The proteoglycans in hypertrophic scar

Sulfated proteoglycans of hypertrophic scar (6 months old after a burn) were extracted with 6 M hot urea, 0.02 M phosphate buffer, pH 7.0, containing protease inhibitors. Two types of proteoglycans, dermatan sulfate proteoglycans and chondroitinsulfate rich proteoglycans, were recovered. The dermatan sulfate proteoglycans, which are capable of binding to concanavalin A, were composed of Mr=53000 core protein and iduronate rich dermatan sulfate. The chondroitin sulfate rich proteoglycans did not bind to concanavalin A but had the same size core proteins as the dermatan sulfate proteoglycans, based on SDS-polyacrylamide gel electrophoresis. The tryptic peptide mappings showed that the core proteins from dermatan sulfate have the same structural sequences as those from chondroitin sulfate rich proteoglycans.     

Steroid-induced 'granulomas' in hypertrophic scar

Intralesional steroids injected into hypertrophic scars and keloids can result in histiocytic and foreign body granulomatous reaction which may be confused with focal mucinosis or necrobiotic process such as rheumatoid nodule. An awareness of this possibility might avoid unnecessary investigations in the patient.     

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.     

增生性瘢痕的预防与治疗进展

瘢痕是人体创伤修复过程的自然产物,但过度修复将导致病理性瘢痕的形成。增生性瘢痕是常见的病理性瘢痕,引起瘙痒、疼痛、烧灼感和不适,严重影响患者生活。目前可从手术设计、术后应用硅胶膜及注射肉毒素方面预防瘢痕发生,新的治疗方法如局部注射药物、激光治疗及中药治疗等都展现了很好的疗效,有望成为治疗瘢痕的主要选择。本文将结合国内外最新文献对增生性瘢痕防治的进展作一综述。     

Crosslink of collagen in hypertrophic scar.

It is conceivable that intramolecular and intermolecular crosslinks of collagen may be involved in the formation of hypertrophic scar, but little is known about the relationship between hypertrophic scar and crosslinks of collagen. We have isolated a new crosslinking amino acid from collagen and have named it pyridinoline. In this investigation, we examined the content of pyridinoline in human normal skin, mature scar and hypertrophic scar. An appreciable amount of pyridinoline was found in collagen of hypertrophic scar, but pyridinoline is virtually absent in collagen of normal skin.     

Collagen degradation in cultured keloid and hypertrophic scar tissue

SUMMARY In order to study collagen catabolism of normal human skin, keloid and hypertrophic scars, explants of these tissues have been cultured for periods of up to 10 days. All three tissues released a similar amount of neutral collagenase activity into the culture medium with maximal yield between days 3 and 7, and the collagenase from scar tissues was found to be identical to the normal skin enzyme with regard to its inhibition by EDTA, cysteine and human serum. The major site of collagenase production in keloid specimens appeared to be, as in normal skin, the upper dermal or epidermal layer, with minimal production occurring in the lower fibrous or nodular areas. Prior to culture the collagen content of each tissue was found to be similar, with approximately 1%, of the total being acid-soluble. During the culture period considerable amounts of insoluble tissue collagen were degraded in all three tissues, as judged by the release of hydroxyproline into the culture medium. These results suggest that the persistence of keloids and hypertrophic scars is attributable neither to an inability of the tissues to produce an active collagenase molecule nor to any resistance of the tissue collagen to degradation.     

Shedding of proangiogenic microvesicles from hypertrophic scar myofibroblasts

Hypertrophic scars are a common complication of burn injuries and represent a major challenge in terms of prevention and treatment. These scars are characterized by a supraphysiological vascular density and by the presence of pathological myofibroblasts (Hmyos) displaying a low apoptosis propensity. However, the nature of the association between these two hallmarks of hypertrophic scarring remains largely unexplored. Here, we show that Hmyos produce signalling entities known as microvesicles that significantly increase the three cellular processes underlying blood vessel formation: endothelial cell proliferation, migration and assembly into capillary‐like structures. The release of microvesicles from Hmyos was dose‐dependently induced by the serum protein α‐2‐macroglobulin. Using flow cytometry, we revealed the presence of the α‐2‐macroglobulin receptor—low‐density lipoprotein receptor‐related protein 1—on the surface of Hmyos. The inhibition of the binding of α‐2‐macroglobulin to its receptor abolished the shedding of proangiogenic microvesicles from Hmyos. These findings suggest that the production of microvesicles by Hmyos contributes to the excessive vascularization of hypertrophic scars. α‐2‐Macroglobulin modulates the release of these microvesicles through interaction with low‐density lipoprotein receptor‐related protein 1.     

Suppressed inflammatory gene expression during human hypertrophic scar compared to normotrophic scar formation

Hypertrophic scar formation is a result of adverse cutaneous wound healing. The pathogenesis of hypertrophic scar formation is still poorly understood. A problem next to the lack of suitable animal models is that often normal skin is compared to hypertrophic scar (HTscar) and not to normotrophic scar (NTscar) tissue. Another drawback is that often only one time period after wounding is studied, while scar formation is a dynamic process over a period of several months. In this study, we compared the expression of genes involved in inflammation, angiogenesis and extracellular matrix (ECM) formation and also macrophage infiltration in biopsies obtained before and up to 52 weeks after standard surgery in five patients who developed HTscar and six patients who developed NTscar. It was found that HTscar formation coincided with a prolonged decreased expression of inflammatory genes (TNFα, IL‐1α, IL‐1RN, CCL2, CCL3, CXCL2, CXCR2, C3 and IL‐10) and an extended increased expression of ECM‐related genes (PLAU, Col3A1, TGFβ3). This coincided with a delayed but prolonged infiltration of macrophages (type 2) in HTscar tissue compared to NTscar tissue. These findings were supported by immunohistochemical localization of proteins coding for select genes named above. Our study emphasizes that human cutaneous wound healing is a dynamic process that is needed to be studied over a period of time rather than a single point of time. Taken together, our results suggest innate immune stimulatory therapies may be a better option for improving scar quality than the currently used anti‐inflammatory scar therapies.     

Neuropeptide-containing nerves in painful hypertrophic human scar tissue

Specimens of hypertrophic scar tissue (n= 9). non-hypertrophic, flat scar tissue (n= 5) and control skin (n= 3) were obtained from eight adult females (aged 22–56) and three adult males (aged 22–59). The specimens were studied histologically and immunohistochemically for vasoactive intestinal polypeptide, neuropeptide Y, calcitonin gene-related peptide, substance P, somatostatin, [Met]enkephalin, [Leu]enkephalin, and the enzyme dopamine β-hydroxylase. The non-hypertrophic scar tissues were not dissimilar to the control tissue, but contained connective tissue in bundles with a greater number of collagen fibres. In the hypertrophic scar tissue of some patients, the dermis contained adipose tissue displaced upwards from the hypodermis. The connective tissue contained densely packed collagen fibres and fibroblasts; this region was devoid of hair follicles, sweat glands and blood vessels, although they were observed in the region of loosely packed connective tissue. The normal skin contained all the neuropeptides studied, except somatostatin-, and dopamine β-hydroxylase-immunoreactive nerves, which were seen as single fibres or in nerve bundles, and were associated with blood vessels in the dermis. Neuropeptide Y-immunoreactive nerves were found in the arrector pili muscle, and neuropeptide Y-, vasoactive intestinal polypeptide-, calcitonin gene-related peptide-, [Met]enkephalin- and dopamine β-hydroxylase-containing nerves were found within sweat glands. In patients with flat, non-hypertrophic scar tissue, neuropeptides and dopamine β- hydroxylase-containing nerves were absent. In patients with hypertrophic scars, the density of neuropeptide Y-, vasoactive intestinal polypeptide-, substance P-, calcitonin gene-related peptide- and dopamine β-hydroxylase-immunoreactive nerves was greater in the dermis when compared with controls. They were found at the base of the epidermis, around blood vessels, and in sweat and sebaceous glands. Only substance P-immunoreactive nerves penetrated the densely packed collagen and fibroblast matrix, whereas neuropeptide Y-, calcitonin gene-related peptide-, vasoactive intestinal polypeptide- and dopamine β-hydroxylase-containing nerves were found in the loosely packed connective tissue. [Met]enkephalin-, [Leu]enkephalin- and somatostatin-immunoreactive nerves were rarely seen in all three groups of patients. In conclusion, neuropeptide-containing nerves appear to be present in patients with painful, hypersensitive, hypertrophic scars, but absent in flat, insensitive, non-hypertrophic scars.     

Where we stand with human hypertrophic and keloid scar models

We have yet to create a human scar model that demonstrates the complex nature of hypertrophic scar and keloid formation as well as ways to prevent them despite emerging advances in our understanding of the immune system, the inflammatory response, and proteomic and genomic changes after injury. Despite more complex in vitro models, we fail to explain the fundamental principles to scar formation, and the timeline of their development. The solution to developing the ideal in vitro scar model is one that mimics the heterogeneous cellular and molecular interactions, as well as the evolving structure and function of human skin.     

The renin-angiotensin system in cutaneous hypertrophic scar and keloid formation

Hypertrophic scar and keloid are two types of fibroproliferative conditions that result from excessive extracellular matrix production. The underlying pathological mechanism is not entirely clear. Activation of the renin-angiotensin system (RAS) is associated with fibrosis in various organs. RAS components including angiotensin II (Ang II), angiotensin AT₁ and AT₂ receptors, and angiotensin-converting enzyme (ACE) are expressed in the skin and act independently from the plasma RAS. AT₁ receptors, which are usually the dominating receptor subtype, promote fibrosis and scar formation, while AT₂ receptors inhibit the aforementioned AT₁ receptor-coupled effects. Elevated angiotensin II (Ang II) levels acting on the AT₁ receptor contribute to skin scar formation through increased expression of inflammatory factors such as interleukin-6 (IL-6), angiogenic factors such as vascular endothelial growth factor (VEGF) and fibrinogenic factors such as transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF), while at the same time suppressing the anti-fibrotic tissue inhibitors of matrix metalloproteinase (TIMPs). First, small clinical trials have provided evidence that inhibition of the ACE/Ang II/ AT₁ receptor axis may be effective in the treatment of hypertrophic scars/keloids. This review provides a detailed overview of the current literature on the RAS in skin, wound healing and scar formation and discusses the translational potential of targeting this hormonal system for treatment and prevention of hypertrophic scars and keloids.     

Growth kinetics of fibroblasts derived from normal skin and hypertrophic scar

In vitro growth kinetics of fibroblasts derived from normal skin and hypertrophic scar were performed using continuous 3H-thymidine labeling method. In fibroblasts derived from normal skin, aging of the donor affects cell growth mainly by growth fraction (GF), but not labeling index (LI) and DNA synthetic time (Ts). When hypertrophic scar-derived fibroblasts are compared with normal fibroblasts, they showed a shorter Ts and lower LI and GF. This result suggests that in hypertrophic scar a small number of fibroblasts proliferate more actively, but most fibroblasts are non-growing cells.     

光动力治疗防治增生性瘢痕的研究进展

光动力治疗是利用光敏剂和光辐射进行疾病治疗的新方法,目前广泛用于实体恶性肿瘤、某些癌前病变和良性病变的治疗。而增生性瘢痕是在皮肤伤口愈合过程中,成纤维细胞和胶原纤维异常增生的结果。由于其发病机理尚未完全清楚,目前仍缺乏十分有效的防治方法。本文主要讨论光动力疗法在增生性瘢痕防治中的应用。     

Laser-Assisted Skin Healing (LASH) in hypertrophic scar revision

Abstract

Laser-Assisted Skin Healing (LASH) is based on the therapeutic effects of controlled thermal post-conditioning. The authors have previously demonstrated on humans that an 810-nm diode-laser system could assist wound closure leading to an improvement of wound healing with a resulting indiscernible scar. A 47-year-old woman (skin type II), who developed systematically hypertrophic scars after surgery, was enrolled for a hypertrophic scar revision. Excess scar tissue was removed. Immediately after the conventional closure of the incision, laser irradiation (120 J/cm²) using a 0.8 cm² spot size (rectangular spot, length = 20 mm, width = 4 mm) was applied. Topical silicone gel sheeting (Cerederm®) was applied for 2 months afterwards to prevent a thick scar from reforming. No complications occurred during the course of this study. No recurrence of hypertrophic scarring was noticed 6 months after scar revision. This study reports, for the first time, the possibility of improving the appearance of hypertrophic scarring in scar revision by altering through thermal stress the wound-healing process. Since the appropriate initial management of wounds is of importance, the LASH technique could be offered as a new approach to prevent hypertrophic scarring.     

EGCG inhibits hypertrophic scar formation in a rabbit ear model

Objective

Hypertrophic scarring is a common skin fibro-proliferative disease, but currently there has no satisfactory drugs for anti-scar treatments. Previous study showed that epigallocatechin gallate (EGCG), the main catechin in green tea, improved wound healing and tissue fibrosis in both rats and mice. In the present study, the therapeutic effects of EGCG on hypertrophic scar were analyzed using a rabbit ear hypertrophic scar model.

Materials

A rabbit ear model of hypertrophic scarring was used. DMSO, 0.5 mg EGCG/wound, 1.0 mg EGCG/wound or triamcinolone were injected subcutaneously once a week for 4 weeks. The scar elevation index (SEI) was measured using HE staining images, the collagen fibers were examined by Masson’ trichrome staining images, and the number of capillaries in hypertrophic scar were calculated by CD31 staining images. The mRNA levels in the scar tissues were detected by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

Gross observation and histological evaluation showed the inhibitory effects of EGCG on hypertrophic scar formation at both doses, and decreased scar height and SEI were detected. EGCG also attenuated the mean collagen area fraction and decreased the number of capillaries in scar tissues. qRT-PCR revealed that EGCG significantly inhibited the mRNA expression of TGF-β1, Col I, Col III, α-SMA, and eNOS.

Conclusion

EGCG may serve as a useful candidate therapeutic drug for hypertrophic scar via inhibiting fibrotic gene expression and suppressing angiogenesis.     

Reduced collagenase gene expression in fibroblasts from hypertrophic scar tissue

Summary The major histopathological feature of hypertrophic scar lesions is fibrosis. characterized by excessive accumulation of collagen. The purpose of this study was to determine if there is not only increased expression of collagen but also decreased expression of collagenase in hypertrophic scar fibroblasts. We compared the expression of mRNA for of α₁ (I) and α₁ (III) collagen, and collagenase in cultured fibroblasis from different portions of hypertrophic scars and normal dermis. the hypertrophic scar fibroblasts. increased levels of α₁ (I) and α₁ (III) collagen mRNAs were observed in fibroblasts from the edge and outside of scar tissue, while normal levels were noted in fibroblasts from the centre of this tissue. In contrast. decreased levels of collagenase mRNA were found in the hypertrophic scar fibroblasts. The reductions were centre (25% of the control) greater than the edge (43% of the control) greater than the outside (84% of the control). The changes in the collagenase mRNA levels of the hypertrophic scar fibroblasts correlated well with decreased collagenolytic activity as determined by the degradation rate of fluorescent isothiocyanate-labelled type I collagen in fibroblast culture supernatant. These results suggest that decreased expression of collagenase in hypertrophic scar fibroblasts may be one possible cause for the excessive accumulation of collagen in the skin lesions of hypertrophic scars.