Intradermal injection of transforming growth factor-beta1 gene enhances wound healing in genetically diabetic mice

Healing the diabetic wound: Unlocking the secrets of genes and pathways

Diabetic wounds (DWs) are open sores that can occur anywhere on a diabetic patient's body. They are often complicated by infections, hypoxia, oxidative stress, hyperglycemia, and reduced growth factors and nucleic acids. The healing process involves four phases: homeostasis, inflammation, proliferation, and remodeling, regulated by various cellular and molecular events. Numerous genes and signaling pathways such as VEGF, TGF-β, NF-κB, PPAR-γ, MMPs, IGF, FGF, PDGF, EGF, NOX, TLR, JAK-STAT, PI3K-Akt, MAPK, ERK, JNK, p38, Wnt/β-catenin, Hedgehog, Notch, Hippo, FAK, Integrin, and Src pathways are involved in these events. These pathways and genes are often dysregulated in DWs leading to impaired healing. The present review sheds light on the pathogenesis, healing process, signaling pathways, and genes involved in DW. Further, various therapeutic strategies that target these pathways and genes via nanotechnology are also discussed. Additionally, clinical trials on DW related to gene therapy are also covered in the present review.

Therapeutic role of growth factors in treating diabetic wound

Wounds in diabetic patients, especially diabetic foot ulcers, are more difficult to heal compared with normal wounds and can easily deteriorate, leading to amputation. Common treatments cannot heal diabetic wounds or control their many complications. Growth factors are found to play important roles in regulating complex diabetic wound healing. Different growth factors such as transforming growth factor beta 1, insulin-like growth factor, and vascular endothelial growth factor play different roles in diabetic wound healing. This implies that a therapeutic modality modulating different growth factors to suit wound healing can significantly improve the treatment of diabetic wounds. Further, some current treatments have been shown to promote the healing of diabetic wounds by modulating specific growth factors. The purpose of this study was to discuss the role played by each growth factor in therapeutic approaches so as to stimulate further therapeutic thinking.

Therapeutic delivery of nucleic acids for skin wound healing

Though wound care has advanced, treating chronic wounds remains a challenge and there are many clinical issues that must be addressed. Gene therapy is a recent approach to treating chronic wounds that remains in its developmental stage. The limited reports available describe the therapeutic applications of various forms of nucleic acid delivery for treating chronic wounds, including DNA, mRNA, siRNA, miRNA and so on. Though these bioactive molecules represent great therapeutic potential, sustaining their bioactivity in the wound bed is a challenge. To overcome this hurdle, delivery systems are also being widely investigated. In this review, nucleic acid-based therapy and its delivery for treating chronic wounds is discussed in detail.

Limited Treatment Options for Diabetic Wounds: Barriers to Clinical Translation Despite Therapeutic Success in Murine Models

Significance: Millions of people worldwide suffer from diabetes mellitus and its complications, including chronic diabetic wounds. To date, there are few widely successful clinical therapies specific to diabetic wounds beyond general wound care, despite the vast number of scientific discoveries in the pathogenesis of defective healing in diabetes. Recent Advances: In recent years, murine animal models of diabetes have enabled the investigation of many possible therapeutics for diabetic wound care. These include specific cell types, growth factors, cytokines, peptides, small molecules, plant extracts, microRNAs, extracellular vesicles, novel wound dressings, mechanical interventions, bioengineered materials, and more. Critical Issues: Despite many research discoveries, few have been translated from their success in murine models to clinical use in humans. This massive gap between bench discovery and bedside application begs the simple and critical question: what is still missing? The complexity and multiplicity of the diabetic wound makes it an immensely challenging therapeutic target, and this lopsided progress highlights the need for new methods to overcome the bench-to-bedside barrier. How can laboratory discoveries in animal models be effectively translated to novel clinical therapies for human patients? Future Directions: As research continues to decipher deficient healing in diabetes, new approaches and considerations are required to ensure that these discoveries can become translational, clinically usable therapies. Clinical progress requires the development of new, more accurate models of the human disease state, multifaceted investigations that address multiple critical components in wound repair, and more innovative research strategies that harness both the existing knowledge and the potential of new advances across disciplines.

SDF-1α Gene-Activated Collagen Scaffold Restores Pro-Angiogenic Wound Healing Features in Human Diabetic Adipose-Derived Stem Cells

Non-healing diabetic foot ulcers (DFUs) can lead to leg amputation in diabetic patients. Autologous stem cell therapy holds some potential to solve this problem; however, diabetic stem cells are relatively dysfunctional and restrictive in their wound healing abilities. This study sought to explore if a novel collagen-chondroitin sulfate (coll-CS) scaffold, functionalized with polyplex nanoparticles carrying the gene encoding for stromal-derived factor-1 alpha (SDF-1α gene-activated scaffold), can enhance the regenerative functionality of human diabetic adipose-derived stem cells (ADSCs). We assessed the impact of the gene-activated scaffold on diabetic ADSCs by comparing their response against healthy ADSCs cultured on a gene-free scaffold over two weeks. Overall, we found that the gene-activated scaffold could restore the pro-angiogenic regenerative response in the human diabetic ADSCs similar to the healthy ADSCs on the gene-free scaffold. Gene and protein expression analysis revealed that the gene-activated scaffold induced the overexpression of SDF-1α in diabetic ADSCs and engaged the receptor CXCR7, causing downstream β-arrestin signaling, as effectively as the transfected healthy ADSCs. The transfected diabetic ADSCs also exhibited pro-wound healing features characterized by active matrix remodeling of the provisional fibronectin matrix and basement membrane protein collagen IV. The gene-activated scaffold also induced a controlled pro-healing response in the healthy ADSCs by disabling early developmental factors signaling while promoting the expression of tissue remodeling components. Conclusively, we show that the SDF-1α gene-activated scaffold can overcome the deficiencies associated with diabetic ADSCs, paving the way for autologous stem cell therapies combined with novel biomaterials to treat DFUs.

MicroRNA 21 Emerging Role in Diabetic Complications: A Critical Update

BACKGROUND

Diabetes Mellitus is a multifactorial disease encompassing various pathogenic pathways. To avoid morbidity and mortality related to diabetic complications, early detection of disease complications as well as targeted therapeutic strategies are essential.

INTRODUCTION

MicroRNAs (miRs) are short non-coding RNA molecules that regulate eukaryotic posttranscriptional gene expression. MicroRNA-21 has diverse gene regulatory functions and plays a significant role in various complications of Type 2 diabetes mellitus (T2DM).

METHODS

The study included electronic database searches on Pubmed, Embase, and Web of Science with the search items MicroRNA21 and each of the diabetic complications. The search was carried out up to November, 2019.

RESULTS

MicroRNA-21 modulates diabetic cardiomyopathy by affecting vascular smooth muscle cell proliferation and apoptosis, cardiac cell growth and death, and cardiac fibroblast functions. At the renal tubules, miR-21 can regulate the mesangial expansion, interstitial fibrosis, macrophage infiltration, podocyte loss, albuminuria and fibrotic and inflammatory gene expression related to diabetic nephropathy. Overexpression of miR-21 has been seen to play a pivotal role in the pathogenesis of diabetic retinopathy by contributing to diabetes-induced endothelial dysfunction as well as low-grade inflammation.

CONCLUSION

Considering the raised levels of miR-21 in various diabetic complications, it may prove to be a candidate biomarker for diabetic complications. Further, miR-21 antagonists have shown great potential in the treatment of diabetic cardiomyopathy, diabetic nephropathy, diabetic retinopathy, and diabetic neuropathy related complications in the future. The current review is the first of its kind encompassing the roles miR-21 plays in various diabetic complications, with a critical discussion of its future potential role as a biomarker and therapeutic target.

Gene Therapy and its Application in Dermatology

Gene therapy is an experimental technique to treat genetic diseases. It is based on the introduction of nucleic acid with the help of a vector, into a diseased cell or tissue, to correct the gene expression and thus prevent, halt, or reverse a pathological process. It is a promising treatment approach for genetic diseases, inherited diseases, vaccination, cancer, immunomodulation, as well as healing of some refractory ulcers. Both viral and nonviral vectors can be used to deliver the correct gene. An ideal vector should have the ability for sustained gene expression, acceptable coding capacity, high transduction efficiency, and devoid of mutagenicity. There are different techniques of vector delivery, but these techniques are still under research for assessment of their safety and effectiveness. The major challenges of gene therapy are immunogenicity, mutagenicity, and lack of sustainable therapeutic benefit. Despite these constraints, therapeutic success was obtained in a few genetic and inherited skin diseases. Skin being the largest, superficial, easily accessible and assessable organ of the body, may be a promising target for gene therapy research in the recent future.

EWMA Document: Negative Pressure Wound Therapy

1. Introduction Since its introduction in clinical practice in the early 1990's negative pressure wounds therapy (NPWT) has become widely used in the management of complex wounds in both inpatient and outpatient care.¹ NPWT has been described as a effective treatment for wounds of many different aetiologies^2,3 and suggested as a gold standard for treatment of wounds such as open abdominal wounds,^4-6 dehisced sternal wounds following cardiac surgery^7,8 and as a valuable agent in complex non-healing wounds.^9,10 Increasingly, NPWT is being applied in the primary and home-care setting, where it is described as having the potential to improve the efficacy of wound management and help reduce the reliance on hospital-based care.¹¹ While the potential of NPWT is promising and the clinical use of the treatment is widespread, highlevel evidence of its effectiveness and economic benefits remain sparse.^12-14 The ongoing controversy regarding high-level evidence in wound care in general is well known. There is a consensus that clinical practice should be evidence-based, which can be difficult to achieve due to confusion about the value of the various approaches to wound management; however, we have to rely on the best available evidence. The need to review wound strategies and treatments in order to reduce the burden of care in an efficient way is urgent. If patients at risk of delayed wound healing are identified earlier and aggressive interventions are taken before the wound deteriorates and complications occur, both patient morbidity and health-care costs can be significantly reduced. There is further a fundamental confusion over the best way to evaluate the effectiveness of interventions in this complex patient population. This is illustrated by reviews of the value of various treatment strategies for non-healing wounds, which have highlighted methodological inconsistencies in primary research. This situation is confounded by differences in the advice given by regulatory and reimbursement bodies in various countries regarding both study design and the ways in which results are interpreted. In response to this confusion, the European Wound Management Association (EWMA) has been publishing a number of interdisciplinary documents^15-19 with the intention of highlighting: The nature and extent of the problem for wound management: from the clinical perspective as well as that of care givers and the patients Evidence-based practice as an integration of clinical expertise with the best available clinical evidence from systematic research The nature and extent of the problem for wound management: from the policy maker and healthcare system perspectives The controversy regarding the value of various approaches to wound management and care is illustrated by the case of NPWT, synonymous with topical negative pressure or vacuum therapy and cited as branded VAC (vacuum-assisted closure) therapy. This is a mode of therapy used to encourage wound healing. It is used as a primary treatment of chronic wounds, in complex acute wounds and as an adjunct for temporary closure and wound bed preparation preceding surgical procedures such as skin grafts and flap surgery. Aim An increasing number of papers on the effect of NPWT are being published. However, due to the low evidence level the treatment remains controversial from the policy maker and health-care system's points of view-particularly with regard to evidence-based medicine. In response EWMA has established an interdisciplinary working group to describe the present knowledge with regard to NPWT and provide overview of its implications for organisation of care, documentation, communication, patient safety, and health economic aspects. These goals will be achieved by the following: Present the rational and scientific support for each delivered statement Uncover controversies and issues related to the use of NPWT in wound management Implications of implementing NPWT as a treatment strategy in the health-care system Provide information and offer perspectives of NPWT from the viewpoints of health-care staff, policy makers, politicians, industry, patients and hospital administrators who are indirectly or directly involved in wound management.

Innovations in gene and growth factor delivery systems for diabetic wound healing

The rise in lower extremity amputations due to nonhealing of foot ulcers in diabetic patients calls for rapid improvement in effective treatment regimens. Administration of growth factors (GFs) are thought to offer an off-the-shelf treatment; however, the dose- and time-dependent efficacy of the GFs together with the hostile environment of diabetic wound beds impose a major hindrance in the selection of an ideal route for GF delivery. As an alternative, the delivery of therapeutic genes using viral and nonviral vectors, capable of transiently expressing the genes until the recovery of the wounded tissue offers promise. The development of implantable biomaterial dressings capable of modulating the release of either single or combinatorial GFs/genes may offer solutions to this overgrowing problem. This article reviews the state of the art on gene and protein delivery and the strategic optimization of clinically adopted delivery strategies for the healing of diabetic wounds.

Gene therapy strategies to improve strength and quality of flexor tendon healing

INTRODUCTION

Rupture of the repair and adhesion around a tendon are two major problems after tendon surgery. Novel biological therapies which enhance healing and reduce adhesions are goals of many investigations. Gene therapy offers a new and promising approach to tackle these difficult problems. In the past decade, we sought to develop methods to augment tendon healing and reduce tendon adhesion through gene therapy.

AREAS COVERED

This review discusses the methods and results of adeno-associated viral (AAV) type 2 vector gene therapy to increase tendon healing strength and reduce adhesions in a chicken model. Micro-RNA related gene therapy is also discussed. We also developed a controlled release system, which incorporates nanoparticles to deliver micro-RNAs to regulate tendon healing.

EXPERT OPINION

We obtained promising results of enhancement of tendon healing strength in a chicken model using AAV2-mediated gene transfer. AAV2-mediated micro-RNA transfer also limited adhesions around the tendon. Controlled release systems incorporating nanoparticles have ideally delivered genes to the healing tendons and resulted in a moderate (but incomplete) reduction of adhesions. It remains to be determined what the best doses are and what other factors are in play in adhesion formation. These are two targets in our future investigations.

Topical fentanyl stimulates healing of ischemic wounds in diabetic rats

BACKGROUND

Topically applied opioids promote angiogenesis and healing of ischemic wounds in rats. We examined if topical fentanyl stimulates wound healing in diabetic rats by stimulating growth-promoting signaling, angiogenesis, lymphangiogenesis and nerve regeneration.

METHODS

We used Zucker diabetic fatty rats that develop obesity and diabetes on a high fat diet due to a mutation in the Leptin receptor. Fentanyl blended with hydrocream was applied topically on ischemic wounds twice daily, and wound closure was analyzed regularly. Wound histology was analyzed by hematoxylin and eosin staining. Angiogenesis, lymphangiogenesis, nerve fibers and phospho-platelet derived growth factor receptor-β (PDGFR-β) were visualized by CD31-, lymphatic vessel endothelium-1, protein gene product 9.5- and anti-phospho PDGFR-β-immunoreactivity, respectively. Nitric oxide synthase (NOS) and PDGFR-β signaling were analyzed using Western immunoblotting.

RESULTS

Fentanyl significantly promoted wound closure as compared to phosphate-buffered saline (PBS). Histology scores were significantly higher in fentanyl-treated wounds, indicative of increased granulation tissue formation, reduced edema and inflammation, and increased matrix deposition. Fentanyl treatment resulted in increased wound angiogenesis, lymphatic vasculature, nerve fibers, nitric oxide, NOS and PDGFR-β signaling as compared to PBS. Phospho-PDGFR-β co-localized with CD31 co-staining for vasculature.

CONCLUSIONS

Topically applied fentanyl promotes closure of ischemic wounds in diabetic rats. Increased angiogenesis, lymphangiogenesis, peripheral nerve regeneration, NO and PDGFR-β signaling are associated with fentanyl-induced tissue remodeling and wound healing.

NFkappaB activation is essential for miR-21 induction by TGFβ1 in high glucose conditions

Transforming growth factor beta1 (TGFβ1) is a pleiotropic growth factor with a very broad spectrum of effects on wound healing. Chronic non-healing wounds such as diabetic foot ulcers express reduced levels of TGFβ1. On the other hand, our previous studies have shown that the microRNA miR-21 is differentially regulated in diabetic wounds and that it promotes migration of fibroblast cells. Although interplay between TGFβ1 and miR-21 are studied in relation to cancer, their interaction in the context of chronic wounds has not yet been investigated. In this study, we examined if TGFβ1 could stimulate miR-21 in fibroblasts that are subjected to high glucose environment. MiR-21 was, in fact, induced by TGFβ1 in high glucose conditions. The induction by TGFβ1 was dependent on NFκB activation and subsequent ROS generation. TGFβ1 was instrumental in degrading the NFκB inhibitor IκBα and facilitating the nuclear translocation of NFκB p65 subunit. EMSA studies showed enhanced DNA binding activity of NFκB in the presence of TGFβ1. ChIP assay revealed binding of p65 to miR-21 promoter. NFκB activation was also required for the nuclear translocation of Smad 4 protein and subsequent direct interaction of Smad proteins with primary miR-21 as revealed by RNA-IP studies. Our results show that manipulation of TGFβ1-NFκB-miR-21 pathway could serve as an innovative approach towards therapeutics to heal diabetic ulcers.

Gene therapy for skin diseases

The skin possesses qualities that make it desirable for gene therapy, and studies have focused on gene therapy for multiple cutaneous diseases. Gene therapy uses a vector to introduce genetic material into cells to alter gene expression, negating a pathological process. This can be accomplished with a variety of viral vectors or nonviral administrations. Although results are promising, there are several potential pitfalls that must be addressed to improve the safety profile to make gene therapy widely available clinically.

Alkylimidazolium end-modified poly(ethylene glycol) to form the mono-ion complex with plasmid DNA for in vivo gene delivery

In this study, we consider that the decrease in the transfection activity of polycations in vivo, compared with that in vitro, results from their polyion complex formation. Namely, owing to cross-linking between polycations and plasmid DNAs (pDNAs), the disadvantage of in vivo gene delivery mainly stems from the difficulty in controlling the properties of the resulting polyion complex at the nanoscale size. To avoid the cross-linking by polycations, we have establish the concept of "mono-ion complex" formation between pDNA and a monocationic biocompatible polymer. Here we have synthesized alkylimidazolium end-modified poly(ethylene glycol), that is, R-Im-PEG, and have tuned the electrostatic interaction between the resulting alkylimidazolium group and the phosphate group of pDNA by the length of the alkyl chain to achieve "mono-ion complex" formation with pDNA for in vivo gene delivery. Instead of a polyion complex, our original concept of the "mono-ion complex" consisting of the Bu-Im-PEG and pDNA is expected to offer unique tools to break through the barriers of in vivo gene delivery. As well as the field of gene delivery, this study is considered to have exploded the common sense that it is impossible to form not a polyion complex but a "mono-ion complex" under aqueous conditions for all fields of the modification of biomacromolecules.

YAP and TAZ regulate skin wound healing

The Hippo signaling pathway regulates organ size, tissue regeneration, and stem cell self-renewal. The two key downstream transcription coactivators in this pathway, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), mediate the major gene regulation and biological functions of the Hippo pathway. The biological functions of YAP and TAZ in many tissues are known; however, their roles in skin wound healing remain unclear. To analyze whether YAP and/or TAZ are required for cutaneous wound healing, we performed small interfering RNA (siRNA)-mediated knockdown of YAP/TAZ in full-thickness skin wounds. YAP is strongly expressed in the nucleus and cytoplasm in the epidermis and hair follicle. Interestingly, YAP is expressed in the nucleus in the dermis at 2 and 7 days after wounding. TAZ normally localizes to the cytoplasm in the dermis but is distributed in both the nucleus and cytoplasm at 1 day after wounding. The knockdown of YAP and TAZ markedly delayed the rate of wound closure and reduced the transforming growth factor-β1 (TGF-β1) expression in the wound. YAP and TAZ also modulate the expression of TGF-β1 signaling pathway components such as Smad-2, p21, and Smad-7. These results suggest that YAP and TAZ localization to the nucleus is required for skin wound healing.

miR-21 regulates skin wound healing by targeting multiple aspects of the healing process

With the clarification of the important roles of microRNAs (miRNAs) in diverse physiologic and pathologic processes, the effects of miRNAs in wound healing have attracted more attention recently. However, the global pattern of miRNA expression in wound tissue is still unknown. In the present study, we depicted the miRNA profile and identified at least 54 miRNAs, including miR-21, changed for more than twofold at the stage of granulation formation during wound healing. These miRNAs were closely related to the major events of wound healing, including cell migration and proliferation, angiogenesis, and matrix remolding. Furthermore, we found that miR-21 was up-regulated after skin injury, mainly in activated and migrating epithelial cells of epidermis and mesenchymal cells of dermis. Locally antagonizing miR-21 by directly injecting antagomir to wound edge caused significant delay of wound closure with impaired collagen deposition. Unexpectedly, we found wounds treated with miR-21 antagomir had an obvious defect in wound contraction at an early stage of wound healing. The significant role of miR-21 in wound contraction was further confirmed by in vivo gain-of-function and in vitro loss-of-function experiments. In conclusion, the present study has for the first time depicted miRNA profiling of wound healing and demonstrated the involvement of miR-21 in regulating the wound contraction and collagen deposition. These results suggest that miR-21 may be a new medical target in skin wound manipulation.

Cytokines, chemokines and growth factors in wound healing

In wound healing, a variety of mediators have been identified throughout the years. The mediators discussed here comprise growth factors, cytokines and chemokines. These mediators act via multiple (specific) receptors to facilitate wound closure. As research in the last years has led to many new findings, there is a need to give an overview on what is known, and on what might possibly play a role as a molecular target for future wound therapy. This review aims to keep the reader up to date with selected important and novel findings regarding growth factors, cytokines and chemokines in wound healing.

Blockade of TSP1-dependent TGF-β activity reduces renal injury and proteinuria in a murine model of diabetic nephropathy

Transforming growth factor-β (TGF-β) is key in the pathogenesis of diabetic nephropathy. Thrombospondin 1 (TSP1) expression is increased in diabetes, and TSP1 regulates latent TGF-β activation in vitro and in diabetic animal models. Herein, we investigate the effect of blockade of TSP1-dependent TGF-β activation on progression of renal disease in a mouse model of type 1 diabetes (C57BL/6J-Ins2(Akita)) as a targeted treatment for diabetic nephropathy. Akita and control C57BL/6 mice who underwent uninephrectomy received 15 weeks of thrice-weekly i.p. treatment with 3 or 30 mg/kg LSKL peptide, control SLLK peptide, or saline. The effects of systemic LSKL peptide on dermal wound healing was assessed in type 2 diabetic mice (db/db). Proteinuria (urinary albumin level and albumin/creatinine ratio) was significantly improved in Akita mice treated with 30 mg/kg LSKL peptide. LSKL treatment reduced urinary TGF-β activity and renal phospho-Smad2/3 levels and improved markers of tubulointerstitial injury (fibronectin) and podocytes (nephrin). However, LSKL did not alter glomerulosclerosis or glomerular structure. LSKL did not increase tumor incidence or inflammation or impair diabetic wound healing. These data suggest that selective targeting of excessive TGF-β activity through blockade of TSP1-dependent TGF-β activation represents a therapeutic strategy for treating diabetic nephropathy that preserves the homeostatic functions of TGF-β.

Effect of pravastatin on experimental diabetic wound healing

BACKGROUND

Impaired wound healing in diabetes has been associated with abnormalities in wound nitric oxide (NO) and nitric oxide synthase (NOS) availability. Efforts to alter the profile of NO expression in the wound microenvironment have proven to be successful in partially restoring wound healing deficits. We investigated the effects of pravastatin, a HMG Co A reductase inhibitor on endothelial nitric oxide synthase (eNOS) expression, NO production, and wound healing in a diabetic acute wound healing model.

MATERIALS AND METHODS

Of 70 male Sprague Dawley rats injected with streptozocin, 62 were confirmed diabetic after 1 wk. Animals were randomized into two groups: (1) diabetic control and (2) diabetic treated with pravastatin. Pravastatin sodium was gavaged at 0.4 mg/kg/d for 5 d, after which all animals underwent dorsal incision with insertion of subcutaneous sponges. Breaking strengths and hydroxyproline were measured on days 1, 3, and 10 post-wounding. Wound fluid was analyzed for nitrate/nitrite production. Tissue samples were analyzed for eNOS expression.

RESULTS

We demonstrated enhanced wound breaking strengths, hydroxyproline accumulation, an up-regulation in eNOS expression, and elevated NO levels in the pravastatin treated group.

CONCLUSION

We have shown that pravastatin, in an experimental model of diabetes may through up-regulation of eNOS and NO expression improve wound healing.

Tissue-engineered bone formation with gene transfer and mesenchymal stem cells in a minimally invasive technique

BACKGROUND

The objective of this study was to use a chitosan-alginate gel to implant bone marrow-derived mesenchymal stem cells subcutaneously in a minimally invasive manner and promote bone formation by the simultaneously transferred osteogenic protein (OP)-1 (bone morphogenic protein-7) gene.

METHOD AND RESULTS

The complex of polyethylenimine/luciferase plasmid DNA embedded in the gel was able to transfect HEK 293 cells on a culture dish or co-encapsulated in the gel. When injected into the subcutaneous space of mice, luciferase expression was two to three orders of magnitude increased above the background. To examine the efficacy of gene-, cell-, and combined gene- and cell-encapsulated gels in tissue generation, samples were injected into the subcutaneous space of 6-week-old athymic nude mice, and the OP-1 plasmid was studied. At 8 weeks after the injection, the gels only maintained their volumetric shape when human mesenchymal stem cells (hMSCs) were encapsulated, but otherwise the gels were partially dissolved. Transgene expression of OP-1 was clearly detected in the samples after 4 weeks but not after 8 weeks. Type II collagen was detected in all the gels containing the OP-1 plasmid, with or without hMSCs. The samples with the combination of OP-1 DNA and hMSCs revealed strong type II collagen expression as well as osteoid foci.

CONCLUSION

These results suggest that combined gene and hMSC delivery within a chitosan-alginate gel could be an interesting approach for tissue engineering.

Thermosensitive Hydrogel PEG–PLGA–PEG Enhances Engraftment of Muscle-derived Stem Cells and Promotes Healing in Diabetic Wound

Regenerating new tissue using cell transplantation has relied on successful cell engraftment in the host; however, cell engraftment into the diabetic skin wound is not as successful as in many other tissues. We used a biodegradable and biocompatible triblock co-polymer poly(ethylene glycol-b-[DL-lactic acid-co-glycolic acid]-b-ethylene glycol) (PEG-PLGA-PEG), which forms a thermosensitive hydrogel, as a wound dressing and scaffold. We found that the thermosensitive hydrogel increased the engraftment of muscle-derived stem cells (MDSCs) by 20- to 30-fold until day 20, when the wound was completely closed in a db/db genetically diabetic mouse model. At day 9, 30% of the transplanted MDSCs were found to remain, and 15% remained at day 20 after transplantation. The increased engraftment resulted in enhanced wound healing, as indicated by the wound closure rate, epithelium migration, and collagen deposition. Using MDSCs stably expressing beta-gal and immunofluorescence, we found that 25% of MDSCs differentiated into fibroblasts, 10% into myofibroblasts, and 10% into endothelial cells. We conclude that using the thermosensitive hydrogel as a scaffold increased the engraftment of MDSCs, which leads to improved diabetic wound healing, possibly by retaining the cells at the wound site for longer.

Acute downregulation of connexin43 at wound sites leads to a reduced inflammatory response, enhanced keratinocyte proliferation and wound fibroblast migration

Experimental downregulation of connexin43 (Cx43) expression at skin wound sites appears to markedly improve the rate and quality of healing, but the underlying mechanisms are currently unknown. Here, we have compared physiological and cell biological aspects of the repair process with and without Cx43 antisense oligodeoxynucleotide treatment. Treated wounds exhibited accelerated skin healing with significantly increased keratinocyte and fibroblast proliferation and migration. In vitro knockdown of Cx43 in a fibroblast wound-healing model also resulted in significantly faster healing, associated with increased mRNA for TGF-beta1, and collagen alpha1 and general collagen content at the wound site. Treated wounds showed enhanced formation of granulation tissue and maturation with more rapid angiogenesis, myofibroblast differentiation and wound contraction appeared to be advanced by 2-3 days. Recruitment of both neutrophils and macrophages was markedly reduced within treated wounds, concomitant with reduced leukocyte infiltration. In turn, mRNA levels of CC chemokine ligand 2 and TNF-alpha were reduced in the treated wound. These data suggest that, by reducing Cx43 protein with Cx43-specific antisense oligodeoxynucleotides at wound sites early in the skin healing process repair is enhanced, at least in part, by accelerating cell migration and proliferation, and by attenuating inflammation and the additional damage it can cause.

Improving wound-healing outcomes in diabetic foot ulcers

The prevalence of diabetes is increasing worldwide and has been forecasted to double in the next 20 years. The major increase in morbidity and mortality of diabetes is due to the development of both macro- and microvascular complications, including failure of the wound-healing process. Foot ulcers occur in 15% of all patients with diabetes and precede 84% of all lower-leg amputations. The essential components of diabetic foot ulcer treatment are to reduce foot bearing pressure (in neuropathic ulcers) and to increase blood supply (in the case of vascular ulcers). Antibacterial therapy is also important. Despite optimized treatment, for reasons not completely understood, some ulcers fail to heal. Previous research studies have shown clearly that failure of healing eventually leads to deep-seated infection and amputation. Therefore, impaired wound healing is the pivotal event responsible for most of the morbidity (and mortality) of diabetic foot disease. Improving wound healing in diabetes requires a multidisciplinary approach in terms of clinical management as well as an increased effort aimed at better understanding the pathogenesis of poor wound healing in diabetes. Consequently, a detailed understanding of the wound-healing process in diabetes and how it can be improved is of great importance. However, efforts to develop new therapies are hampered by a lack of knowledge of the molecular mechanisms responsible for the pathologies, as well as a lack of suitable models for the study of chronic wounds. Therefore, this review will address both clinical and biochemical aspects of wound healing in diabetes.

[Role of gene therapy in trauma and orthopedic surgery]

Modern molecular and genetic technologies enable the modification of a cellular genome through transfer of specific genes. The various procedures alter specific cell functions, which allow the transfected cell to produce any encoded transgene information. The transfected cell then synthesizes proteins that are normally not produced or only in very small amounts. Numerous animal studies have demonstrated that gene therapy may support and accelerate the healing and regeneration of specific tissues such as skin, tendons, cartilage, and bones. Currently, further animal studies are evaluating new vectors with reduced immunogenicity in the continuous effort to improve the efficacy and safety of gene transfer. In the forthcoming decade we expect gene therapy to have an important influence on the treatment of fractures, cartilage lesions, and infection.

Functional expression of HGF and HGF receptor/c-met in adult human mesenchymal stem cells suggests a role in cell mobilization, tissue repair, and wound healing

Human mesenchymal stem cells (hMSC) are adult stem cells with multipotent capacities. The ability of mesenchymal stem cells to differentiate into many cell types, as well as their high ex vivo expansion potential, makes these cells an attractive therapeutic tool for cell transplantation and tissue engineering. hMSC are thought to contribute to tissue regeneration, but the signals governing their mobilization, diapedesis into the bloodstream, and migration into the target tissue are largely unknown. Here we report that hepatocyte growth factor (HGF) and the cognate receptor HGFR/c-met are expressed in hMSC, on both the RNA and the protein levels. The expression of HGF was downregulated by transforming growth factor beta. HGF stimulated chemotactic migration but not proliferation of hMSC. Therefore the HGF/c-met signaling system may have an important role in hMSC recruitment sites of tissue regeneration. The controlled regulation of HGF/c-met expression may be beneficial in tissue engineering and cell therapy employing hMSC.

Gene therapy in the treatment of lower extremity wounds

This article presents a brief overview of the etiology of chronic wounds of the lower extremities and their current medical and surgical treatment. Gene therapy as a potential tool for treating therapeutically challenging wounds is described in terms of the vectors employed in gene transfer, as well as the strategies used to promote wound healing. Results from animal model studies, as well as clinical trials, are presented.

Effects of topical elk velvet antler on cutaneous wound healing in streptozotocin-induced diabetic rats

OBJECTIVE

Wound repair is a finely orchestrated process involving cellular, molecular, physiologic, and biochemical interactions that restore the integrity of damaged tissue. Cyclic replacement of deer antlers requires rapid regenerative growth, in many ways analogous to that encountered during tissue repair. Molecular mechanisms regulating these processes are not fully understood, but it is increasingly apparent that growth factors are important mediators. Previous studies have shown that elk velvet antler (EVA) contains various growth factors and that a water-soluble extract stimulates dermal fibroblast growth in vitro.

DESIGN

The efficacy of EVA water-soluble extract on wound healing in streptozotocin-induced diabetic rats was EVAluated using a full-thickness cutaneous wound model. Animals were randomly selected to receive topical application of either control or EVA gel. Daily photographs of the wounds served to measure the rate of wound closure. Wound-edge biopsies obtained on postoperative days 2 and 10 allowed histologic evaluation and measurement of transforming growth factor-beta 1 (TGF-beta (1)) concentrations by enzyme-linked immunoabsorbent assay.

RESULTS

Wounds treated with the EVA topical gel were significantly smaller by postoperative day 6. TGF- beta (1) protein expression was not different in EVA-treated wounds compared to control wounds.

CONCLUSIONS

This study indicates that topical treatment with an EVA water-soluble extract accelerates repair of cutaneous wounds in diabetic rats. Further studies are warranted to reveal the mechanisms involved in EVA enhancement of wound closure and to determine if this compound is an economical pharmacologic agent in the treatment of normal and compromised wounds.

Electroporative transfection with KGF-1 DNA improves wound healing in a diabetic mouse model

We recently demonstrated that electroporation enhances transfection in a mouse wound-healing model. Keratinocyte growth factor (KGF) is an inducer of epithelial cell proliferation and differentiation and has been shown to be under expressed in the wounds of diabetic individuals. We hypothesized that KGF delivered into an excisional wound via naked DNA injection with subsequent electroporation would be a novel and potentially effective method to enhance wound closure in a diabetic mouse model. ELISA assays confirmed production of KGF protein in cultured mouse cells and RT-PCR assays confirmed KGF mRNA in skin samples taken from mice. In all, 32 genetically diabetic mice were given two identical excisional wounds of their dorsum and split into two groups with one group receiving KGF DNA injection and electroporation with the other group receiving no treatment. Over 90% of wounds healed in the presence of KGF and electroporation versus 40% in the untreated group by day 12. Histological analysis of the wounds demonstrated that untreated wounds contained microulcers with thin or incomplete epithelium with unresolved inflammation as compared to treated wounds where intact and mature epithelium was observed. Taken together these findings suggest that a single injection of KGF DNA encoded on a plasmid coupled with electroporation improves and accelerates wound closure in a delayed wound-healing model.

Electroporatic delivery of TGF-beta1 gene works synergistically with electric therapy to enhance diabetic wound healing in db/db mice

Electrical stimulation (ES) is a therapeutic treatment for wound healing. Electroporation, a type of ES, is a well-established method for gene delivery. We hypothesize that proper conditions can be found with which both electrical and gene therapies can be additively applied to treat diabetic wound healing. For the studies of transforming growth factor-beta1 (TGF-beta1) local expression and therapeutic effects, full thickness excisional wound model of db/db mice was used, we measured TGF-beta1 cytokine level at 24 h postwounding and examined wounds histologically. Furthermore, wound closure was evaluated by wound-area measurements at each day for 14 d. We found that syringe electrodes are more effective than the conventional caliper electrodes. Furthermore, diabetic skin was more sensitive to the electroporative damage than the normal skin. The optimal condition for diabetic skin was six pulses of 100 V per cm for 20 ms. Under such condition, the healing rate of electrically treated wound was significantly accelerated. Furthermore, when TGF-beta1 gene was delivered by electric pulses, the healing rate was further enhanced. Five to seven days postapplication of intradermal injection of plasmid TGF-beta1 followed by electroporation, the wound bed showed an increased reepithelialization rate, collagen synthesis, and angiogenesis. The data indicates that indeed the electric effect and gene effect work synergistic in the genetically diabetic model.