Andréa Monte Alto Costa

Fibrillin-1 and elastin are differentially expressed in hypertrophic scars and keloids

Hypertrophic scars and keloids are two forms of excessive cutaneous scarring. Considering the importance of extracellular matrix elements in tissue repair, a morphological and quantitative analysis of the elastic system components (fibrillin‐1 and elastin) was performed in normal skin, normal scars, hypertrophic scars, and keloids. In superficial and deep dermis, fibrillin‐1 volume density was significantly higher in normal skin compared with normal scars, hypertrophic scars, and keloids. The fibrillin‐1 volume density did not show differences between hypertrophic scars and keloids in superficial or deep dermis. In superficial dermis, elastin volume density was higher in normal skin compared with normal scars, hypertrophic scars, and keloids. In deep dermis, the elastin volume density was higher in keloids compared with normal skins, normal scars, and hypertrophic scars. We showed that the distribution of fibrillin‐1 and elastin is disrupted in all kinds of scars analyzed, but there are two patterns: one for normal scars and another for excessive scars.

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.

S-nitrosoglutathione-containing hydrogel accelerates rat cutaneous wound repair

Background  Nitric oxide (NO) plays a key role in wound repair and S‐nitrosothiols like S‐nitrosoglutathione (GSNO) are well known NO donors.

Expression and cellular localization of fibrillin-1 in normal and pathological human liver.

BACKGROUND The expression and the distribution of fibrillin-1 and elastin were studied in normal and pathological human liver samples. METHODS As controls, histologically normal/subnormal liver samples (n = 24) were used. Pathological samples corresponded to seven cirrhosis and eight hepatocellular carcinomas (HCC) developed on cirrhotic (four) or noncirrhotic (four) liver. RESULTS In normal liver, fibrillin-1 and elastin co-localized in vessel walls and portal tract connective tissue. Fibrillin-1 alone was detected along sinusoids and in portal spaces at the interface with the limiting hepatocytic plates and close to the basement membrane of bile ducts. By transmission electron microscopy, typical bundles of microfibrils were detected both in Disse space and in portal zones. Cirrhotic nodules were usually rich in fibrillin-1 along sinusoids; fibrillin-1 and elastin were co-localized in fibrotic septa surrounding nodules. In HCC, fibrillin-1 was present between tumoral hepatocytes; stromal reaction around the tumors contained both fibrillin-1 and elastin. CONCLUSIONS Fibrillin-1 was associated with elastin in portal mesenchyme and vessel walls of normal liver, in fibrotic septa around cirrhotic nodules and stromal reaction around HCC, but was expressed alone in the perisinusoidal space. The functional roles for fibrillin-1 in non-elastic tissues, such as the liver, remain to be elucidated.

Normal scarring: importance of myofibroblasts

Granulation tissue fibroblasts (myofibroblasts) develop several ultrastructural and biochemical features of smooth muscle cells, including the presence of microfilament bundles and the expression of a-smooth muscle actin, the actin isoform typical of contractile vascular smooth muscle cells. Myofibroblasts have been proposed to play a retractile role in wound contraction. Myofibroblasts are also the main cell type implicated in the synthesis of extracellular matrix components. During granulation tissue formation, a high proportion of myofibroblasts have been found to express a-smooth muscle actin. When contraction stops and the wound is fully epithelialized, myofibroblasts containing a-smooth muscle actin disappear by apoptosis and the scar becomes less cellular and composed of typical fibroblasts with well-developed rough endoplasmic reticulum that no longer show abundant microfilaments. Drugs that can decrease myofibroblastic differentiation and granulation tissue formation (c-interferon, pentoxifylline, trans-resveratrol) may display antiscarring activities. Recently, it has been suggested that myofibroblastic differentiation represents an adaptative response to modification of the extracellular matrix environment. Granulation tissue remodeling also involves the degradation of extracellular matrix components and high levels of extracellular proteolytic activities. The balance between matrix-degrading enzymes and their endogenous inhibitors may be important in this process and may also have a role in regulating cell death during scar resolution. Further studies on granulation tissue formation and remodeling will be useful for understanding the mechanisms of development and regression of pathological processes such as excessive scarring. As with many organs, three tissue layers are observed in the skin: epithelia, basement membrane, and stroma. The epidermis, which is the external tissue layer of the skin and which contains keratinocytes arranged in several layers, protects the organism against dehydration and acts as a physical barrier against invasion by microorganisms. It also protects against diverse insults, including those of thermal, chemical, mechanical, and ultraviolet origin. The epidermis is attached to the dermis by a thin basement membrane. The dermis, which is the inner layer of the skin, consists of two zones: directly underneath the basement membrane is the papillary dermis, which comprises thin collagen fibers, vascular loops, and nerves; below this is the reticular dermis with thick and closely packed collagen fibers. The dermis, which contains elastic fibers allowing deformability, absorbs mechanical forces including shear, tensile, and compressive forces, thereby preventing dramatic epithelium damage, and with its rich vascular system, provides an efficient metabolic support for the avascular epidermis. Injury to skin is reversible when it is confined to the epidermis, leading to spontaneous regeneration. Injury becomes irreversible, requiring repair, when it penetrates the basement membrane and enters into the dermis. During cutaneous wound repair, different outcomes may be observed: the fetus possesses the unique ability to heal cIFN c-interferon GM-CSF Granulocyte macrophage-colony stimulating factor iNOS Inducible nitric oxide synthase MMP Matrix metalloproteinase TGF-b1 Transforming growth factor-b1 TIMP Tissue inhibitor of metalloproteinase

Overweight induced by high-fat diet delays rat cutaneous wound healing

Prolonged wound healing is a complication that contributes to morbidity and mortality. Overweight people regularly undergo surgery and trauma, and often develop chronic wounds, but the effects of the adipose tissue excess on cutaneous wound healing are not well understood. This study tested the hypothesis that overweight induced by a high-fat diet impairs rat cutaneous wound healing. Male Wistar rats were fed with either a high-fat or a standard (control) diet. After 15 weeks, an excisional lesion was done and the animals were killed 21 d later. Wound contraction and re-epithelialization, blood pressure, glucose and retroperitoneal fat were evaluated. After killing, lesion and adjacent normal skin were formol-fixed and paraffin-embedded. Inflammatory infiltrate, myofibroblasts, collagen fibres and cellular proliferation were analysed and blood vessels were evaluated using stereological methods. There was no difference in blood pressure and glucose, but retroperitoneal fat increased in the high-fat diet group. Animals fed with the high-fat diet presented delayed wound contraction and re-epithelialization. It was found that 21 d after wounding, overweight induced by a high-fat diet increased the inflammatory infiltrate and delayed myofibroblastic differentiation, collagen deposition, epithelial and connective tissue cell proliferation, and angiogenesis. These findings support the hypothesis that a high-fat diet exerts negative effects on rat cutaneous wound healing, due mainly to the prolongation of the inflammatory phase.

Nitric oxide synthesis inhibition alters rat cutaneous wound healing

Background:  Nitric oxide (NO) is an important molecule that participates in wound repair, but its effects on cutaneous wound healing are not well understood. The aim of this study was to investigate the effects of NO synthesis blockade on rat cutaneous wound healing by the administration of NG‐nitro‐l‐arginine methyl ester (l‐NAME), a non‐selective inhibitor of NO synthases.

Sympathetic denervation accelerates wound contraction but delays reepithelialization in rats

Participation of the peripheral nervous system in wound healing is not well understood. The aim of this study was to investigate the effects of sympathetic denervation on rat excisional cutaneous wound healing. Male rats were chemically denervated with intraperitoneal administration of 6‐hydroxydopamine (6‐OHDA) in 1% ascorbic acid. 6‐OHDA or vehicle was administered twice a week until euthanasia, beginning 7 days before wounding. A full‐thickness excisional lesion was performed and the lesion area measured to evaluate wound contraction. After euthanasia, the lesion and adjacent normal skin were formalin‐fixed and paraffin‐embedded. Sections were stained with hematoxylin and eosin or toluidine blue, or immunostained for α‐smooth muscle actin. Animals treated with 6‐OHDA showed acceleration in wound contraction, increase in myofibroblastic differentiation, reduction in mast cell migration, and a delay in reepithelialization. To investigate the effects of neurogenic inflammation, a group of animals was treated with 6‐OHDA only after the acute inflammatory phase, and these animals showed delayed wound contraction 3 and 7 days after wounding when compared to those treated before the lesion. In conclusion, the present study shows that sympathetic denervation affects cutaneous wound healing, probably by a decrease in neurogenic inflammation during the initial phase of healing and the absence of catecholamines throughout the final phase.

BLOCKADE OF β1- AND β2-ADRENOCEPTORS DELAYS WOUND CONTRACTION AND RE-EPITHELIALIZATION IN RATS

1 The participation of sympathetic efferent fibres in wound healing is not well understood. The aim of the present study was to investigate the effects of b1‐ and b2‐adrenoceptor blockade on rat excisional cutaneous wound healing. 2 Male rats were treated orally with propranolol dissolved in drinking water (50 mg/kg per day), whereas the control group received drinking water without propranolol. Propranolol was administered daily until rats were killed. A full‐thickness excisional lesion was performed. The lesion area was measured to evaluate wound contraction. After rats had been killed, lesion and adjacent normal skin were formol fixed and paraffin embedded. Sections were stained with haematoxylin–eosin, Sirius red or Toluidine blue and immunostained for a‐smooth muscle actin or proliferating cell nuclear antigen. 3 Propranolol‐treated rats presented delayed wound contraction and epidermal healing and decreased hydroxyproline levels, collagen density and neo‐epidermis thickness. Blockade of b1‐ and b2‐adrenoceptors increased epidermal and connective tissue cell proliferation, polymorphonuclear leucocyte migration, myofibroblast density and mast cell migration. The volume density of blood vessels was increased and vessels were more dilated in propranolol‐treated animals. 4 Thus, we conclude that b1‐ and b2‐adrenoceptor blockade impairs cutaneous wound healing. This information should be considered by physicians during the treatment of patients who present with hypertension and problems in the healing process (such as venous ulcers).

Effects of Cigarette Smoke in Mice Wound Healing is Strain Dependent

It has been clinically and experimentally shown that cigarette smokers suffer from impaired wound healing, but the mechanisms that lead to the alterations are not well understood. The aim of this study was to investigate if the effects of cigarette smoke exposure on excisional cutaneous wound healing are different depending on the strain (Swiss, BALB/c and C57BL/6 mice) studied. Male mice were exposed to smoke of nine whole cigarettes per day, 3 times/day, daily, for 10 days. In the 11th day a full-thickness excisional wound was performed. Control group was sham-exposed and also had a full-thickness excisional wound. The cigarette smoke exposure protocol was performed until euthanasia. Animals were euthanatized 14 days after wounding. Wound contraction was evaluated 7 and 14 days after lesion. Sections were stained with hematoxylin-eosin, Sirius red or toluidine blue and immunostained for alpha-smooth muscle actin. Smoke exposed animals presented delay in wound contraction, in fibroblastic and inflammatory cells recruitment and in myofibroblastic differentiation; those alterations were strain dependent. Cigarette smoke exposure also affected mast cells recruitment and neoepidermis thickness. In conclusion, the present study demonstrated that the effects of cigarette smoke in mice cutaneous wound healing are related to mice strain studied.