Delayed appearance of decorin in healing burn scars

AIMS: We have previously shown that hypertrophic scar tissue from burn patients contains abnormally high amounts of the proteoglycans versican and biglycan and reduced amounts of decorin, in comparison with normal dermis or mature scar. The lack of decorin may account for the poor organization of collagen fibrils in the nodular areas of these scars. Decorin has also been reported to neutralize the fibrogenic growth factor TGF-beta1. This study was conducted to monitor the time-course of expression of decorin in healing burn wounds by in-situ hybridization to determine whether its absence from hypertrophic scars could result from reduced synthesis. METHODS AND RESULTS: Scar tissue from 19 patients and normal dermis from six patients, was fixed in paraformaldehyde, embedded in paraffin and sectioned. Digoxigenin-labelled cRNA probes were prepared from a plasmid containing a 622-bp insert of human decorin cDNA and used for in-situ hybridization. Total numbers of connective tissue cells and cells positive for decorin mRNA were counted in 10 random fields in the upper (papillary), middle and lower (reticular) one-thirds of the dermis. In all regions the number and percentages of cells with decorin mRNA were low during the first 12 months after injury (eight samples), much higher between 12 and 36 months (seven samples) and low and similar to those in normal skin after 36 months (five samples). The differences between intermediate and early or late stage samples were statistically significant (one-way ANOVA). Immunohistochemistry showed little staining for decorin in early stage samples and much stronger staining in mid-stage. Late stage tissue showed intense staining for decorin, almost comparable to that in normal dermis. CONCLUSION: Expression of decorin in burn wounds is suppressed for about 12 months and then increases at a time when resolution of hypertrophic scarring is generally considered to occur.     

Versican in human fetal skin development

 The extracellular matrix of human fetal skin differs substantially from that of adult skin. Fetal skin contains sparse amounts of fibrillar collagen enmeshed in a highly hydrated amorphous matrix composed of hyaluronan and sulfated proteoglycans. Both fetal and adult skin contain two major interstitial proteoglycans that are extracted by chaotrophic agents and detergents. These are the large chondroitin sulfate proteoglycan versican and the small dermatan sulfate proteoglycan decorin. For this study, proteoglycans extracted from fetal and adult skin were compared on Western blots to determine the relative amounts of versican. Decorin present in the same samples provided an internal standard for these studies. Fetal skin differed from adult skin in that it contained a significantly higher proportion of versican than did adult skin. Immunohistochemical studies compared early-fetal with mid-fetal skin and found that versican was a significant component of the interstitial extracellular matrix at both of these stages of skin development. However, by the mid-fetal period, interstitial versican became restricted to the upper half of the dermis, although versican also continued to be highly expressed around hair follicles, glands, and vasculature in the lower half of the dermis. Fetal skin extracts differed from an adult skin extract by the presence of a 66-kDa protein immunologically related to versican and by the absence of a 17-kDa core protein of a proteoglycan related to decorin. Both of these molecular species may represent degradation products of their respective proteoglycans. Monoclonal antibodies which detect epitopes in native chondroitin sulfate glycosaminoglycan chains recognized versican extracted from fetal skin. However, the tissue distribution of these antigens did not entirely conform to that for versican core protein, suggesting that versican in different regions of the skin may be substituted with glycosaminoglycan chains with different microchemistries. The results of these studies indicate that human fetal skin is structurally different from adult skin in terms of both the distribution and the composition of the large, aggregating chondroitin sulfate proteoglycan versican. Accepted: 13 July 1998     

Epidermal participation in post-burn hypertrophic scar development

 The reconstruction of epidermal architecture over time in normotrophic and hypertrophic scars in untransplanted, spontaneously healed partial-thickness burns has scarcely been studied, unlike the regeneration of epidermal grafts used to cover burn wounds and the regeneration of the dermis during hypertrophic scarring. The expression of markers of epidermal proliferation, differentiation and activation in normotrophic and hypertrophic scars in spontaneously healed partial-thickness burns was assessed and compared with the expression of these markers in normal control skin of healthy persons to determine whether hypertrophic scarring is associated with abnormalities in the phenotype of keratinocytes. Punch biopsies were taken both of partial-thickness burns after re-epithelialisation and of matched unburned skin. At 4 and 7 months post-burn, biopsies were taken of normotrophic and hypertrophic scars that had developed in these wounds. The biopsies were analysed using immunostaining for markers of keratinocyte proliferation, differentiation and activation (keratins 5, 10, 16 and 17, filaggrin, transglutaminase and CD36). We observed a higher expression of markers for proliferation, differentiation and activation in the epidermis of scars at 1 month post-burn than in normal control skin of healthy persons. There was a striking difference between normotrophic and hypertrophic scars at 4 months post-burn. Keratinocytes in hypertrophic scars displayed a higher level of proliferation, differentiation and activation than did normotrophic scars. At 7 months post-burn all keratinocyte proliferation and differentiation markers showed normal expression, but the activation marker CD36 remained upregulated in both normotrophic and hypertrophic scars. Surprisingly, in matched unburned skin of burn patients, a state of hyperactivation was observed at 1 month. Our results suggest that keratinocytes may be involved in the pathogenesis of hypertrophic scarring. Received: 16 September 1998 / Accepted: 28 September 1998     

Differential proteoglycan and hyaluronan distribution in calcified aortic valves

BackgroundWhile the prevalence of calcified aortic valve disease continues to rise and no pharmacological treatments exist, little is known regarding the pathogenesis of the disease. Proteoglycans and the glycosaminoglycan hyaluronan are involved in calcification in arteriosclerosis and their characterization in calcified aortic valves may lend insight into the pathogenesis of the disease.MethodsFourteen calcified aortic valves removed during valve replacement surgery were immunohistochemically stained for the proteoglycans decorin, biglycan, and versican, as well as the glycosaminoglycan hyaluronan. Staining intensity was evaluated in the following regions of interest: center of calcified nodule, edge of nodule, tissue directly surrounding the nodule; center and tissue surrounding small “prenodules”; and fibrosa layer of normal regions of the leaflet distanced from the nodule.ResultsDecorin, biglycan, and versican, as well as hyaluronan, were abundantly present immediately surrounding the calcified nodules, but minimally within the nodule itself. Expression of decorin and biglycan in and surrounding prenodules was greater than in the edge and center regions of mature nodules. The levels of expression of the proteoglycans and hyaluronan were highly correlated with one another in the different regions of the valve.ConclusionsThe three proteoglycans and hyaluronan demonstrated distinctive localization relative to nodules within calcified aortic valves, where they likely mediate lipid retention, cell proliferation, and extracellular matrix remodeling, and motivate further study. Comparisons between expression of these components in mature nodules and prenodules suggest distinct roles for these components in nodule progression, especially in the tissues surrounding the nodules.     

Alterations in proteoglycan synthesis common to healing wounds and tumors.

Wound healing and tumor stroma generation share several important properties, including hyperpermeable blood vessels, extravasation of fibrinogen, and extravascular clotting. In both, the deposits of fibrin gel serve initially as provisional stroma and later are replaced by granulation tissue. Proteoglycans (PG) are also important constituents of the extracellular matrix, but their composition and role in healing wounds and tumor stroma generation are poorly understood. The authors used immunohistochemical and biochemical methods to investigate the dermatan sulfate proteoglycan (DSPG) and chondroitin sulfate proteoglycan (CSPG) composition of healing skin wounds and solid tumors. By immunohistochemistry, the great majority of normal guinea pig and human dermis stained weakly for CSPG and strongly for decorin. In contrast, the granulation tissue of healing skin wounds and scars stained intensely for CSPG and weakly or not at all for decorin; however decorin staining was restored to normal intensity after digestion with chondroitin ABC lyase, suggesting that decorin antigenic sites had been masked by glycosaminoglycan (GAG) chains. Like wounds, the stroma of several carcinomas (line 1 guinea pig, human breast, colon, basal cell, and squamous) stained strongly for CSPG and weakly or not at all for decorin, but decorin staining developed after chondroitin ABC lyase digestion. Thus healing wounds and tumor stroma express a common pattern of altered PG staining, adding another to the properties these pathologic entities share. Proteoglycans extracted from healing wounds after in situ labelling with [35S] Na sulfate contained more CSPG than normal dermis with significantly longer GAG chains. Granulation tissue also synthesized more DSPG than normal skin, with greater heterogeneity and longer GAG chains. These alterations in PG synthesis correlate with the cell proliferation, migration, and collagen synthesis that accompany wound healing and may provide clues to the mechanisms responsible for both wound healing and tumor stroma generation.     

Abundance and location of proteoglycans and hyaluronan within normal and myxomatous mitral valves

IntroductionExtracellular matrix changes occur in many heart valve pathologies. For example, myxomatous mitral valves are reported to contain excess proteoglycans and hyaluronan. However, it is unknown which specific proteoglycans are altered in myxomatous valves. Because proteoglycans perform varied functions in connective tissues, this study was designed to identify and localize three matrix-associated proteoglycans, as well as hyaluronan and the hyaluronan receptor for endocytosis, within myxomatous and normal mitral valves.MethodsHuman mitral posterior leaflets (control, n=6–9; myxomatous, n=14–21; mean age, 61 years for all groups) were histochemically stained for proteoglycan core proteins, hyaluronan, and the hyaluronan receptor for endocytosis. Stain intensity was semiquantitatively graded to determine differences in marker abundance between normal and myxomatous valves. The proteoglycans were localized to different regions of the leaflet by correspondence to parallel Movat-stained sections.ResultsThe proteoglycans decorin, biglycan, and versican were more abundant in myxomatous valves than in normal controls (P<.03). There was a gender effect on proteoglycan presence, but no age-related trends were observed. Hyaluronan and the hyaluronan receptor for endocytosis were distributed throughout all valves. There was no significant difference in hyaluronan between groups, but expression of the hyaluronan receptor for endocytosis was reduced in myxomatous valves compared to normal controls (P<.002).ConclusionExcess decorin, biglycan, and versican may be associated with the remodeling of other matrix components in myxomatous mitral valves. Decreased expression of the hyaluronan receptor for endocytosis in myxomatous valves suggests that hyaluronan metabolism could be altered in myxomatous mitral valve disease. These findings contribute towards elucidating the pathogenesis of myxomatous mitral valve disease and developing potential new therapies.     

深Ⅱ度烧伤愈合后Bcl-xl、Bax蛋白表达与增生性瘢痕的相关性

目的探讨Bcl-xl和Bax蛋白在深Ⅱ度烧伤愈合后不同时期增生性瘢痕中的表达特点。方法人深Ⅱ度烧伤愈合后不同时期的增生性瘢痕皮肤40例,正常皮肤组织10例。分为增生期组、减退早期组、减退晚期组、成熟期组,正常对照组。免疫组织化学染色,检测Bcl-xl和Bax蛋白的表达。结果深Ⅱ度烧伤创面愈合后,Bcl-xl和Bax蛋白主要表达于表皮基底细胞和真皮层成纤维细胞,增生期和减退早期Bcl-xl和Bax蛋白产物光密度值明显高于正常皮肤(p<0.01),减退晚期和成熟期随瘢痕成熟而逐渐递减接近正常皮肤。结论 Bcl-xl和Bax蛋白表达与深Ⅱ度烧伤创面愈合后增生性瘢痕的发生和瘢痕成熟相关。     

Vascularization pattern in hypertrophic scars and keloids: a stereological analysis

Wound healing is a complex process that does not always occur harmoniously and may lead to pathological scar development, such as hypertrophic scars and keloids. Considering that vascularization can play a role in the development of these scars, and that the literature is controversial, we performed a stereological analysis of dermal for vessels of normal skin, normal scars, hypertrophic scars, and keloids. The parameters studied concerned vessels: surface density, length density; for vessels and myofibroblasts: volume density, in papillary and reticular dermis. The pattern of dermal vascularization in normal skin and normal scar showed no differences. In papillary demis, the number of vessels was higher in hypertrophic scars and keloids than in normal skin (p < 0.05). Vessels of hypertrophic scars were more dilated than those of normal skin (p < 0.01). In reticular dermis, vessels were present in higher amount in hypertrophic scars and keloids than in normal skin (p < 0.025; p < 0.001, respectively). The pattern of vascularization did not show any differences between hypertrophic scars and keloids. Our results show that hypertrophic scars and keloids have a distinct pattern of vascularization compared to normal skin and normal scars. This indicates that abnormal vascularization can be involved in the development of hypertrophic scars and keloids.     

瘢痕组织中α-平滑肌肌动蛋白的表达与细胞凋亡的关系

目的:观察α-平滑肌肌动蛋白在瘢痕组织中的表达,了解病理性瘢痕形成过程中凋亡所扮演的角色及其与肌成纤维细胞在真皮中变化的关系。方法:瘢痕标本来自烧伤后来我院进行整形手术的病人,同时取病人手术供皮区的正常皮肤作为对照。 8例瘢痕组织标本 (含 2例愈合较为平坦的瘢痕和 6例增生性瘢痕组织)被分成增殖期和成熟期两组。运用caspase-3mRNA及其蛋白的表达及TUNEL方法检测瘢痕及正常组织中的凋亡细胞,并以免疫组化法检测瘢痕及正常皮肤真皮内α-平滑肌肌动蛋白单克隆抗体的表达。结果:瘢痕组织中细胞凋亡的数目与正常组织明显不同。瘢痕内的TUNEL标记阳性细胞数多于正常组织;增殖期瘢痕内的细胞凋亡的数目多于成熟期。增殖期TUNEL标记阳性的细胞多于平坦瘢痕,而成熟期两者无显著差别,Caspase-3mRNA及其蛋白的表达与TUNEL标记结果具有一致性。随着瘢痕组织的成熟,α-平滑肌肌动蛋白单克隆抗体的表达逐渐降低,平坦的瘢痕组织中的表现尤为明显;增生性瘢痕中,增殖期与成熟期之间无显著差别。结论:正常伤口愈合过程中,肌成纤维细胞暂时性的表达,可引起伤口的收缩,随着真皮再塑形,含有α-平滑肌肌动蛋白的肌成纤维细胞因凋亡而消失,而病理性的愈合结局可能是它持续表达的结果。     

Changes in paraurethral connective tissue at menopause are counteracted by estrogen

Objective: To study whether the transition to menopause is accompanied by changes in the paraurethral connective tissue and if these changes are modified by estrogen replacement therapy. Study design: Biopsies were obtained from the paraurethral tissue from 34 women; 12 menstruating, 14 postmenopausal without estrogen treatment, and 8 with estrogen treatment. Collagen concentration and collagen extractability by pepsin digestion were measured. Proteoglycan composition and concentration were analysed using Alcian blue. The mRNA levels for collagen I and III, the small proteoglycans (PGS) decorin and biglycan, and the large proteoglycan versican, were estimated. Results: The paraurethral biopsies consisted of fibrous connective tissue, with collagen fibers as dominating structure. Several proteoglycans were identified; versican, heparansulphate proteoglycans, biglycan and decorin. The small proteoglycan decorin represented 85% of all proteoglycans. The collagen concentration was almost doubled in postmenopausal biopsies compared to premenopausal. The collagen fibril organization was also changed with higher cross-linking after menopause whereas the amount and the composition of the proteoglycans were unchanged. The proteoglycan/ collagen ratio was significantly decreased. Estrogen replacement therapy resulted in decreased collagen concentration, decreased cross-linking of the collagen and reversal of the PGS/collagen ratio to almost premenopausal level. The therapy resulted in increased levels of mRNA for collagen I and III which suggests that the changes are due to an increased turnover. Conclusion: The decrease in estrogen levels at menopause results in a connective tissue with different qualities after menopause. Estrogen replacement therapy tends to restore the metabolism of the genitourinary connective tissue to premenopausal conditions.     

Versican but not decorin accumulation is related to metastatic potential and neovascularization in testicular germ cell tumours

AIMS: To investigate the expression of versican and decorin in patients with testicular germ cell tumours (GCTs) and to correlate this with the clinicopathological findings. Matrix proteoglycans versican and decorin are frequently overexpressed in various malignancies and are involved in the progression of cancer. METHODS AND RESULTS: Overexpression of versican and decorin was detected in GCTs by immunoblotting. Immunohistochemical staining for proteoglycans was performed on 71 cases of paraffin-embedded tissues. In most of the cases increased decorin and versican stromal staining was demonstrated. In both seminomas and non-seminomatous germ cell tumours (NSGCTs) strong staining of decorin was not found to be related to any of the clinicopathological variables. Accumulation of versican was found to be associated with vascular and lymphatic invasion, nodal metastasis and disease stage in seminomas and NSGCTs and, in addition, with tumour size and distant metastasis only in NSGCTs. Additionally, only the deposition of versican was linearly correlated with the number of microvessels in the tumour stroma in GCTs. CONCLUSIONS: Ectopic versican and decorin expression is a frequent feature in GCTs. Versican but not decorin accumulation in GCTs is related to metastatic potential and neovascularization and might be a useful marker for testicular malignancy.     

Changes in paraurethral connective tissue at menopause are counteracted by estrogen

Objective: To study whether the transition to menopause is accompanied by changes in the paraurethral connective tissue and if these changes are modified by estrogen replacement therapy. Study design: Biopsies were obtained from the paraurethral tissue from 34 women; 12 menstruating, 14 postmenopausal without estrogen treatment, and 8 with estrogen treatment. Collagen concentration and collagen extractability by pepsin digestion were measured. Proteoglycan composition and concentration were analysed using Alcian blue. The mRNA levels for collagen I and III, the small proteoglycans (PGS) decorin and biglycan, and the large proteoglycan versican, were estimated. Results: The paraurethral biopsies consisted of fibrous connective tissue, with collagen fibers as dominating structure. Several proteoglycans were identified; versican, heparansulphate proteoglycans, biglycan and decorin. The small proteoglycan decorin represented 85% of all proteoglycans. The collagen concentration was almost doubled in postmenopausal biopsies compared to premenopausal. The collagen fibril organization was also changed with higher cross-linking after menopause whereas the amount and the composition of the proteoglycans were unchanged. The proteoglycan/collagen ratio was significantly decreased. Estrogen replacement therapy resulted in decreased collagen concentration, decreased cross-linking of the collagen and reversal of the PGS/collagen ratio to almost premenopausal level. The therapy resulted in increased levels of mRNA for collagen I and III which suggests that the changes are due to an increased turnover. Conclusion: The decrease in estrogen levels at menopause results in a connective tissue with different qualities after menopause. Estrogen replacement therapy tends to restore the metabolism of the genitourinary connective tissue to premenopausal conditions.     

Defective glycosylation of decorin and biglycan, altered collagen structure, and abnormal phenotype of the skin fibroblasts of an Ehlers-Danlos syndrome patient carrying the novel Arg270Cys substitution in galactosyltransferase I (beta4GalT-7)

The Ehlers–Danlos syndrome (EDS) is a heterogeneous group of connective tissue disorders affecting skin and joint function. Molecular defects in extracellular matrix proteins, including collagen (type I, III, and V) and tenascin X are associated with different forms of EDS. Compound heterozygous mutations in the B4GALT7 gene, resulting in aberrant glycosylation of the dermatan sulfate proteoglycan decorin, had been described in a single patient affected with the progeroid form of EDS. We have studied the molecular phenotype of decorin, biglycan, and collagen type I containing fibrils in skin fibroblasts of a patient carrying the novel homozygous C808T point mutation in the B4GALT7 gene, which causes an Arg270Cys substitution in β4GalT-7. Compared to control fibroblasts, galactosyltransferase activity in β4GalT-7^Arg270Cys cells was approximately three times reduced over a temperature range of 25–41°C. Pulse-chase experiments and confocal microscopy demonstrated that synthesis and secretion of decorin were normal in β4GalT-7^Arg270Cys cells. However, about 50% of decorin were synthesized as a protein core in addition to its proteoglycan form. Biglycan was found in a monoglycanated form in addition to its mature form. Glycosaminoglycan chains were of the dermatan/chondroitin sulfate type both in β4GalT-7^Arg270Cys and control cells, and epimerization was reduced for decorin and biglycan. Compared to control cells, β4GalT-7^Arg270Cys cells showed altered, highly spread or stretched phenotypes and decreased proliferation rates. At the ultrastructural level, an intracellular accumulation of multiple secondary lysosomes and degenerative vacuoles was seen in β4GalT-7^Arg270Cys cells. Furthermore, the collagen suprastructures were altered in the β4GalT-7^Arg270Cys cells. The reduced β4GalT-7 activity resulting in defective glycosylation of decorin and biglycan may be responsible for the complex molecular pathology in β4GalT-7 deficient EDS patients, given the role of these proteoglycans in bone formation, collagen fibrillogenesis, and skeletal muscle development.     

Enhanced expression of transforming growth factor-beta type I and type II receptors in wound granulation tissue and hypertrophic scar.

In the present study we have analyzed and compared, by immunohistochemistry and in situ hybridization, the expression pattern of the R4/ALK5 transforming growth factor (TGF)-beta type I receptor (RI) and the TGF-beta type II receptor (RII) in normal human skin, in wounded skin at various stages during the transition of wound granulation tissue to scar, and in long-persisting post-burn hypertrophic scars. In normal human skin, expression of RI and RII was clearly visible in the epidermis, in epidermal appendages, and in vascular cells, although only a small number of dermal fibroblasts revealed detectable levels of TGF-beta receptor expression. In contrast, granulation tissue fibroblasts showed strong expression of both TGF-beta receptor types, although in normal-healing excisional wounds their density decreased during granulation tissue remodeling. However, in post-burn hypertrophic scars, RI- and RII-overexpressing fibroblasts were found in high densities up to 20 months after injury. From these findings we suggest that the repair process of deep wounds involves the transformation of a subset of fibroblastic cells toward an increased TGF-beta responsiveness and a transient accumulation of these cells at the wound site. In addition, our study provides evidence that excessive scarring is associated with a failure to eliminate TGF-beta receptor-overexpressing fibroblasts during granulation tissue remodeling, which leads to a persistent autocrine, positive feedback loop that results in over-production of matrix proteins and subsequent fibrosis.     

Mechanical evaluation of the resistance and elastance of post-burn scars after topical treatment with tretinoin

OBJECTIVE:

After burn injuries, scarred skin lacks elasticity, especially in hypertrophic scars. Topical treatment with tretinoin can improve the appearance and quality of the skin (i.e., texture, distensibility, color, and hydration). The objective of this prospective study was to examine the effects of treatment with 0.05% tretinoin for one year on the biomechanical behavior and histological changes undergone by facial skin with post-burn scarring. Setting: Tertiary, Institutional.

METHOD:

Fifteen female patients who had suffered partial thickness burns with more than two years of evolution were selected. Skin biopsies were obtained initially and after one year of treatment. The resistance and elastance of these skin biopsies were measured using a mechanical oscillation analysis system. The density of collagen fibers, elastic fibers, and versican were determined using immunohistochemical analysis.

RESULTS:

Tretinoin treatment significantly lowered skin resistance and elastance, which is a result that indicates higher distensibility of the skin. However, tretinoin treatment did not significantly affect the density of collagen fibers, elastic fibers, or versican.

CONCLUSION:

Topical tretinoin treatment alters the mechanical behavior of post-burn scarred skin by improving its distensibility and thus leads to improved quality of life for patients.     

Ultrastructure of proteoglycans in tissue-engineered cardiovascular structures

Proteoglycans such as versican, decorin, and perlecan are important components of the extracellular matrix in various tissues. They play an important role in water homeostasis, tissue elasticity, prevention of calcification, and thrombogenicity. The aim of our study was to detect such proteoglycans in engineered tissue and compare them with the proteoglycans of native porcine heart valves. Myofibroblasts were seeded on a type I collagen scaffold. Thereafter, endothelial cells were seeded onto the presettled myofibroblasts. The newly formed tissue was histologically and immunohistochemically examined. Cupromeronic blue was used for ultracytochemical staining of proteoglycans. Radiolabeled proteoglycans were isolated by ion-exchange chromatography and characterized by enzymatic degradation. Three differently sized proteoglycan precipitates were found. The large-sized proteoglycan (154 nm) was located outside the collagen bundles in a rarely structured extracellular matrix compound. The small-sized proteoglycan (46 nm) was aligned along the collagen bundles at intervals of 60 nm. The intermediate-sized proteoglycan (56 nm) was detected on the cell surface of myofibroblasts. The glycosaminoglycans included 80% chondroitin and dermatan sulfate and 20% heparan sulfate. We conclude that proteoglycans play an important role in the functional integrity of cardiovascular tissues. This study shows the successful production of a heart valve-like tissue with proteoglycans resembling, in terms of type, production, and distribution, proteoglycans of native heart valves.     

Increased fibronectin production by cell lines from hypertrophic scar and keloid

Primary cell lines of fibroblasts from 8 tissues were established--three from hypertrophic scars (HS), one keloid (K) and four from the normal uninvolved dermis adjacent to each lesion. The objective was to quantify and compare all eight cell lines on the basis of fibronectin (FN) produced per cell and per total protein (PR). Two hypertrophic scars and their adjacent skin cell lines were evaluated by the ELISA method for FN and a micro Lowry assay for PR. The scar lines showed statistically significant increases in the amount of FN/cell compared to the cell lines from their adjacent normal dermis. The third hypertrophic scar and the keloid with their adjacent skin cell lines were assayed for FN and PR by radioimmunoprecipitation. Subconfluent cells were metabolically labeled with 35S-methionine for 20 hours. Harvested media and cell monolayers were assayed for radioactivity incorporated into FN and PR. The percentage of FN/PR was significantly higher in media for HS and K compared to the adjacent normal skin lines in the three passages tested. These results support our previous immunofluorescence studies and demonstrate that a fibroblast-type cell line from a hypertrophic scar or keloid produces more FN/PR over time than the normal fibroblast-type cell line from adjacent uninvolved dermis.     

Pathologic scar formation. Morphologic and biochemical correlates.

Morphologic and biochemical analyses were performed to compare normal skin and mature scars to hypertrophic scar and keloid. Correlation of morphologic findings with biochemical profiles of the skin and scar samples proved feasible and enlightening. Scanning electron microscopy (SEM) was used to characterize the architectural arrangement of collagen fibers in skin and scars. Cultured fibroblasts from each specimen were also examined with the SEM. A biochemical profile of each tissue specimen was constructed, characterizing the collagen component of the specimen by sequential molecular sieve and ion exchange chromatography to determine a) the degree of intermolecular crosslinking, b) amino acid analysis, and c) levels of lysyl oxidase activity. Results indicate that collagen fibers and fiber bundles display a decreasing level of organization as the clinical degree of scar abnormality increases, and this structural gradient correlates with the gradient of intermolecular crosslinking in the same tissue--normal skin and mature scar being highly crosslinked, hypertrophic and keloid successively less so. Surprisingly, the level of the crosslinking enzyme lysyl oxidase is normal or elevated in hypertrophic scar and keloid despite the relative lack of crosslinking. Amino acid content was uniform for all specimens. Scanning electron microscopy examination of cultured fibroblasts from the tissue specimens demonstrated three phenotypically distinctive fibroblasts whose numerical and volumetric proportions correlated with the tissue of origin.     

Anomalous expression of HLA class II molecules on keratinocytes and fibroblasts in hypertrophic scars consequent to thermal injury.

Immunoperoxidase staining of skin sections obtained from 11 hypertrophic scars, six normotrophic scars and three samples of normal skin were performed using anti-HLA monoclonal antibodies (HLA-DR, -DQ, class I), anti-interleukin-2 receptor (IL-2R) and anti-CD1. Sections from all hypertrophic scars showed an anomalous expression of HLA-DR molecules on keratinocytes and fibroblasts. Moreover hypertrophic scars were characterized by dense infiltrates of IL-2R-positive cells and by the presence of abundant Langerhans (CD1+) cells in the epidermis and dermis. These results support the hypothesis that immunologic mechanisms play an important role in hypertrophic scarring and point to an involvement of cell-mediated immune phenomena.