Lin Huang

A comparative study of the cytotoxicity of silver‐based dressings in monolayer cell, tissue explant, and animal models

Over the past decade, a variety of advanced silver‐based dressings have been developed. There are considerable variations in the structure, composition, and silver content of these new preparations. In the present study, we examined five commercially available silver‐based dressings (Acticoat™, Aquacel® Ag, Contreet® Foam, PolyMem® Silver, Urgotul®SSD). We assessed their cytotoxicity in a monolayer cell culture, a tissue explant culture model, and a mouse excisional wound model. The results showed that Acticoat™, Aquacel® Ag, and Contreet® Foam, when pretreated with specific solutes, were likely to produce the most significant cytotoxic effects on both cultured keratinocytes and fibroblasts, while PolyMem® Silver and Urgotul®SSD demonstrated the least cytotoxicity. The cytotoxicity correlated with the silver released from the dressings as measured by silver concentration in the culture medium. In the tissue explant culture model, in which the epidermal cell proliferation was evaluated, all silver dressings resulted in a significant delay of reepithelialization. In the mouse excisional wound model, Acticoat™ and Contreet® Foam indicated a strong inhibition of wound reepithelialization on the postwounding‐day 7. These findings may, in part, explain the clinical observations of delayed wound healing or inhibition of wound epithelialization after the use of certain topical silver dressings. Caution should be exercised in using silver‐based dressings in clean superficial wounds such as donor sites and superficial burns and also when cultured cells are being applied to wounds.

Hypertrophic response and keloid diathesis: two very different forms of scar.

Learning Objectives: After studying this article, the participant should be able to: 1. Have a greater appreciation of the extent of differences and similarities between keloid and hypertrophic scarring. 2. Have a greater appreciation of the significance of the stage of maturation of a keloid or hypertrophic scar with regard to its morphologic, biochemical, and molecular profile. 3. More critically review basic science research that is based on poorly characterized scar tissue. 4. More critically review clinical studies that are based on poorly characterized scar tissue. Background: Hypertrophic and keloid scars remain extremely challenging, particularly in their variable response to treatment. The understanding of hypertrophic and keloid scarring is evolving from a position where they were regarded as different stages of the same process to the contemporary perspective of two separate entities. This article reviews the differences in the two forms of scarring and discusses the implications for future research. Methods: The authors conducted a MEDLINE search of all English language reviews linking key words “hypertrophic,” “keloid,” and “scarring.” Results: Over the past four decades, there has been considerable clinical and experimental research looking at the biological nature and therapeutic response of keloid and hypertrophic scarring. As more differences are emerging regarding the fundamental biology of the scars, investigators are giving more detailed characterization of their source material. It is evident that even within the broad categories of hypertrophic and keloid scarring there is a heterogenous distribution of pathologic con-nective tissue matrix biology. Conclusion: Considerable advances have been made in our understanding of the fundamental biology of scarring. As research methodology becomes even more sophisticated, it will be even more crucial to extensively characterize source material, recognizing major differences not only between keloid and hypertrophic scar but also between scars of varying stages of maturation and histomorphological, biochemical, and molecular variations within individual scars.

HA modulation of epidermal morphogenesis in an organotypic keratinocyte-fibroblast co-culture model.

Please cite this paper as: HA modulation of epidermal morphogenesis in an organotypic keratinocyte‐fibroblast co‐culture model. Experimental Dermatology 2010; 19: e336–e339.

Low-dose 5-fluorouracil induces cell cycle G2 arrest and apoptosis in keloid fibroblasts

Backgroundu2002 Intralesional injection of low‐dose 5‐fluorouracil (5‐FU) has recently been used as an experimental modality for treating keloid scarring and has shown promising efficacy in improving scar appearance and preventing recurrence of the keloid.

CD9 Is Critical for Cutaneous Wound Healing through JNK Signaling

Cutaneous injury triggers a cascade of signaling events essential for wound re-epithelialization. CD9, a cell-surface protein, has been implicated in a number of cellular processes by coupling to intracellular signaling; however, its exact role in wound healing remains unidentified. We reported that CD9 was downregulated in migrating epidermis, and reelevated to basal level when re-epithelialization was completed. Although low level of CD9 appears to be required for normal wound healing, a significant healing delay was found in CD9-null mice, with wounds gaping wider on day 5 and day 7 post wounding. Further analysis showed that re-epithelialization was adversely affected in CD9-null mice, due to impaired migration of epidermis. Notably, CD9 deficiency caused a persistent enhancement of C-JUN NH2 terminal kinase (JNK) signaling primarily in migrating epidermis with abnormal elevation of matrix metalloproteinase (MMP)-9 detected in CD9-null wounds, leading to excessive degradation of type IV collagen, and thus a defective basement membrane at the wound site. JNK suppression reduced MMP-9 production and therefore ameliorated the healing delay with the appearance of significantly elongated migrating epidermis in CD9-null mice. Our study demonstrated the importance of CD9 in wound re-epithelialization, linking this molecule directly to basement membrane formation and epidermal migration through participating in the regulation of the JNK/MMP-9 pathway.

An update review of stem cell applications in burns and wound care

The ultimate goal of the treatment of cutaneous burns and wounds is to restore the damaged skin both structurally and functionally to its original state. Recent research advances have shown the great potential of stem cells in improving the rate and quality of wound healing and regenerating the skin and its appendages. Stem cell-based therapeutic strategies offer new prospects in the medical technology for burns and wounds care. This review seeks to give an updated overview of the applications of stem cell therapy in burns and wound management since our previous review of the “stem cell strategies in burns care”.

Stem cell-like properties of human umbilical cord lining epithelial cells and the potential for epidermal reconstitution

BACKGROUND AIMSnStem cells are particularly attractive for many cell-based therapeutic interventions because of their ability to self-renew and their capacity to differentiate into site-specific differentiating cells. Restoration of the integrity of epithelial continuity is an essential aspect of wound repair and tissue regeneration. We are currently looking at the potential of human umbilical cord lining cells as a source of epithelial stem cells with appropriate differentiation capacity for potential epidermal reconstitution.nnnMETHODSnWe isolated human umbilical cord lining epithelial cells (CLEC) and characterized their phenotype from the perspective of proliferative potential, telomere length, expression of epidermal differentiation markers, as well as stem cell-specific markers, and clonogenicity. Their potential for epidermal reconstitution was investigated in an organotypic culture model.nnnRESULTSnThe results demonstrated that CLEC present a long telomere length and have a relatively high proliferative potential and passaging ability in culture. CLEC display some of the stem cell-specific markers for epithelial as well as pluripotent stem cells, including CK19, p63, OCT-4, SSEA-4, TRA-1-60, SOX2 and Nanog. CLEC are capable of generating a fully stratified epithelium in organotypic culture.nnnCONCLUSIONSnThe potential of CLEC to be used in clinical applications for specialized epithelial reconstruction is still unexplored. The demonstration that CLEC have stem cell-like properties and are capable of generating fully stratified epithelium provides support for their potential clinical application in epidermal reconstitution.

A histological study on the effect of pressure therapy on the activities of myofibroblasts and keratinocytes in hypertrophic scar tissues after burn

Although pressure therapy (PT) has been widely used as the first-line treatment for hypertrophic scars (HS), the histopathological changes involved have seldom been studied. This study aimed to examine the longitudinal effect of PT on the histopathological changes in HS. Ten scar samples were selected from six patients with HS after burn and they were given a standardized PT intervention for 3 months while 16 scar samples were obtained on those without PT. The scar biopsies were collected pre-treatment, 1 and 3 months post-intervention for both clinical and histopathological examinations. Clinical assessments demonstrated significant improvement in the thickness and redness of the scars after PT. Histological examination revealed that cell density in the dermal layer was markedly reduced in the 3-months post-pressurized scar tissues, while the arrangement of the collagen fiber was changed from nodular to wave-like pattern. The α-smooth muscle actin immunoreactivity was significantly decreased after 1-month pressure treatment. There was a significant reduction of myofibroblasts population and a concomitant increase in the apoptotic index in the dermal layer in the 3-months post-pressurized scars. A significant negative correlation was found between the myofibroblasts population and the apoptotic index. The keratinocyte proliferation was found inhibited after PT. Results demonstrated that PT appeared to promote HS maturation by inhibiting the keratinocyte proliferation and suppressing myofibroblasts population, the latter possibly via apoptosis.

A study of the combination of triamcinolone and 5-fluorouracil in modulating keloid fibroblasts in vitro

BACKGROUNDnPreliminary clinical trials suggest a superior effect when steroids and 5-fluorouracil are injected together for the intralesional therapy of keloids. In addition, it has been proposed that low-dose 5-fluorouracil may have advantages over conventional high dosages. We explored the molecular basis for the potential synergy involved in the combined treatment with triamcinolone and 5-fluorouracil.nnnMETHODSnThe effects of triamcinolone alone or in combination with low-dose 5-fluorouracil on cell proliferation, cell-cycle progression, apoptosis and regulation of p53, p21, type I collagen (Col-1), vascular endothelial growth factor (VEGF), transforming growth factor-beta1 (TGF-beta1) and matrix metalloproteinase-2 (MMP-2) production in primary cultured keloid fibroblasts were examined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), flow cytometric and Western blotting assays.nnnRESULTSnTriamcinolone suppressed cell proliferation and induced G1 cell-cycle arrest but not apoptosis. By contrast, 5-fluorouracil induced G2 cell-cycle arrest and apoptosis that may be associated with p53 activation and p21 up-regulation. The modulation of Col-1, VEGF, TGF-beta1 and MMP-2 expression by triamcinolone and 5-fluorouracil alone or their combination varied between individual cell lines; the trend is to promote a reduction in Col-1 and TGF-beta1 but up-regulation of MMP-2 expression. 5-Fluorouracil played a predominant role in the combined treatment leading to more significant cell proliferation inhibition, apoptosis, Col-1 suppression and MMP-2 induction (pxa0<xa00.05).nnnCONCLUSIONSnOur data provide the molecular-based evidence for the observed clinical benefits of adding 5-fluorouracil to a steroid injection for improved scar regression and reduced recurrence of keloids. We expect fewer undesirable side effects in the combined treatment when the lower therapeutic dose of the individual drugs is to be used.

A reappraisal of the biological effects of hyaluronan on human dermal fibroblast

Hyaluronan (HA) is a fundamental component of many biomaterials. Reports on the biological effects of HA are, however, both inconsistent and contradictory. This particularly refers to fibroblast contraction in the presence of high concentrations of HA. In this study we used a broad range of molecular weight (MW) and concentrations of HA to assay its influence on human dermal fibroblasts in both two and three-dimensional culture models. High-MW HA in high concentrations demonstrated inhibitory effects on both cell attachment and proliferation. HA-coated surfaces appeared less adhesive to fibroblasts than collagen-coated surfaces. In the fibroblast-populated collagen lattice, HA supplementation dose-dependently retarded gel contraction, which was associated with reduced cell division and spreading. Although gene transcripts of collagen type I and III were not significantly upregulated in the monolayer culture as determined by real-time PCR analysis, more type III collagen was present in HA-incorporated collagen gels by Sirius red staining. Type III collagen was homogeneously distributed and well organized in the presence of HA. Our data indicates that HA has both a qualitative and quantitative effect on cell-matrix interactions. Optimum parameters in terms of MW and concentration need to be determined when HA-based biomaterials are being prepared for tissue-repair purposes.