Extracellular matrix components of oral mucosa differ from skin and resemble that of foetal skin

OBJECTIVE

Wounds of both the oral mucosa and early-to-mid gestation foetuses have a propensity to heal scarless. Repair of skin wounds in adults, however, regularly results in scar formation. The extracellular matrix (ECM) plays an important role in the process of healing. The fate of scarless or scar forming healing may already be defined by the ECM composition, prior to wounding. In this study, the presence of several ECM components in oral mucosa (palatum) and skin was investigated.

DESIGN

Immunohistochemical stainings of different ECM components were performed on skin, obtained from abdominal dermolipectomy surgery, and oral mucosa, derived after pharynx reconstruction.

RESULTS

Expression of fibronectin, its splice variant ED-A, and chondroitin sulphate was elevated in oral tissue, whereas elastin expression was higher in skin. Tenascin-C, hyaluronic acid, biglycan, decorin, and syndecan-1 were expressed at similar levels in both tissues. Oral mucosa contained more blood vessels than skin samples. Finally, oral keratinocytes proliferated more, while dermal keratinocytes demonstrated higher differentiation.

CONCLUSIONS

Comparing ECM components of the skin and oral mucosa coincides with differences earlier observed between foetal and adult skin, and this might indicate that some ECM components are involved in the mode of repair.

Intralesional cryotherapy versus excision and corticosteroids or brachytherapy for keloid treatment: study protocol for a randomised controlled trial

BACKGROUND

Keloids are a burden for patients due to physical, aesthetic and social complaints and treatment remains a challenge because of therapy resistance and high recurrence rates. The main goal of treatment is to improve the quality of life (QoL); this implies that, apart from surgical outcomes, patient-reported outcome measures (PROMs) need to be taken into account. Decision making in keloid treatment is difficult due to heterogeneity of the condition and the lack of comparative studies.

METHODS/DESIGN

This is a multicentre, randomised controlled open trial that compares 1) intralesional cryotherapy versus excision and corticosteroids for primary keloids, and 2) intralesional cryotherapy versus excision and brachytherapy for therapy-resistant keloids. The primary outcome is the Patient and Observer Scar Assessment Scale (POSAS), a 12-item scale (with score 12 indicating the best and 120 indicating the worst scar imaginable). A difference of six points on the total score is considered to be of clinical importance. Secondary outcomes are recurrence rates, volume reduction, Skindex-29 scores, SF-36 scores and complication rates. Primary and secondary outcome measurements are taken at baseline, and at 2, 12, 26 and 52 weeks postoperatively. For analysis, a linear mixed model is used. A total of 176 patients will be included over a period of 2.5 years. The protocol is approved by the Medical Ethics Committee of the Erasmus University Medical Centre Rotterdam and follows good clinical practice guidelines.

DISCUSSION

The outcomes of this study will improve evidence-based decision making for the treatment of keloids, as well as patient education.

TRIAL REGISTRATION

Dutch Trial Register NTR4151.

Women with silicone breast implants and unexplained systemic symptoms: a descriptive cohort study

BACKGROUND

Since their introduction, the safety of silicone breast implants has been under debate. Although an association with systemic diseases was never established, women continuously blamed implants for their unexplained systemic symptoms. In 2011, a pattern of symptoms caused by systemic reactions to adjuvants (e.g. vaccines, silicone) was identified: 'autoimmune syndrome induced by adjuvants' (ASIA). Our aim was to collect a cohort of women with silicone breast implants and unexplained systemic symptoms to identify a possible pattern and compare this with ASIA.

METHODS

Women with silicone breast implants and unexplained systemic symptoms were invited through national media to visit a special outpatient clinic in Amsterdam. All were examined by experienced consultant physicians and interviewed. Chest X-ray and laboratory tests were performed.

RESULTS

Between March 2012 and 2013, 80 women were included, of which 75% reported pre-existent allergies. After a symptom-free period of years, a pattern of systemic symptoms developed, which included fatique, neurasthenia, myalgia, arthralgia and morning stiffness in more than 65% of women. All had at least two major ASIA criteria and 79% fulfilled ≥ 3 typical clinical ASIA manifestations. After explantation, 36 out of 52 women experienced a significant reduction of symptoms.

CONCLUSIONS

After excluding alternative explanations, a clear pattern of signs and symptoms was recognised. Most women had pre-existent allergies, suggesting that intolerance to silicone or other substances in the implants might cause their symptoms. In 69% of women, explantation of implants reduced symptoms. Therefore, physicians should recognise this pattern and consider referring patients for explantation.

Minimal extracorporeal circulation (MECC) does not result in less hypertrophic scar formation as compared to conventional extracorporeal circulation (CECC) with dexamethasone

INTRODUCTION

Cardiopulmonary bypass surgery is associated with a systemic inflammatory response through the interaction of air, blood and synthetic components in the bypass system and the physical trauma of surgery. An alternative cardiopulmonary bypass system, minimal extracorporeal circulation (MECC), has shown promising results in terms of reducing the inflammatory response. We hypothesized that this system may reduce pathological excessive scarring. To study this assumption, the effects of MECC and the effects of conventional extracorporeal circulation (CECC) with dexamethasone on skin scarring were compared in a standardized wound-healing model.

METHODS AND RESULTS

Pre-sternal scars were evaluated prospectively at four and 12 months postoperatively. The height and width of the scars were measured, using a slide caliper and sonography. The scars were scored using the validated Patient and Observer Scar Assessment Scale. Additional risk factors for hypertrophic scar formation were identified by means of a questionnaire. During surgery, MECC was used in 45 patients and CECC/dexamethasone in 42 patients. Four months postoperatively, 22 patients of the MECC group (49%) and 18 patients in the CECC/dexamethasone group (43%) had developed hypertrophic scars. Twelve months postoperatively, the hypertrophic scars in four patients of the MECC group and in two patients of the CECC/dexamethasone group had become normotrophic. In 18 patients of the MECC group (38%) and 16 patients of the CECC group (41%) the scars remained hypertrophic at 12 months. These differences between the two groups were not statistically significant.

CONCLUSION

MECC does not reduce hypertrophic scar formation compared with CECC with dexamethasone, but its use is more beneficial than the use of CECC/dexamethasone because of the circulatory and immunological advantages and because treatment with dexamethasone can be omitted.

Differential response of human adipose tissue-derived mesenchymal stem cells, dermal fibroblasts, and keratinocytes to burn wound exudates: potential role of skin-specific chemokine CCL27

Many cell-based regenerative medicine strategies toward tissue-engineered constructs are currently being explored. Cell-cell interactions and interactions with different biomaterials are extensively investigated, whereas very few studies address how cultured cells will interact with soluble wound-healing mediators that are present within the wound bed after transplantation. The aim of this study was to determine how adipose tissue-derived mesenchymal stem cells (ASC), dermal fibroblasts, and keratinocytes will react when they come in contact with the deep cutaneous burn wound bed. Burn wound exudates isolated from deep burn wounds were found to contain many cytokines, including chemokines and growth factors related to inflammation and wound healing. Seventeen mediators were identified by ELISA (concentration range 0.0006-9 ng/mg total protein), including the skin-specific chemokine CCL27. Burn wound exudates activated both ASC and dermal fibroblasts, but not keratinocytes, to increase secretion of CXCL1, CXCL8, CCL2, and CCL20. Notably, ASC but not fibroblasts or keratinocytes showed significant increased secretion of vascular endothelial growth factor (5-fold) and interleukin-6 (253-fold), although when the cells were incorporated in bi-layered skin substitute (SS) these differences were less pronounced. A similar discrepancy between ASC and dermal fibroblast mono-cultures was observed when recombinant human-CCL27 was used instead of burn wound exudates. Although CCL27 did not stimulate the secretion of any of the wound-healing mediators by keratinocytes, these cells, in contrast to ASC or dermal fibroblasts, showed increased proliferation and migration. Taken together, these results indicate that on transplantation, keratinocytes are primarily activated to promote wound closure. In contrast, dermal fibroblasts and, in particular, ASC respond vigorously to factors present in the wound bed, leading to increased secretion of angiogenesis/granulation tissue formation factors. Our findings have implications for the choice of cell type (ASC or dermal fibroblast) to be used in regenerative medicine strategies and indicate the importance of taking into account interactions with the wound bed when developing advanced therapies for difficult-to-close cutaneous wounds.

Detrimental dermal wound healing: what can we learn from the oral mucosa?

Wounds in adults are frequently accompanied by scar formation. This scar can become fibrotic due to an imbalance between extracellular matrix (ECM) synthesis and ECM degradation. Oral mucosal wounds, however, heal in an accelerated fashion, displaying minimal scar formation. The exact mechanisms of scarless oral healing are yet to be revealed. This review highlights possible mechanisms involved in the difference between scar-forming dermal vs. scarless oral mucosal wound healing. Differences were found in expression of ECM components, such as procollagen I and tenascin-C. Oral wounds contained fewer immune mediators, blood vessels, and profibrotic mediators but had more bone marrow-derived cells, a higher reepithelialization rate, and faster proliferation of fibroblasts compared with dermal wounds. These results form a basis for further research that should be focused on the relations among ECM, immune cells, growth factors, and fibroblast phenotypes, as understanding scarless oral mucosal healing may ultimately lead to novel therapeutic strategies to prevent fibrotic scars.

Development, validation and testing of a human tissue engineered hypertrophic scar model

Adverse hypertrophic scars can form after healing of full-thickness skin wounds. Currently, reliable animal and in vitro models to identify and test novel scar reducing therapeutics are scarce. Here we describe the development and validation of a tissue-engineered human hypertrophic scar (HTscar) model based on reconstructed epidermis on a dermal matrix containing adipose derived mesenchymal stem cells (ASC). Although obtained from normal, healthy skin, ASC, in contrast to dermal mesenchymal cells, were found to facilitate HTscar formation. Quantifiable HTscar parameters were identified: contraction; thickness of dermis, collagen-1 secretion, epidermal outgrowth, epidermal thickness, and cytokine secretion (IL-6, CXCL8). The model was validated with therapeutics currently used for treating scars (5-fluorouracil, triamcinolon) and a therapeutic known to be unsuccessful in scar reduction (1,25-dihydroxyvitamin-D3). Furthermore, it was shown that atorvastatin, but not retinoic-acid, may provide a suitable alternative for scar treatment. Each therapeutic selectively affected a different combination of parameters, suggesting combined therapy may be most beneficial. This animal-free hypertrophic scar model may provide an alternative model for mechanistic studies as well as a novel in vitro means to test anti-scar therapeutics, thereby reducing the use of animals.

Randomized clinical trial of donor-site wound dressings after split-skin grafting

Background

The aim was to study which dressing material was best for healing donor-site wounds (DSWs) after split-skin grafting as there is wide variation in existing methods, ranging from classical gauze dressings to modern silicone dressings.

Methods

This 14-centre, six-armed randomized clinical trial (stratified by centre) compared six wound dressing materials in adult patients with DSWs larger than 10 cm2. Primary outcomes were time to complete re-epithelialization and pain scores measured on a visual analogue scale (VAS) over 4 weeks. Secondary outcomes included itching (VAS, over 4 weeks), adverse events and scarring after 12 weeks rated using the Patient and Observer Scar Assessment Scale (POSAS).

Results

Between October 2009 and December 2011, 289 patients were randomized (of whom 288 were analysed) to either alginate (45), film (49), gauze (50), hydrocolloid (49), hydrofibre (47) or silicone (48) dressings. Time to complete re-epithelialization using hydrocolloid dressings was 7 days shorter than when any other dressing was used (median 16 versus 23 days; P < 0·001). Overall pain scores were low, and slightly lower with use of film dressings (P = 0·038). The infection rate among patients treated with gauze was twice as high as in those who had other dressings (18 versus 7·6 per cent; relative risk 2·38, 95 per cent confidence interval 1·14 to 4·99). Patients who had a film dressing were least satisfied with overall scar quality.

Conclusion

This trial showed that use of hydrocolloid dressings led to the speediest healing of DSWs. Gauze dressing should be discontinued as they caused more infections. Registration number: NTR1849 (http://www.trialregister.nl).

Platelet derived growth factor-CC secreted by M2 macrophages induces alpha-smooth muscle actin expression by dermal and gingival fibroblasts

Dermal wounds can heal detrimentally by formation of excess fibrosis or hypertrophic scarring. These phenomena are normally absent in the oral mucosa. Macrophages play an important role in wound repair, have a marked heterogeneity and are thought to contribute to fibrosis. To investigate to what extend macrophages are involved in the occurrence of fibrosis, the effect of differently activated macrophages on dermal and gingival fibroblasts was studied in vitro. Macrophages were differentiated into a classical (M1) or alternative (M2) phenotype, which was assessed by receptor expression (CD40/mannose receptor) and cytokine secretion (interleukin-4 and -12). Fibroblasts were exposed to these macrophages and/or conditioned medium (cm), and differentiation into α-SMA-expressing myofibroblasts was quantified. M2, but not M1 macrophages induced α-SMA expression in both dermal and gingival fibroblasts. Blocking of transforming growth factor-β1 did not decrease the α-SMA expression mediated by M2 macrophages. It appeared that this induction was mediated by platelet derived growth factor-CC (PDGF-CC), produced by M2 macrophages. The expression and role of this growth factor was confirmed by ELISA, RT-PCR, and blocking experiments. Our results indicate that M2 macrophages are able to induce myofibroblast differentiation via production of PDGF-CC. Based on our findings we conclude that PDGF-CC may play a hitherto unknown role in the differentiation of myofibroblasts.

Scoring systems of cleft-related facial deformities: a review of literature

Objective :  There is a need for an internationally agreed objective method of assessing cleft-related deformities in order to compare the results of individual surgeons and different surgical techniques or to determine the optimal timing for primary lip closure. To assess the current methods, an overview of the recent developments in postoperative scoring systems of cleft-related deformities was made. Methods :  A Medline search from June 2003 through July 2011 was conducted, and references in the selected articles were checked. This search yielded 428 articles, and after application of the inclusion and exclusion criteria, 40 articles were included in this review. Results :  Twenty-five studies used two-dimensional (2D) photographs for the assessment of cleft-related deformities. Fourteen of these studies used a subjective method for the assessment and 11 performed anthropometric measurements. Good reliability has been found for subjective assessments and measurements from 2D photographs. Fifteen studies assessed three-dimensional (3D) imaging. Conclusions :  Although there is a wide variety in study design, 3D imaging seems most reliable in assessing cleft-related facial deformities. However, scoring on 2D photographs is easier to perform and more applicable in daily practice because all cleft patients are photographed through the course of their treatment.

Formation of hypertrophic scars: evolution and susceptibility

Formation of hypertrophic scars is a common complication of wound healing, and at present little is known about the incidence and risk factors. Our aim was to analyse the incidence, progression, and regression of postoperative hypertrophic scars over time and to identify risk factors of hypertrophic scars. Patients who had had bilateral reduction mammoplasty or median sternotomy incision were included in the study. All patients were examined at 3 and 12 months postoperatively. We recorded: height, weight, allergy status, smoking status, skin type, tanning, and shape of the scar 3 and 12 months postoperatively. Of the 204 patients who were included, 122 (60%) developed a hypertrophic scar within 12 months of operation. Of these patients, 117 (96%) developed a hypertrophic scar within 3 months of operation. Twelve months postoperatively, 66/204 patients (32%) had a hypertrophic scar. In 31 of the 66 of the patients with a hypertrophic scar 3 months postoperatively (47%), the hypertrophic scar(s) regressed after 3 and 12 months. Smoking and age were associated with formation of hypertrophic scars. In conclusion, 60% of patients developed hypertrophic scars postoperatively, typically during the first three months. Most hypertrophic scars that are present after three months are still hypertrophic after 12 months. Young, non-smoking patients are more susceptible to formation of hypertrophic scars.

Time course of the angiogenic response during normotrophic and hypertrophic scar formation in humans

Previous research suggests that in hypertrophic scars (HSs), an excess of microvessels is present compared with normotrophic scars (NSs). The aim of our study was to quantify vascular densities in HSs and normotrophic scars and to provide an insight into the kinetics of changes in the expression of angiogenic factors in time during wound healing and HS formation. Human presternal wound healing after cardiothoracic surgery through a sternotomy incision was investigated in a standardized manner. Skin biopsies were collected at consecutive time points, i.e., during surgery and 2, 4, 6, 12, and 52 weeks postoperatively. The expression levels of angiopoietin-1, angiopoietin-2, Tie-2, vascular endothelial growth factor, and urokinase-type plasminogen activator were measured by real-time reverse transcription-polymerase chain reaction. Quantification of angiogenesis and cellular localization of the proteins of interest were based on immunohistochemical analysis. Microvessel densities were higher in the HSs compared with the normotrophic scars 12 weeks (p=0.017) and 52 weeks (p=0.030) postoperatively. Angiopoietin-1 expression was lower in the hypertrophic group (p<0.001), which, together with a nonsignificant increase of angiopoietin-2 expression, represented a considerable decrease in the angiopoietin-1/angiopoietin-2 ratio in the hypertrophic group 4 weeks (p=0.053), 12 weeks (p<0.001), and 52 weeks (p<0.001) postoperatively. The expression of urokinase-type plasminogen activator was up-regulated during HS formation (p=0.008). Vascular endothelial growth factor expression was not significantly different when comparing both groups. In summary, the differential expression of angiopoietin-1, angiopoietin-2, and urokinase-type plasminogen activator in time is associated with an increased vascular density in HSs compared with normotrophic scars.

Therapeutic hotline: An alternative adjuvant treatment after ear keloid excision using a custom-made methyl methacrylate stent

The efficacy of most pressure devices developed for treatment of ear keloids is limited by the insufficient control of the applied pressure, sometimes causing pain and repeated bleeding with a subsequently increased risk of infections and cosmetic problems. The present study aims to describe the efficacy of the custom-made methyl methacrylate stent in patients that were surgically treated for ear keloids and afterward underwent pressure therapy. The recurrence rate of the ear keloids was evaluated after at least 12 months. Adjuvant treatment with the methyl methacrylate stent resulted in an 83% success rate in our experience with 23 patients that completed the intended therapeutic duration of 18 months. No cases of severe complications were seen during or after the treatment. Furthermore, all the items of the Patient and Observer Scar Assessment Scale resulted in a statistically significant improvement of the scar (p < 0.05). Postoperative pressure therapy with the custom-made methyl methacrylate stent seems efficacious, safe, and is usable for keloids of both the helix and the earlobe.

Freshly isolated stromal cells from the infrapatellar fat pad are suitable for a one-step surgical procedure to regenerate cartilage tissue

BACKGROUND AIMS

Stem cell therapies are being evaluated as promising alternatives for cartilage regeneration. We investigated whether stromal vascular fraction cells (SVF) from the infrapatellar (Hoffa) fat pad are suitable for a one-step surgical procedure to treat focal cartilage defects.

METHODS

SVF was harvested from patients undergoing knee arthroplasty (n = 53). Colony-forming unit (CFU) assays, growth kinetics and surface marker profiles were determined, and the chondrogenic differentiation capacity of freshly isolated SVF was assessed after seeding in three-dimensional poly (L-lactic-co-epsilon-caprolactone) scaffolds.

RESULTS

SVF yield per fat pad varied between 0.55 and 16 x 10(6) cells. CFU frequency and population doubling time were 2.6 +/- 0.6% and +/-2 days, respectively. Surface marker profiles matched those of subcutaneous-derived adipose-derived stem cells (ASC). CFU from Hoffa SVF showed differentiation toward osteogenic and adipogenic lineages. Cartilage differentiation was confirmed by up-regulation of the cartilage genes sox9, aggrecan, collagen type II and cartilage oligomeric matrix protein (COMP), collagen II immunostaining, Alcian Blue staining and glycosaminoglycan production. Compared with passaged cells, SVF showed at least similar chondrogenic potential.

CONCLUSIONS

This study demonstrates that SVF cells from the infrapatellar fat pad are suitable for future application in a one-step surgical procedure to regenerate cartilage tissue. SVF shows similar favorable characteristics as cultured ASC, and chondrogenic differentiation even appears to be slightly better. However, because of variable harvesting volumes and yields, SVF from the infrapatellar fat pad might only be applicable for treatment of small focal cartilage defects, whereas for larger osteoarthritic defects subcutaneous adipose tissue depot would be preferable.

Differences in collagen architecture between keloid, hypertrophic scar, normotrophic scar, and normal skin: An objective histopathological analysis

Normotrophic, hypertrophic, and keloidal scars are different types of scar formation, which all need a different approach in treatment. Therefore, it is important to differentiate between these types of scar, not only clinically but also histopathologically. Differences were explored for collagen orientation and bundle thickness in 25 normal skin, 57 normotrophic scar, 56 hypertrophic scar, and 56 keloid biopsies, which were selected on clinical diagnosis. Image analysis was performed by fast fourier transformation. The calculated collagen orientation index ranged from 0 (random orientation) to 1 (parallel orientation). The bundle distance was calculated by the average distance between the centers of the collagen bundles. The results showed that compared with all three types of scars, the collagen orientation index was significantly lower in normal skin, which indicates that scars are organized in a more parallel manner. No differences were found between the different scars. Secondly, compared with normal skin, normotrophic scar, and hypertrophic scar, the bundle distance was significantly larger in keloidal scar, which suggests that thicker collagen bundles are present in keloidal scar. This first extensive histological study showed objective differences between normal skin, normotrophic, hypertrophic, and keloidal scar.

Tissue expansion for correction of baldness in aplasia cutis congenita

Aplasia cutis is a congenital absence of the skin, usually presenting on the scalp. In 20% of all cases, part of the skull is also absent. A residual area of baldness may still be present some years after surgical or conservative treatment. It is possible to excise the scarred hairless region and cover that area with expanded hair-bearing skin from the rest of the skull. We present three patients who underwent tissue expansion and discuss the indications and pitfalls of this procedure.

CONCLUSION

Tissue expansion can be used to cover a residual alopecia defect in young children with aplasia cutis congenita and associated bone abnormalities. The quality of the bone appears to be normal in our three patients. We demonstrate that even in young children with aplasia cutis and an underlying bony defect, tissue expansion is a safe and effective modality as a second stage reconstruction procedure.

Potential cellular and molecular causes of hypertrophic scar formation

A scar is an expected result of wound healing. However, in some individuals, and particularly in burn victims, the wound healing processes may lead to a fibrotic hypertrophic scar, which is raised, red, inflexible and responsible for serious functional and cosmetic problems. It seems that a wide array of subsequent processes are involved in hypertrophic scar formation, like an affected haemostasis, exaggerated inflammation, prolonged reepithelialization, overabundant extracellular matrix production, augmented neovascularization, atypical extracellular matrix remodeling and reduced apoptosis. Platelets, macrophages, T-lymphocytes, mast cells, Langerhans cells and keratinocytes are directly and indirectly involved in the activation of fibroblasts, which in turn produce excess extracellular matrix. Following the chronology of normal wound healing, we unravel, clarify and reorganize the complex molecular and cellular key processes that may be responsible for hypertrophic scars. It remains unclear whether these processes are a cause or a consequence of unusual scar tissue formation, but raising evidence exists that immunological responses early following wounding play an important role. Therefore, when developing preventive treatment modalities, one should aim to put the early affected wound healing processes back on track as quickly as possible.

Hypertrophic scar formation is associated with an increased number of epidermal Langerhans cells

The exact pathogenesis of hypertrophic scar and keloid formation is still unknown and a good therapy to prevent or treat these scars is lacking. Because immunological processes seem to be important in excessive scar formation, immunological cells and parameters were studied in a standardized breast reduction wound-healing model in the present study. Standardized scar samples were taken from infra-mammary breast reduction scars, 3 and 12 months following surgery. The samples were investigated for their number of mast cells, Langerhans cells, T-lymphocytes, and macrophages, and the presence of interleukin-4 (IL-4) and counter-regulating interferon-gamma (gamma-IFN), in relation to the scar's clinical appearance--normal or hypertrophic. In this study, hypertrophic scar formation was significantly associated with an increased number of epidermal Langerhans cells (p=0.0001) and significantly (p<0.05) increased expression of epidermal IL-4. No relationship was found between mast cell, T-lymphocyte and macrophage numbers or gamma-IFN staining and the formation of normal or hypertrophic scars. These results, combined with previous observation of abnormal keratinocyte behaviour in this context, indicate that the epidermal immune barrier plays an important role in the development of hypertrophic scars.

Keratinocyte-derived growth factors play a role in the formation of hypertrophic scars

In predisposed individuals, wound healing can lead to hypertrophic scar or keloid formation, characterized by an overabundant extracellular matrix. It has recently been shown that hypertrophic scars are accompanied by abnormal keratinocyte differentiation and proliferation, and significantly increased acanthosis, compared with normal scars. This study addressed the question of whether the development of normal and hypertrophic scars is regulated by differences in the growth factor profiles of both the epidermis and the dermis. The presence of interleukin-1alpha (IL-1alpha), IL-1beta, tumour necrosis factor-alpha (TNF-alpha), platelet-derived growth factor (PDGF), transforming growth factor-beta1 (TGF-beta1), and basic fibroblast growth factor (bFGF) was investigated in biopsies taken from breast reduction scars at 3 and 12 months following surgery. The samples were analysed by immunohistological methods and categorized as scars that remained hypertrophic (HH), became normal (HN) or remained normal after 12 months (NN). The epidermal expression of IL-1alpha was significantly increased in NN scars compared with HN and HH scars 3 and 12 months following operation, whereas the dermal expression showed no difference. PDGF was significantly increased in the dermis of normal scars after 3 months and in both the epidermis and the dermis of hypertrophic scars after 12 months. IL-1beta, TNF-alpha, TGF-beta and bFGF showed no differences. It is hypothesized that impaired production of keratinocyte-derived growth factors, such as IL-1alpha, leads to a decrease in the catabolism of the dermal matrix, whereas augmented epidermal PDGF production leads to increased formation of the dermal matrix in hypertrophic scars. These observations support the possibility that the epidermis is involved in preventing the formation of hypertrophic scars.