Glucocorticoid-regulated gene expression during cutaneous wound repair

Immunohistochemical analysis of PDGFR-α for wound age determination

Immunohistochemical analysis of platelet-derived growth factor receptor-α (PDGFR-α) was performed on human skin wounds obtained from forensic autopsy cases. Thirty human skin wounds were collected at different post-infliction intervals as follows: Group I, 4 h to 3 days (n = 16); Group II, 4 to 7 days (n = 7); Group III, 9 to 10 days (n = 3); and Group IV, 14 to 20 days (n = 4). Immunopositive reactions for PDGFR-α were not observed in the uninjured human skin specimens. In a semi-quantitative morphometrical analysis, the number of PDGFR-α-positive cells was observed increased in Group II, with the average number of PDGFR-α-positive cells being the highest in Group II. Additionally, in Group II, all specimens showed PDGFR-α-positive cells, with an average number of > 200 cells in five fields of view, suggesting a wound age of 4 to 7 days. Taken together, the immunohistochemical detection of PDGFR-α in human skin wounds can be a useful tool for wound age determination.

Rodents as an animal model for studying tooth extraction-related medication-related osteonecrosis of the jaw: assessment of outcomes

OBJECTIVE

To assess the outcomes of several rodent animal models for studying tooth extraction-related medication-related osteonecrosis of the jaw (MRONJ).

DESIGN

After a search of the databases, 2004 articles were located, and 118 corroborated the inclusion factors (in vivo studies in rodents evaluating tooth extraction as a risk factor for the development of MRONJ).

RESULTS

Numerous studies attempting to establish an optimal protocol to induce MRONJ were found. Zoledronic acid (ZA) was the most used drug, followed by alendronate (ALN). Even when ZA did not lead to the development of MRONJ, its effect compromised the homeostasis of the bone and soft tissue. The association of other risk factors (dexamethasone, diabetes, and tooth-related inflammatory dental disease) besides tooth extraction also played a role in the development of MRONJ. In addition, studies demonstrated a relationship between cumulative dose and MRONJ.

CONCLUSIONS

Both ZA and ALN can lead to MRONJ in rodents when equivalent human doses (in osteoporosis or cancer treatment) are used. Local oral risk factors and tooth-related inflammatory dental disease increase the incidence of MRONJ in a tooth extraction-related rodent model.

Topical corticosteroids inhibit allergic skin inflammation but are ineffective in impeding the formation and expansion of resident memory T cells

BACKGROUND

Tissue-resident memory T (TRM ) cells are detrimental in allergic contact dermatitis (ACD), in which they contribute to the chronicity and severity of the disease.

METHODS

We assessed the impact of a standard topical corticosteroid (TCS) treatment, triamcinolone acetonide (TA), on the formation, maintenance and reactivation of epidermal TRM cells in a preclinical model of ACD to 2,4-dinitrofluorobenzene. TA 0.01% was applied at different time points of ACD response and we monitored skin inflammation and tracked CD8+ CD69+ CD103+ TRM by flow cytometry and RNA sequencing.

RESULTS

The impact of TA on TRM formation depended on treatment regimen: (i) in a preventive mode, that is, in sensitized mice before challenge, TA transiently inhibited the infiltration of effector T cells and the accumulation of TRM upon hapten challenge. In contrast, (ii) in a curative mode, that is, at the peak of the ACD response, TA blocked skin inflammation but failed to prevent the formation of TRM . Finally, (iii) in a proactive mode, that is, on previous eczema lesions, TA had no effect on the survival of skin TRM , but transiently inhibited their reactivation program upon allergen reexposure. Indeed, specific TRM progressively regained proliferative functions upon TA discontinuation and expanded in the tissue, leading to exaggerated iterative responses. Interestingly, TRM re-expansion correlated with the decreased clearance of hapten moieties from the skin induced by repeated TA applications.

CONCLUSIONS

Our results demonstrate that TCS successfully treat ACD inflammation, but are mostly ineffective in impeding the formation and expansion of allergen-specific TRM , which certainly restricts the induction of lasting tolerance in patients with chronic dermatitis.

Fractional CO 2 Laser versus Fractional CO 2 Laser Plus Betamethasone/Calcipotriol Ointment in the Treatment of Nail Psoriasis

BACKGROUND

Nail psoriasis has a major negative impact on the physical and psychological aspects of the patient's life. Treatment is often unsatisfactory because of the difficult penetration of the drug into the nail.

OBJECTIVE

To compare the efficacy of fractional CO 2 laser monotherapy versus combined fractional CO 2 laser and calcipotriol/betamethasone ointment preparation in treatment of nail psoriasis.

PATIENTS AND METHODS

Thirty patients with nail psoriasis with at least 2 affected fingernails were recruited for this study. Target NAPSI (tNAPSI) score was calculated at the start of the study and at 3 months after the last laser session. One affected fingernail of each patient received 6 sessions of fractional CO 2 laser with 4-week intervals. Another affected fingernail of each patient received topical betamethasone/calcipotriol ointment once daily in addition to the 6 fractional CO 2 laser sessions.

RESULTS

In the monotherapy group, there was significant improvement in the nail matrix score, nail bed score, and tNAPSI score. In the combined therapy group, there was significant improvement in nail bed score and tNAPSI score, but nail matrix score showed no statistically significant improvement. Overall, there was no statistically significant difference between the 2 studied groups.

CONCLUSION

Fractional CO 2 laser can be an effective and promising new treatment for nail psoriasis.

Cellular and biological factors involved in healing wounds and burns and treatment options in tissue engineering

Severe traumatic wounds and burns have a high chance of mortality and can leave survivors with many functional disabilities and cosmetic problems, including scars. The healing process requires a harmonious interplay of various cells and growth factors. Different structures of the skin house numerous cells, matrix components and growth factors. Any disturbance in the balance between these components can impair the healing process. The function of cells and growth factors can be manipulated and facilitated to aid tissue repair. In the current review, the authors focus on the importance of the skin microenvironment, the pathophysiology of various types of burns, mechanisms and factors involved in skin repair and wound healing and regeneration of the skin using tissue engineering approaches.

New insights into the cell- and tissue-specificity of glucocorticoid actions

Glucocorticoids (GCs) are endogenous hormones that are crucial for the homeostasis of the organism and adaptation to the external environment. Because of their anti-inflammatory effects, synthetic GCs are also extensively used in clinical practice. However, almost all cells in the body are sensitive to GC regulation. As a result, these mediators have pleiotropic effects, which may be undesirable or detrimental to human health. Here, we summarize the recent findings that contribute to deciphering the molecular mechanisms downstream of glucocorticoid receptor activation. We also discuss the complex role of GCs in infectious diseases such as sepsis and COVID-19, in which the balance between pathogen elimination and protection against excessive inflammation and immunopathology needs to be tightly regulated. An understanding of the cell type- and context-specific actions of GCs from the molecular to the organismal level would help to optimize their therapeutic use.

Glucocorticoids Disrupt Skeletal Angiogenesis Through Transrepression of NF-κB-Mediated Preosteoclast Pdgfb Transcription in Young Mice

In the growing skeleton, angiogenesis is intimately coupled with osteogenesis. Chronic, high doses of glucocorticoids (GCs) are associated with decreased bone vasculature and induce osteoporosis and growth failure. The mechanism of GC-suppression of angiogenesis and relationship to osteoporosis and growth retardation remains largely unknown. Type H vessels, which are regulated by preosteoclast (POC) platelet-derived growth factor-BB (PDGF-BB), are specifically coupled with bone formation and development. We determined the effect of GCs on POC synthesis of PDGF-BB in relation to type H vessel formation, bone mass, and bone growth in the distal femur of 2-week-old young mice receiving prednisolone or vehicle for 2, 4, or 6 weeks. After 2 weeks of prednisolone, the number of POCs were unchanged while POC synthesis of PDGF-BB was reduced. Longer treatment with prednisolone reduced POCs numbers and PDGF-BB. These changes were associated with a reduction in type H vessels, bone formation rate, bone mass, and bone length at each time point. In vitro, excessive concentrations of prednisolone (10^-6 M) resulted in decreased PDGF-BB concentration and POC numbers. Conditioned medium from POC cultures treated with control concentration of prednisolone (10^-7 M) or recombinant PDGF-BB stimulated endothelial tube formation, whereas conditioned medium from control concentration of prednisolone-treated POC cultures neutralized by PDGF-BB antibody or excessive prednisolone inhibited endothelial tube formation. Administration of excessive prednisolone attenuated the P65 subunit of nuclear factor kappa B (NF-κB) binding to the Pdgfb promoter, resulting in lower Pdgfb transcription. Co-treatment with excessive prednisolone and the glucocorticoid receptor (GR) antagonist (RU486), GR siRNA, or TNFα rescued NF-κB binding to the Pdgfb promoter and endothelial tube formation. These results indicate that PDGF-BB synthesis in POCs is suppressed by GCs through transrepression of GR/NF-κB, thus inhibiting type H vessel formation and associated osteoporosis and growth failure. © 2020 American Society for Bone and Mineral Research.

Cushing Syndrome: The Role of MSCs in Wound Healing, Immunosuppression, Comorbidities, and Antioxidant Imbalance

Cushing syndrome (CS), caused by glucocorticoid (GCs) excess, is strictly connected to onset of different metabolic diseases and impaired wound healing. The source of excessively high levels of GCs allows the identification of endogenous and exogenous (iatrogenic) CS. Iatrogenic patients usually receive also anti-metabolites serving as the foundation to modern steroid-sparing immunosuppressive therapy. Tissues mainly targeted by CS are bone and fat, both derived from progenitor cells named mesenchymal stem cells (MSCs). In addition, the pathogenic role of MSCs in other diseases sharing common properties with CS, such as an altered inflammatory profile and increased oxidative stress, has been identified. In this light, MSCs isolated from skin of control healthy subjects (C-MSCs), patients affected by endogenous CS (ENDO-MSCs), patients affected by iatrogenic CS (IATRO-MSCs) and patients affected by exogenous CS receiving steroid-sparing drugs (SS-MSCs), respectively, have been isolated and analyzed. ENDO- and IATRO-MSCs showed a reduced differentiative potential toward osteogenic and adipogenic lineages compared to C-MSCs, whereas SS-MSCs re-acquired the ability to differentiate, with a trend similar to control cells. In addition, MSCs from CS groups, compared to control MSCs, displayed a reduction in the secretion of cytokines (immune-suppression), a decreased expression of genes related to wound healing and a dysregulation of the enzymes/genes related to antioxidant capacity. In conclusion, our results suggest that the hallmarks of CS, such as wound healing impairment and immunosuppression, are already detectable in undifferentiated cells, which could be considered a potential therapeutic early target for control of CS.

Pharmacological and Genetic Inhibition of Caveolin-1 Promotes Epithelialization and Wound Closure

Chronic wounds-including diabetic foot ulcers, venous leg ulcers, and pressure ulcers-represent a major health problem that demands an urgent solution and new therapies. Despite major burden to patients, health care professionals, and health care systems worldwide, there are no efficacious therapies approved for treatment of chronic wounds. One of the major obstacles in achieving wound closure in patients is the lack of epithelial migration. Here, we used multiple pre-clinical wound models to show that Caveolin-1 (Cav1) impedes healing and that targeting Cav1 accelerates wound closure. We found that Cav1 expression is significantly upregulated in wound edge biopsies of patients with non-healing wounds, confirming its healing-inhibitory role. Conversely, Cav1 was absent from the migrating epithelium and is downregulated in acutely healing wounds. Specifically, Cav1 interacted with membranous glucocorticoid receptor (mbGR) and epidermal growth factor receptor (EGFR) in a glucocorticoid-dependent manner to inhibit cutaneous healing. However, pharmacological disruption of caveolae by MβCD or CRISPR/Cas9-mediated Cav1 knockdown resulted in disruption of Cav1-mbGR and Cav1-EGFR complexes and promoted epithelialization and wound healing. Our data reveal a novel mechanism of inhibition of epithelialization and wound closure, providing a rationale for pharmacological targeting of Cav1 as potential therapy for patients with non-healing chronic wounds.

The discovery and development of topical medicines for wound healing

INTRODUCTION

Chronic, nonhealing skin wounds claim >3% of the health-care budget in industrialized countries, and the incidence is rising. Currently, two parallel trends influence innovations within the field of wound healing: the need to reduce spread of antibiotic resistance and the emerging use of health economy and value-based models. Areas covered: This review focuses on the discovery of drug candidates and development of treatments aiming to enhance wound healing in the heterogeneous group of patients with nonhealing wounds. Expert opinion: Nonhealing wounds are multifaceted and recognized as difficult indications. The majority of products currently in use are medical device dressings, or concepts of negative pressure or hyperbaric oxygen treatment. Global best practice guidelines for the treatment of diabetic foot ulcers recommend debridement, redressing, as well as infection control, and are critical to the lack of coherent clinical evidence for many approved products in active wound care. To accelerate wound healing, there is an emerging trend toward biologics, gene therapy, and novel concepts for drug delivery in research and in the pipeline for clinical trials. Scientific delineation of the therapeutic mechanism of action is, in our opinion, vital for clinical trial success and for an increased fraction of medical products in the pharmaceutical pipeline.

Macrophage and Fibroblast Interactions in Biomaterial-Mediated Fibrosis

Biomaterial-mediated inflammation and fibrosis remain a prominent challenge in designing materials to support tissue repair and regeneration. Despite the many biomaterial technologies that have been designed to evade or suppress inflammation (i.e., delivery of anti-inflammatory drugs, hydrophobic coatings, etc.), many materials are still subject to a foreign body response, resulting in encapsulation of dense, scar-like extracellular matrix. The primary cells involved in biomaterial-mediated fibrosis are macrophages, which modulate inflammation, and fibroblasts, which primarily lay down new extracellular matrix. While macrophages and fibroblasts are implicated in driving biomaterial-mediated fibrosis, the signaling pathways and spatiotemporal crosstalk between these cell types remain loosely defined. In this review, the role of M1 and M2 macrophages (and soluble cues) involved in the fibrous encapsulation of biomaterials in vivo is investigated, with additional focus on fibroblast and macrophage crosstalk in vitro along with in vitro models to study the foreign body response. Lastly, several strategies that have been used to specifically modulate macrophage and fibroblast behavior in vitro and in vivo to control biomaterial-mediated fibrosis are highlighted.

Treatment of limb wounds of horses with orf virus IL-10 and VEGF-E accelerates resolution of exuberant granulation tissue, but does not prevent its development

Bandaging of limb wounds in horses leads to formation of exuberant granulation tissue (EGT) that retards healing due to protracted inflammation, aberrant vascularisation and delayed epithelialisation. EGT is not observed if wounds are left undressed or when wounds are on the body. A previous study showed that short-term administration of proteins derived from orf virus dampened inflammation and promoted epithelialisation of open wounds in horses. Here, we investigated the impact of orf virus interleukin-10 and vascular endothelial growth factor-E on the development and resolution of EGT. Excisional wounds were created on the forelimb of four horses, and bandages were maintained until full healing to induce EGT formation. Matching body wounds were created to ensure EGT was limited to the limb, and to differentiate the effects of the viral proteins on normal healing and on EGT formation. Viral proteins or the hydrogel vehicle control were administered topically to site-matched wounds at day 1, with repeat administration at day 8. Wound healing and EGT formation were monitored macroscopically. Wound margin samples were harvested at 2, 7 and 14 days, and at full healing, with histology used to observe epithelialisation, immunofluorescence used to detect inflammatory cells, angiogenesis and cell death, and qPCR to measure expression of genes regulating inflammation and angiogenesis. Limb wounds developed EGT, and exhibited slower healing than body wounds. Viral protein treatment did not accelerate healing at either location nor limit EGT formation in limb wounds. Treatment of limb wounds did however increase epithelialisation and angiogenesis, without dampening inflammatory cell infiltration or gene expression. The healed wounds also had less occlusion and death of blood vessels and fewer epidermal rete ridges following viral protein treatment. These findings indicate that the viral protein treatment does not suppress wound inflammation or EGT formation, but does promote vascular and epidermal repair and EGT resolution.

Chronic stress impairs the local immune response during cutaneous repair in gilthead sea bream (Sparus aurata, L.)

Scale removal in fish triggers a damage-repair program to re-establish the lost epidermis and scale and an associated local immune response. In mammals, chronic stress is known to delay wound healing and to modulate the cutaneous stress axis, but this is unstudied in teleost fish the most successful extant vertebrates. The present study was designed to test the hypothesis that chronic stress impairs cutaneous repair in teleost fish as a consequence of suppression of the immune response. The hypothesis was tested by removing the scales and damaging the skin on one side of the body of fish previously exposed for 4 weeks to a chronic crowding stress and then evaluating cutaneous repair for 1 week. Scale removal caused the loss of the epidermis although at 3days it was re-established. At this stage the basement membrane was significantly thicker (p=0.038) and the hypodermis was significantly thinner (p=0.016) in the regenerating skin of stressed fish relative to the control fish. At 3days, stressed fish also had a significantly lower plasma osmolality (p=0.015) than control fish indicative of reduced barrier function. Chronic stress caused a significant down-regulation of the glucocorticoid receptor (gr) in skin before damage (time 0, p=0.005) and of star at 3 and 7days (p<0.05) after regeneration relative to control fish. In regenerating skin key transcripts of cutaneous repair, pcna, colivα1 and mmp9, and the inflammatory response, tgfβ1, csf-1r, mpo and crtac2, were down-regulated (p<0.05) by chronic stress. Irrespective of chronic stress and in contrast to intact skin many hyper pigmented masses, putative melanomacrophages, infiltrated the epidermis of regenerating skin. This study reveals that chronic stress suppresses the local immune response to scale removal and impairs the expression of key transcripts of wound healing. Elements of the stress axis were identified and modulated by chronic stress during cutaneous repair in gilthead seabream skin.

Epidermal Mineralocorticoid Receptor Plays Beneficial and Adverse Effects in Skin and Mediates Glucocorticoid Responses

Glucocorticoids (GCs) regulate skin homeostasis and combat cutaneous inflammatory diseases; however, adverse effects of chronic GC treatments limit their therapeutic use. GCs bind and activate the GC receptor and the mineralocorticoid receptor (MR), transcription factors that recognize identical hormone responsive elements. Whether epidermal MR mediates beneficial or deleterious GC effects is of great interest for improving GC-based skin therapies. MR epidermal knockout mice exhibited increased keratinocyte proliferation and differentiation and showed resistance to GC-induced epidermal thinning. However, crucially, loss of epidermal MR rendered mice more sensitive to inflammatory stimuli and skin damage. MR epidermal knockout mice showed increased susceptibility to phorbol 12-myristate 13-acetate-induced inflammation with higher cytokine induction. Likewise, cultured MR epidermal knockout keratinocytes had increased phorbol 12-myristate 13-acetate-induced NF-κB activation, highlighting an anti-inflammatory function for MR. GC-induced transcription was reduced in MR epidermal knockout keratinocytes, at least partially due to decreased recruitment of GC receptor to hormone responsive element-containing sequences. Our results support a role for epidermal MR in adult skin homeostasis and demonstrate nonredundant roles for MR and GC receptor in mediating GC actions.

Transition from inflammation to proliferation: a critical step during wound healing

The ability to rapidly restore the integrity of a broken skin barrier is critical and is the ultimate goal of therapies for hard-to-heal-ulcers. Unfortunately effective treatments to enhance healing and reduce scarring are still lacking. A deeper understanding of the physiology of normal repair and of the pathology of delayed healing is a prerequisite for the development of more effective therapeutic interventions. Transition from the inflammatory to the proliferative phase is a key step during healing and accumulating evidence associates a compromised transition with wound healing disorders. Thus, targeting factors that impact this phase transition may offer a rationale for therapeutic development. This review summarizes mechanisms regulating the inflammation-proliferation transition at cellular and molecular levels. We propose that identification of such mechanisms will reveal promising targets for development of more effective therapies.

The role of nuclear hormone receptors in cutaneous wound repair

The cutaneous wound repair process involves balancing a dynamic series of events ranging from inflammation, oxidative stress, cell migration, proliferation, survival and differentiation. A complex series of secreted trophic factors, cytokines, surface and intracellular proteins are expressed in a temporospatial manner to restore skin integrity after wounding. Impaired initiation, maintenance or termination of the tissue repair processes can lead to perturbed healing, necrosis, fibrosis or even cancer. Nuclear hormone receptors (NHRs) in the cutaneous environment regulate tissue repair processes such as fibroplasia and angiogenesis. Defects in functional NHRs and their ligands are associated with the clinical phenotypes of chronic non-healing wounds and skin endocrine disorders. The functional relationship between NHRs and skin niche cells such as epidermal keratinocytes and dermal fibroblasts is pivotal for successful wound closure and permanent repair. The aim of this review is to delineate the cutaneous effects and cross-talk of various nuclear receptors upon injury towards functional tissue restoration.

Development of the HPA axis: where and when do sex differences manifest?

Sex differences in the response to stress contribute to sex differences in somatic, neurological, and psychiatric diseases. Despite a growing literature on the mechanisms that mediate sex differences in the stress response, the ontogeny of these differences has not been comprehensively reviewed. This review focuses on the development of the hypothalamic-pituitary-adrenal (HPA) axis, a key component of the body's response to stress, and examines the critical points of divergence during development between males and females. Insight gained from animal models and clinical studies are presented to fully illustrate the current state of knowledge regarding sex differences in response to stress over development. An appreciation for the developmental timelines of the components of the HPA axis will provide a foundation for future areas of study by highlighting both what is known and calling attention to areas in which sex differences in the development of the HPA axis have been understudied.

An innovative procedure for the treatment of primary and recurrent capsular contracture (CC) following breast augmentation

BACKGROUND

Capsular contracture (CC) is the most frequently reported complication following alloplastic breast augmentation. At present, none of the available preventive measures are effective, and various treatment modalities have been advocated. Reduction of the inflammatory process is critical for successful treatment. Late intracapsular glucocorticosteroid (GC) injections have been somewhat effective for the treatment, but the fine balance between the effectiveness of therapeutic GC dosages and their potential serious side effects is of utmost importance.

OBJECTIVES

The authors investigate whether instillation of a rapid-acting water-soluble GC in the implant pocket during the early proliferative phase of wound healing is more effective than delayed instillation during the remodeling phase.

METHODS

Between 2003 and 2009, 33 consecutive patients presenting with CC (Baker grades III and IV) were managed by capsulectomy with implant replacement and corticosteroid therapy immediately as well as 2 to 3 days later through an indwelling catheter left in place for that period. This delayed but early administration is a novel technique for GC injection.

RESULTS

Complete correction of the contracture with no recurrence was achieved in all patients with a follow-up range of 2 to 10 years.

CONCLUSIONS

This GC administration technique avoids the potential complications of long-term, slow corticosteroid release. It has a targeted anti-inflammatory effect, probably at a critical stage of the healing process, and could effectively prevent CC following alloplastic breast augmentation.

Selective non-steroidal glucocorticoid receptor agonists attenuate inflammation but do not impair intestinal epithelial cell restitution in vitro

Introduction

Despite the excellent anti-inflammatory and immunosuppressive action of glucocorticoids (GCs), their use for the treatment of inflammatory bowel disease (IBD) still carries significant risks in terms of frequently occurring severe side effects, such as the impairment of intestinal tissue repair. The recently-introduced selective glucocorticoid receptor (GR) agonists (SEGRAs) offer anti-inflammatory action comparable to that of common GCs, but with a reduced side effect profile.

Methods

The in vitro effects of the non-steroidal SEGRAs Compound A (CpdA) and ZK216348, were investigated in intestinal epithelial cells and compared to those of Dexamethasone (Dex). GR translocation was shown by immunfluorescence and Western blot analysis. Trans-repressive effects were studied by means of NF-κB/p65 activity and IL-8 levels, trans-activation potency by reporter gene assay. Flow cytometry was used to assess apoptosis of cells exposed to SEGRAs. The effects on IEC-6 and HaCaT cell restitution were determined using an in vitro wound healing model, cell proliferation by BrdU assay. In addition, influences on the TGF-β- or EGF/ERK1/2/MAPK-pathway were evaluated by reporter gene assay, Western blot and qPCR analysis.

Results

Dex, CpdA and ZK216348 were found to be functional GR agonists. In terms of trans-repression, CpdA and ZK216348 effectively inhibited NF-κB activity and IL-8 secretion, but showed less trans-activation potency. Furthermore, unlike SEGRAs, Dex caused a dose-dependent inhibition of cell restitution with no effect on cell proliferation. These differences in epithelial restitution were TGF-β-independent but Dex inhibited the EGF/ERK1/2/MAPK-pathway important for intestinal epithelial wound healing by induction of MKP-1 and Annexin-1 which was not affected by CpdA or ZK216348.

Conclusion

Collectively, our results indicate that, while their anti-inflammatory activity is comparable to Dex, SEGRAs show fewer side effects with respect to wound healing. The fact that SEGRAs did not have a similar effect on cell restitution might be due to a different modulation of EGF/ERK1/2 MAPK signalling.

Keratinocyte-targeted overexpression of the glucocorticoid receptor delays cutaneous wound healing

Delayed wound healing is one of the most common secondary adverse effects associated to the therapeutic use of glucocorticoid (GC) analogs, which act through the ligand-dependent transcription factor GC-receptor (GR). GR function is exerted through DNA-binding-dependent and –independent mechanisms, classically referred to as transactivation (TA) and transrepression (TR). Currently both TA and TR are thought to contribute to the therapeutical effects mediated by GR; however their relative contribution to unwanted side effects such as delayed wound healing is unknown. We evaluated skin wound healing in transgenic mice with keratinocyte-restricted expression of either wild type GR or a mutant GR that is TA-defective but efficient in TR (K5-GR and K5-GR-TR mice, respectively). Our data show that at days (d) 4 and 8 following wounding, healing in K5-GR mice was delayed relative to WT, with reduced recruitment of granulocytes and macrophages and diminished TNF-α and IL-1β expression. TGF-β1 and Kgf expression was repressed in K5-GR skin whereas TGF-β3 was up-regulated. The re-epithelialization rate was reduced in K5-GR relative to WT, as was formation of granulation tissue. In contrast, K5-GR-TR mice showed delays in healing at d4 but re-established the skin breach at d8 concomitant with decreased repression of pro-inflammatory cytokines and growth factors relative to K5-GR mice. Keratinocytes from both transgenic mice closed in vitro wounds slower relative to WT, consistent with the in vivo defects in cell migration. Overall, the delay in the early stages of wound healing in both transgenic models is similar to that elicited by systemic treatment with dexamethasone. Wound responses in the transgenic keratinocytes correlated with reduced ERK activity both in vivo and in vitro. We conclude that the TR function of GR is sufficient for negatively regulating early stages of wound closure, while TA by GR is required for delaying later stages of healing.

Glucose sensor membranes for mitigating the foreign body response

Continuous glucose monitoring devices remain limited in their duration of use due to difficulties presented by the foreign body response (FBR), which impairs sensor functionality immediately following implantation via biofouling and leukocyte infiltration. The FBR persists through the life of the implant, culminating with fibrous encapsulation and isolation from normal tissue. These issues have led researchers to develop strategies to mitigate the FBR and improve tissue integration. Studies have often focused on abating the FBR using various outer coatings, thereby changing the chemical or physical characteristics of the sensor surface. While such strategies have led to some success, they have failed to fully integrate the sensor into surrounding tissue. To further address biocompatibility, researchers have designed coatings capable of actively releasing biological agents (e.g., vascular endothelial growth factor, dexamethasone, and nitric oxide) to direct the FBR to induce tissue integration. Active release approaches have proven promising and, when combined with biocompatible coating materials, may ultimately improve the in vivo lifetime of subcutaneous glucose biosensors. This article focuses on strategies currently under development for mitigating the FBR.

Wound healing activity of the human antimicrobial peptide LL37

Antimicrobial peptides (AMPs) are part of the innate immune system and are generally defined as cationic, amphipathic peptides, with less than 50 amino acids, including multiple arginine and lysine residues. The human cathelicidin antimicrobial peptide LL37 can be found at different concentrations in many different cells, tissues and body fluids and has a broad spectrum of antimicrobial and immunomodulatory activities. The healing of wound is a complex process that involves different steps: hemostasis, inflammation, remodeling/granulation tissue formation and re-epithelialization. Inflammation and angiogenesis are two fundamental physiological conditions implicated in this process. We have recently developed a new method for the expression and purification of recombinant LL37. In this work, we show that the recombinant peptide P-LL37 with a N-terminus proline preserves its immunophysiological properties in vitro and in vivo. P-LL37 neutralized the activation of macrophages by lipopolysaccharide (LPS). Besides, the peptide induced proliferation, migration and tubule-like structures formation by endothelial cells. Wound healing experiments were performed in dexamethasone-treated mice to study the effect of LL37 on angiogenesis and wound regeneration. The topical application of synthetic and recombinant LL37 increased vascularization and re-epithelialization. Taken together, these results clearly demonstrate that LL37 may have a key role in wound regeneration through vascularization.

Systemic lupus erythematosus complicated by recurrent pneumothorax: Case report and literature review

Pneumothorax is a rare pleuropulmonary manifestation of systemic lupus erythematosus. We encountered a 37-year-old Japanese woman who had systemic lupus erythematosus complicated by recurrent pneumothorax during treatment for recurrent serositis with glucocorticoid therapy. She was admitted for the third episode of lupus peritonitis in December 2005. Intravenous cyclophoshamide and increased dose of oral prednisolone were administered. In early January 2006, hemoptysis was observed and bronchofiberscopy revealed hemorrhage from the left lower lobe. After intravenous methylprednisolone pulse therapy and oral cyclosporine therapy were added, pleurisy and pulmonary hemorrhage improved. On February 22nd, she suddenly developed pneumothorax on the right side, followed by pneumothorax on the left side after 2 days. This pneumothorax on the left side did not improve despite chest tube drainage for over one month. She underwent thoracoscopic partial lobectomy of lower lobe of the left lung, and her symptoms improved. Review of the literature identified 10 case reports of systemic lupus erythematosus complicated by pneumothorax. All of the patients including our case had underlying pulmonary lesions, and 9/11 patients had pleurisy. Besides 10/11 patients received glucocorticoid therapy before the occurrence of pneumothorax. Tissue fragility caused by these factors might contribute to the complication of pneumothorax in patients with systemic lupus erythematosus.

Skin wound healing in diabetic β6 integrin-deficient mice

Integrin αvβ6 is a heterodimeric cell surface receptor, which is absent from the normal epithelium, but is expressed in wound-edge keratinocytes during re-epithelialization. However, the function of the αvβ6 integrin in wound repair remains unclear. Impaired wound healing in patients with diabetes constitutes a major clinical problem worldwide and has been associated with the accumulation of advanced glycated endproducts (AGEs) in the tissues. AGEs may account for aberrant interactions between integrin receptors and their extracellular matrix ligands such as fibronectin (FN). In this study, we compared healing of experimental excisional skin wounds in wild-type (WT) and β6-knockout (β6(-/-) ) mice with streptozotocin-induced diabetes. Results showed that diabetic β6(-/-) mice had a significant delay in early wound closure rate compared with diabetic WT mice, suggesting that αvβ6 integrin may serve as a protective role in re-epithelialization of diabetic wounds. To mimic the glycosylated wound matrix, we generated a methylglyoxal (MG)-glycated variant of FN. Keratinocytes utilized αvβ6 and β1 integrins for spreading on both non-glycated and FN-MG, but their spreading was reduced on FN-MG. These findings indicated that glycation of FN and possibly other integrin ligands could hamper keratinocyte interactions with the provisional matrix proteins during re-epithelialization of diabetic wounds.

Corticosteroid-associated laminitis

A direct causal association between corticosteroid use and laminitis has yet to be proven scientifically, and there have been few studies specifically addressing this aspect. New evidence, however, is improving the understanding of the causes of laminitis, particularly related to endocrine factors. The focus of this article is discussing the circumstances under which steroids might cause this condition.

Biomaterial adjuvant effect is attenuated by anti-inflammatory drug delivery or material selection

Biomaterials have been shown to differentially support dendritic cell (DC) maturation, a prerequisite for an adjuvant effect. Treatment of DCs with poly(D,L-lactic-co-glycolic acid) (PLGA) films resulted in DC maturation but agarose films did not. In these studies, the biomaterial adjuvant effect was attenuated by material selection (PLGA or agarose scaffolds) or local delivery of an anti-inflammatory/immunosuppressive glucocorticoid, dexamethasone (DX), from PLGA scaffolds. Porous scaffolds (SCs) of PLGA or agarose were produced to deliver equivalent amounts of model antigen, ovalbumin (OVA). Alternatively, PLGA SCs with incorporated OVA were produced with or without DX. These SCs were implanted individually, subcutaneously, and dorsally in C57BL/6 mice. Blood was collected from mice at specific times over a 12-week duration for measurement of antibody production against OVA. Scaffolds were explanted at 12 weeks for histological examination of foreign body response. Scaffolds of PLGA, but not of agarose, were found to elicit higher antibody production against co-delivered OVA, than negative controls. Short-term delivery of DX from PLGA SCs delivering OVA temporarily delayed onset of anti-OVA antibody production. More sustained release of DX at an effective dose and with an appropriate time course is expected to extend the effect of DX on the biomaterial adjuvant effect. The immunomodulatory ability of biomaterials to affect the immune response to co-delivered antigen is demonstrated wherein this immunomodulatory ability correlates with the observed in vitro differential effects of biomaterials on DC maturation.

ZFP36L1 is regulated by growth factors and cytokines in keratinocytes and influences their VEGF production

Keratinocyte-derived growth factors and cytokines play an important role in epidermal homeostasis and particularly in cutaneous wound repair. Thus, we analyzed a potential role of the ZFP36/tristetraprolin family of zinc finger proteins, which are targets of these factors, but also regulate their production, in keratinocytes. We show that expression of ZFP36, ZFP36L1, and ZFP36L2 is induced by a broad variety of growth factors and cytokines, and by scratch wounding. Since ZFP36L1 is a modulator of vascular endothelium growth factor (VEGF) mRNA stability, we subsequently used siRNA technology to inhibit ZFP36L1 gene expression. Notably, this treatment resulted in prolonged maintenance of elevated VEGF levels in HaCaT keratinocytes upon epidermal growth factor stimulation of these cells. Taken together, our results suggest an important role of ZFP36L1 in wound healing.

Molecular basis for hair loss in mice carrying a novel nonsense mutation (Hrrh-R ) in the hairless gene (Hr)

Animal models carrying mutations in the hairless (Hr) gene provide a rich resource for study of hair follicle biology. A spontaneous mouse mutant with a phenotype strikingly similar to rhino mutants of Hr arose spontaneously in the mouse facility at Oak Ridge National Laboratory. Sequence analysis of Hr in these mutants uncovered a nonsense mutation in exon 12, designated as Hr(rh-R) (rhino, Oak Ridge). The mutation led to significant reduction in Hr mRNA levels, predicted to be due to nonsense-mediated decay. Histological analysis indicated dilated hair follicle infundibula at 14 days of age that rapidly became filled with cornified material. Microarray analyses revealed that expression levels of many genes involved in keratinocyte differentiation, epidermal regeneration, and wound healing were significantly upregulated before morphological detection of the phenotype, suggesting their role in onset of the Hr(rh-R) phenotype. Identification of this new Hr allele and the underlying molecular alterations allows further understanding of the role of Hr in hair follicle biology.

Poly(lactide-co-glycolide) nanoparticle assembly for highly efficient delivery of potent therapeutic agents from medical devices

Controlled delivery of therapeutic agents from medical devices can improve their safety and effectiveness in vivo, by ameliorating the surrounding tissue responses and thus maintaining the functional integrity of the devices. Previously, we presented a new method for providing simultaneous controlled delivery from medical devices, by surface assembly of biodegradable polymer nanoparticles (NPs) encapsulating fluorescent dyes. Here, we continue our investigation with NPs loaded with therapeutic agents, dexamethasone (DEX) or plasmid DNA, and evaluated the bioactivity of the released molecules with macrophage cells associated with inflammation. Over a period of one week, NPs encapsulating DEX released 24.9+/-0.8ng from the probe surface and was successful at suppressing macrophage cell growth by 40+/-10%. This percentage of suppression corresponded to approximately 100% drug delivery efficiency, in comparison with the unencapsulated drug. DNA NP coatings, in contrast, released approximately 1ng of plasmid DNA and were effective at transfecting macrophage cells to express the luciferase gene at 300+/-200 relative luminescence/mg total protein. This amount of luciferase activity corresponded to 100% gene delivery efficiency. Thus, NP coatings were capable of providing continuous release of bioactive agents in sufficient quantities to induce relevant biological effects in cell culture studies. These coatings also remained intact, even after 14 days of incubation with phosphate buffered saline. Although the maximum loading for NP coatings is inherently lower than the more established matrix coating, our study suggests that the NP coatings are a more versatile and efficient approach toward drug delivery or gene delivery from a medical device surface and are perhaps best suited for continuous release of highly potent therapeutic agents.

Mice lacking beta6 integrin in skin show accelerated wound repair in dexamethasone impaired wound healing model

Integrin alphavbeta6 is an epithelial-specific receptor that is absent from the healthy epidermis but synthesized de novo during wound repair. However, its function in wound repair is unknown. Integrin-mediated transforming growth factor-beta1 (TGF-beta1) activation is the main activation mechanism of this key cytokine in vivo. Impaired wound healing caused by glucocorticoids is a major clinical problem and is associated with a disturbed balance of TGF-beta1 activity. Therefore, alphavbeta6 integrin-mediated regulation of TGF-beta1 activity may be involved in this process. To determine the function of alphavbeta6 integrin in glucocorticoid-induced impaired wound healing, both beta6 integrin-deficient (beta6-/-) and wild-type mice were exposed to dexamethasone treatment. Multiple wound parameters, keratinocyte proliferation, inflammation, and TGF-beta1 activation were assessed. Wound healing was significantly accelerated in the dexamethasone-treated beta6-/- mice compared with the corresponding wild-type mice. The dexamethasone-treated beta6-/- mice showed enhanced keratinocyte proliferation in both wound epithelium and hair follicles while the production of proinflammatory cytokines and TGF-beta1 activation were reduced. Accelerated wound repair in the dexamethasone-treated beta6-/- mice might be associated with the reduced antiproliferative and proinflammatory effects of TGF-beta1. Inhibition of alphavbeta6 integrin may provide a future target for treatment of impaired wound healing.

Differential effects of glucocorticoids in the establishment and maintenance of endotoxin tolerance

Gram-negative infections can result in endotoxic shock, which is the most common cause of death in intensive care units. Most of the undesirable effects in sepsis and septic shock have been ascribed to lipopolysaccharide (LPS), a normal constituent of the bacterial wall. The response to LPS involves rapid secretion of proinflammatory cytokines [tumour necrosis factor-alpha, interleukin (IL)-1, IL-6, IL-8, interferon-gamma] and the concomitant induction of anti-inflammatory mediators such as IL-10 and transforming growth factor-beta and glucocorticoids (GC), which render the host temporarily refractory to subsequent lethal doses of LPS challenge in a process known as LPS or endotoxin tolerance. Although protective from the development of sepsis or systemic inflammation, endotoxin tolerance has also been pointed out as the principal cause of the non-specific immunosuppression described in these patients. In this report we demonstrate, using a mouse model, that while the maintenance of tolerance is dependent upon GC, the establishment of tolerance by LPS could be inhibited by dexamethasone (Dex), a synthetic GC. Conversely, we demonstrated that mifepristone (RU486), a known GC receptor antagonist, was capable of inducing a transient and reversible disruption of endotoxin tolerance, also permitting partial restoration of the humoral immune response in LPS tolerant/immunosuppressed mice. These results are encouraging for the management of immunosuppression in sepsis and/or non-infectious shock, and deserve further investigation in the future.

RIP4 is a target of multiple signal transduction pathways in keratinocytes: implications for epidermal differentiation and cutaneous wound repair

Receptor interacting protein 4 (RIP4) is an important regulator of epidermal morphogenesis during embryonic development. We could previously show that expression of the rip4 gene is strongly downregulated in cutaneous wound repair, which might be initiated by a broad variety of growth factors and cytokines. Here, we demonstrate that in keratinocytes, rip4 expression is controlled by a multitude of different signal transduction pathways, such as the p38 mitogen-activated protein kinase (MAPK) and the nuclear factor kappa B (NF-kappaB) cascade, in a unique and specific manner. Furthermore, we show that the steroid dexamethasone abolishes the physiological rip4 downregulation after injury and might thus contribute to the phenotype of reduced and delayed wound reepithelialization seen in glucocorticoid-treated patients. As a whole, our data indicate that rip4 expression is regulated in a complex manner, which might have therapeutic implications.

Simultaneous release of multiple molecules from poly(lactide-co-glycolide) nanoparticles assembled onto medical devices

Cell and tissue responses to implanted biomaterials often limit their effectiveness and lifetime. This is particularly true for materials implanted into the brain. We present here a new approach for the modification of materials to enable release of multiple agents, which might be useful in modulating tissue responses, without changing the properties of the underlying material, in this case, a silicon probe. Poly(lactide-co-glycolide) nanoparticles (NPs) were assembled onto silicon probe surfaces by electrostatic interactions. Charged NPs were fabricated by altering the properties of the surfactant. NPs formed with poly(ethylene-alt-maleic anhydride) (PEMA) were strongly negatively charged; these NPs assembled onto probes best when suspended at nearly physiological conditions (surface density approximately 83,600+/-3000 particles/mm(2)). The percentage of surface area coverage by the NPs was estimated to be approximately 13% and was maintained over two weeks during constant exposure to PBS. Multiple fluorescent NP populations were attached to the same probe to allow visualization of simultaneous delivery of multiple agents by fluorescence microscopy. Release from NP coatings was reproducible and controllable. The distinct release profiles of each agent from the coatings were preserved upon attachment to the surfaces. The unique feature of this new system is that NPs encapsulating various molecules (i.e. drugs, proteins, or DNA) can be fabricated separately, in advance, and simply mixed prior to attachment. The versatility of this delivery system, therefore, makes it suitable for many applications.

Microgravity and the implications for wound healing

Wound healing is a sophisticated response ubiquitous to various traumatic stimuli leading to an anatomical/functional disruption. The aim of present article was to review the current evidence regarding the effects of microgravity on wound healing dynamics. Modulation of haemostatic phase because of alteration of platelet quantity and function seems probable. Furthermore, production of growth factors that are released from activated platelets and infiltration/function of inflammatory cells seem to be impaired by microgravity. Proliferation of damaged structures is dependent on orchestrated function of various growth factors, for example transforming growth factors, platelet-derived growth factor and epidermal growth factor, all of which are affected by microgravitational status. Moreover, gravity-induced alterations of gap junction, neural inputs, and cell populations have been reported. It may be concluded that different cellular and extracellular element involved in the healing response are modified through effect of microgravity which may lead to impairment in healing dynamics.

Transcriptional control of wound repair

Injury to the skin initiates a complex process of events involving inflammation as well as the formation and remodeling of new tissue. These processes result in at least partial reconstitution of the injured skin. However, wounds in adult mammals heal with a scar, which is accompanied by functional and aesthetic impairments. In addition to this problem, a large number of patients, in particular in the aged population, suffer from chronic, nonhealing ulcers. Therefore, there is a strong need to improve the wound healing process. This requires a thorough understanding of the underlying molecular and cellular mechanisms. During the past several years, important regulators of the wound healing process have been identified. In particular, the growth factors and matrix proteins, which orchestrate skin repair, have been characterized in detail. By contrast, much less is known about the transcription factors, which regulate gene expression at the wound site. This review summarizes recent data on the expression of transcription factors in skin wounds and their functions in the repair process.

Tissue homeostasis and cancer

Epithelial cells are known to release an important amount of cytokines capable to modulate immune system functions. On the other hand, immune system cells can release cytokines, which play an important role in the control of the growth of epithelial cells. In this paper, we stand the hypothesis that a mutual (reciprocal) growth regulation exists between epithelial cells and immune system. We propose a model describing plausible cytokine circuits that may regulate (inhibit) both epithelial growth and epithelial inflammation. In addition, we describe how dysfunction of these circuits could lead to tumoral growth, excessive inflammation or both. A failure in the regulation of epithelial growth by the immune system could give rise to a neoplasm, and a failure in the regulation of the immune system by the epithelium could give rise to inflammatory or autoimmune diseases. This model may satisfactorily explain the link between inflammation and cancer.

Androstenediol reduces the anti-inflammatory effects of restraint stress during wound healing

Restraint stress (RST) delays wound closure and suppresses pro-inflammatory gene expression by a glucocorticoid-dependent mechanism. Because androstenediol (AED) ameliorates many of the anti-inflammatory influences of glucocorticoids (GC) in vitro, it was hypothesized that treatment of stressed animals with AED would ameliorate the suppressive influence of restraint and restore healing to control levels. To test this hypothesis, male CD1 mice were subjected to nightly cycles of RST beginning 3 days prior to placement of two 3.5 mm full-thickness cutaneous wounds. To assess the influence of AED treatment on wound repair, mice were injected subcutaneously with 2.0 mg of AED or an equivalent volume of delivery vehicle (VEH) prior to wounding. The rate of wound closure was assessed daily by photoplanimetry. In addition, at 3, 6, 12, and 24 h post wounding, IL-1beta, MCP-1, and PDGF RNAs were quantified in wounds as a measure of inflammatory gene expression. The data showed that RST significantly delayed closure as compared to controls. In parallel, RST significantly decreased IL-1beta and PDGF gene expression as early as 12 h after wounding. In contrast, treatment with AED prevented the stress-induced delay in healing. Whereas wounds on VEH/RST mice did not achieve 50% closure until day 7, wounds on AED-treated animals, whether subjected to RST or not, had closed by 50% within 3 days of wounding. In addition, AED treatment prevented the stress-induced suppression of IL-1beta and PDGF gene expression 24 h after injury. Therefore, AED may provide a pharmacologic approach to ameliorate the anti-inflammatory effects of behavioral stress and in doing so, may improve tissue repair.

The αvβ6 integrin plays a role in compromised epidermal wound healing

The alphavbeta6 integrin is an exclusively epithelial integrin that is highly expressed during fetal development. In adult tissue, alphavbeta6 integrin is expressed during inflammation, carcinogenesis, and in wound healing. We previously reported that alphavbeta6 integrin is highly expressed in poorly healing human wounds and its over-expression is associated with chronic wounds in a mouse model. The objective of this study was to investigate the role of alphavbeta6 integrin in compromised wound healing induced by hydrocortisone treatment or aging by using young and old mice deficient in or overexpressing the beta6 integrin subunit in the epidermis. Untreated aged beta6 integrin-deficient (beta6-/-) animals showed a significant delay in wound healing when compared to their age-matched controls or younger beta6-/- mice. The most significant delay was observed at the stages where granulation tissue deposition was occurring. Hydrocortisone treatment significantly delayed wound healing in wild-type and beta6 integrin-deficient mice in comparison with the untreated controls. However, hydrocortisone treatment in beta6 integrin overexpressing animals did not cause a significant delay in wound healing. The results of this study suggest that alphavbeta6 integrin plays an important role in wound healing in animals compromised by either age or stress mimicked by hydrocortisone.