Experimental evaluation of cyadox phototoxicity to Balb/c mouse skin

BACKGROUND: Cyadox is a veterinary drug mainly used as an effective antimicrobial promoter in animal husbandry. It was reported that the other quinoxaline-1,4-dioxide compounds had phototoxicity, but only few data are reported on phototoxicity of cyadox. This study was performed to evaluate the phototoxicity of cyadox on skin. METHODS: Eighty mice were equally divided into eight groups. Five groups with ultraviolet A (UVA) irradiation for 2 h (21 J/cm2) were administered at doses of 0, 10, 50, 200 mg/kg cyadox and 50 mg/kg olaquindox, respectively, and others as controls without irradiation administered at doses of 0, 200 mg/kg cyadox and 50 mg/kg olaquindox, respectively. Drugs were administered by gavage once daily with a suspension in 0.8% carboxymethyl-cellulose for consecutive 4 days. After administration, a recovery period of 7 days was arranged. Histopathological examination of auricular skin was performed on days 5 and 12. Measurement of auricular thickness, gross pathology and erythema score were conducted once daily. RESULTS: Cyadox groups (200, 50 and 10 mg/kg) with irradiation had erythema and oedema of auricular skin with dose-response relationship, which gradually convalesced after dosing and irradiation ceased. Severe erythema, oedema and necrosis of auricles were observed on olaquindox group with irradiation. CONCLUSION: The phototoxicity of cyadox was mild and reversible, which demonstrated a good safety profile of cyadox in terms of phototoxicity.     

A novel model of wound healing in the SCID mouse using a cultured human skin substitute

Studies of skin graft behaviour in rodent excisional wound models are limited by the dominance of wound contracture and graft sloughing as primary healing responses. To slow skin contraction, polytetrafluoroethylene (Teflon) rings were inserted into dorso-lateral full-thickness wounds in SCID mice. Cultured skin substitutes (OrCel), composed of cultured human keratinocytes and fibroblasts in a bovine collagen sponge, were implanted within the rings. Examination and histology of grafts 14 days later showed graft take in four of six recipients, with 90% epithelialization and wound contraction of 31–47%. Immunohistochemical studies, using human-specific antisera to distinguish graft from host tissues, showed that regenerated tissue was predominantly human. Staining with anticytokeratin, revealed a multilayered, stratified neoepidermis. HBG were identified in keratinocytes in all epidermal layers. Langerhans cells were absent. Antihuman vimentin, used as a fibroblast marker, confirmed that cells of the neodermis were primarily of human origin. Neoepidermal keratinocytes, primarily in the basal and suprabasal layers, were also stained. Results suggest that the poly(tetrafluoroethylene) ring inhibited graft sloughing and provided a more favourable environment for the skin substitute to regenerate a substantially normal human skin.     

An advanced mouse model for human skin wound healing

Here, we report a model for studying wound repair based on skin regenerated from human tissue culture‐expanded cells. The reconstituted skin (hRSK) responds to injury similar to that of intact human skin, and its constituent cells contribute to the healing process. As we have demonstrated that hRSK composed of GFP‐labelled cells also heals “normally,” we believe this model will be useful in analysing the wound repair process using genetically modified human cells.     

Wound healing of human skin transplanted onto the nude mouse after a superficial excisional injury: human dermal reconstruction is achieved in several steps by two different fibroblast subpopulations

Abstract It has been established that human skin grafted onto the nude mouse is able to regenerate after being subjected to a full-thickness wound. In the present work, we sought to determine the cells involved in the connective tissue repair process following superficial wounding. Two months after transplantation, superficial wounds were made at the center of the graft using mechanical dermabrasion. At various times thereafter, ranging from 2 days to 6 weeks, healing grafts were harvested and processed for immunohistological study with species-specific and cross-reacting antibodies directed against human or mouse antigens. The grafted human skin regenerated according to the following series of events. First, the human dermis underneath the scab became devoid of human fibroblasts while the surrounding human dermis preserved its own characteristics. The TUNEL reaction on early-phase healing wounds indicated that apoptosis occurred steadily within this area and could be the mechanism by which cells disappeared. Moreover, cell death was reduced when the wound was covered with an occlusive dressing. The human dermis beneath the wound was then invaded by mouse cells which deposited type I collagen on the human extracellular matrix and produced mouse granulation tissue at the surface above it. Human keratinocytes migrated over the mouse granulation tissue to reconstruct the epidermis. Eventually, the mouse granulation tissue was progressively invaded by human fibroblasts, which formed a human neodermis. The overall process appeared to depend upon several successive epithelial-mesenchymal interactions, which were not species-specific. This suggests that myofibroblasts arise from a specific subpopulation of fibroblasts, probably located at the interface between the dermis and adipose tissue, and that the granulation tissue is eventually remodeled by another population of fibroblasts present in the human dermis. Received: 31 March 1999 / Accepted after revision: 15 July 1999 / Accepted: 13 August 1999     

Determination and correlation of in vitro viability for hairless mouse and human neonatal whole skin and stratum corneum/epidermis

Background and design: Viable tissue is essential to assess the rate and extent of biotransformation during percutaneous absorption in vitro. We assessed the viability of hairless mouse whole skin (WS) and stratum corneum/epidermis (SCE) and human neonatal SCE following separation from the dermis by EDTA phosphate-buffered saline (EDTA-PBS) incubation or by heat treatment by measuring the conversion of dextrose to lactate. Lactate concentrations in receptor fluid samples were determined using a Sigma diagnostic lactate determination kit. A standard curve was prepared and samples assayed spectrophotometrically at 340 nm using a lambda 2β spectrophotometer. Standard curves were prepared for each experiment and correlation coefficient values ( r ) were calculated. Results: Our results showed that heirless mouse SCE was associated with glucose conversion to lactic acid at an increased rate if incubated in EDTA-PBS for 4 h and used immediately. Lactate production was greater with the dermis present (EDTA-PBS WS). The rate of glucose to lactate conversion in hairless mouse SCE was 20–25% of that found in WS. Compared with Dulbecco’s modified PBS (DMPBS)-treated WS controls, the rate of lactate production in EDTA-PBS-treated WS was nearly a 50% less. Heat treatment in water at 60° C to separate SCE from hairless mouse WS appeared to eliminate viability. Viability of hairless mouse SCE, as measured by glucose conversion to lactate, was comparable to human neonatal SCE. Conclusions: These results suggest that the dermis is a significant contributor to glucose metabolism and that incubation in EDTA-PBS is a contributing factor to the overall decrease in metabolic capacity of the tissue. As a result of these findings, hairless mouse SCE appears to be useful as a model for human neonatal SCE in percutaneous absorption studies. Received: 1 September 1995     

Hyperpigmentation of human skin grafted on to athymic nude mice: immunohistochemical study

Human skin grafted on to athymic nude mice (BALB/C-nu/nu) spontaneously hyperpigments. We wished to identify the morphological and molecular bases for the hyperpigmentation for this phenomenon. We present data on the relationship of healing, regeneration of melanocytes and production of some melanogenic stimuli. Biopsies were taken at preset times post-graft and studied by histological and immunohistochemical methods. DOPA-positive melanocytes first became visible 120 h post-graft and melanin deposition became visible along the basal cell layer 2 weeks post-graft and increased in quantify with time. By immunochemical stains the quantity of three melanocyte specific enzymes, i.e. tyrosinase, tyrosinase-related protein-1 (TRP-1) and DOPA-chrome tautomerase (TRP-2), was markedly enhanced 1 week after grafting and persisted until 4 weeks post-graft. α-Melanocyte-stimulating hormone and adrenocorticotrophic hormone were clearly detected in the epidermis soon after grafting. They were still strongly detected in the epidermis and in the dermis 2–4 weeks post-graft. We conclude that hyperpigmentation in the grafted skin accompanies a marked increase in the quantity of melanogenic enzymes and melanogenic peptides. The neouropeptides might be one of many factors which stimulate melanogenesis.     

Xenobiotic metabolizing enzymes in human skin and SkinEthic reconstructed human skin models

Skin metabolism is becoming a major consideration in the development of new cosmetic ingredients, skin being the first organ exposed to them. In order to replace limited samples of Excised human skin (EHS), in vitro engineered human skins have been developed. 3D models are daily used to develop and evaluate new cosmetic ingredients and have to be characterized and compared with EHS in terms of metabolic capabilities. This work presents the determination of apparent catalytic parameters (apparent Vmax, Km and the ratio Vmax/Km) in 3D models compared with EHS for cytochrome P450 dependent monooxygenase isoforms involved in drug metabolism, esterases, alcohol dehydrogenases, aldehyde dehydrogenases, peroxidases, glutathione S‐transferases, N‐acetyl transferases, uridinyl diphosphate glucuronyl transferases and sulfotransferases. Results show that all these enzymes involved in the metabolism of xenobiotics are expressed and functional in the EHS and 3D models. Also, the Vmax/Km ratios (estimating the intrinsic metabolic clearances) show that the metabolic abilities are the most often comparable between the skin models and EHS. These results indicate that the 3D models can substitute themselves for EHS to select cosmetic ingredients on the basis of their metabolism, efficacy or/and safety.     

Is there an easier way to autograft skin in chronic leg ulcers? ‘Minced micrografts’, a new technique

Background Chronic venous leg ulcers represent an urgent and increasing problem for public health. The use of skin autografts results in a greater therapeutic success in healing chronic ulcers. Objective A simple method of skin autografting that could permit a wider use of skin grafts in outpatients is needed. A new technique allowing skin autografting in a simple one‐step process, without complex surgical procedures or expensive technical supplies, is presented. Methods A small, full‐thickness skin specimen taken from the patient is finely minced and spread on his leg ulcer bed allowing to cover a surface many times wider than the sample itself. Results This method induces faster re‐epithelization of chronic leg ulcers that failed to heal despite good conservative local therapy and give the possibility to repair very large ulcers with small fragments of skin. A clinical case is shown as an example out of 20 ulcers we recently treated. Conclusion Our preliminary report shows that this technique results in a greater therapeutic success (18 of 20 cases) in healing chronic leg ulcers, a common pathology that often affects outpatients treated for very long periods at home or in the Dermatologist's office. In our experience, this new and successful reparative possibility makes ‘mince grafting’ a recommendable procedure.     

Topical beta-carotene is converted to retinyl esters in human skin ex vivo and mouse skin in vivo

Human epidermis contains endogenous retinoids (retinol and retinyl esters) and carotenoids (mostly beta-carotene). Previous studies have shown that the enzymes involved in retinoid metabolism are present in human epidermis. There is still a controversy about the presence in the skin of the enzymes able to convert beta-carotene into vitamin A (retinol), although a recent study demonstrated the conversion of beta-carotene into retinol in human cultured epidermal cells. In this study, we addressed the question of the possible bioconversion of topical beta-carotene into vitamin A or derivatives by human and mouse skin. Surgically excised human abdominal skin was mounted on Franz perfusion chambers to assess the cutaneous penetration of topical beta-carotene as well as its metabolism, after a 24-h incubation period, whereas hairless mice received topical beta-carotene 24 h before assaying epidermal beta-carotene and retinoid concentrations. Epidermal retinoid and beta-carotene concentrations were determined by high-pressure liquid chromatography. Topical beta-carotene penetrated well into human and mouse epidermis and induced a 10-fold (human) and a threefold (mouse) increase of epidermal retinyl esters, which demonstrates that topical beta-carotene is converted into retinyl esters by human and mouse epidermis and thus appears as a precursor of epidermal vitamin A.     

The quality of human skin xenografts on SCID mice: a noninvasive bioengineering approach

BACKGROUND: Animal models are important tools for studies in skin physiology and pathophysiology. Due to substantial differences in skin characteristics such as thickness and number of adnexa, the results of animal studies cannot always be directly transferred to the human situation. Therefore, transplantation of human skin on to SCID (severe combined immunodeficiency) mice might offer a promising tool to perform studies in viable human skin without the direct need for human volunteers. OBJECTIVES: To characterize the physiological and anatomical changes of a human skin transplant on a SCID animal host. METHODS: In this study human skin was transplanted on to 32 SCID mice and followed for 6 months. Barrier function was assessed by transepidermal water loss (TEWL; tewametry) and moisture content of the stratum corneum was studied by measurement of electrical capacitance (corneometry). RESULTS: The results showed considerable deviations of TEWL values and skin hydration between the grafts and human skin in vivo. The human skin showed epidermal hyperkeratosis and moderate sclerosis of the corium 4 and 6 months after transplantation on to SCID mice. CONCLUSIONS: Our results indicate that human skin does not completely preserve its physiological and morphological properties after transplantation on to SCID mice. Therefore, results from experiments using this model system need to be discussed cautiously.     

Remittance spectroscopy mapping of human skin in vivo

Remittance spectroscopy of human skin may be influenced by probe application pressure and body site.

Methods:

We investigated remittance spectroscopy qualities of human skin in vivo in different areas: a) forearm, b) frontal, c) back, d) back of the hand, e) palms and f) cheek. Twenty volunteers of skin type 2–3 free of inflammatory skin diseases, were enrolled into the study. Spectroscopy readings were performed with a fiber optic spectrometer (Ocean Optics, USA). The readings were taken with standardized force (0 and 100 pont) by applying the probe vertically to the skin surface. The remittance in relation to wavelength was registered. White light with wavelengths from 420 to 750 nm were used. Individual remittance values and their standard deviations were obtained from 20 readings each.

Results/Conclusions:

Spectroscopic patterns of skin are influenced by external force and regional factors. Standardization remains critical for the use of this approach in bioengineering of skin.     

Exosomes in chronic inflammatory skin diseases and skin tumors

Exosomes are membrane vesicles of endocytic origin that can mediate communication between cells and the transport of cellular components such as microRNAs, mRNAs, proteins and DNA. Recently, exosomes have been under investigation for their significant roles in both healthy physiology and disease states. Herein, we review the role of exosomes in chronic inflammatory skin diseases and skin tumors, especially focusing on systemic lupus erythematosus, psoriasis, atopic dermatitis, bullous pemphigoid and melanoma. Moreover, we emphasize the involvement of changes in exosome cargo in the regulation of these diseases.     

Mast cell accumulation and cytokine expression in the tight skin mouse model of scleroderma

The tight skin (Tsk) mouse develops many pathological changes seen in human scleroderma, such as increased collagen content and mast cell density. Although associations between mast cell expansion and skin fibrosis have been reported, the mechanisms underlying mast cell accumulation remain unclear. In this study, we have measured the density of skin mast cells in Tsk mice and their normal littermates (pa/pa) of 4-36 weeks of age, and in the skin heterografted between Tsk and pa/pa mice. Cytokines related to mast cell differentiation, proliferation and migration were examined by using RNase protection assays. Skin mast cell density in Tsk mice was significantly increased from 12 weeks of age, compared to that in pa/pa mice. The expression of transforming growth factor-beta1 (TGF-beta1), and to a lesser extent, stem cell factor (SCF) and interleukin-15 (IL-15) mRNA was higher in Tsk mice, compared to that in control mice. Mast cell density was unchanged in Tsk skin grafted onto pa/pa hosts, but dramatically increased in pa/pa skin grafted onto Tsk hosts. This latter mast cell hyperplasia was associated with the increases in mRNA levels of TGF-beta1, SCF and IL-15, whereas little change in cytokine levels was seen in heterografted Tsk skin. These results suggest that locally produced cytokines in Tsk skin influence mast cell accumulation in this animal model of human scleroderma.     

Prostaglandin E1 in normal human skin: Methodological evaluation,topographical distribution and data related to sex and age

Summary A methodological evaluation of a radioimmunoassay technique for PGE₁ measurement was applied to normal human skin. The detection limit of the assay was 15 pg and recovery (mean±SD) was 90±6%. The mean value of PGE₁ (±SEM) in nine punch biopsy specimens (4 mm in diameter) from a piece of skin surgically removed from one person was 117±14 pg/mg dry weight. The individual variation of PGE₁ activity in biopsy specimens from the same topographical area in ten persons belonging to the same sex and age group was 33±4 pg/mg dry weight. The influence has been elucidated of temperature and tissue processing, local anaesthesia, sex, age and topographical distribution on endogenous PGE₁ activity.Supported by grant 512–8125, 512–15539 and 12–1690 from the Danish Medical Research Council     

Late skin reaction to iodixanol (Visipaque): clinical manifestations, patch test study, and histopathological evaluation

Late reactions to iodinated contrast media are frequent. Cutaneous manifestations are the commonest, in which maculopapular exanthema, a type of cutaneous presentation, is widespread. Controversy exists about the utility of the skin test in the management of these reactions. The aim of this study is to analyse the clinical characteristics, the histopathological findings, and the results of the patch test in patients who developed a late skin reaction (LSR) to the nonionic, dimeric, iodinated contrast media Visipaque. We retrospectively reviewed the patients with LSR to Visipaque, seen in the Dermatology Department between 1999 and 2005. A total of 12 patients participated in this study (7 men and 5 women), ages ranging from 39 to 76 years (mean 56). 11 of the patients had significant medical history. All the patients developed a maculopapular exanthema between 2 hr and 3 days after the radiological examination, involving the trunk and proximal limbs, although some of the patients showed involvement of distal areas. The skin biopsy, performed in 6 patients, showed nonspecific findings consistent with drug reaction. In 3 patients, patch tests to Visipaque and iodixanol were positive. The most frequent manifestation of LSR to iodixanol is a maculopapular exanthema, involving the trunk and the limbs, although distal involvement can be seen. Histopathological findings are nonspecific and cannot be distinguished from other drug reaction. Patch tests have a limited value, and in cases where they were negative, reintroduction of the drug triggered a new LSR.     

1320nm激光对小鼠皮肤组织病理和生理特性的影响

目的:研究1320 nm激光对小鼠皮肤组织病理和部分皮肤生理指标的影响。方法:用该波长激光对小鼠背部皮肤照射,于照射前、照射后1 h3、d7、d、15 d、30 d取皮肤做病理,同时用MPA皮肤多功能测试系统测定其皮肤回声值、黑素含量、皮肤血红蛋白含量、经皮失水量、表皮含水量和皮脂含量。结果:激光照射后1 h,真皮纤维组织排列致密。照射后3 d,真皮炎症细胞和成纤维细胞增多。照射后15 d真皮层增厚、胶原增加。激光照射后短期内对于皮肤弹性、皮肤血红蛋白含量、经皮失水量、皮脂含量、表皮含水量,均有一定程度暂时性影响,对皮肤黑素含量无影响。结论:1320 nm激光可引起小鼠成纤维细胞增生和胶原蛋白合成增加,改善皮肤弹性,但在短期内对皮肤生理状态可产生一定的负面影响。     

皮肤点刺试验检测慢性荨麻疹变应原的临床意义

目的探讨皮肤点刺试验检测慢性荨麻疹变应原的临床意义。方法用20种不同的变应原进行皮肤点刺试验,生理盐水为阴性对照,组胺为阳性对照。结果292例慢性荨麻疹患者中,有210例为阳性反应,阳性率为71.92%,单个变应原中,以吸入性粉尘螨的阳性率为最高,达63.69%。结论皮肤点刺试验特异性高,为慢性荨麻疹患者寻找可能的变应原提供依据,并力求避免接触,以提高患者的生活质量。