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.     

肥厚性瘢痕和瘢痕瘤的病因病理学研究进展

在皮肤的愈合过程中，产生的瘢痕组织会高出皮肤表面，引起红、肿、热、痛及活动受限，甚者可导致严重的功能性问题或影响容貌，即所谓的瘢痕组织过度增生，包括肥厚性瘢痕和瘢痕瘤。本文对肥厚性瘢痕和瘢痕瘤的病因病理研究进行综述：     

Factor XIIIa-positive dermal dendritic cells in keloids and hypertrophic and mature scars

Keloids and hypertrophic scars have several common features. Both are reddish, firm, slightly protruding lesions that consist of proliferative fibroblastic cells and collagenous tissues. The aim of the present study was to evaluate the contribution of factor XIIIa (FXIIIa)-positive dermal dendritic cells to formation of keloids and hypertrophic scars. The numbers of FXIIIa-positive cells were counted in the keloid, hypertrophic scar and mature scar, each of which was divided into fibrocollagenous area and superficial dermal area overlying the nodular lesion. The features of the FXIIIa-positive cells were examined using immunohistochemical and immunoelectron microscopic techniques. More FXIIIa-positive cells were present in the overlying dermal area than in the fibrocollagenous area, commonly in three types of dermal lesion. The number of FXIIIa-positive dendritic cells was significantly greater in the overlying dermal area of keloids than in the corresponding area of hypertrophic or mature scar. Immunoelectron microscopic examination showed that the immunoreactivity for FXIIIa was seen mainly at the periphery of the cytoplasm of dermal dendritic cells. These results suggest that FXIIIa-positive dendritic cells in the overlying dermal area play active roles in formation of keloids and may contribute to dermal-epidermal interactions in keloids.     

Use of nude (athymic) mice for the study of hypertrophic scars and keloids: vascular continuity between mouse and implants

Hypertrophic scars and keloids appear to be unique to humans since animals are not known to form these lesions. Therefore, in an effort to develop an experimental model for their study, implants of these human lesions were made in nude (athymic) mice (nu/nu) in suprascapular subcutaneous pockets. The implants were recovered from 2 to 246 days. By histological and fine structural parameters all implants remained viable and their morphological character was maintained. Selected mice were injected with barium to confirm by microangiography vascular flow between mouse and implant. Hoechst stain for DNA, used to distinguish mouse cells from human cells, confirmed vascular anastamosis between host and implant: barium-filled vessels in the interior of the implant demonstrated human endothelial cells. Peripheral vascularization of the implant with minimal ingrowth of mouse vessels occurs during the first 8 days. Anastamosis probably occurs sometime before 16 days postimplantation, or earlier, depending upon the availability of patent microvessels in the implanted tissue. The presence of the implant does not appear to prompt a continuing vascular growth into or throughout the implant. The time frame of 16 days postimplantation should be taken into account when developing schemata of experimental or therapeutic modalities.     

A quantitative ultrastructural study of collagen fibrils in human skin normal scars,and hypertrophic scars

The diameter-distribution of collagen fibrils in the dermis of human skin and scar tissue has been investigated. In samples of normal skin, normal scar, and hypertrophic scar, prepared for transmission electron microscopy, collagen fibrils were systematically random-sampled and their diameters measured. There was a statistically significant difference between the diameter-distribution of fibrils in the papillary and reticular layers of dermis in normal skin. A similar pattern was found in normal scar, but not in hypertrophic scar. © 1995 WiIey-Liss, Inc.     

Contribution of epidermal stem cells to hypertrophic scars pathogenesis

Hypertrophic scars are fibroproliferative disorders of excessive wound healing due to an imbalance between synthesis and degradation and the mechanism leading to hypertrophic scars formation is poorly understood and currently no successful treatment modality exists.We hypothesize epidermal stem cells (ESCs), which could inhibit epidermal fibrosis, plays a substantial contributory role in the pathogenesis of hypertrophic scars.Accepting the hypothesis to be correct, a therapy that inhibits cell and extracellular matrix proliferation can be used to prevent the hypertrophic scars formation.Current therapies are only partially effective and safe because they couldn’t inhibit the cell and extracellular matrix proliferation and eliminate other relative factors of hypertrophic scars formation at all, such as: absence of epidermal–mesenchymal interaction, and at the same time inducing death (apoptosis and necrosis) of other normal cells.A more efficient prevention of hypertrophic scars could be achieved using tissue engineering skin enriched with ESCs and introduced recombinant genes into ESCs which could inhibit hypertrophic scars formation.     

Activated keratinocytes in the epidermis of hypertrophic scars.

The etiology of hypertrophic scarring, a pathological end point of wound healing, is unknown. The scars most commonly occur when epithelialization has been delayed during, for example, the healing of deep dermal burn wounds. Hypertrophic scars are conventionally described as a dermal pathology in which the epidermis has only a passive role. In this study, the expression of keratin intermediate filament proteins and filaggrin has been investigated in the epidermis of hypertrophic scars and site-matched controls from the same patients. Hypertrophic scar epidermis was found to express the hyperproliferative keratins K6 and K16 in interfollicular epidermis in association with K17 and precocious expression of filaggrin. K16 mRNA was localized by in situ hybridization using a highly specific cRNA probe. In contrast to the immunohistochemical location of K16 protein, the K16 mRNA was found to be expressed in the basal cell layer of normal skin. In hypertrophic scars the mRNA distribution corroborated the abnormal K16 protein distribution. These results suggest the keratinocytes in hypertrophic scar epidermis have entered an alternative differentiation pathway and are expressing an activated phenotype. Activated keratinocytes are a feature of the early stages of wound healing producing growth factors that influence fibroblasts, endothelial cells, and the inflammatory response. We propose that cellular mechanisms in the pathogenesis of hypertrophic scarring are more complex than isolated dermal phenomena. The persistence of activated keratinocytes in hypertrophic scar epidermis implicates abnormal epidermal-mesenchymal interactions.     

Keloids and hypertrophic scars of Caucasians show distinctive morphologic and immunophenotypic profiles

The aim of this study was to identify possible morpho-phenotypic differences between keloids (K) and hypertrophic scars (HS) in a Caucasian population. Young HS (< or =1 year of age) presented a high number of diffusely distributed spindle-shaped cells (alpha-smooth-muscle actin+ and fibronectin+). Fully developed HS (> 1 year of age and <3 years of age) were characterized by the frequent presence of distinct collagenous cellular nodules (cells: alpha-smooth-muscle actin+ and fibronectin+). Old HS (> or =3 years of age) showed widespread collagenization phenomena. The histological profile of K was not related to the age of the lesion and was characterized by the almost constant presence of abnormally thick, hyalinized collagen fibers, the presence of collagenous cellular nodules, and variable--albeit lower than in HS-- expression of alpha-smooth-muscle actin and fibronectin. Ultrastructurally, myofibroblasts were the predominant cell type in young and fully developed HS and in K. The immune-cell infiltrate was composed of CD3+, CD45RO+, CD4+, human lymphocyte antigen (HLA)-DR+, and lymphocyte function associated antigen (LFA)-1+ T lymphocytes, strictly associated with CD1a+/ CD36+, HLA-DR+, and intercellular adhesion molecule (ICAM)-1+ dendritic cells, both in HS and K. However, different amounts of immune cells were observed in relation to the type and age of the lesion, and these findings support the hypothesis that cell-mediated, major histocompatibility complex (MHC)-class II-restricted immune responses play an important role in the development of HS and K.     

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.     

Epidermis promotes dermal fibrosis: role in the pathogenesis of hypertrophic scars

Hypertrophic scarring is a pathological process characterized by fibroblastic hyperproliferation and by excessive deposition of extracellular matrix components. It has been hypothesized that abnormalities in epidermal-dermal crosstalk explain this pathology. To test this hypothesis, a tissue-engineered model of self-assembled reconstructed skin was used in this study to mimic interactions between dermal and epidermal cells in normal or pathological skin. These skin equivalents were constructed using three dermal cell types: normal wound (Wmyo) or hypertrophic wound (Hmyo) myofibroblasts and normal skin fibroblasts (Fb). Epidermis was reconstructed with normal skin keratinocytes (NK) or hypertrophic scar keratinocytes (HK). In the absence of keratinocytes, Hmyo formed a thicker dermis than Wmyo. When seeded with NK, the dermal thickness of Hmyo (121.2 +/- 31.4 microm vs 196.2 +/- 27.8 microm) and Fb (43.7 +/- 7.1 microm vs 83.6 +/- 16.3 microm) dermis was significantly (p < 0.05) reduced, while that of Wmyo (201.5 +/- 15.7 microm vs 160.7 +/- 21.1 microm) was increased. However, the presence of HK always induced significantly thicker dermis formation than observed with NK (Wmyo: 238.8 +/- 25.9 microm; Hmyo: 145.5 +/- 22.4 microm; Fb: 74.2 +/- 11.2 microm). These results correlated with collagen and MMP-1 secretion and with cell proliferation, which were increased when keratinocytes were added, except for the collagen secretion of Hmyo and Fb in the presence of NK. The level of dermal apoptosis was not different when epidermis was added to the dermis (<1% in each category). These observations strongly suggest that hypertrophic scar keratinocytes play a role in the development of pathological fibrosis by influencing the behaviour of dermal cells.     

Smad泛素化调节因子-2及其mRNA在增生性瘢痕组织中的表达

目的研究烧伤后增生性瘢痕组织中Smad泛素化调节因子－2（Smurf2）及其mRNA的表达。方法选取烧伤后增生性瘢痕患者9例,取材于患者整形手术切除的瘢痕,同时取同一患者剩余正常皮肤作为对照。Western blotting方法检测smurf2蛋白水平,RT—PCR检测其mRNA表达;进一步分离培养人正常皮肤和增生性瘢痕成纤维细胞,加入外源件转化生长凶子β1（TGF—β1）刺激,观察Smurf2蛋白和mRNA水平的变化。结果增生性瘢痕组织中Smurf2蛋白水平和mRNA表达显著高于正常皮肤（P〈0．05）,而且,在外源性TGF—β1刺激下,瘢痕成纤维细胞中Smurf2蛋白和mRNA表达呈时间依赖性增加。结论烧伤后增生性搬痕组织中Smurf2及其mRNA表达增强;在TGF—β1刺激下,瘢痕成纤维细胞中Smurf2及儿mRNA表达逐渐增加。     

基质金属蛋白酶13和转化生长因子β1在瘢痕疙瘩和增生性瘢痕中的表达

背景：与瘢痕疙瘩和增生性瘢痕发生机制相关的基质金属蛋白酶13和转化生长因子β1信号传递通路研究多集中在体外成纤维细胞的培养上,而在组织中的相关研究少见报道。 目的：观察瘢痕疙瘩和增生性瘢痕中基质金属蛋白酶13和转化生长因子β1蛋白的表达。 方法：取自2004/2008唐山市工人医院烧伤整形科手术患者,瘢痕疙瘩54例,增生性瘢痕42例。选取同期45例因非感染手术切除的正常瘢痕组织作为对照组,选取同期45例正常皮肤组织作为正常对照组。应用流式细胞仪检测4组中基质金属蛋白酶13和转化生长因子β1的表达,分析两者的相关性。 结果与结论：瘢痕疙瘩和增生性瘢痕中转化生长因子β1的表达明显高于正常瘢痕组织和正常皮肤组织;正常瘢痕组织中转化生长因子β1的表达明显则高于正常皮肤组织,而基质金属蛋白酶13的表达与之相反。瘢痕疙瘩、增生性瘢痕和正常瘢痕组织中基质金属蛋白酶13和转化生长因子β1表达呈负相关。由此推测基质金属蛋白酶13和转化生长因子β1在瘢痕组织中异常表达,二者可能具有协同负向作用,共同参与病理性瘢痕的发生发展。     

干扰素a-2b对增生性瘢痕HLA-DR和CD1a分子的影响

目的:探讨干扰素a-2b对增生性瘢痕HLA-DR和CD1α。分子的作用。方法 利用免疫组织化学方法检测6例增生性瘢痕（HS）和6例正常皮肤HLA-DR和CD1α分子的分布及密度,观察干扰素a-2b治疗后HS HLA-DR和CD1α分子的变化。结果:（1）HS组织表皮HLA-DR LC的数量806.67±101.72个//mm2和表皮CD1α LC的数量700.00±108.82个/mm2明显高于正常皮肤510.00±45.07个/mm2,521.24±57.87个/mm（P<0.05）。（2）HS组织HLA-DR分子在角质形成细胞和成纤维细胞中异常出现。（3）于扰素a-2b治疗3d时HS表皮HLA-DR LC及CD1α LC的数量分别为283.34±73.12个/mm2,220.00±83.92个/mm2,7d时516±49.67个/mm2,589.10±108.82个/mm2,干扰素a-2b治疗后HS表皮HLA-DR LC及CD1αLC的数量明显降低（P<0.05）。结论:（1）HLA-DR和CD1α分子数量的增加提示HS和K局部组织可能处于高兔疫应答状态;（2）干扰素a-2b可能通过抑制HLA-DR和CD1α分子降低HS高免疫应答的状态。     

In vivo inhibition of hypertrophic scars by implantable ginsenoside-Rg3-loaded electrospun fibrous membranes

Clinically, hypertrophic scarring (HS) is a major concern for patients and has been a challenge for surgeons, as there is a lack of treatments that can intervene early in the formation of HS. This study reports on a Chinese drug, 20(R)-ginsenoside Rg3 (GS-Rg3), which can inhibit in vivo the early formation of HS and later HS hyperplasia by inducing the apoptosis of fibroblasts, inhibiting inflammation and down-regulating VEGF expression. Implantable biodegradable GS-Rg3-loaded poly(l-lactide) (PLA) fibrous membranes were successfully fabricated using co-electrospinning technology to control drug release and improve drug utilization. The in vivo releasing time of GS-Rg3 lasts for 3 months, and the drug concentration released in rabbits can be controlled by varying the drug content of the electrospun fibers. Histological observations of HE staining indicate that GS-Rg3/PLA significantly inhibits the HS formation, with obvious improvements in terms of dermis layer thickness, epidermis layer thickness and fibroblast proliferation. The results of immunohistochemistry staining and Masson’s trichrome staining demonstrate that GS-Rg3/PLA electrospun fibrous membranes significantly inhibit HS formation, with decreased expression of collagen fibers and microvessels. VEGF protein levels are much lower in the group treated with GS-Rg3/PLA eletrospun membranes compared with other groups. These results demonstrate that GS-Rg3 is a novel drug, capable of inhibiting the early formation of HS and later HS hyperplasia. GS-Rg3/PLA electrospun membrane is a very promising new treatment for early and long-term treatment of HS.     

Mechanical forces induce scar remodeling. Study in non-pressure-treated versus pressure-treated hypertrophic scars.

Reparative process of second and third degree burns usually results in hypertrophic scar formation that can be treated by pressure. Although this method is efficient, its mechanisms of action are not known. In this work, we have studied the histological organization of hypertrophic scars submitted to pressure. Skin biopsies were performed 2 to 7 months after the onset of treatment in two adjacent regions of the scar, non-pressure- or pressure-treated and analyzed by immunohistochemistry and transmission electron microscopy for extracellular matrix organization and cellular morphology. In non-pressure-treated regions, fibrillin deposits did not present the classical candelabra-like pattern under epidermis and were reduced in dermis; in pressure-treated regions the amount was increased compared to non-pressure-treated regions but the organization was still disturbed. In non-pressure-treated regions, elastin was present in patch deposits; in pressure-treated regions elastin formed fibers, smaller than in normal dermis. Tenascin was present in the whole dermis in non-pressure-treated regions, whereas in pressure-treated regions it was observed only under epidermis and around vessels, as in normal skin. alpha-Smooth muscle actin-expressing myofibroblasts were absent in normal skin, present in large amounts in non-pressure-treated regions, and almost absent in pressure-treated regions. The disturbed ultrastructural organization of dermal-epidermal junction observed in non-pressure-treated regions disappeared after pressure therapy; typical features of apoptosis in fibroblastic cells and morphological aspects of collagen degradation were observed in pressure-treated regions. Our results show that, in hypertrophic scars, pressure therapy restores in part the extracellular matrix organization observed in normal scar and induces the disappearance of alpha-smooth muscle actin-expressing myofibroblasts, probably by apoptosis. We suggest that the pressure acts by accelerating the remission phase of the postburn reparative process.