Porous Alumina Membrane-Based Electrochemical Biosensor for Protein Biomarker Detection in Chronic Wounds.

A label-free electrochemical detection platform for the sensitive and rapid detection of Flightless I (Flii) protein, a biomarker of wound chronicity, has been developed using nanoporous anodic alumina (NAA) membranes modified with Flii antibody recognition sites. The electrochemical detection is based on the nanochannel blockage experienced upon Flii capture by immobilized antibodies within the nanochannels. This capture impedes the diffusion of redox species [[Fe(CN)6]4-/3-] toward a gold electrode attached at the backside of the modified NAA membrane. Partial blockage causes a decrease in the oxidation current of the redox species at the electrode surface which is used as an analytical signal by the reported biosensor. The resulting biosensing system allows detection of Flii at the levels found in wounds. Two types of assays were tested, sandwich and direct, showing <3 and 2 h analysis time, respectively, a significant reduction in time from the nearly 48 h required for the conventional Western blot assay. Slightly higher sensitivity values were observed for the sandwich-based strategy. With faster analysis, lack of matrix effects, robustness, ease of use and cost-effectiveness, the developed sensing platform has the potential to be translated into a point-of-care (POC) device for chronic wound management and as a simple alternative characterization tool in Flii research.

Recombinant Leucine-Rich Repeat Flightless-Interacting Protein-1 Improves Healing of Acute Wounds through Its Effects on Proliferation Inflammation and Collagen Deposition.

Wound healing is an increasing clinical problem involving substantial morbidity, mortality, and rising health care costs. Leucine-rich repeat flightless-interacting protein-1 (LRRFIP-1) regulates toll-like receptor (TLR)-mediated inflammation, suggesting a potential role in the healing of wounds. We sought to determine the role of LRRFIP-1 in wound repair and whether the exogenous addition of recombinant LRRFIP-1 (rLRRFIP-1) affected healing responses. Using a model of full-thickness incisional acute wounds in BALB/c mice, we investigated the effect of wounding on LRRFIP-1 expression. The effect of rLRRFIP-1 on cellular proliferation, inflammation, and collagen deposition was also investigated. LRRFIP-1 was upregulated in response to wounding, was found to directly associate with flightless I (Flii), and significantly increased cellular proliferation both in vitro and in vivo. rLRRFIP-1 reduced Flii expression in wounds in vivo and resulted in significantly improved healing with a concurrent dampening of TLR4-mediated inflammation and improved collagen deposition. Additionally, decreased levels of TGF-ß1 and increased levels of TGF-ß3 were observed in rLRRFIP-1-treated wounds suggesting a possible antiscarring effect of rLRRFIP-1. Further studies are required to elucidate if the mechanisms behind LRRFIP-1 action in wound repair are independent of Flii. However, these results identify rLRRFIP-1 as a possible treatment modality for improved healing of acute wounds.

Development of Topical Delivery Systems for Flightless Neutralizing Antibody.

Flightless I (Flii) is an actin remodeling protein important for cytoskeletal regulation and cellular processes including migration, proliferation, and adhesion. Previous studies have clearly identified Flii as a novel therapeutical target for improved wound repair and have demonstrated Flii regulation using Flii neutralizing antibodies (FnAb) in different models of wound healing in vivo. Here we describe the development of an optimized topical delivery system that can neutralize Flii activity in the epidermis. Topical delivery of FnAb is an attractive approach as it provides a convenient application, sustained release, localized effect, and reduced dosage. Three successful formulations were developed, and their physical and chemical stability examined. The in vitro release revealed prolonged and sustained release of FnAb in all the tested formulations. Additionally, penetration studies using intact porcine skin showed that FnAb penetrated the epidermis and upper papillary dermis. The penetrated FnAb significantly reduced Flii expression compared to dosed matched IgG controls. This study has successfully developed a topical delivery system for FnAb that could serve as a potential platform for future localized wound treatments.

Delivery of Flightless I Neutralizing Antibody from Porous Silicon Nanoparticles Improves Wound Healing in Diabetic Mice.

Flightless I (Flii) is elevated in human chronic wounds and is a negative regulator of wound repair. Decreasing its activity improves healing responses. Flii neutralizing antibodies (FnAbs) decrease Flii activity in vivo and hold significant promise as healing agents. However, to avoid the need for repeated application in a clinical setting and to protect the therapeutic antibody from the hostile environment of the wound, suitable delivery vehicles are required. In this study, the use of porous silicon nanoparticles (pSi NPs) is demonstrated for the controlled release of FnAb to diabetic wounds. We achieve FnAb loading regimens exceeding 250 µg antibody per mg of vehicle. FnAb-loaded pSi NPs increase keratinocyte proliferation and enhance migration in scratch wound assays. Release studies confirm the functionality of the FnAb in terms of Flii binding. Using a streptozotocin-induced model of diabetic wound healing, a significant improvement in healing is observed for mice treated with FnAb-loaded pSi NPs compared to controls, including FnAb alone. FnAb-loaded pSi NPs treated with proteases show intact and functional antibody for up to 7 d post-treatment, suggesting protection of the antibodies from proteolytic degradation in wound fluid. pSi NPs may therefore enable new therapeutic approaches for the treatment of diabetic ulcers.

Delivery of Flightless I siRNA from Porous Silicon Nanoparticles Improves Wound Healing in Mice.

Flightless I (Flii), a cytoskeletal actin remodelling protein, is elevated in wounds and is a negative regulator of wound healing. Gene silencing using small interfering RNA (siRNA) is an attractive approach to antagonize Flii, and therefore holds significant promise as a therapeutic intervention. The development of siRNA therapeutics has been limited by an inability of the siRNA to cross the cell surface plasma membrane of target cells and also by their degradation due to endogenous nuclease action. To overcome these limitations, suitable delivery vehicles are required. Porous silicon (pSi) is a biodegradable and high surface area material commonly used for drug delivery applications. Here we investigated the use of pSi nanoparticles (pSiNPs) for the controlled release of Flii siRNA to wounds. Thermally hydrocarbonized pSiNPs (THCpSiNPs) were loaded with Flii siRNA and then coated with a biocompatible chitosan layer. Loading regimens in the order of 50 µg of Flii siRNA per mg of pSi were achieved. The release rate of Flii siRNA was sustained over 35 h. With addition to keratinocytes in vitro, reduced Flii gene expression in conjunction with lowered Flii protein was observed, in concert with increased cell migration and proliferation. A significant improvement in the healing of acute excisional wounds compared to controls was observed from day 5 onward when Flii siRNA-THCpSiNPs were intradermally injected. THCpSiNPs therefore are an effective vehicle for delivering siRNA, and nanoparticle-based siRNA delivery represents a promising therapeutic approach to improve wound healing.

Cytoskeletal protein Flightless I inhibits apoptosis, enhances tumor cell invasion and promotes cutaneous squamous cell carcinoma progression.

Flightless I (Flii) is an actin remodeling protein that affects cellular processes including adhesion, proliferation and migration. In order to determine the role of Flii during carcinogenesis, squamous cell carcinomas (SCCs) were induced in Flii heterozygous (Flii+/-), wild-type and Flii overexpressing (FliiTg/Tg) mice by intradermal injection of 3-methylcholanthrene (MCA). Flii levels were further assessed in biopsies from human SCCs and the human SCC cell line (MET-1) was used to determine the effect of Flii on cellular invasion. Flii was highly expressed in human SCC biopsies particularly by the invading cells at the tumor edge. FliiTg/Tg mice developed large, aggressive SCCs in response to MCA. In contrast Flii+/- mice had significantly smaller tumors that were less invasive. Intradermal injection of Flii neutralizing antibodies during SCC initiation and progression significantly reduced the size of the tumors and, in vitro, decreased cellular sphere formation and invasion. Analysis of the tumors from the Flii overexpressing mice showed reduced caspase I and annexin V expression suggesting Flii may negatively regulate apoptosis within these tumors. These studies therefore suggest that Flii enhances SCC tumor progression by decreasing apoptosis and enhancing tumor cell invasion. Targeting Flii may be a potential strategy for reducing the severity of SCCs.

Attenuation of flightless I improves wound healing and enhances angiogenesis in a murine model of type 1 diabetes.

AIMS/HYPOTHESIS: Skin lesions and ulcerations are severe complications of diabetes that often result in leg amputations. In this study we investigated the function of the cytoskeletal protein flightless I (FLII) in diabetic wound healing. We hypothesised that overexpression of FLII would have a negative effect on diabetic wound closure and modulation of this protein using specific FLII-neutralising antibodies (FnAb) would enhance cellular proliferation, migration and angiogenesis within the diabetic wound. METHODS: Using a streptozotocin-induced model of diabetes we investigated the effect of altered FLII levels through Flii genetic knockdown, overexpression or treatment with FnAb on wound healing. Diabetic wounds were assessed using histology, immunohistochemistry and biochemical analysis. In vitro and in vivo assays of angiogenesis were used to assess the angiogenic response. RESULTS: FLII levels were elevated in the wounds of both diabetic mice and humans. Reduction in the level of FLII improved healing of murine diabetic wounds and promoted a robust pro-angiogenic response with significantly elevated von Willebrand factor (vWF) and vascular endothelial growth factor (VEGF)-positive endothelial cell infiltration. Diabetic mouse wounds treated intradermally with FnAb showed improved healing and a significantly increased rate of re-epithelialisation. FnAb improved the angiogenic response through enhanced formation of capillary tubes and functional neovasculature. Reducing the level of FLII led to increased numbers of mature blood vessels, increased recruitment of smooth muscle actin-α-positive cells and improved tight junction formation. CONCLUSIONS/INTERPRETATION: Reducing the level of FLII in a wound may be a potential therapeutic approach for the treatment of diabetic foot ulcers.

Flightless I over-expression impairs skin barrier development, function and recovery following skin blistering.

Development of an intact epidermis is critical for maintaining the integrity of the skin. Patients with epidermolysis bullosa (EB) experience multiple erosions, which breach the epidermal barrier and lead to increased microbial colocalization of wounds, infections and sepsis. The cytoskeletal protein Flightless I (Flii) is a known regulator of both development and wound healing. Using Flii(+/-), WT and Flii(Tg/Tg) mice, we investigated the effect of altering Flii levels in embryos and adult mice on the development of the epidermal barrier and, consequently, how this affects the integrity of the skin in EB. Flii over-expression resulted in delayed formation of the epidermal barrier in embryos and decreased expression of tight junction (TJ) proteins Claudin-1 and ZO-2. Increased intercellular space and transepidermal water loss was observed in Flii(Tg)(/Tg) adult mouse skin, while Flii(Tg/Tg) keratinocytes showed altered TJ protein localization and reduced transepithelial resistance. Flii is increased in the blistered skin of patients with EB, and over-expression of Flii in experimental EBA showed impaired Claudin-1 and -4 TJ protein expression and delayed recovery of functional barrier post-blistering. Immunoprecipitation confirmed Flii associated with TJ proteins and in vivo actin assays showed that the effect of Flii on actin polymerization underpinned the impaired barrier function observed in Flii(Tg/Tg) mice. These results therefore demonstrate an important role for Flii in the development and regulation of the epidermal barrier, which may contribute to the impaired healing and skin fragility of EB patients.

The influence of Flightless I on Toll-like-receptor-mediated inflammation in a murine model of diabetic wound healing.

Impaired wound healing and ulceration represent a serious complication of both type 1 and type 2 diabetes. Cytoskeletal protein Flightless I (Flii) is an important inhibitor of wound repair, and reduced Flii gene expression in fibroblasts increased migration, proliferation, and adhesion. As such it has the ability to influence all phases of wound healing including inflammation, remodelling and angiogenesis. Flii has the potential to modulate inflammation through its interaction with MyD88 which it an adaptor protein for TLR4. To assess the effect of Flii on the inflammatory response of diabetic wounds, we used a murine model of streptozocin-induced diabetes and Flii genetic mice. Increased levels of Flii were detected in Flii transgenic murine wounds resulting in impaired healing which was exacerbated when diabetes was induced. When Flii levels were reduced in diabetic wounds of Flii-deficient mice, healing was improved and decreased levels of TLR4 were observed. In contrast, increasing the level of Flii in diabetic mouse wounds led to increased TLR4 and NF- κ B production. Treatment of murine diabetic wounds with neutralising antibodies to Flii led to an improvement in healing with decreased expression of TLR4. Decreasing the level of Flii in diabetic wounds may therefore reduce the inflammatory response and improve healing.

Robust, reversible gene knockdown using a single lentiviral short hairpin RNA vector.

Manipulation of gene expression is an invaluable tool to study gene function in vitro and in vivo. The application of small inhibitory RNAs to knock down gene expression provides a relatively simple, elegant, but transient approach to study gene function in many cell types as well as in whole animals. Short hairpin structures (shRNAs) are a logical advance as they can be expressed continuously and are hence suitable for stable gene knockdown. Drug-inducible systems have now been developed; however, application of the technology has been hampered by persistent problems with low or transient expression, leakiness or poor inducibility of the short hairpin, and lack of reversibility. We have developed a robust, versatile, single lentiviral vector tool that delivers tightly regulated, fully reversible, doxycycline-responsive knockdown of target genes (FOXP3 and MYB), using single short hairpin RNAs. To demonstrate the capabilities of the vector we targeted FOXP3 because it plays a critical role in the development and function of regulatory T cells. We also targeted MYB because of its essential role in hematopoiesis and implication in breast cancer progression. The versatility of this vector is hence demonstrated by knockdown of distinct genes in two biologically separate systems.

Genome-wide identification of human FOXP3 target genes in natural regulatory T cells.

The transcription factor FOXP3 is essential for the formation and function of regulatory T cells (Tregs), and Tregs are essential for maintaining immune homeostasis and tolerance. This is demonstrated by a lethal autoimmune defect in mice lacking Foxp3 and in immunodysregulation polyendocrinopathy enteropathy X-linked syndrome patients. However, little is known about the molecular basis of human FOXP3 function or the relationship between direct and indirect targets of FOXP3 in human Tregs. To investigate this, we have performed a comprehensive genome-wide analysis for human FOXP3 target genes from cord blood Tregs using chromatin immunoprecipitation array profiling and expression profiling. We have identified 5579 human FOXP3 target genes and derived a core Treg gene signature conserved across species using mouse chromatin immunoprecipitation data sets. A total of 739 of the 5579 FOXP3 target genes were differentially regulated in Tregs compared with Th cells, thus allowing the identification of a number of pathways and biological functions overrepresented in Tregs. We have identified gene families including cell surface molecules and microRNAs that are differentially expressed in FOXP3(+) Tregs. In particular, we have identified a novel role for peptidase inhibitor 16, which is expressed on the cell surface of >80% of resting human CD25(+)FOXP3(+) Tregs, suggesting that in conjunction with CD25 peptidase inhibitor 16 may be a surrogate surface marker for Tregs with potential clinical application.

Mutational analysis of 105 mucopolysaccharidosis type VI patients.

Mucopolysaccharidosis type VI (MPS VI; Maroteaux-Lamy syndrome) is a lysosomal storage disorder caused by mutations in the N-acetylgalactosamine-4-sulfatase (arylsulfatase B, ARSB) gene. ARSB is a lysosomal enzyme involved in the degradation of the glycosaminoglycans (GAG) dermatan and chondroitin sulfate. ARSB mutations reduce enzyme function and GAG degradation, causing lysosomal storage and urinary excretion of these partially degraded substrates. Disease onset and rate of progression is variable, producing a spectrum of clinical presentation. In this study, 105 MPS VI patients-representing about 10% of the world MPS VI population-were studied for molecular genetic and biochemical parameters. Direct sequencing of patient genomic DNA was used to identify ARSB mutations. In total, 83 different disease-causing mutations were found, 62 of which were previously unknown. The novel sequence changes included: 38 missense mutations, five nonsense mutations, 11 deletions, one insertion, seven splice-site mutations, and four polymorphisms. ARSB mutant protein and residual activity were determined on fibroblast extracts for each patient. The identification of many novel mutations unique to individuals/their families highlighted the genetic heterogeneity of the disorder and provided an appropriate cohort to study the MPS VI phenotypic spectrum. This mutation analysis has identified a clear correlation between genotype and urinary GAG that can be used to predict clinical outcome.

Mutational analysis of mucopolysaccharidosis type VI patients undergoing a phase II trial of enzyme replacement therapy.

Mucopolysaccharidosis type VI (MPS VI; Maroteaux-Lamy syndrome) is a lysosomal storage disorder caused by mutations in the N-acetylgalactosamine-4-sulfatase (ARSB) gene. These mutations result in a deficiency of ARSB activity. Ten MPS VI patients were involved in a phase II clinical study of enzyme replacement therapy. Direct sequencing of genomic DNA from these patients was used to identify ARSB mutations. Each individual exon of the ARSB gene was amplified by PCR and subsequently sequenced. Thirteen substitutions (c.215T>G [p.L72R] c.284G>A [p.R95Q], c.305G>A [p.R102H], c.323G>T [p.G108V], c.389C>T [p.P130L], c.511G>A [p.G171S], c.904G>A [p.G302R], c.944G>A [p.R315Q], c.1057T>C [p.W353R], c.1151G>A [p.S384N], c.1178A>C [p.H393P], c.1289A>G [p.H430R] and c.1336G>C [p.G446R]), one deletion (c.238delG), and two intronic mutations (c.1213+5G>A and c.1214-2A>G) were identified. Nine of the 16 mutations identified were novel (R102H, G108V, P130L, G171S, W353R, H430R, G446R, c.1213+5G>A and c.1214-2A>G). The two common polymorphisms c.1072G>A [p.V358M] and c.1126G>A [p.V376M] were identified in some of the patients, along with the silent mutations c.972A>G and c.1191A>G. Cultured fibroblast ARSB mutant protein and residual activity were determined for each patient and, together with genotype information, used to predict the expected clinical severity of each patient.

Immortalisation of a mucopolysaccharidosis type IIIC fibroblast cell line via expression of SV40 T antigen.

Mucopolysaccharidosis type IIIC is caused by a deficiency of acetyl-CoA: alpha-glucosaminidase-N-acetyltransferase activity. This enzyme is unique among enzymes involved in the lysosomal degradation of glycosaminoglycans in that it catalyses an anabolic reaction, the addition of an acetyl group to glucosamine at the non-reducing terminus of heparan sulphate. We have identified a mucopolysaccharidosis type IIIC skin fibroblast cell line with undetectable levels of residual acetyl-CoA: alpha-glucosaminidase-N-acetyltransferase activity and immortalised it via expression of simian virus 40 large T antigen. Enzymatic analysis of two immortalised cell lines demonstrated that they both retained the original mucopolysaccharidosis IIIC phenotype. Variable number tandem repeat analysis confirmed that both were derived from the parental cell line.