Glucocorticoid-regulated gene expression during cutaneous wound repair

Expression profiles of elastase1 (NvElastaseI) and secretory leukocyte protease inhibitor (NvSLPI) during forelimb regeneration in adult Notophthalmus viridescens suggest a role in epithelial remodeling and delamination

Extracellular proteases and their inhibitors may regulate a number of important processes involved in forelimb regeneration in the adult newt, including epithelial remodeling, breakdown of extracellular matrix, and dedifferentiation. We have identified a newt homologue of human ElastaseI (NvElastaseI) and its potential inhibitor, SLPI (NvSLPI), and evaluated their spatial and temporal expression during limb regeneration. NvElastaseI is upregulated early in regeneration and is associated with subdermal and wound epithelial cells, suggesting an involvement in wound healing and the generation of the wound epithelium. Up until 15 days post-amputation, NvElastaseI is also scattered throughout the developing blastema and may have a role in the dedifferentiation of stump tissues. NvSLPI is found at the interface between the intact skin and the wound epithelium, and may limit NvElastaseI activity. NvSLPI is also expressed in dermal glands, and is likely involved in anti-microbial activity or function. Quite apart from regeneration, complementary patterns of expression of NvElastaseI and NvSLPI are associated with newt epithelial sloughing.

Molecular pathogenesis of chronic wounds: the role of beta-catenin and c-myc in the inhibition of epithelialization and wound healing

Lack of understanding of the molecular mechanisms and pathogenesis of impaired healing in chronic ulcers is a serious health issue that contributes to excessive limb amputations and mortality. Here we show that beta-catenin and its downstream targets in keratinocytes, c-myc, and keratins K6 and K16, play important roles in the development of chronic wounds. In contrast to normal epidermis, we observed a significant nuclear presence of beta-catenin and elevated c-myc expression at the nonhealing wound edge of chronic ulcers from 10 patients. In vitro studies indicated that stabilization of nuclear beta-catenin inhibited wound healing and keratinocyte migration by blocking epidermal growth factor response, inducing c-myc and repressing the K6/K16 keratins (cytoskeletal components important for migration). The molecular mechanism of K6/K16 repression involved beta-catenin and arginine methyltransferase (CARM-1) acting as co-repressors of glucocorticoid receptor monomers. We conclude that activation of the beta-catenin/c-myc pathway(s) contributes to impaired healing by inhibiting keratinocyte migration and altering their differentiation. The presence of activated beta-catenin and c-myc in the epidermis of chronic wounds may serve as a molecular marker of impaired healing and may provide future targets for therapeutic intervention.

Chronic wounds

Chronic wounds are a challenge to treat for the clinician. We present a current overview of intrinsic and extrinsic factors in the development chronic nonhealing wounds. Solutions to some of these difficult problems are presented.

In vitro characterization of vascular endothelial growth factor and dexamethasone releasing hydrogels for implantable probe coatings

Anti-fouling hydrogel coatings, copolymers of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidinone, and polyethylene glycol, were investigated for the purpose of improving biosensor biocompatibility. These coatings were modified to incorporate poly(lactide-co-glycolide) (PLGA) microspheres in order to release dexamethasone (DX) and/or vascular endothelial growth factor (VEGF). DX and VEGF release kinetics from microspheres, hydrogels, and microspheres embedded in hydrogels were determined in 2-week and 1-month studies. Overall, monolithic, non-degradable hydrogel drug release had an initial burst followed by release at a significantly lower amount. Microsphere drug release kinetics exhibited an initial burst followed by sustained release for 1 month. Embedding microspheres in hydrogels resulted in attenuated drug delivery. VEGF release from embedded microspheres, 1.1+/-0.3 ng, was negligible compared to release from hydrogels, 197+/-33 ng. After the initial burst from DX-loaded hydrogels, DX release from embedded microspheres was similar to that of hydrogels. The total DX release from hydrogels, 155+/-35 microg, was greater than that of embedded microspheres, 60+/-6 microg. From this study, hydrogel sensor coatings should be prepared incorporating VEGF in the hydrogel and DX either in the hydrogel or in DX microspheres embedded in the hydrogel.

Enhancement of wound healing by shikonin analogue 93/637 in normal and impaired healing

Wound healing is a complicated biological process, which involves interactions of multiple cell types, various growth factors, their mediators and the extracellular matrix proteins. In this study, we evaluated the effects of shikonin analogue 93/637 (SA), derived from the plant Arnebia nobilis, on normal and hydrocortisone-induced impaired healing in full thickness cutaneous punch wounds in rats. SA (0.1%) was applied topically daily as an ointment in polyethylene glycol base on wounds. SA treatment significantly accelerated healing of wounds, as measured by wound contraction compared to controls in hydrocortisone-impaired animals. SA treatment promoted formation of granulation tissue including cell migration and neovascularization, collagenization and reepithelialization. The expression of basic fibroblast growth factor (bFGF) was higher as revealed by immunohistochemistry in treated wounds compared to controls. However, the expression of transforming growth factor-beta(1) was not affected by SA treatment. Since bFGF is known to accelerate wound healing, the increased expression of bFGF by SA may be partly responsible for the enhancement of wound healing. These studies suggest that SA could be further studied for clinical use to enhance wound healing.

Tissue repair in rheumatoid arthritis: challenges and opportunities in the face of a systemic inflammatory disease

Rheumatoid arthritis (RA) is a systemic inflammatory disease that can elicit a variable disease course, can influence a variable number of joints, and can exhibit a variable response to treatment. All of these factors contribute to the degree and extent of damage to joint components, as well as the potential for repair of other injured joint tissues/components. Furthermore, some of the RA treatments/drugs themselves can influence repair and injury responses, as well as the outcome of surgical interventions for advanced disease. However, as treatments and interventions become more sophisticated and successful in patient populations, the opportunity to initiate the repair/replacement of the damaged joint tissues also becomes more of a reality. This review will address the current clinical findings in the literature, and then discuss the issues and opportunities to initiate repair of damaged or injured joint tissues in order to restore joint function. These include growth factors, gene therapy, and bioengineered tissues, alone or in combination to augment endogenous repair or replace tissue damaged beyond such repair capabilities.

Cryotherapy modifies synthetic activity and differentiation of keloidal fibroblastsin vitro

In order to obtain a persuasive explanation for the beneficial clinical effect of cryotherapy on keloids, we developed a reproducible model to apply freezing temperatures on cell cultures, and investigated their influence on proliferation, viability, synthetic activity and differentiation of dermal fibroblasts in vitro. Cell cultures were established from 13 untreated keloids and 10 healthy skin specimens matched for age and skin localization to the donors. No significant influence of cell freezing on the proliferation rates of both keloidal and normal fibroblasts was documented, but mechanical cell destruction with a wide variation in lethality rates (29% average lethal effect on keloidal fibroblasts and 41% on normal ones) was observed. When comparing specimens of keloidal and normal tissue derived from the same four donors, the keloidal fibroblasts were similar regarding their synthetic activity but presented enhanced tenascin-C expression compared with the normal fibroblasts. After cryotherapy, delayed collagen III increase was detected in both cell types (P = 0.03). The collagen II/collagen I ratio increased from 1.6 to 2.8 in the keloidal and only from 1.9 to 2.2 in the normal fibroblasts after subcultivation. Normal fibroblasts exhibited a significantly lasting increase in fibronectin synthesis after freezing (P = 0.03). The intensity of staining against tenascin-C was decreased in five of nine keloidal fibroblast cultures after cryotherapy (P < 0.05) but increased in four of five normal fibroblast cultures (P = 0.016), so that the intensity of tenascin-C staining after freezing became identical in both cell types. Immunoblot studies in four patients and two controls confirmed a temporary decrease of tenascin-C in keloidal but not in normal fibroblasts immediately after freezing. Significantly decreased staining with two markers of myogenic differentiation, myosin in keloidal fibroblasts (P = 0.002) and desmin (P = 0.007) in normal fibroblasts, could also be detected after treatment. In summary, with the help of a model for controlled cell freezing in vitro, cryotherapy was found to modify collagen synthesis and differentiation of keloidal fibroblasts.

Healing responses of skin and muscle in critical illness

OBJECTIVE

Many aspects of the care and underlying pathologies in patients suffering critical illness can detrimentally influence the normal healing processes of skin and soft tissues. Although a great diversity of pathologies exists, some aspects of the diseases and their treatments are common in critically ill patients. We aimed to identify some features, both common and specific, that could influence wound healing and the mechanisms by which they may do so.

DESIGN

In this review, we first outline the biology of normal skin and muscle healing and then explore how critical illness may influence the normal healing cascade.

FINDINGS

The healing of skin and skeletal muscle in critical illness is influenced by both underlying disease processes and the intensive care environment. Local and systemic factors can contribute to impaired healing, with the potential to prolong functional disability and increase the likelihood of wound complications. The frequency and number of soft tissue injuries derived from accidental injury, surgical intervention, and the need for invasive monitoring and therapies in the intensive care unit setting are likely to compromise the innate immunity and potentially further jeopardize the patient's ability to heal. Alterations in coagulation, tissue perfusion, inflammation, immune functioning, metabolism, nutrition, and drug therapies will influence healing responses by modifying the biological responses to tissue disruption. Locally, wound contamination, sepsis, tissue hypoxia, edema, and excessive or prolonged local pressure all have the potential to compromise soft tissue healing. One or more of these factors may be present at any time.

CONCLUSION

The skin and soft tissues are vulnerable to both injury and compromised healing when a patient is critically ill and exposed to a critical care environment. The identification of risk factors may aid in forming and modifying treatment strategies when caring for the critically ill patient with soft tissue injuries.

Regulation of wound healing by growth factors and cytokines

Cutaneous wound healing is a complex process involving blood clotting, inflammation, new tissue formation, and finally tissue remodeling. It is well described at the histological level, but the genes that regulate skin repair have only partially been identified. Many experimental and clinical studies have demonstrated varied, but in most cases beneficial, effects of exogenous growth factors on the healing process. However, the roles played by endogenous growth factors have remained largely unclear. Initial approaches at addressing this question focused on the expression analysis of various growth factors, cytokines, and their receptors in different wound models, with first functional data being obtained by applying neutralizing antibodies to wounds. During the past few years, the availability of genetically modified mice has allowed elucidation of the function of various genes in the healing process, and these studies have shed light onto the role of growth factors, cytokines, and their downstream effectors in wound repair. This review summarizes the results of expression studies that have been performed in rodents, pigs, and humans to localize growth factors and their receptors in skin wounds. Most importantly, we also report on genetic studies addressing the functions of endogenous growth factors in the wound repair process.

SEGRAs: a novel class of anti-inflammatory compounds

Dissociated GCs show a separation between anti-inflammatory effects and certain side effects. This renders them as attractive compounds with better effect/side-effect profile as promising drug candidates and tool compounds for analyzing the molecular mechanisms of single side effects. A number of the GC-mediated side effects (e.g., osteoporosis, skin atrophy) are regulated in a very complex manner and use more than one molecular mechanism of the GR. Thus, theoretical predictions about the behavior of selective GR agonists regarding these effects are very difficult to make. Investigations of SEGRA compounds in relevant animal models will be the only way to get this important information. By availability of these tool compounds we now are in the advantageous situation to test them in vivo and to learn more about the possibilities and even the limitations of the selective GR agonists. Considering that the compounds have a non-steroidal structure, i.e., totally unrelated to steroids or other hormones at all, displaying only partially the molecular effects of GCs and are dissociated in their clinical profile, they should not be considered as GCs. Therefore, we introduced the term selective glucocorticoid receptor agonists (SEGRAs). These SEGRAs seem to represent a useful novel therapeutic modality which may complement existing therapeutic principles for the topical and especially the systemic treatment of inflammatory diseases. In summary, we and others are convinced that dissociated GCs are therapeutic compounds that exert many of the anti-inflammatory and immunosuppressive effects of standard GCs, while their potential to induce side effects is reduced. Whereas the in vitro dissociated profile of other compound classes (Belvisi et al. 2001) was not translated into a separation between anti-inflammatory activity and the induction of side effects in in vivo models, we could demonstrate this for the SEGRA compounds. Regarding the diversity of molecular mechanisms involved in mediating the complex side effects of GCs, it might be that only some of these unwanted effects can be reduced. However, as GCs are one of the most important anti-inflammatory therapeutics in the treatment of severe and chronic inflammatory diseases, even a partial reduction of side effect induction would be a great advantage for many patients.

Nitric oxide and wound repair: role of cytokines?

Wound healing involves platelets, inflammatory cells, fibroblasts, and epithelial cells. All of these cell types are capable of producing nitric oxide (NO), either constitutively or in response to inflammatory cytokines, through the activity of nitric oxide synthases (NOSs): eNOS (NOS3; endothelial NOS) and iNOS (NOS2; inducible NOS), respectively. Indeed, pharmacological inhibition or gene deletion of these enzymes impairs wound healing. The wound healing mechanisms that are triggered by NO appear to be diverse, involving inflammation, angiogenesis, and cell proliferation. All of these processes are controlled by defined cytokine cascades; in many cases, NO appears to modulate these cytokines. In this review, we summarize the history and present state of research on the role of NO in wound healing within the framework of modulation of cytokines.

Glucocorticoids and laminitis in the horse

The administration of exogenously administered GCs and syndromes associated with GC excess are both attended by increased risk for the development of laminitis in adult horses. However, there exists substantial controversy as to whether excess GCs cause laminitis de novo. If true, the pathogenesis of laminitis arising from the effects of GC excess is probably different from that associated with diseases of the gastrointestinal tract and endotoxemia. Although a satisfactory explanation for the development of laminitis as a consequence of GC action is currently lacking, numerous possible and plausible theoretical mechanisms do exist. Veterinarians must exert caution with respect to the use of GCs in adult horses. The extent to which individual horses are predisposed to laminitis as a result of GC effect cannot be predicted based on current information. However, the administration of systemic GCs to horses that have been previously affected by laminitis should be used only with extreme caution, and should be accompanied by careful monitoring for further signs of laminitis. The risk of laminitis appears to be greater during treatment using some GCs (especially dexamethasone and triamcinalone) compared with others (prednisone and prednisolone). Whenever possible, to reduce the risk of laminitis, GCs should be administered locally. For example, the risk of GC-associated laminitis is evidently considerably reduced in horses affected with chronic obstructive pulmonary disease (COPD) if GC treatment is administered via inhalation. We have hypothesized that structural changes in the equine hoof that resemble laminitis may arise as a consequence of excess GC effect. Although these changes are not painful per se, and are not associated with inflammation, they could likely predispose affected horses to the development of bona fide laminitis for other reasons. Moreover, the gross morphological appearance of the chronically GC-affected hoof resembles that of a chronically foundered hoof in some respects. Further investigation into the effect of GC on the hoof lamellar interface is clearly needed.

A role for endogenous glucocorticoids in wound repair

Exogenous glucocorticoids are known to inhibit wound repair, but the roles and mechanisms of action of endogenous glucocorticoids during the healing process are as yet unknown. Therefore, we wounded mice expressing a DNA-binding-defective mutant version of the glucocorticoid receptor (GR(dim) mice) and also analysed fibroblasts from these animals in vitro. We found a remarkably enlarged granulation tissue with a high fibroblast density in GR(dim) mice. This difference is likely to result from an increased migratory and proliferative capacity of GR(dim) fibroblasts and from elevated expression levels of soluble factors involved in granulation tissue formation in wounds of GR(dim) mice. In spite of the larger granulation tissue seen in early wounds, late wounds appeared normal, most likely due to an enhanced ability of GR(dim) fibroblasts to contract collagen. These results demonstrate an as yet unidentified role of endogenous glucocorticoids in the regulation of wound repair.

Differential glucocorticoid effects on repair mechanisms and NF-kappaB activity in the intestinal epithelium

Glucocorticoids are effective agents in the management of inflammatory bowel diseases. However, information about their effects on repair mechanisms of the intestinal epithelium is incomplete.Therefore, the aim was to analyse in vitro effects of glucocorticoids on proliferation, restitution, and apoptosis as well as their effects on activity and expression of nuclear factor (NF)-kappaB, a known regulator of apoptosis and inflammation, in intestinal epithelial cells.Non-transformed rat jejunum epithelial cells (IEC-6) were cultured in the presence and absence of various concentrations of prednisolone and budesonide. IEC-6 cell proliferation was assessed by [3H]-thymidine incorporation. Restitution was analysed by an IEC-6 in vitro assay. Apoptosis was evaluated by ELISA and fluorescence microscopy. DNA binding activity and nuclear expression of NF-kappaB was determined by electrophoretic mobility shift assays and Western blotting, respectively. Prednisolone and budesonide stimulated IEC-6 cell proliferation at low to medium pharmacologic concentrations (prednisolone: 10(-9) to 10(-6) M; budesonide: 10(-11) to 10(-8) M). In contrast, high concentrations (>5 x 10(-5) M) had inhibitory effects on proliferation. 10(-7) M prednisolone and 10(-8) M budesonide increased restitution of IEC-6 cells, whereas high concentrations (10(-4) M) of prednisolone and budesonide decreased restitution. Apoptosis of IEC-6 cells was substantially enhanced by 10(-4) M budesonide; apoptosis was slightly increased by the highest prednisolone concentration used (5 x 10(-4) M). Furthermore, both glucocorticoids inhibited DNA binding activity and nuclear NF-kappaB expression in IEC-6 cells in a dose- and time-dependent fashion. In conclusion, prednisolone and budesonide modulate repair mechanisms of intestinal epithelial cells in vitro in a dose-dependent manner and profoundly modulate the inflammatory regulator NF-kappaB.

Cytokines and therapy in COPD: a promising combination?

COPD is a major health problem, with patients showing a progressively declining, largely irreversible, change in lung function. This is associated with chronic airways inflammation and structural remodeling, including loss of alveolar walls, and goblet cell metaplasia with mucus hypersecretion. Inflammatory cells may contribute to the airway remodeling via secretion of proteases, fibrotic or mitogenic growth factors, and cytokines. In turn, airway remodeling may contribute to the clinical symptoms of COPD. Currently available therapies are directed to improvement of clinical symptoms and reduction of the airways inflammation. The commonly used glucocorticosteroids are expected to reduce the inflammation by acting on kinases or transcription factors necessary for expression of pro-inflammatory cytokines or chemokines. However, several long-term and short-term studies showed that glucocorticosteroids are rather ineffective in improving lung function and reducing the airway inflammation in patients with COPD. New therapeutic strategies may reduce the inflammation and alleviate the clinical symptoms of COPD. Tumor necrosis factor-alpha, interleukin-8, and monocyte chemoattractant protein-1 are important chemotactic proteins for macrophages and neutrophils, the predominant inflammatory cells associated with COPD. As lung levels of these cytokines are higher in COPD compared to non-COPD patients, they may represent targets for novel therapies.

Physiologic levels of epidermal growth factor in saliva stimulate cell migration of an oral epithelial cell line, HO-1-N-1

An oral epithelial cell line derived from buccal mucosa squamous cell carcinoma, HO-1-N-1, was used to elucidate the role of epidermal growth factor (EGF) in saliva on wound healing of the oral mucosa. The effects of EGF on DNA synthesis, and cell migration was studied and the related signal transduction pathways examined. DNA synthesis by HO-1-N-1 cells was stimulated dose-dependently by 1-10 ng ml(-1) EGF, but significantly inhibited by addition of a PI3-K inhibitor (wortmannin), a p38 MAPK inhibitor (SB203580) or an MEKs inhibitor (PD98059). Cell migration was also accelerated by addition of 1-10 ng ml(-1) EGF; however, the migration rate was decreased to 30% by adding PD98059, to 40% by adding a tyrosine kinase inhibitor (herbimycin A), and to 60% by adding wortmannin or dexamethasone. These results indicate that the physiologic concentration of EGF in saliva may stimulate proliferation and migration of oral epithelial cells for wound healing, when the oral mucosa has been injured. Furthermore, this study revealed that EGF-stimulated signal transduction pathways for epithelial cell proliferation and cell migration are different.

Expression of transforming growth factor-beta isoforms and their receptors in chronic tendinosis

Chronic tendon lesions are degenerative conditions and may represent a failure to repair or remodel the extracellular matrix after repeated micro-injury. Since TGF-beta is strongly associated with tissue repair, we investigated the expression of TGF-beta isoforms (beta1, beta2 and beta3) and their 2 signalling receptors (TGF-betaRI and TGF-betaRII) in normal and pathological Achilles tendons. In all tissues, all 3 TGF-beta isoforms and the 2 receptors were present at sites of blood vessels. Cells in the matrix showed no staining for TGF-beta1 or beta3, while TGF-beta2 was associated with cells throughout the normal cadaver tendon. Tissue from tendons with pathological lesions showed an increase in cell numbers and percentage TGF-beta2 expression. TGF-betaRII showed a wide distribution in cells throughout the tissue sections. As with TGF-beta2, there was an increase in the number of cells expressing TGF-betaRII in pathological tissue. TGF-betaRI was restricted to blood vessels and was absent from the fibrillar matrix. We conclude that despite the presence and upregulation of TGF-beta2, TGF-beta signalling is not propagated due to the lack of TGF-betaRI. This might explain why chronic tendon lesions fail to resolve and suggests that the addition of exogenous TGF-beta will have little effect on chronic tendinopathy.

Induction of interleukin-8 in human retinal pigment epithelial cells after denuding injury

AIM

To determine interleukin 8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) expression in response to mechanical injury in human retinal pigment epithelial (HRPE) cells.

METHODS

Enzyme linked immunosorbent assay (ELISA) was performed to determine IL-8 and MCP-1 secretion by HRPE cells after mechanical denudation. IL-8 and MCP-1 mRNA expression by HRPE cells was assessed using semiquantitative RT-PCR. The effects of immunosuppressive drugs, dexamethasone (DEX) and cyclosporin A (CSA), as well as immunosuppressive cytokines, interleukin 4 (IL-4), interleukin 10 (IL-10), and interleukin 13 (IL-13), on chemokine expression in HRPE cells after denuding injury were analysed.

RESULTS

Mechanical injury induced HRPE IL-8 mRNA and IL-8 secretion. Although MCP-1 mRNA was enhanced slightly after denuding injury, MCP-1 secretion was not increased. DEX and CSA inhibited HRPE chemokine expression after injury. IL-4 and IL-13 enhanced IL-8 and MCP-1 production by HRPE cells after injury while IL-10 had no effect.

CONCLUSIONS

These results suggest that IL-8 may be involved in retinal inflammatory responses to injury and that DEX and/or CSA treatment may help control the inflammatory components of retinal diseases such as proliferative vitreoretinopathy.

Downregulation of human type VII collagen (COL7A1) promoter activity by dexamethasone. Identification of a glucocorticoid receptor binding region

Type VII collagen is the major collagenous component of the anchoring fibrils, attachment structures that stabilize the association of the cutaneous basement membrane zone to the underlying dermis. It is expressed by both epidermal keratinocytes and dermal fibroblasts. In this study, we have examined the pharmacological control of COL7A1 gene expression by the glucocorticorticoid dexamethasone. We demonstrate that dexamethasone is a potent transcriptional inhibitor of COL7A1 promoter activity in dermal fibroblasts, and we identify a potential glucocorticoid response element in the region -318/-212 of the promoter. In addition, we have determined that dexamethasone antagonizes transforming growth factor-beta (TGF-beta) activation of the COL7A1 promoter. This effect occurred without dexamethasone interfering with TGF-beta-induced Smad-specific gene transcription. These results indicate potential deleterious effects of glucocorticosteroids on epidermal wound healing, as reduced COL7A1 expression likely leads to decreased anchoring fibril formation, which may translate into delayed or impaired reepithelialization.