuals. Although several factors have been postulated in the aetiopathogenesis of this condition, there has been growing evidence to suggest a role for Transforming Growth Factor beta (TGFbeta) family members in its pathogenesis. TGFbeta has also been found to be associated with fibrotic diseases affecting different organs of the body including liver, kidney, lung as well as skin. In this review article, we will discuss the morphology and mechanism of action of TGFbeta and its isoforms and present the most up to date literature discussing the role of TGFbeta isoforms, their receptors, and intracellular signalling pathways (the SMAD pathway) in the pathogenesis of keloid disease. Understanding the role of TGFbeta in keloid disease could lead to the development of clinically useful therapeutic modalities for treatment of this condition.

Nitric oxide produced by iNOS is associated with collagen synthesis in keloid scar formation

Nitric oxide (NO) has emerged as an important mediator of many physiological functions. Recent reports have shown that NO participates in the wound healing process, however, its role in keloid formation remains unclear. This study aimed to investigate the effect of NO on keloid fibroblasts (KF) and to determine the levels of inducible nitric oxide synthase (iNOS) expression in clinical specimens of keloid. Scar tissue from seven keloid patients with matched perilesion skin tissue controls was studied for inducible nitric oxide synthase expression and location. In addition, primary keloid and normal scar skin fibroblast cultures were set up to investigate the effects of NO in inducing collagen type I expression. Inducible nitric oxide synthase expression, and NO production were elevated in keloid scar tissues but not in matched perilesion skin tissues. Furthermore, exposure of KF to exogenous NO resulted in increased expression of collagen type I in a dose-dependent manner. NO exposure also induced time-course dependent collagen I expression that peaked at 24h in KF. Taken together, these results indicate that excess collagen formations in keloid lesion may be attributed to iNOS overexpression.

Epidemiology, aetiology and management of abnormal scarring: a review of the literature

Keloid and hypertrophic scars are the result of abnormal processes in scar formation. This paper reviews the literature and the many debates concerning the processes that cause abnormal scarring.

Histopathological Differential Diagnosis of Keloid and Hypertrophic Scar

Distinguishing hypertrophic scar (HS) from keloid histopathologically is sometimes difficult because thickened hyalinized collagen (keloidal collagen), the hallmark of keloid, is not always detectable and alpha-smooth muscle actin (alpha-SMA), a differentiating marker of HS, is variably expressed in both forms of scar. The aim of this study was to investigate additional distinguishing features to facilitate differentiation between keloid and HS. We compared various histologic features and the expression of alpha-SMA in 40 specimens of keloid and 10 specimens of HS. The features more commonly seen in keloids were: (a) no flattening of the overlying epidermis, (b) no scarring of the papillary dermis, (c) presence of keloidal collagen, (d) absence of prominent vertically oriented blood vessels, (e) presence of prominent disarray of fibrous fascicles/nodules, (f) presence of a tongue-like advancing edge underneath normal-appearing epidermis and papillary dermis, (g) horizontal cellular fibrous band in the upper reticular dermis, and (h) prominent fascia-like fibrous band. The last three features were found in keloid specimens only, including the ones lacking detectable keloidal collagen. Our study confirmed the diagnostic value of keloidal collagen, but it was only found in 55% of keloid specimens. Alpha-SMA expression was found in both HS (70%) and keloid (45%), thus it would not be a differentiating marker. In scars with no detectable keloidal collagen, the presence of the following feature(s) favors the diagnosis of keloid: non-flattened epidermis, non-fibrotic papillary dermis, a tongue-like advancing edge, horizontal cellular fibrous band in the upper reticular dermis, and prominent fascia-like band.

Inflammatory mediators in wound healing

This article provides much evidence that the inflammatory process has direct effects on normal and abnormal wound healing. As better understanding develops for the mechanism for these outcomes, targeted proinflammatory and anti-inflammatory interventions are likely to be successful. When inflammation is maintained as a regulated and orchestrated response, effective and normal wound healing is likely to result.

A new surgical treatment of keloid: keloid core excision

Keloids and hypertrophic scars result from excessive collagen deposition, the cause of which is not yet known. Unlike hypertrophic scars, keloids frequently persist at the site of injury, often recur after excision and always overgrow the boundaries of the original wound. There have been many trials to control keloids, but most of them have been unsuccessful. The authors propose a new surgical technique to treat keloids and name it keloid core extirpation. They excise the inner fibrous core from the keloid and cover the defect with a keloid rind flap, which is arterialized by the subcapsular vascular plexus. The authors treated 24 keloids of the ear, trunk, face, and genitalia with keloid core excision. Four cases of partial rind flap congestion or necrosis occurred. Those patients who healed primarily after surgery showed no evidence of keloid recurrence as long as they were followed. The authors have found the keloid core extirpation technique to be excellent in preventing keloid recurrence, with no adjuvant therapy after surgery.

Keloids in rural black South Africans. Part 1: general overview and essential fatty acid hypotheses for keloid formation and prevention

In the first part of this study a general overview on the hypertrophic scar and keloid phenomena regarding history, epidemiology, histopathology and aetiology, in general, together with an essential fatty acid approach as basis for hypotheses of keloid formation and prevention are given. Upon reviewing the literature in planning a strategy for prevention and treatment of keloids, one encounters an overwhelming amount of hypotheses on this topic. Based on a preliminary study on total fatty acid compositions in keloids, compared with normal skin of keloid prone and non-keloid prone patients, there can be argued as follows: an essential fatty acid deficiency of precursors and inflammatory competitors for arachidonic acid may be a factor in the multifactorial aetiology of keloid formations, and apart from a local essential fatty acid deficiency in the wound area, nutrition may also be a contributing factor in rural black South Africans. To confirm or refute the stated hypotheses of the role of essential fatty acids in keloid formation and prevention (outlined in this part of the study), dietary questionnaires and blood (plasma and red blood cell) phospholipid analyses for general information and true fatty acid intake and metabolism, respectively, in the diets of these patients (outlined in part II of this study), as well as a lipid model for keloid formations regarding phospholipids, triglycerides, cholesterol esters and free fatty acids (outlined in part III of this study), are given. The purpose of this comprehensive fatty acid study was an attempt to assess the enigma surrounding keloids and to end the nightmare of the plastic and reconstructive surgeon, since these dermal tumours are notoriously recurrent.

Exogenous transforming growth factor beta(2) modulates collagen I and collagen III synthesis in proliferative scar xenografts in nude rats

BACKGROUND

Keloid and hypertrophic scars are fibrous dermal tumors characterized by overabundant collagen deposition. Previous studies demonstrated that exogenous transforming growth factor beta (TGF-beta) might increase collagen production in incisional wound models and in vitro. Using an in vivo model of human scar xenografts maintained in congenitally athymic, asplenic "nude" rats, we examined endogenous TGF-beta(2), collagen I, and collagen III levels in keloids and burn hypertrophic scars treated with TGF-beta(2) and TGF-beta(2) antibody.

METHODS

Fresh keloid and burn hypertrophic scar specimens excised from human subjects were explanted to pedicled flaps based on the superficial inferior epigastric vessels in athymic "nude" rats. These flaps were allowed to mature for 3 weeks, after which the scar explants were directly perfused with 200 ng of TGF-beta(2) or 250 microg of TGF-beta(2) antibody daily for 5 consecutive days, then again on Days 10, 15, and 20. Biopsies were taken 30 and 120 days following the initiation of treatment. Immunohistochemical staining was then performed for TGF-beta(2), collagen I, and collagen III. The intensity of staining was quantified.

RESULTS

Our results demonstrated that treatment of human proliferative scars with exogenous TGF-beta(2) results in a significant increase in endogenous TGF-beta(2), collagen I, and collagen III production. By contrast, exogenous addition of anti-TGF-beta(2) antibody significantly decreased endogenous TGF-beta(2), collagen I, and collagen III production.

CONCLUSION

This study supports a causative role for TGF-beta(2) in the formation of proliferative scars and suggests that TGF-beta(2) antibody may be a new potential antiscarring agent.

Angiogenesis in pathological and surgical scars

We identified immunohistochemically vessels within cutaneous scars to test the hypothesis that they are qualitatively and quantitatively different in pathological and normally healing scars. The vascular density within and adjacent to 58 cutaneous scars was measured on histological sections stained for factor VIII-related antigen. Four scar types were studied; surgical scars (n = 25), hypertrophic scars (n = 10), keloid (n = 12), and periocular scars (n = 11). Statistical analyses were performed to test the hypothesis that vessel numbers were different in the varying types of scar. Results were also compared with mast cell counts previously derived from the same tissues. A significant reduction was found in the vascular density in keloids compared with surgical and hypertrophic scars (P < .05). No correlation was found between the vascular density and the number of mast cells in the lesions. We have shown quantitatively that keloids have a reduced vascular component compared with hypertrophic scars and normally healing surgical scars at periocular and systemic sites. The formation of keloid scars may be related to their reduced level of vascularization mediated through tissue hypoxia.

The use of silicone occlusive sheeting (Sil-K) and silicone occlusive gel (Epiderm) in the prevention of hypertrophic scar formation

The development of hypertrophic scars and keloids is an unsolved problem in the process of wound healing. For this reason, a successful treatment to prevent excessive scar formation still has not been found. Over the last decade, however, a promising new treatment has been introduced. Silicone materials have proved to reduce the amount of scar tissue and are believed even to prevent hypertrophic scar and keloid formation. In this study, the prophylactic effect of a silicone occlusive sheeting (Sil-K, Degania, Israel) and a silicone occlusive gel (Epiderm, Inamed B.V., The Netherlands) was investigated in a bilateral breast-reduction scar model in which the nontreated scars were supported by nonocclusive Micropore (3M, The Netherlands). The inframammary scars of 129 female patients with a mean age of 31 years ( 14 to 69 years) were studied up to 1 year after the operation. The width and height were measured, and B-scan ultrasound, laser-Doppler flowmetry, and color measurements were used as objective indicators to distinguish between normal and exuberant scars. Three months following the operation, 64.3 percent of the patients developed a hypertrophic scar, which was reduced to 56.6 percent after 6 months and down to 35.3 percent after 1 year. No keloids were seen. Patients with an easily tanning skin, nonsmokers, and patients with an allergy showed more hypertrophic scar formation. Neither Sil-K, used in 68 patients, nor Epiderm, used in 61 patients, could prevent the formation of hypertrophic scars. If both groups were taken together, the scars treated with silicone materials even developed significantly more hypertrophy compared with the Micropore-applicated scars.

A comparison of the ability of intra-oral and extra-oral fibroblasts to stimulate extracellular matrix reorganization in a model of wound contraction

Intra-oral wounds, like wounds in children, demonstrate privileged healing when compared with adult wounds at extra-oral sites. This study investigated whether this preferential healing is related to an increased ability of oral mucosal fibroblasts to reorganize extracellular matrix (ECM) when compared with their dermal counterparts. ECM reorganization was investigated by means of a fibroblast-populated collagen lattice (FPCL) system. The effect of donor age was also investigated in this system. Differences in ECM reorganization and FPCL contraction were evident: FPCL contraction was more rapid by oral mucosal fibroblasts than dermal fibroblasts (p < 0.01). FPCL contraction was also greater in child (donor < 10 years) than adult (donor > 18 years) oral mucosal fibroblasts (p < 0.01). These differences were not related to phenotypic differences in cell viability (p > 0.5), DNA synthesis (p > 0.05), and cell number (p > 0.5) within the FPCLs, or cellular attachment to collagen (p > 0.07). FPCL contraction was not stimulated by the addition of conditioned medium from oral mucosal or dermal fibroblasts (p > 0.05). These data show that the significantly increased ability of oral mucosal fibroblasts to reorganize ECM in vitro, when compared with dermal fibroblasts, represents a distinct phenotypic contractile difference, rather than differences in their production of soluble mediators or cell attachment to ECM.

An investigation of the interaction between alcohol and fibroblasts in wound healing

This study investigated the effect of clinical concentrations of alcohol on fibroblast function (proliferation and ECM synthesis) in vitro. Basal and TGF-beta-induced collagen synthesis was assayed in confluent cultures in serum-free medium at 48 h with a commercial collagen assay system. At concentrations of alcohol > 5%, fibroblast proliferation was significantly inhibited. Although noninhibitory, subclinical concentrations of alcohol failed to inhibit basal collagen synthesis (P > 0.1), they significantly decreased TGF-beta-induced collagen synthesis (P < 0.03). These data support the notion that the local, as well as the systemic, effects of alcohol are important in mediating delayed healing in alcoholic patients.