Effect of healing on the expression of transforming growth factor beta(s) and their receptors in chronic venous leg ulcers

Comparative analysis of electrochemical and optical sensors for detection of chronic wounds biomarkers: A review

Chronic wounds (CW) present a significant healthcare challenge due to their prolonged healing time and associated complications. To effectively treat these wounds and prevent further deterioration, monitoring their healing progress is crucial. Traditional wound assessment methods relying on visual inspection and subjective evaluation are prone to inter-observer variability. Biomarkers play a critical role in objectively evaluating wound status and predicting healing outcomes, providing quantitative measures of wound healing progress, inflammation, infection, and tissue regeneration. Recent attention has been devoted to identifying and validating CW biomarkers. Various studies have investigated potential biomarkers, including growth factors, cytokines, proteases, and extracellular matrix components, shedding light on the complex molecular and cellular processes within CW. This knowledge enables a more targeted and personalized approach to wound management. Accurate and sensitive techniques are necessary for detecting CW biomarkers. Thus, this review compares and discusses the use of electrochemical and optical sensors for biomarker determination. The advantages and disadvantages of these sensors are highlighted. Differences in detection capabilities and characteristics such as non-invasiveness, portability, high sensitivity, specificity, simplicity, cost-effectiveness, compatibility with point-of-care applications, and real-time monitoring of wound biomarkers will be pointed out and compared. In summary, this work provides an overview of CW, explores the emerging field of CW biomarkers, and discusses methods for detecting these biomarkers, with a specific focus on optical and electrochemical sensors. The potential of further research and development in this field for advancing wound care and improving patient outcomes will also be noted.

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

Amniotic Membrane Restores Chronic Wound Features to Normal in a Keratinocyte TGF-β-Chronified Cell Model

Unsuccessful wound closure in chronic wounds can be linked to altered keratinocyte activation and their inability to re-epithelize. Suggested mechanisms driving this impairment involve unbalanced cytokine signaling. However, the molecular events leading to these aberrant responses are poorly understood. Among cytokines affecting keratinocyte responses, Transforming Growth Factor-β (TFG-β) is thought to have a great impact. In this study, we have used a previously characterized skin epidermal in vitro model, HaCaT cells continuously exposed to TGF-β1, to study the wound recovery capabilities of chronified/senescent keratinocytes. In this setting, chronified keratinocytes show decreased migration and reduced activation in response to injury. Amniotic membrane (AM) has been used successfully to manage unresponsive complicated wounds. In our in vitro setting, AM treatment of chronified keratinocytes re-enabled migration in the early stages of wound healing, also promoting proliferation at later stages. Interestingly, when checking the gene expression of markers known to be altered in TGF-β chronified cells and involved in cell cycle regulation, early migratory responses, senescence, and chronic inflammation, we discovered that AM treatment seemed to reset back to keratinocyte status. The analysis of the evolution of both the levels of keratinocyte activation marker cytokeratin 17 and the spatial-temporal expression pattern of the proliferation marker Ki-67 in human in vivo biopsy samples suggests that responses to AM recorded in TGF-β chronified HaCaT cells would be homologous to those of resident keratinocytes in chronic wounds. All these results provide further evidence that sustained TGF-β might play a key role in wound chronification and postulate the validity of our TGF-β chronified HaCaT in vitro model for the study of chronic wound physiology.

Microparticles Decorated with Cell-Instructive Surface Chemistries Actively Promote Wound Healing

Wound healing is a complex biological process involving close crosstalk between various cell types. Dysregulation in any of these processes, such as in diabetic wounds, results in chronic nonhealing wounds. Fibroblasts are a critical cell type involved in the formation of granulation tissue, essential for effective wound healing. 315 different polymer surfaces are screened to identify candidates which actively drive fibroblasts toward either pro- or antiproliferative functional phenotypes. Fibroblast-instructive chemistries are identified, which are synthesized into surfactants to fabricate easy to administer microparticles for direct application to diabetic wounds. The pro-proliferative microfluidic derived particles are able to successfully promote neovascularization, granulation tissue formation, and wound closure after a single application to the wound bed. These active novel bio-instructive microparticles show great potential as a route to reducing the burden of chronic wounds.

Ozone improved the wound healing in type 2 diabetics via down-regulation of IL- 8, 10 and induction of FGFR expression

Background and aim:

We aimed to investigate the effect of ozonated autohaemotherapy (OA) on the wound healing, serum values of interleukin (IL) - 6, 8, 10, tumor necrosis factor-alpha (TNF-α), basic fibroblast growth factor (bFGF) and local expression of fibroblast growth factor receptors (FGFR) in type 2 diabetics with the acute soft-tissue infections.

Methods:

Patients in the first cohort (n-30) received a basic comprehensive treatment (BCT-group), and the second (n=28) also received OA (OA-group). Blood samples for ELISA and tissue specimens for the immunohistochemical examinations were collected at admission (day 0) and at the 9th day of inpatient treatment.

Results:

The additional using of OA has accelerated the timing of a single and the complete wound granulation and the timing to marginal epithelization, compared with the results of the standard treatment. The use of OA has significantly reduced the production of IL-8, 10 at 9th day. OA-group patients were characterized by consistently high levels of bFGF production in contrast to the BCT-group, where the decreasing in the serum bFGF level was observed. The maximum number of bFGFR - immunopositive labels was observed in OA-group out to 9th day (319,45 (249,90-348,43) versus baseline 192,65 (171,93-207,72), versus BCT-group 123,30 (105,23- 141,10), p<0,001).

Conclusions:

Application of OA in the complex treatment of the acute soft-tissue infections in diabetics makes it possible to achieve the significant reductions in the duration of the wound inflammation and regeneration phases by eliminating of overproduction of IL- 8, 10 and induction of expression of bFGF and its receptors. (www.actabiomedica.it)

Immune Inhibitory Properties and Therapeutic Prospects of Transforming Growth Factor-Beta and Interleukin 10 in Autoimmune Hepatitis

Transforming growth factor-beta and interleukin 10 have diverse immune inhibitory properties that have restored homeostatic defense mechanisms in experimental models of autoimmune disease. The goals of this review are to describe the actions of each cytokine, review their investigational use in animal models and patients, and indicate their prospects as interventions in autoimmune hepatitis. English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed. Transforming growth factor-beta expands the natural and inducible populations of regulatory T cells, limits the proliferation of natural killer cells, suppresses the activation of naïve CD8⁺ T cells, decreases the production of interferon-gamma, and stimulates fibrotic repair. Interleukin 10 selectively inhibits the CD28 co-stimulatory signal for antigen recognition and impairs antigen-specific activation of uncommitted CD4⁺ and CD8⁺ T cells. It also inhibits maturation of dendritic cells, suppresses Th17 cells, supports regulatory T cells, and limits production of diverse pro-inflammatory cytokines. Contradictory immune stimulatory effects have been associated with each cytokine and may relate to the dose and accompanying cytokine milieu. Experimental findings have not translated into successful early clinical trials. The recombinant preparation of each agent in low dosage has been safe in human studies. In conclusion, transforming growth factor-beta and interleukin 10 have powerful immune inhibitory actions of potential therapeutic value in autoimmune hepatitis. The keys to their therapeutic application will be to match their predominant non-redundant function with the pivotal pathogenic mechanism or cytokine deficiency and to avoid contradictory immune stimulatory actions.

Curcumin upregulates transforming growth factor-β1, its receptors, and vascular endothelial growth factor expressions in an in vitro human gingival fibroblast wound healing model

BACKGROUND

Curcumin accelerates healing of oral wounds; however, the responsible mechanisms remain underexplored. Our hypothesis is curcumin regulates the expression of wound healing-related genes in human gingival fibroblasts (hGFs). This study investigated whether curcumin regulates transforming growth factor (TGF)-β1, type I TGF-β receptor (TGF-βRI), type II TGF-β receptor (TGF-βRII), and vascular endothelial growth factor (VEGF) expression in unwounded hGFs and an in vitro hGF wound healing model.

METHODS

The cytotoxicity of curcumin was evaluated using the MTT assay. Unwounded hGFs were treated with non-cytotoxic concentrations of curcumin for 24 h. Gene expression was determined by quantitative polymerase chain reaction. Then, hGFs were treated with 1 µM curcumin in an in vitro wound healing model. PD98059 pretreatment was performed to determine whether extracellular signal-regulated kinase (ERK) signaling was required for regulation of gene expression by curcumin.

RESULTS

Curcumin at 0.1-20 µM caused no significant change in cell viability. In unwounded hGFs, curcumin had no significant effect on TGF-β1, TGF-βRI, TGF-βRII, or VEGF expression. Conversely, curcumin significantly upregulated the expression of these genes in the in vitro wound healing model. PD98059 significantly attenuated the curcumin-stimulated TGF-βRI, TGF-βRII, and VEGF expression, whereas it had no effect on TGF-β1 expression.

CONCLUSIONS

Curcumin upregulated TGF-β1, TGF-βRI, TGF-βRII, and VEGF expression in an in vitro hGF wound healing model. The ERK pathway is required for TGF-βRI, TGF-βRII, and VEGF induction by curcumin. Our findings support the development of curcumin as a therapeutic agent for gingival ulcers.

Growth Factors, Reactive Oxygen Species, and Metformin-Promoters of the Wound Healing Process in Burns?

Burns can be caused by various factors and have an increased risk of infection that can seriously delay the wound healing process. Chronic wounds caused by burns represent a major health problem. Wound healing is a complex process, orchestrated by cytokines, growth factors, prostaglandins, free radicals, clotting factors, and nitric oxide. Growth factors released during this process are involved in cell growth, proliferation, migration, and differentiation. Reactive oxygen species are released in acute and chronic burn injuries and play key roles in healing and regeneration. The main aim of this review is to present the roles of growth factors, reactive oxygen species, and metformin in the healing process of burn injuries.

Immunomodulatory biomaterials and their application in therapies for chronic inflammation-related diseases

The degree of tissue injuries such as the level of scarring or organ dysfunction, and the immune response against them primarily determine the outcome and speed of healing process. The successful regeneration of functional tissues requires proper modulation of inflammation-producing immune cells and bioactive factors existing in the damaged microenvironment. In the tissue repair and regeneration processes, different types of biomaterials are implanted either alone or by combined with other bioactive factors, which will interact with the immune systems including immune cells, cytokines and chemokines etc. to achieve different results highly depending on this interplay. In this review article, the influences of different types of biomaterials such as nanoparticles, hydrogels and scaffolds on the immune cells and the modification of immune-responsive factors such as reactive oxygen species (ROS), cytokines, chemokines, enzymes, and metalloproteinases in tissue microenvironment are summarized. In addition, the recent advances of immune-responsive biomaterials in therapy of inflammation-associated diseases such as myocardial infarction, spinal cord injury, osteoarthritis, inflammatory bowel disease and diabetic ulcer are discussed.

Why Venous Leg Ulcers Have Difficulty Healing: Overview on Pathophysiology, Clinical Consequences, and Treatment

Venous leg ulcers (VLUs) are one of the most common ulcers of the lower extremity. VLU affects many individuals worldwide, could pose a significant socioeconomic burden to the healthcare system, and has major psychological and physical impacts on the affected individual. VLU often occurs in association with post-thrombotic syndrome, advanced chronic venous disease, varicose veins, and venous hypertension. Several demographic, genetic, and environmental factors could trigger chronic venous disease with venous dilation, incompetent valves, venous reflux, and venous hypertension. Endothelial cell injury and changes in the glycocalyx, venous shear-stress, and adhesion molecules could be initiating events in VLU. Increased endothelial cell permeability and leukocyte infiltration, and increases in inflammatory cytokines, matrix metalloproteinases (MMPs), reactive oxygen and nitrogen species, iron deposition, and tissue metabolites also contribute to the pathogenesis of VLU. Treatment of VLU includes compression therapy and endovenous ablation to occlude the axial reflux. Other interventional approaches such as subfascial endoscopic perforator surgery and iliac venous stent have shown mixed results. With good wound care and compression therapy, VLU usually heals within 6 months. VLU healing involves orchestrated processes including hemostasis, inflammation, proliferation, and remodeling and the contribution of different cells including leukocytes, platelets, fibroblasts, vascular smooth muscle cells, endothelial cells, and keratinocytes as well as the release of various biomolecules including transforming growth factor-β, cytokines, chemokines, MMPs, tissue inhibitors of MMPs (TIMPs), elastase, urokinase plasminogen activator, fibrin, collagen, and albumin. Alterations in any of these physiological wound closure processes could delay VLU healing. Also, these histological and soluble biomarkers can be used for VLU diagnosis and assessment of its progression, responsiveness to healing, and prognosis. If not treated adequately, VLU could progress to non-healed or granulating VLU, causing physical immobility, reduced quality of life, cellulitis, severe infections, osteomyelitis, and neoplastic transformation. Recalcitrant VLU shows prolonged healing time with advanced age, obesity, nutritional deficiencies, colder temperature, preexisting venous disease, deep venous thrombosis, and larger wound area. VLU also has a high, 50-70% recurrence rate, likely due to noncompliance with compression therapy, failure of surgical procedures, incorrect ulcer diagnosis, progression of venous disease, and poorly understood pathophysiology. Understanding the molecular pathways underlying VLU has led to new lines of therapy with significant promise including biologics such as bilayer living skin construct, fibroblast derivatives, and extracellular matrices and non-biologic products such as poly-N-acetyl glucosamine, human placental membranes amnion/chorion allografts, ACT1 peptide inhibitor of connexin 43, sulodexide, growth factors, silver dressings, MMP inhibitors, and modulators of reactive oxygen and nitrogen species, the immune response and tissue metabolites. Preventive measures including compression therapy and venotonics could also reduce the risk of progression to chronic venous insufficiency and VLU in susceptible individuals.

AM251, a cannabinoid receptor 1 antagonist, prevents human fibroblasts differentiation and collagen deposition induced by TGF-β - An in vitro study

Previous studies showed that cannabinoid 1 receptor (CB₁) is linked with skin fibrosis and scar tissue formation in mice. Therefore, the topical use of cannabinoids may have a role in the prevention or treatment of local fibrotic and wound healing diseases as hypertrophic scars or keloids. In this study, we asked whether CB₁ activation or inactivation would change fibroblast differentiation into myofibroblast and collagen deposition in skin human fibroblast. Primary cultures of adult human fibroblasts were obtained from abdominal human skin. Cells were stimulated with transforming growth factor-beta (TGF-β, 10ng/ml) and treated with a CB₁ selective agonist (arachidonyl-2-chloroethylamide, ACEA 1 μM) and an antagonist (AM251 1, 5 and 10 μM). Alpha-smooth muscle actin (α-SMA) was quantified using Immunocytochemistry and Western Blot. Collagen was quantified with Sirius Red staining assay. Significance was assessed by One-way ANOVA. P < 0.05 was considered significant. TGF-β significantly increases α-SMA expression. ACEA 1 μM significantly increases collagen deposition but does not change α-SMA expression. AM251 10 μM added in the absence and the presence of ACEA reduces α-SMA expression and collagen content in TGF-β treated cells. AM251 shows a concentration-dependent effect over collagen deposition with a pIC50 of 5.5 (4.6-6.4). TGF-β significantly increases CB₁ receptor expression. CB₁ inactivation with AM251 prevents fibroblasts differentiation and collagen deposition, induced by TGF-β in human fibroblasts. The outcome supports that CB₁ is a molecular target for wound healing disorders and in vivo and pre-clinical studies should be implemented to clarify this premise.

Cellular Response to Vitamin C-Enriched Chitosan/Agarose Film with Potential Application as Artificial Skin Substitute for Chronic Wound Treatment

The treatment of chronic wounds is still a meaningful challenge to physicians. The aim of this work was to produce vitamin C-enriched chitosan/agarose (CHN/A) film that could serve as potential artificial skin substitute for chronic wound treatment. The biomaterial was fabricated by a newly developed and simplified method via mixing acidic chitosan solution with alkaline agarose solution that allowed to obtain slightly acidic pH (5.97) of the resultant material, which is known to support skin regeneration. Vitamin C was immobilized within the matrix of the film by entrapment method during production process. Produced films (CHN/A and CHN/A + vit C) were subjected to comprehensive evaluation of cellular response with the use of human skin fibroblasts, epidermal keratinocytes, and macrophages. It was demonstrated that novel biomaterials support adhesion and growth of human skin fibroblasts and keratinocytes, have ability to slightly reduce transforming growth factor-beta 1 (TGF-β1) (known to be present at augmented levels in the epidermis of chronic wounds), and increase platelet-derived growth factor-BB (PDGF-BB) secretion by the cells. Nevertheless, addition of vitamin C to the biomaterial formulation does not significantly improve its biological properties due to burst vitamin release profile. Obtained results clearly demonstrated that produced CHN/A film has great potential to be used as cellular dermal, epidermal, or dermo-epidermal graft pre-seeded with human skin cells for chronic wound treatment.

Role of TGF-β in Skin Chronic Wounds: A Keratinocyte Perspective

Chronic wounds are characterized for their incapacity to heal within an expected time frame. Potential mechanisms driving this impairment are poorly understood and current hypotheses point to the development of an unbalanced milieu of growth factor and cytokines. Among them, TGF-β is considered to promote the broadest spectrum of effects. Although it is known to contribute to healthy skin homeostasis, the highly context-dependent nature of TGF-β signaling restricts the understanding of its roles in healing and wound chronification. Historically, low TGF-β levels have been suggested as a pattern in chronic wounds. However, a revision of the available evidence in humans indicates that this could constitute a questionable argument. Thus, in chronic wounds, divergences regarding skin tissue compartments seem to be characterized by elevated TGF-β levels only in the epidermis. Understanding how this aspect affects keratinocyte activities and their capacity to re-epithelialize might offer an opportunity to gain comprehensive knowledge of the involvement of TGF-β in chronic wounds. In this review, we compile existing evidence on the roles played by TGF-β during skin wound healing, with special emphasis on keratinocyte responses. Current limitations and future perspectives of TGF-β research in chronic wounds are discussed.

Human Skin Keratinocytes on Sustained TGF-β Stimulation Reveal Partial EMT Features and Weaken Growth Arrest Responses

Defects in wound closure can be related to the failure of keratinocytes to re-epithelize. Potential mechanisms driving this impairment comprise unbalanced cytokine signaling, including Transforming Growth Factor-β (TFG-β). Although the etiologies of chronic wound development are known, the relevant molecular events are poorly understood. This lack of insight is a consequence of ethical issues, which limit the available evidence to humans. In this work, we have used an in vitro model validated for the study of epidermal physiology and function, the HaCaT cells to provide a description of the impact of sustained exposure to TGF-β. Long term TGF-β1 treatment led to evident changes, HaCaT cells became spindle-shaped and increased in size. This phenotype change involved conformational re-arrangements for actin filaments and E-Cadherin cell-adhesion structures. Surprisingly, the signs of consolidated epithelial-to-mesenchymal transition were absent. At the molecular level, modified gene expression and altered protein contents were found. Non-canonical TGF-β pathway elements did not show relevant changes. However, R-Smads experienced alterations best characterized by decreased Smad3 levels. Functionally, HaCaT cells exposed to TGF-β1 for long periods showed cell-cycle arrest. Yet, the strength of this restraint weakens the longer the treatment, as revealed when challenged by pro-mitogenic factors. The proposed setting might offer a useful framework for future research on the mechanisms driving wound chronification.

RIPK4 suppresses the TGF-β1 signaling pathway in HaCaT cells

Receptor-interacting serine/threonine kinase 4 (RIPK4) and transforming growth factor-β 1 (TGF-β1) play critical roles in the development and maintenance of the epidermis. A negative correlation between the expression patterns of RIPK4 and TGF-β signaling during epidermal homeostasis-related events and suppression of RIPK4 expression by TGF-β1 in keratinocyte cell lines suggest the presence of a negative regulatory loop between the two factors. So far, RIPK4 has been shown to regulate nuclear factor-κB (NF-κB), protein kinase C (PKC), wingless-type MMTV integration site family (Wnt), and (mitogen-activated protein kinase) MAPK signaling pathways. In this study, we examined the effect of RIPK4 on the canonical Smad-mediated TGF-β1 signaling pathway by using the immortalized human keratinocyte HaCaT cell line. According to our results, RIPK4 inhibits intracellular Smad-mediated TGF-β1 signaling events through suppression of TGF-β1-induced Smad2/3 phosphorylation, which is reflected in the upcoming intracellular events including Smad2/3-Smad4 interaction, nuclear localization, and TGF-β1-induced gene expression. Moreover, the kinase activity of RIPK4 is required for this process. The in vitro wound-scratch assay demonstrated that RIPK4 suppressed TGF-β1-mediated wound healing through blocking TGF-β1-induced cell migration. In conclusion, our results showed the antagonistic effect of RIPK4 on TGF-β1 signaling in keratinocytes for the first time and have the potential to contribute to the understanding and treatment of skin diseases associated with aberrant TGF-β1 signaling.

Drug therapies and delivery mechanisms to treat perturbed skin wound healing

Acute wound healing is an orderly process of four overlapping events: haemostasis, inflammation, proliferation and remodelling. A drug delivery system with a temporal control of release could promote each of these events sequentially. However, acute wound healing normally proceeds very well in healthy individuals and there is little need to promote it. In the elderly and diabetics however, healing is often slow and wounds can become chronic and we need to promote their healing. Targeting the events of acute wound healing would not be appropriate for a chronic wound, which have stalled in the proinflammatory phase. They also have many additional problems such as poor circulation, low oxygen, high levels of leukocytes, high reactive oxygen species, high levels of proteolytic enzymes, high levels of proinflammatory cytokines, bacterial infection and high pH. The future challenge will be to tackle each of these negative factors to create a wound environment conducive to healing.

In vitro molecular study of wound healing using biosynthesized bacteria nanocellulose/silver nanocomposite assisted by bioinformatics databases

Background

In recent years, bacterial nanocellulose (BNC) based nanocomposites have been developed to promote healing property and antibacterial activity of BNC wound dressing. Molecular study can help to better understanding about interaction of genes and pathways involved in healing progression.

Objectives

The aim of this study was to prepare bacterial nanocellulose/silver (BNC/Ag) nanocomposite films as ecofriendly wound dressing in order to assess their physical, cytotoxicity and antimicrobial properties. The in vitro molecular study was performed to evaluate expression of genes involved in healing of wounds after treatment with BNC/Ag biofilms.

Study design materials and methods

Silver nanoparticles were formed by using Citrullus colocynthis extract within new isolated bacterial nanocellulose (BNC) RM1. The nanocomposites were characterized using X-ray diffraction, Fourier transform infrared, and field emission scanning electron microscopy. Besides, swelling property and Ag release profile of the nanocomposites were studied. The ability of nanocomposites to promote wound healing of human dermal fibroblast cells in vitro was studied. Bioinformatics databases were used to identify genes with important healing effect. Key genes which interfered with healing were studied by quantitative real time PCR.

Results

Spherical silver nanoparticles with particle size ranging from 20 to 50 nm were synthesized and impregnated within the structure of BNC. The resulting nanocomposites showed significant antibacterial activities with inhibition zones ranging from 7±0.25 to 16.24±0.09 mm against skin pathogenic bacteria. Moreover, it was compatible with human fibroblast cells (HDF) and could promote in vitro wound healing after 48h. Based on bioinformatics databases, the genes of TGF-β1, MMP2, MMP9, CTNNB1, Wnt4, hsa-miR-29b-3p and hsa-miR-29c-3p played important role in wound healing. The nanocomposites had an effect in expression of the genes in healing. Thus, the BNC/Ag nanocomposite can be used to heal wound in a short period and simple manner.

Conclusion

This eco-friendly nanocomposite with excellent antibacterial activities and healing property confirming its utility as potential wound dressings.

Descriptive vs mechanistic scientific approach to study wound healing and its inhibition: Is there a value of translational research involving human subjects?

The clinical field of wound healing is challenged by numerous hurdles. Not only are wound-healing disorders complex and multifactorial, but the corresponding patient population is diverse, often elderly and burdened by multiple comorbidities such as diabetes and cardiovascular disease. The care of such patients requires a dedicated, multidisciplinary team of physicians, surgeons, nurses and scientists. In spite of the critical clinical need, it has been over 15 years since a treatment received approval for efficacy by the FDA in the United States. Among the reasons contributing to this lack of effective new treatment modalities is poor understanding of mechanisms that inhibit healing in patients. Additionally, preclinical models do not fully reflect the disease complexity of the human condition, which brings us to a paradox: if we are to use a "mechanistic" approach that favours animal models, we can dissect specific mechanisms using advanced genetic, molecular and cellular technologies, with the caveat that it may not be directly applicable to patients. Traditionally, scientific review panels, for either grant funding or manuscript publication purposes, favour such "mechanistic" approaches whereby human tissue analyses, deemed "descriptive" science, are characterized as a "fishing expedition" and are considered "fatally flawed." However, more emerging evidence supports the notion that the use of human samples provides significant new knowledge regarding the molecular and cellular mechanisms that control wound healing and contribute to inhibition of the process in patients. Here, we discuss the advances, benefits and challenges of translational research in wound healing focusing on human subject research.

Chronic Venous Insufficiency: Transforming Growth Factor-β Isoforms and Soluble Endoglin Concentration in Different States of Wound Healing

Venous leg ulcer (VLU) is a huge healthcare problem with poorly understood pathophysiology. Transforming growth factor-β (TGF-β) and endoglin (Eng), are inflammatory and wound healing mediators. Eng, co-receptor for TGF-β type-II receptors, may be cleaved forming soluble Eng (sEng), antagonizing TGF-β signaling, a crucial process in vascular pathologies. We evaluated the accumulation in wound fluid (WF) of TGF-β isoforms and sEng in healing stages, showing the effects of sulodexide treatments, a glycosaminoglycan with clinical efficacy in VLU healing. Patients with inflammatory (Infl) and granulating (Gran) VLU were recruited. WFs and THP-1 monocytes exposed to Infl and Gran WF (treated/untreated with sulodexide) were analyzed for TGF-β isoforms and sEng by multiplex immunoassay. In both Infl and Gran WF, TGF-β1 and β2 were similar; TGF-β3 was significantly increased in Infl compared to Gran WFs (p = 0.033). sEng was significantly elevated in Gran compared to Infl WFs (p = 0.002). In THP-1 monocytes there was a significant increase in sEng after co-treatment of WF and sulodexide. The increase in TGF-β3 found in Infl WF highlights its negative effect on wound healing, while the increased levels of sEng in Gran WF affects the leukocyte adhesion/transmigration through the endothelium, reducing the inflammatory response and favoring the wound healing. Glycosaminoglycan sulodexide potentiates the effects of sEng release from monocyte, representing an important therapeutic option for wound healing.

Development of Novel Mouse Model of Ulcers Induced by Implantation of Magnets

We developed a novel mouse model of human refractory cutaneous ulcers that more faithfully reflects pathology and evaluated the effects of mixed cell sheets comprising peripheral blood mononuclear cells and fibroblasts, which we previously developed for treating refractory cutaneous ulcers. Model development involved sandwiching the skin between two magnets, one of which was implanted under the skin for 7 consecutive days. This magnet-implanted ulcer model produced persistently large amounts of exudate and induced the infiltration of the ulcer with inflammatory cells. The model mice had a thicker epidermis and impaired transforming growth factor-β (TGF-β) signaling followed by SMAD2 down-regulation, which causes epidermal hyperplasia in chronic ulcers. Impaired TGF-β signaling also occurred in the ulcers of critical limb ischemia patients. Mixed cell implantation in this ulcer model reduced TNF-α and IL-6 levels in the tissues surrounding the mixed cell sheet-treated ulcers compared with controls or mice treated with trafermin (FGF2). Seven days after commencing therapy, the epidermis was thinner in mice treated with the mixed cell sheets than in controls. This model may therefore serve as a clinically relevant model of human ulcers, and our mixed cell sheets may effectively relieve chronic inflammation and inhibit refractoriness mechanisms.

Biology and Biomarkers for Wound Healing

BACKGROUND

As the population grows older, the incidence and prevalence of conditions that lead to a predisposition for poor wound healing also increase. Ultimately, this increase in nonhealing wounds has led to significant morbidity and mortality with subsequent huge economic ramifications. Therefore, understanding specific molecular mechanisms underlying aberrant wound healing is of great importance. It has and will continue to be the leading pathway to the discovery of therapeutic targets, as well as diagnostic molecular biomarkers. Biomarkers may help identify and stratify subsets of nonhealing patients for whom biomarker-guided approaches may aid in healing.

METHODS

A series of literature searches were performed using Medline, PubMed, Cochrane Library, and Internet searches.

RESULTS

Currently, biomarkers are being identified using biomaterials sourced locally from human wounds and/or systemically using high-throughput "omics" modalities (genomic, proteomic, lipidomic, and metabolomic analysis). In this review, we highlight the current status of clinically applicable biomarkers and propose multiple steps in validation and implementation spectrum, including those measured in tissue specimens, for example, β-catenin and c-myc, wound fluid, matrix metalloproteinases and interleukins, swabs, wound microbiota, and serum, for example, procalcitonin and matrix metalloproteinases.

CONCLUSIONS

Identification of numerous potential biomarkers using different avenues of sample collection and molecular approaches is currently underway. A focus on simplicity and consistent implementation of these biomarkers, as well as an emphasis on efficacious follow-up therapeutics, is necessary for transition of this technology to clinically feasible point-of-care applications.

IL-36 Induces Bisphosphonate-Related Osteonecrosis of the Jaw-Like Lesions in Mice by Inhibiting TGF-β-Mediated Collagen Expression

Long-term administration of nitrogen-containing bisphosphonates can induce detrimental side effects such as bisphosphonate-related osteonecrosis of the jaw (BRONJ) in human. Although inflammation is known to be associated with BRONJ development, the detailed underlying mechanism remains unknown. Here, we report that the pro-inflammatory cytokine IL-36α is, in part, responsible for the BRONJ development. We found a notably higher level of IL-36α and lower level of collagen in the BRONJ lesions in mice. We also found that IL-36α remarkably suppressed TGF-β-mediated expression of Collα1 and α-Sma via the activation of Erk signaling pathway in mouse gingival mesenchymal stem cells. When IL-36 signaling was abrogated in vivo, development of BRONJ lesions was ameliorated in mice. Taken together, we showed the pathologic role of IL-36α in BRONJ development by inhibiting collagen expression and demonstrated that IL-36α could be a potential marker and a therapeutic target for the prevention and treatment of BRONJ. © 2016 American Society for Bone and Mineral Research.

Innovative Therapies in Wound Healing

Background:

Apligraf is a bioengineered skin product composed of neonatal fibroblasts and keratinocytes. The FDA has approved Apligraf for the treatment of chronic venous ulcers and diabetic ulcers.

Objective:

We review the development of bioengineered skin, examine the cellular activities of various growth factors that may facilitate wound healing, and discuss the results of clinical trials with a particular construct, Apligraf, as proof of principle.

Conclusion:

Bioengineered skin acts as a “smart” delivery system for growth factors and other stimulatory substances. Not only does it present a novel treatment for chronic and diabetic ulcers, but it could also be considered for application to other types of acute wounds.

Wound Fluids: A Window Into the Wound Environment?

Wound healing of the skin is a complex biologic process involving temporal interactions between numerous types of cells, extracellular matrix molecules, and soluble factors. The process of repair can be viewed as involving 3 or 4 phases: homeostasis, inflammation, synthesis, and remodeling. These phases occur at different times and differ in their cellular, biochemical, and physiologic requirements. Disruption of one or more of these interactions can significantly interfere with the repair process. Such comorbidities as age, nutrition, immune status, and underlying disease status (eg, diabetes or venous stasis) contribute additional intricacy to the repair process. Because of this complexity, care of chronic wounds remains highly individualized, and it should not come as a surprise that treatment of these wounds as a group with single target therapies have met with only modest success. A major hurdle in the progression toward improved treatment regimens has been the lack of objective biochemical and physiological landmarks that can be used to assess wound status. Collection and biochemical characterization of wound fluids presents the opportunity to noninvasively obtain information reflecting the status of the wound and of specific biomarkers. This review discusses the collection of wound fluid and highlights biomarkers that may be useful to this end.

Downregulation of miR-205 in migrating epithelial tongue facilitates skin wound re-epithelialization by derepressing ITGA5

Keratinocyte migration is essential for re-epithelialization during skin wound healing, but the molecular mechanisms regulating this cellular response remain to be completely clarified. Here we show that keratinocyte-specific miR-205 is significantly downregulated in the leading edge of the migrating epithelial tongue after skin injury in mice. In HaCaT keratinocytes, miR-205 could be downregulated by TGF-β1 stimulation. And similar to the effect of TGF-β1, miR-205 knockdown could promote keratinocyte migration in wound scratch model in vitro. Furthermore, topical inhibition of miR-205 by administrating Pluronic gel containing antagomir-205 could accelerate re-epithelialization in mouse skin wound model in vivo. Moreover, we identified integrin alpha 5 (ITGA5) as one key functional miR-205 target in the re-epithelialization process and epidermal downregulation of miR-205 may desilence ITGA5 to promote keratinocyte migration. And knockdown of ITGA5 would abolish the pro-migratory effects of miR-205 inhibition in vitro. What's more, we found dysregulation of miR-205 and its target ITGA5 in epidermis of clinical chronic wound samples with persistence of high level miR-205 and absence of ITGA5. Our findings indicate that downregulation of miR-205 in the leading migrating keratinocytes is critical for re-epithelialization and miR-205 may be a potential therapeutic target for chronic wounds.

Biomarkers for wound healing and their evaluation

A biological marker (biomarker) is a substance used as an indicator of biological state. Advances in genomics, proteomics and molecular pathology have generated many candidate biomarkers with potential clinical value. Research has identified several cellular events and mediators associated with wound healing that can serve as biomarkers. Macrophages, neutrophils, fibroblasts and platelets release cytokines molecules including TNF-α, interleukins (ILs) and growth factors, of which platelet-derived growth factor (PDGF) holds the greatest importance. As a result, various white cells and connective tissue cells release both matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs). Studies have demonstrated that IL-1, IL-6, and MMPs, levels above normal, and an abnormally high MMP/TIMP ratio are often present in non-healing wounds. Clinical examination of wounds for these mediators could predict which wounds will heal and which will not, suggesting use of these chemicals as biomarkers of wound healing. There is also evidence that the application of growth factors like PDGF will alleviate the recuperating process of chronic, non-healing wounds. Finding a specific biomarker for wound healing status would be a breakthrough in this field and helping treat impaired wound healing.

Non-healing foot ulcers in diabetic patients: general and local interfering conditions and management options with advanced wound dressings

Medical knowledge about wound management has improved as recent studies have investigated the healing process and its biochemical background. Despite this, foot ulcers remain an important clinical problem, often resulting in costly, prolonged treatment. A non-healing ulcer is also a strong risk factor for major amputation. Many factors can interfere with wound healing, including the patient's general health status (i.e., nutritional condition indicated by albumin levels) or drugs such as steroids that can interfere with normal healing. Diabetic complications (i.e., renal insufficiency) may delay healing and account for higher amputation rates observed in diabetic patients under dialysis treatment. Wound environment (e.g., presence of neuropathy, ischaemia, and infection) may significantly influence healing by interfering with the physiological healing cascade and adding local release of factors that may worsen the wound. The timely and well-orchestrated release of factors regulating the healing process, observed in acute wounds, is impaired in non-healing wounds that are blocked in a chronic inflammatory phase without progressing to healing. This chronic phase is characterised by elevated protease activity (EPA) of metalloproteinases (MMPs) and serine proteases (e.g., human neutrophil elastase) that interfere with collagen synthesis, as well as growth factor release and action. EPA (mainly MMP 9, MMP-8 and elastase) and inflammatory factors present in the wound bed (such as IL-1, IL-6, and TNFa) account for the catabolic state of non-healing ulcers. The availability of wound dressings that modulate EPA has added new therapeutic options for treating non-healing ulcers. The literature confirms advantages obtained by reducing protease activity in the wound bed, with better outcomes achieved by using these dressings compared with traditional ones. New technologies also allow a physician to know the status of the wound bed environment, particularly EPA, in a clinical setting. These may be helpful in guiding a clinician's options in treating very difficult-to-heal ulcers.

Expression and integrity of dermatopontin in chronic cutaneous wounds: a crucial factor in impaired wound healing

Chronic cutaneous wound (CCW) is a major health care burden wherein the healing process is slow or rather static resulting in anatomical and functional restriction of the damaged tissue. Dysregulated expression and degradation of matrix proteins, growth factors and cytokines contribute to the disrupted and uncoordinated healing process of CCW. Therefore, therapeutic approaches for effective management of CCW should be focused towards identifying and manipulating the molecular defects, such as reduced bioavailability of the pro-healing molecules and elevated activity of proteases. This study essentially deals with assessing the expression and integrity of an extracellular matrix protein, Dermatopontin (DPT), in CCW using real-time quantitative reverse transcriptase PCR and immunological techniques. The results indicate that, despite DPT's high mRNA expression, the protein levels are markedly reduced in both CCW tissue and its exudate. To elucidate the cause for this contradiction in mRNA and protein levels, the stability of DPT is analyzed in the presence of wound exudates and various proteases that are naturally elevated in CCW. DPT was observed to be degraded at higher rates when incubated with certain recombinant proteases or chronic wound exudate. In conclusion, the susceptibility of DPT protein to specific proteases present at high levels in the wound milieu resulted in the degradation of DPT, thus leading to impaired healing response in CCW.

The Role of TGFβ Signaling in Wound Epithelialization

Significance: Transforming growth factor β (TGFβ) has a crucial role in maintaining skin homeostasis. TGFβ signaling is important for re-epithelialization, inflammation, angiogenesis, and granulation tissue formation during wound healing. This review will discuss the most important findings regarding the role of TGFβ in epidermal maintenance and its restoration after injury. Recent Advances: Latest findings on the role of TGFβ signaling in normal and impaired wound healing, including the role of TGFβ pathway in tissue regeneration observed in super-healer animal models, will be reviewed. Critical Issues: The TGFβ pathway is attenuated in nonhealing wounds. Observed suppression of TGFβ signaling in chronic ulcers may contribute to the loss of tissue homeostasis and the inability of keratinocytes to migrate and close a wound. Future Directions: A better understanding of TGFβ signaling may provide new insights not only in the normal epithelialization process, but also in tissue regeneration. Future studies focused on TGFβ-mediated crosstalk between multiple cell types involved in wound healing may lead to development of novel therapeutic advances for chronic wounds.

Which dressings reduce inflammation and improve venous leg ulcer healing

Chronic venous leg ulcers (VLU) affect around 1% of the adult population in the Western world. The impact of VLU is both social and economic, with significant expenditures on active venous ulcers to provide medical treatment and eventual healing. At the core of VLU is venous hypertension which affects the venous macrocirculation. The changes incurred in venous hemodynamics leads to microcirculatory changes affecting the postcapillary venule and surrounding tissues. Inflammation by leukocytes affecting the venous endothelium, promotes a complex cascade and activation of adhesion molecules expression, chemokines and cytokines released, altered growth factor responses, and activation of protease (e.g. tPA) and proteinase (e.g. MMPs) activity that causes dysregulation and compromise of tissue integrity with eventual dermal damage and ulcer development. A critical component to treating VLU is correcting the abnormal venous hemodynamics and compression therapy. Unfortunately, VLU recurrence ranges between 30–70%, and other modalities in therapy along with compression are required. The goal for adjuvant products is to restore the balance from an inflammatory chronic wound to that of a reparative wound that will promote provisional matrix and epithelialization. There are many products on the market that can be used as adjuvant to compression therapy, but it must be recognized that there is a paucity of clinical trials that have evaluated the clinical effectiveness of specific products with clearly defined end points, and most importantly a healed VLU with a low recurrence rate. This review will discuss the fundamentals of VLU inflammation, and evaluate the available literature that may have benefit in reducing inflammation and lead to effective VLU healing.

The differential proliferative response of fetal and adult human skin fibroblasts to TGF-β is retained when cultured in the presence of fibronectin or collagen

BACKGROUND

Transforming growth factor-β is a multifunctional and pleiotropic factor with decisive role in tissue repair. In this context, we have shown previously that TGF-β inhibits the proliferation of fetal human skin fibroblasts but stimulates that of adult ones. Given the dynamic reciprocity between fibroblasts, growth factors and extracellular matrix (ECM) in tissue homeostasis, the present study aims to investigate the role of fibronectin and collagen in the proliferative effects of TGF-β on fetal and adult cells.

METHODS

Human fetal and adult skin fibroblasts were grown either on plastic surfaces or on surfaces coated with fibronectin or collagen type-I, as well as, on top or within three-dimensional matrices of polymerized collagen. Their proliferative response to TGF-β was studied using tritiated thymidine incorporation, while the signaling pathways involved were investigated by Western analysis and using specific kinase inhibitors.

RESULTS

Fetal skin fibroblast-proliferation was inhibited by TGF-β, while that of adult cells was stimulated by this factor, irrespective of the presence of fibronectin or collagen. Both inhibitory and stimulatory activities of TGF-β on the proliferation of fetal and adult fibroblasts, respectively, were abrogated when the Smad pathway was blocked. Moreover, inhibition of fetal fibroblasts was mediated by PKA activation, while stimulation of adult ones was effected through the autocrine activation of FGF receptor and the MEK-ERK pathway.

CONCLUSIONS

Fetal and adult human skin fibroblasts retain their differential proliferative response to TGF-β when cultured in the presence of fibronectin and unpolymerized or polymerized collagen.

GENERAL SIGNIFICANCE

The interplay between TGF-β and ECM supports the pleiotropic nature of this growth factor, in concordance with the different repair strategies between fetuses and adults. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Rotator cuff repair augmentation with local autogenous bone marrow via humeral cannulation in a rat model

BACKGROUND

Growth factors have been shown to improve healing after rotator cuff repair. Bone marrow is a potential vehicle for growth factor augmentation, yet methods of delivering marrow to cuff repair sites are still under-researched. We hypothesized that a cannulated humeral implant would deliver local bone marrow and thereby improve healing in a rat model.

METHODS

Twenty-eight rats underwent bilateral rotator cuff injury and repair. Each rat acted as its own control, randomized to a cannulated humeral implant in one shoulder and a solid implant in the other. Rats were euthanized at 4 and 8 weeks to create 4 time-treatment cohorts. Tendon healing was evaluated by dimensional measurements, biomechanical testing, and histology.

RESULTS

Tendon thickness, all biomechanical measures, and semi-quantitative histologic scores improved over time (P < .05) but not with treatment. The most common site of biomechanical tendon failure was midsubstance in the 8-week cannulated cohort and at the tendon footprint in the other 3 cohorts. Intraluminal bone growth was evident in all cannulated implants.

CONCLUSIONS

Humeral cannulation did not quantifiably improve tendon-to-bone healing in a rat model. The diminutive size of implants in rats, however, may have prevented sufficient delivery of local autogenous bone marrow; hence, further study in a larger animal is recommended.

Steroidal glycosides from the bulbs of Easter lily (Lilium longiflorum Thunb.) promote dermal fibroblast migration in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Preparations derived from bulbs of various Lilium species have been used to promote the healing of skin abrasions, sores and burns and to aid in healing wounds in Traditional Chinese and Greco-Roman Medicine.

AIM OF THE STUDY

To evaluate fractionated Easter lily bulb extracts and their steroidal glycosides (1-5) for the promotion of dermal fibroblast migration in vitro, a model for the early events in wound healing.

MATERIALS AND METHODS

An activity-guided screening approach was used by coupling sequential solvent extraction, gel permeation chromatography (GPC), and semi-preparative reverse-phase high performance liquid chromatography (RP-HPLC) with an in vitro dermal fibroblast migration assay. Cytotoxicity was evaluated with methyl thiazole tetrazolium (MTT). To gain insight into the mode of action of the steroidal glycosides, nitric oxide (NO) production, and expression of genes for transforming growth factor beta-1 (TGF-β) and its receptors were evaluated.

RESULTS

Fractionated bulb extracts and the two isolated steroidal glycoalkaloids (1) and (2) induced NO production and TGF-β receptor I mRNA expression in fibroblast cell culture. In a cytotoxicity assay, steroidal glycosides (1) and (3) had IC50 values of 8.2 and 8.7 µM, but the natural acetylation of the C-6″' hydroxy of the terminal glucose unit in (2) resulted in a 3-fold decrease in cell cytotoxicity when compared with (1). Results from the dermal fibroblast migration assay revealed that the steroidal glycoalkaloids (1) and (2), and the furostanol saponin (3) promoted fibroblast migration from the range of 23.7±5.7 to 37.7±5.1%, as compared with the control.

CONCLUSION

Collectively, our data demonstrate that the steroidal glycosides present in Easter lily bulbs induce, at least in part, the observed dermal fibroblast migration activity of the bulb extracts. This is the first evidence that steroidal glycosides from Lilium longiflorum may potentially play a role in the wound healing process and may provide a scientific basis for the historical use of lily bulbs for this purpose.

Molecular Wound Assessments: Matrix Metalloproteinases

SIGNIFICANCE

The process of wound healing includes the regulated destruction of proteins via enzymes called proteinases. However, when the proteolytic process becomes excessive, pro-healing factors are destroyed and the wound healing process stalls. Matrix metalloproteinases (MMPs) are one key class of proteinases that have been observed to be elevated in many cases of failed wound healing.

RECENT ADVANCES

Two key advances have been made in recent years. First is that, until recently, MMPs were only implicated in impaired healing of chronic wounds. Measurements of MMPs in wound fluids and serum from individuals with acute traumatic wounds have revealed that elevated MMPs are predictive of both impaired healing and of dehiscence of surgically closed wounds. The second advance is in the development of at least three clinically viable methods for measuring MMPs at the point of care.

CRITICAL ISSUES

At present there is no objective method of determining proteinase levels within a wound. Since elevated MMPs have now been shown to be predictive of dehiscence in surgically closed acute wounds, a new clinical utility for measuring MMPs has been established. With the advent of several new technologies to measure MMPs, the translation of this valuable molecular knowledge into improved therapeutic regimens is nearly complete.

FUTURE DIRECTIONS

The clinical utility of measuring MMPs continues to expand and be further validated with each new investigation. The tools that will enable clinicians to leverage this valuable information are nearing maturity and integration into the clinic.

Cytoskeletal regulation of dermal regeneration

Wound healing results in the repair of injured tissues however fibrosis and scar formation are, more often than not the unfortunate consequence of this process. The ability of lower order vertebrates and invertebrates to regenerate limbs and tissues has been all but lost in mammals; however, there are some instances where glimpses of mammalian regenerative capacity do exist. Here we describe the unlocked potential that exists in mammals that may help us understand the process of regeneration post-injury and highlight the potential role of the actin cytoskeleton in this process. The precise function and regulation of the cytoskeleton is critical to the success of the healing process and its manipulation may therefore facilitate regenerative healing. The gelsolin family of actin remodelling proteins in particular has been shown to have important functions in wound healing and family member Flightless I (Flii) is involved in both regeneration and repair. Understanding the interactions between different cytoskeletal proteins and their dynamic control of processes including cellular adhesion, contraction and motility may assist the development of therapeutics that will stimulate regeneration rather than repair.

Acute and impaired wound healing: pathophysiology and current methods for drug delivery, part 2: role of growth factors in normal and pathological wound healing: therapeutic potential and methods of delivery

This is the second of 2 articles that discuss the biology and pathophysiology of wound healing, reviewing the role that growth factors play in this process and describing the current methods for growth factor delivery into the wound bed.

Cellular events and biomarkers of wound healing

Researchers have identified several of the cellular events associated with wound healing. Platelets, neutrophils, macrophages, and fibroblasts primarily contribute to the process. They release cytokines including interleukins (ILs) and TNF-α, and growth factors, of which platelet-derived growth factor (PDGF) is perhaps the most important. The cytokines and growth factors manipulate the inflammatory phase of healing. Cytokines are chemotactic for white cells and fibroblasts, while the growth factors initiate fibroblast and keratinocyte proliferation. Inflammation is followed by the proliferation of fibroblasts, which lay down the extracellular matrix. Simultaneously, various white cells and other connective tissue cells release both the matrix metalloproteinases (MMPs) and the tissue inhibitors of these metalloproteinases (TIMPs). MMPs remove damaged structural proteins such as collagen, while the fibroblasts lay down fresh extracellular matrix proteins. Fluid collected from acute, healing wounds contains growth factors, and stimulates fibroblast proliferation, but fluid collected from chronic, nonhealing wounds does not. Fibroblasts from chronic wounds do not respond to chronic wound fluid, probably because the fibroblasts of these wounds have lost the receptors that respond to cytokines and growth factors. Nonhealing wounds contain high levels of IL1, IL6, and MMPs, and an abnormally high MMP/TIMP ratio. Clinical examination of wounds inconsistently predicts which wounds will heal when procedures like secondary closure are planned. Surgeons therefore hope that these chemicals can be used as biomarkers of wounds which have impaired ability to heal. There is also evidence that the application of growth factors like PDGF will help the healing of chronic, nonhealing wounds.

Rosiglitazone modulates the behaviors of diabetic host-derived fibroblasts in a carboxymethyllysine-modified collagen model

Utilizing a three-dimensional in vitro glycated collagen model, we evaluated the therapeutic effects of a peroxisome proliferator-activated receptor-γ ligand, rosiglitazone, and its potential as a topical treatment of diabetic chronic wounds. Rosiglitazone induced fibroblast migration, α-smooth muscle actin production, and transformation into myofibroblasts in the presence of advanced glycation end products. Both transforming growth factor β and peroxisome proliferator-activated receptor-γ expression were induced, while the receptor for advanced glycation end products was suppressed. Lastly, the reduced activities of matrix metalloproteinase-2 and matrix metalloproteinases-9 in the carboxymethyllysine-modified collagen matrices by rosiglitazone increases extracellular matrix deposition. Our findings identify rosiglitazone as a candidate for localized topical treatment of diabetic chronic wounds.

TGFβ (transforming growth factor β) and keratocyte motility in 24 h zebrafish explant cultures

Fish keratocytes are used as a model system for the study of the mechanics of cell motility because of their characteristic rapid, smooth gliding motion, but little work has been done on the regulation of fish keratocyte movement. As TGFβ (transforming growth factor β) plays multiple roles in primary human keratinocyte cell migration, we investigated the possible involvement of TGFβ in fish keratocyte migration. Studying the involvement of TGFβ1 in 24 h keratocyte explant allows the examination of the cells before alterations in cellular physiology occur due to extended culture times. During this initial period, TGFβ levels increase 6.2-fold in SFM (serum-free medium) and 2.4-fold in SFM+2% FBS (fetal bovine serum), while TGFβ1 and TGFβRII (TGFβ receptor II) mRNA levels increase ∼3- and ∼5-fold respectively in each culture condition. Two measures of motility, cell sheet area and migration distance, vary with the amount of exogenous TGFβ1 and culture media. The addition of 100 ng/ml exogenous TGFβ1 in SFM increases both measures [3.3-fold (P = 4.5×10-5) and 26% (P = 2.1×10-2) respectively]. In contrast, 100 ng/ml of exogenous TGFβ1 in medium containing 2% FBS decreases migration distance by 2.1-fold (P = 1.7×10-7), but does not affect sheet area. TGFβ1 (10 ng/ml) has little effect on cell sheet area in SFM cultures, but leads to a 1.8-fold increase (P = 1.5×10-2) with 2% FBS. The variable response to TGFβ1 may be, at least in part, explained by the effect of 2% FBS on cell morphology, mode of motility and expression of endogenous TGFβ1 and TGFβRII. Together, these results suggest that expression of TGFβ and its receptor are up-regulated during zebrafish keratocyte explant culture and that TGFβ promotes fish keratocyte migration.

Dynamic reciprocity in the wound microenvironment

Here, we define dynamic reciprocity (DR) as an ongoing, bidirectional interaction among cells and their surrounding microenvironment. In this review, we posit that DR is especially meaningful during wound healing as the DR-driven biochemical, biophysical, and cellular responses to injury play pivotal roles in regulating tissue regenerative responses. Such cell-extracellular matrix interactions not only guide and regulate cellular morphology, but also cellular differentiation, migration, proliferation, and survival during tissue development, including, e.g., embryogenesis, angiogenesis, as well as during pathologic processes including cancer, diabetes, hypertension, and chronic wound healing. Herein, we examine DR within the wound microenvironment while considering specific examples across acute and chronic wound healing. This review also considers how a number of hypotheses that attempt to explain chronic wound pathophysiology may be understood within the DR framework. The implications of applying the principles of DR to optimize wound care practice and future development of innovative wound healing therapeutics are also briefly considered.

Deconstructing fibrosis research: do pro-fibrotic signals point the way for chronic dermal wound regeneration?

Chronic wounds are characterized by inadequate matrix synthesis, no re-epithelialization, infection and ultimately no wound resolution. In contrast, fibrosis is characterized by overproduction of matrix and excess matrix contraction. As research in the fields of chronic wounds and fibrosis surges forward, important parallels can now be drawn between the dysfunctions in fibrotic diseases and the needs of chronic wounds. These parallels exist at both the macroscopic level and at the molecular level. Thus in finding the individual factors responsible for the progression of fibrotic diseases, we may identify new therapeutic targets for the resolution of chronic wounds. The aim of this review is to discuss how recent advances in fibrosis research have found a home in the treatment of chronic wounds and to highlight the benefits that can be obtained for chronic wound treatments by employing a translational approach to molecules identified in fibrosis research.

Does inflammation have a role in the pathogenesis of venous ulcers? A critical review of the evidence

Chronic venous disease, a disorder involving venous return from the legs, is a growing epidemic in the developed world. Numerous studies have been conducted in the past two decades in an attempt to elucidate its underlying pathophysiology. Many theories have been proposed to address the profound inflammatory dysregulation, with the majority focusing on fibrin trap, inflammatory trap, cytokines, growth factors, and matrix metalloproteinases. Although many of these theories have obtained great momentum, much of the data are contradictory. Moreover, many treatments built on these theories have claimed overwhelming success despite insufficient evidence. At the same time, there are few reviews that critically analyze and evaluate these data. Therefore, in this paper, we will provide summaries of the background data and evolution of these theories and examine their supporting evidence.