Adenoviral-mediated overexpression of platelet-derived growth factor-B corrects ischemic impaired wound healing

Gene therapy in wound healing using nanotechnology

Wound healing is a complex and highly regulated process that is susceptible to a variety of failures leading to delayed wound healing or chronic wounds. This is becoming an increasingly global burden on the healthcare system. Treatment of wounds has evolved considerably to overcome barriers to wound healing especially within the field of regenerative medicine that focuses on the replacement of tissues or organs. Improved understanding of the pathophysiology of wound healing has enabled current advances in technology to allow better optimization of microenvironment within wounds. This approach may help tackle wounds that are difficult to treat and help reduce the global burden of the disease. This article provides an overview of the physiology in wound healing and the application of gene therapy using nanotechnology in the management of wounds.

Effect of PDGF-B Gene-Activated Acellular Matrix and Mesenchymal Stem Cell Transplantation on Full Thickness Skin Burn Wound in Rat Model

BACKGROUND

Full thickness burn wounds are lack of angiogenesis, cell migration, epithelialisation and finally scar tissue formation. Tissue engineered composite graft can provide sustained release of growth factor and promote the wound healing by cell migration, early angiogenesis and proliferation of extracellular matrix and wound remodeling. The objective of this study was to evaluate the gene embedded (pDNA-platelet-derived growth factor, PDGF-B) porcine acellular urinary bladder matrix with transfected mesenchymal stem cells (rBMSC) on healing of full thickness burn wound in rat model.

METHODS

Full thickness burn wound of 2 × 2 cm size was created in dorsum of rat model under general anesthesia. Burn wounds were treated with silver sulfadiazine; porcine acellular urinary bladder matrix (PAUBM); PAUBM transfected with pDNA-PDGF-B; PAUBM seeded with rBMSC; PAUBM seeded with rBMSC transfected with pDNA-PDGF-B in groups A, B, C, D and E respectively. The wound healing was assessed based on clinical, macroscopically, immunologically, histopathological and RT-qPCR parameters.

RESULTS

Wound was significantly healed in group E and group D with early extracellular matrix deposition, enhanced granulation tissue formation and early angiogenesis compared to all other groups. The immunologic response against porcine acellular matrix showed that PDGF-B gene activated matrix along with stem cell group showed less antibody titer against acellular matrix than other groups in all intervals. PDGF gene activated matrix releasing the PDGF-B and promote the healing of full thickness burn wound with neovascularization and neo tissue formation. PDGF gene also enhances secretion of other growth factors results in PDGF mediated regenerative activities. This was confirmed in RT-qPCR at various time intervals.

CONCLUSION

Gene activated matrix encoded for PDGF-B protein transfected stem cells have been clinically proven for early acceleration of angiogenesis and tissue regeneration in burn wounds in rat models. Evaluation of PDGF-B gene-activated acellular matrix and mesenchymal stem cell in full thickness skin burn wound in rat.

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.

Therapeutic effects of platelet derived growth factor overexpressed-mesenchymal stromal cells and sheets in canine skin wound healing model

Adipose-derived mesenchymal stromal cells (Ad-MSCs) have excellent potential for skin wound repair. Moreover, platelet-derived growth factor (PDGF) has strong wound healing properties. The purpose of the present study was to compare the healing effects of PDGF-overexpressing canine allogeneic Ad-MSCs (PDGF-MSCs) and their cell sheets (PDGF-CSs) as compared to unexpressed Ad-MSCs (U-MSCs) and their cell sheets (UCSs) in a cutaneous wound healing model induced upon dogs. In in vitro study, the expression of immunomodulatory and growth factors was assessed by qRT-PCR. In in vivo study, cells and sheets were transplanted into a square-shaped full-thickness (1.5×1.5 cm) skin defect model created in 12 dogs. After 5 and 10 days, wounds were harvested and evaluated macroscopically and histopathologically. The qRT-PCR results showed that the PDGF-B gene was significantly upregulated (p<0.05) in PDGF-CS and PDGF-MSCs groups. Upon gross analysis of the wound, all stromal cells and their sheet groups showed accelerated (p<0.05) cutaneous wound healing compared to the negative control groups. As compared to U-MSCs and UCSs, the PDGF-MSCs showed significant epithelization on days 5 and 10 of healing, whereas PDGF-CSs showed improved epithelization only on day 10. In the granulation tissue analysis, PDGF-CSs and UCSs promoted more formation (p<0.05) of upper granulation tissue, collagen, and activated fibroblasts than PDGF-MSCs, and U-MSCs. Especially, the PDGF-CSs presented the highest formation and maturation of granulation tissue among all groups. All considered, PDGF overexpressed stromal cells or cells sheets can improve cutaneous wound healing in a canine model.

Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies

Cutaneous wound healing in adult mammals is a complex multi-step process involving overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodelling. Re-epithelialization describes the resurfacing of a wound with new epithelium. The cellular and molecular processes involved in the initiation, maintenance, and completion of epithelialization are essential for successful wound closure. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here, we focus on cellular mechanisms underlying keratinocyte migration and proliferation during epidermal closure. Inability to re-epithelialize is a clear indicator of chronic non-healing wounds, which fail to proceed through the normal phases of wound healing in an orderly and timely manner. This review summarizes the current knowledge regarding the management and treatment of acute and chronic wounds, with a focus on re-epithelialization, offering some insights into novel future therapies.

Localised non-viral delivery of nucleic acids for nerve regeneration in injured nervous systems

Axons damaged by traumatic injuries are often unable to spontaneously regenerate in the adult central nervous system (CNS). Although the peripheral nervous system (PNS) has some regenerative capacity, its ability to regrow remains limited across large lesion gaps due to scar tissue formation. Nucleic acid therapy holds the potential of improving regeneration by enhancing the intrinsic growth ability of neurons and overcoming the inhibitory environment that prevents neurite outgrowth. Nucleic acids modulate gene expression by over-expression of neuronal growth factor or silencing growth-inhibitory molecules. Although in vitro outcomes appear promising, the lack of efficient non-viral nucleic acid delivery methods to the nervous system has limited the application of nucleic acid therapeutics to patients. Here, we review the recent development of efficient non-viral nucleic acid delivery platforms, as applied to the nervous system, including the transfection vectors and carriers used, as well as matrices and scaffolds that are currently used. Additionally, we will discuss possible improvements for localised nucleic acid delivery.

Nanomedicines and gene therapy for the delivery of growth factors to improve perfusion and oxygenation in wound healing

Oxygen plays a key role in wound healing, and hypoxia is a major cause of wound healing impairment; therefore, treatments to improve hemodynamics and increase wound oxygenation are of particular interest for the treatment of chronic wounds. This article describes the roles of oxygen and angiogenesis in wound healing as well as the tools used to evaluate tissue oxygenation and perfusion and then presents a review of nanomedicines and gene therapies designed to improve perfusion and oxygenation and accelerate wound healing.

A review of genetic engineering biotechnologies for enhanced chronic wound healing

Traditional methods for addressing chronic wounds focus on correcting dysfunction by controlling extracellular elements. This review highlights technologies that take a different approach - enhancing chronic wound healing by genetic modification to wound beds. Featured cutaneous transduction/transfection methods include viral modalities (ie adenoviruses, adeno-associated viruses, retroviruses and lentiviruses) and conventional non-viral modalities (ie naked DNA injections, microseeding, liposomal reagents, particle bombardment and electroporation). Also explored are emerging technologies, focusing on the exciting capabilities of wound diagnostics such as pyrosequencing as well as site-specific nuclease editing tools such as CRISPR-Cas9 used to both transiently and permanently genetically modify resident wound bed cells. Additionally, new non-viral transfection methods (ie conjugated nanoparticles, multi-electrode arrays, and microfabricated needles and nanowires) are discussed that can potentially facilitate more efficient and safe transgene delivery to skin but also represent significant advances broadly to tissue regeneration research.

High Efficiency Low Cost Fibroblast Nucleofection for GMP Compatible Cell-based Gene Therapy

Background: Dermal fibroblast is a powerful tool for the study of ex vivo DNA delivery in development of both cell therapy and tissue engineering products. Using genetic modification, fibroblasts can be diversely adapted and made suitable for clinical gene therapy. In this study, we first compared several non-viral transfection methods including nucleofection in rat and human primary dermal fibroblast. In addition, the original protocol for nucleofection of primary mammalian fibroblasts was modified in order to achieve the highest possible transfection efficiency, as determined by flow cytometry analysis of the green fluorescent protein (GFP) expression. Results: the results showed that transfection performance of Dulbecco's Modified Eagle Medium (DMEM) supplemented with 10% Fetal Calf Serum (FCS) yielded the best transfection efficiency with rat dermal fibroblasts and ITS (insulin, transferrin, and sodium selenite solution) was comparable to the standard nucleofection solution for human dermal fibroblasts. Conclusion: Our results suggest a promising application of the modified nucleofection method for GMP compatible therapeutic translational medical 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.

Compromised Wound Healing in Ischemic Type 2 Diabetic Rats

Ischemia is one of the main epidemic factors and characteristics of diabetic chronic wounds, and exerts a profound effect on wound healing. To explore the mechanism of and the cure for diabetic impaired wound healing, we established a type 2 diabetic rat model. We used an 8weeks high fat diet (HFD) feeding regimen followed by multiple injections of streptozotocin (STZ) at a dose of 10mg/kg to induce Wister rat to develop type 2 diabetes. Metabolic characteristics were assessed at the 5th week after the STZ injections to confirm the establishment of diabetes mellitus on the rodent model. A bipedicle flap, with length to width ratio 1.5, was performed on the back of the rat to make the flap area ischemic. Closure of excisional wounds on this bipedicle flap and related physiological and pathological changes were studied using histological, immunohistochemical, real time PCR and protein immunoblot approaches. Our results demonstrated that a combination of HFD feeding and a low dose of STZ is capable of inducing the rats to develop type 2 diabetes with noticeable insulin resistance, persistent hyperglycemia, moderate degree of insulinemia, as well as high serum cholesterol and high triglyceride levels. The excision wounds on the ischemic double pedicle flap showed deteriorative healing features comparing with non-ischemic diabetic wounds, including: delayed healing, exorbitant wound inflammatory response, excessive and prolonged ROS production and excessive production of MMPs. Our study suggested that HFD feeding combined with STZ injection could induce type 2 diabetes in rat. Our ischemic diabetic wound model is suitable for the investigation of human diabetic related wound repair; especically for diabetic chronic wounds.

A Current View of Functional Biomaterials for Wound Care, Molecular and Cellular Therapies

The intricate process of wound healing involves activation of biological pathways that work in concert to regenerate a tissue microenvironment consisting of cells and external cellular matrix (ECM) with enzymes, cytokines, and growth factors. Distinct stages characterize the mammalian response to tissue injury: hemostasis, inflammation, new tissue formation, and tissue remodeling. Hemostasis and inflammation start right after the injury, while the formation of new tissue, along with migration and proliferation of cells within the wound site, occurs during the first week to ten days after the injury. In this review paper, we discuss approaches in tissue engineering and regenerative medicine to address each of these processes through the application of biomaterials, either as support to the native microenvironment or as delivery vehicles for functional hemostatic, antibacterial, or anti-inflammatory agents. Molecular therapies are also discussed with particular attention to drug delivery methods and gene therapies. Finally, cellular treatments are reviewed, and an outlook on the future of drug delivery and wound care biomaterials is provided.

Lentiviral-mediated overexpression of homeobox A4 by human umbilical cord mesenchymal stem cells repairs full-thickness skin defects

A number of types of stem cells have been shown to be effective in wound repair. In the present study the effect of homeobox A4 (HOXA4) overexpression by human umbilical cord mesenchymal stem cells (hUMSCs) on full‑thickness skin repair was evaluated. Isolated hUMSCs were transfected with a lentivirus expressing HOXA4 and cultured for 21 days. Expression of the epidermal cell‑specific markers, cytokeratins 14 and 18, was detected by immunohistochemistry and flow cytometry. Full‑thickness skin defects (1.5 cm x 1.5 cm) were made on the backs of 45 nude mice, which were randomly divided into the following three treatment groups: Collagen membrane with lenti‑HOXA4 hUMSC seed cells; collagen membrane with lentivirus expressing green fluorescent protein; and collagen membrane alone. On days 7, 14 and 21 following transplantation, tissue samples were harvested and examined by histology and western blot analysis. Flow cytometry showed that the transfection efficiency was 95.41% at a multiplicity of infection of 100, and that the lenti‑HOXA4 hUMSCs differentiated into epidermal cells, expressing cytokeratins 14 and 18. In addition, re‑epithelialization of wounds treated with lenti‑HOXA4 hUMSCs was significantly greater than that in the control groups in the first week. By week three the epidermis was significantly thicker in the lenti‑HOXA4 group than the control groups. Thus, transplantation of hUMSCs modified with Ad‑HOXA4 promoted wound healing.

Growth factors in wound healing: the present and the future?

Numerous clinical studies have confirmed the pivotal role growth factors play in wound healing and their diminished levels in the chronic wound. Despite promising early studies treating chronic wounds with growth factors, results with traditional bolus dosing of a single growth factor have yielded insignificant results. Disappointing results have been theorized to be the result of growth factors inherent short half-life, a hostile microenvironment rich in protease activity, and poor delivery mechanisms failing to deliver effective dosages in an appropriate temporal manner. Advances in tissue engineering and regenerative medicine have provided technologies capable of delivering multiple growth factors in a spatially oriented approach. These technologies include polymer systems, scaffolds, and hydrogels that have demonstrated improved response by target tissues when growth factors are delivered in this biomimetic fashion. With improved delivery systems, treatment of chronic wounds with growth factors has the potential to accelerate healing in a manner not previously realized with traditional delivery approaches.

A comprehensive review of advanced biopolymeric wound healing systems

Wound healing is a complex and dynamic process that involves the mediation of many initiators effective during the healing process such as cytokines, macrophages and fibroblasts. In addition, the defence mechanism of the body undergoes a step-by-step but continuous process known as the wound healing cascade to ensure optimal healing. Thus, when designing a wound healing system or dressing, it is pivotal that key factors such as optimal gaseous exchange, a moist wound environment, prevention of microbial activity and absorption of exudates are considered. A variety of wound dressings are available, however, not all meet the specific requirements of an ideal wound healing system to consider every aspect within the wound healing cascade. Recent research has focussed on the development of smart polymeric materials. Combining biopolymers that are crucial for wound healing may provide opportunities to synthesise matrices that are inductive to cells and that stimulate and trigger target cell responses crucial to the wound healing process. This review therefore outlines the processes involved in skin regeneration, optimal management and care required for wound treatment. It also assimilates, explores and discusses wound healing drug-delivery systems and nanotechnologies utilised for enhanced wound healing applications.

A CMP-based method for tunable, cell-mediated gene delivery from collagen scaffolds

Collagen mimetic peptides (CMP)s were used to tailor release vs. retention of DNA polyplexes from collagen while preserving polyplex activity.

Wound coverage technologies in burn care: novel techniques

Improvements in burn wound care have vastly decreased morbidity and mortality in severely burned patients. Development of new therapeutic approaches to increase wound repair has the potential to reduce infection, graft rejection, and hypertrophic scarring. The incorporation of tissue-engineering techniques, along with the use of exogenous proteins, genes, or stem cells to enhance wound healing, heralds new treatment regimens based on the modification of already existing biological activity. Refinements to surgical techniques have enabled the creation of protocols for full facial transplantation. With new technologies and advances such as these, care of the severely burned will undergo massive changes over the next decade. This review centers on new developments that have recently shown great promise in the investigational arena.

The effects of adenoviral transfection of the keratinocyte growth factor gene on epidermal stem cells: an in vitro study

Epidermal stem cells (ESCs) are characterized as slowcycling, multi-potent, and self-renewing cells that not only maintain somatic homeostasis but also participate in tissue regeneration and repair. To examine the feasibility of adenoviral vector-mediated keratinocyte growth factor (KGF) gene transfer into in vitro-expanded ESCs, ESCs were isolated from samples of human skin, cultured in vitro, and then transfected with recombinant adenovirus (Ad) carrying the human KGF gene (AdKGF) or green fluorescent protein gene (AdGFP). The effects of KGF gene transfer on cell proliferation, cell cycle arrest, cell surface antigen phenotype, and β-catenin expression were investigated. Compared to ESCs transfected with AdGFP, AdKGFtransfected ESCs grew well, maintained a high proliferative capacity in keratinocyte serum-free medium, and expressed high levels of β-catenin. AdKGF infection increased the number of ESCs in the G0/G1 phase and promoted ESCs entry into the G2/M phase, but had no effect on cell surface antigen phenotype (CD49f(+)/CD71(-)). The results suggest that KGF gene transfer can stimulate ESCs to grow and undergo cell division, which can be applied to enhance cutaneous wound healing.

Topical secretoneurin gene therapy accelerates diabetic wound healing by interaction between heparan-sulfate proteoglycans and basic FGF

Diabetic foot ulcers represent a therapeutic problem of high clinical relevance. Reduced vascular supply, neuropathy and diminished expression of growth factors strongly contribute to wound healing impairment in diabetes. Secretoneurin, an angiogenic neuropeptide, has been shown to improve tissue perfusion in different animal models by increasing the amount of vessels in affected areas. Therefore, topical secretoneurin gene therapy was tested in a full thickness wound healing model in diabetic db/db mice. Secretoneurin significantly accelerated wound closure in these mice and immunohistochemistry revealed higher capillary and arteriole density in the wounded area compared to control mice. In-vitro, the mechanism of action of secretoneurin on human dermal microvascular endothelial cells was evaluated in normal and diabetic cells. Secretoneurin shows positive effects on in vitro angiogenesis, proliferation and apoptosis of these cells in a basic fibroblast growth factor dependent manner. A small molecular weight inhibitor revealed fibroblast growth factor receptor 3 as the main receptor for secretoneurin mediated effects. Additionally, we could identify heparan-sulfates as important co-factor of secretoneurin induced binding of basic fibroblast growth factor to human dermal endothelial cells. We suggest topical secretoneurin plasmid therapy as new tool for delayed wound healing in patients suffering from diabetes.

The role of gene therapy in regenerative surgery: updated insights

BACKGROUND

In the past two decades, regenerative surgeons have focused increasing attention on the potential of gene therapy for treatment of local disorders and injuries. Gene transfer techniques may provide an effective local and short-term induction of growth factors without the limits of other topical therapies. In 2002, Tepper and Mehrara accurately reviewed the topic: given the substantial advancement of research on this issue, an updated review is provided.

METHODS

Literature indexed in the National Center for Biotechnology Information database (PubMed) has been reviewed using variable combinations of keywords ("gene therapy," "regenerative medicine," "tissue regeneration," and "gene medicine"). Articles investigating the association between gene therapies and local pathologic conditions have been considered. Attention has been focused on articles published after 2002. Further literature has been obtained by analysis of references listed in reviewed articles.

RESULTS

Gene therapy approaches have been successfully adopted in preclinical models for treatment of a large variety of local diseases affecting almost every type of tissue. Experiences in abnormalities involving skin (e.g., chronic wounds, burn injuries, pathologic scars), bone, cartilage, endothelia, and nerves have been reviewed. In addition, the supporting role of gene therapies to other tissue-engineering approaches has been discussed. Despite initial reports, clinical evidence has been provided only for treatment of diabetic ulcers, rheumatoid arthritis, and osteoarthritis.

CONCLUSIONS

Translation of gene therapy strategies into human clinical trials is still a lengthy, difficult, and expensive process. Even so, cutting-edge gene therapy-based strategies in reconstructive procedures could soon set valuable milestones for development of efficient treatments in a growing number of local diseases and injuries.

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.

Pseudotyped adeno-associated viral vector tropism and transduction efficiencies in murine wound healing

Cell specific gene transfer and sustained transgene expression are goals of cutaneous gene therapy for tissue repair and regeneration. Adeno-associated virus serotype 2 (AAV2/2) mediated gene transfer to the skin results in stable transgene expression in the muscle fascicles of the panniculus carnosus in mice, with minimal gene transfer to the dermal or epidermal elements. We hypothesized that pseudotyped AAV vectors may have a unique and characteristic tropism and transduction efficiency profile for specific cells in the cutaneous wounds. We compared transduction efficiencies of cells in the epidermis, cells in the dermis, and the fascicles of the panniculus carnosus by AAV2/2 and three pseudotyped AAV vectors, AAV2/5, AAV2/7, and AAV2/8 in a murine excisional wound model. AAV2/5 and AAV2/8 result in significantly enhanced transduction of cells both in the epidermis and the dermis compared to AAV2/2. AAV2/5 transduces both the basilar and supra-basilar keratinocytes. In contrast, AAV2/8 transduces mainly supra-basilar keratinocytes. Both AAV2/7 and AAV2/8 result in more efficient gene transfer to the muscular panniculus carnosus compared to AAV2/2. The capsid of the different pseudotyped AAV vectors produces distinct tropism and efficiency profiles in the murine wound healing model. Both AAV2/5 and AAV2/8 administration result in significantly enhanced gene transfer. To further characterize cell specific transduction and tropism profiles of the AAV pseudotyped vectors, we performed in vitro experiments using human and mouse primary dermal fibroblasts. Our data demonstrate that pseudotyping strategy confers a differential transduction of dermal fibroblasts, with higher transduction of both human and murine cells by AAV2/5 and AAV2/8 at early and later time points. At later time points, AAV2/2 demonstrates increased transduction. Interestingly, AAV2/8 appears to be more efficacious in transducing human cells as compared to AAV2/5. The pseudotype-specific pattern of transduction and tropism observed both in vivo and in vitro suggests that choice of AAV vectors should be based on the desired target cell and the timing of transgene expression in wound healing for gene transfer therapy in dermal wounds.

Harnessing growth factors to influence wound healing

Cutaneous wound healing is a dynamic process with the ultimate goal of restoring skin integrity. On injury to the skin, inflammatory cells, endothelial cells, fibroblasts, and keratinocytes undergo changes in gene expression and phenotype, leading to cell proliferation, migration, and differentiation. Cytokines and growth factors play an essential role in initiating and directing the phases of wound healing. These signaling peptides are produced by a variety of cells and lead to a concerted effort to restore the skin barrier function.

Hypoxia inducible microRNA 210 attenuates keratinocyte proliferation and impairs closure in a murine model of ischemic wounds

Ischemia complicates wound closure. Here, we are unique in presenting a murine ischemic wound model that is based on bipedicle flap approach. Using this model of ischemic wounds we have sought to elucidate how microRNAs may be implicated in limiting wound re-epithelialization under hypoxia, a major component of ischemia. Ischemia, evaluated by laser Doppler as well as hyperspectral imaging, limited blood flow and lowered tissue oxygen saturation. EPR oximetry demonstrated that the ischemic wound tissue had pO(2) <10 mm Hg. Ischemic wounds suffered from compromised macrophage recruitment and delayed wound epithelialization. Specifically, epithelial proliferation, as determined by Ki67 staining, was compromised. In vivo imaging showed massive hypoxia inducible factor-1alpha (HIF-1alpha) stabilization in ischemic wounds, where HIF-1alpha induced miR-210 expression that, in turn, silenced its target E2F3, which was markedly down-regulated in the wound-edge tissue of ischemic wounds. E2F3 was recognized as a key facilitator of cell proliferation. In keratinocytes, knock-down of E2F3 limited cell proliferation. Forced stabilization of HIF-1alpha using Ad-VP16- HIF-1alpha under normoxic conditions up-regulated miR-210 expression, down-regulated E2F3, and limited cell proliferation. Studies using cellular delivery of miR-210 antagomir and mimic demonstrated a key role of miR-210 in limiting keratinocyte proliferation. In summary, these results are unique in presenting evidence demonstrating that the hypoxia component of ischemia may limit wound re-epithelialization by stabilizing HIF-1alpha, which induces miR-210 expression, resulting in the down-regulation of the cell-cycle regulatory protein E2F3.

Placental gene transfer: transgene screening in mice for trophic effects on the placenta

OBJECTIVE

We hypothesized that gene transfer of select growth factors to the placenta may enhance placental and fetal growth. Thus, we examined the effect of 8 growth factor transgenes on murine placenta.

STUDY DESIGN

Adenoviral-mediated site-specific intraplacental gene transfer of 8 different growth factor transgenes at embryonic day (e) 14 was performed. Transgenes included angiopoietin-1, angiopoietin-2 (Ang-2), basic fibroblast growth factor, hepatocyte growth factor, insulin-like growth factor-1 (IGF-1), placenta growth hormone, platelet-derived growth factor-B (PDGF-B), and vascular endothelial growth factor(121). Fetuses and placentas were harvested at e17 and assessed for survival, gene transfer efficiency, placenta area, and fetal and placental weights.

RESULTS

Efficient gene transfer to the placenta was detected with minimal dissemination to the fetus. Overexpression of IGF-1, PDGF-B, and Ang-2 resulted in an increase in placenta cross-sectional area. Only Ang-2 gene transfer resulted in increased fetal weight, and only Ang-2 and basic fibroblast growth factor resulted in a change in placental weight.

CONCLUSION

Site-specific placental gene transfer results in efficient gene transfer with minimal dissemination to the fetus. Adenoviral-mediated IGF-1, adenoviral-mediated PDGF-B, and adenoviral-mediated Ang-2 significantly increase placenta growth.

Accelerated adhesion of grafted skin by laser-induced stress wave-based gene transfer of hepatocyte growth factor

Gene therapy using wound healing-associated growth factor gene has received much attention as a new strategy for improving the outcome of tissue transplantation. We delivered plasmid DNA coding for human hepatocyte growth factor (hHGF) to rat free skin grafts by the use of laser-induced stress waves (LISWs); autografting was performed with the grafts. Systematic analysis was conducted to evaluate the adhesion properties of the grafted tissue; angiogenesis, cell proliferation, and reepithelialization were assessed by immunohistochemistry, and reperfusion was measured by laser Doppler imaging as a function of time after grafting. Both the level of angiogenesis on day 3 after grafting and the increased ratio of blood flow on day 4 to that on day 3 were significantly higher than those in five control groups: grafting with hHGF gene injection alone, grafting with control plasmid vector injection alone, grafting with LISW application alone, grafting with LISW application after control plasmid vector injection, and normal grafting. Reepithelialization was almost completed on day 7 even at the center of the graft with LISW application after hHGF gene injection, while it was not for the grafts of the five control groups. These findings demonstrate the validity of our LISW-based HGF gene transfection to accelerate the adhesion of grafted skins.

Single subcutaneous administration of RGDK-lipopeptide:rhPDGF-B gene complex heals wounds in streptozotocin-induced diabetic rats

Development of effective therapeutics for chronic wounds remains a formidable clinical challenge. Deficiency of growth factors is of paramount importance among the multitude of factors contributing to the pathogenesis of diabetic wounds. Clinical interest has been witnessed in the past for exogenous applications of platelet derived growth factor B (PDGF-B) in chronic nonhealing wounds. However, accomplishing even modest favorable clinical effects in such topical applications requires large and repeated doses of PDGF-B proteins. Chronic wounds are being increasingly circumvented by gene therapy approach and to this end, cationic liposomes are emerging as promising nonviral carriers for delivering various growth factors encoding therapeutic genes to wound beds. However, as in case of topical application of growth factors, all the prior studies on the use of cationic liposomes in nonviral gene therapy of wounds involved repeated injections of cationic liposome:cDNA complexes over several weeks for ensuring complete wound healing. Herein, we show that a single subcutaneous administration of an electrostatic complex of rhPDGF-B plasmid, integrin receptor selective RGDK-lipopeptide 1 and cholesterol (as auxiliary lipid) is capable of healing wounds in streptozotocin-induced diabetic Sprague-Dawley rats (as model of chronic wounds). Western blot analysis revealed significant expression of rhPDGF-B in mouse fibroblast cells transfected with RGDK-lipopeptide 1:rhPDGF-B lipoplex. The transfection efficiencies of the RGDK-lipopeptide 1 in mouse and human fibroblast cells preincubated with various monoclonal anti-integrin receptor antibodies support the notion that the cellular uptake of the RGDK-lipopeptide 1:DNA complexes in fibroblast cells is likely to be selectively mediated by alpha5beta1 integrin receptors. Findings in the histopathological stainings using both hematoxylin and eosin (H & E) as well as Masson's Trichrome staining revealed a significantly higher degree of epithelization, keratization, fibrocollagenation and blood vessel formation in rats treated with RGDK-lipopeptide 1:rhPDGF compared to those in rats treated with vehicle alone.

Fibrin scaffold promotes adenoviral gene transfer and controlled vector delivery

Gene therapy using adenoviral vectors in tissue regeneration is hindered by a short duration of transgene expression. It is hypothesized that a fibrin scaffold will enhance delivery of the adenovirus to a wound site, precluding the need for high repeated doses. It was aimed to analyze whether fibrin could deliver a low single dose of viral vector to a wound site, without compromising transfection efficiency. Fibrin scaffold containing adenovirus encoding beta-galactosidase, fibrin alone, adenovirus alone, and no treatment groups were applied to a rabbit ear ulcer model. beta-Galactosidase transgene expression was measured at 7 and 14 days. Transgene expression was enhanced in the fibrin containing adenovirus group at 7 days. By 14 days, there was low expression and no difference between groups. Stereological methods assessing wound healing aimed to determine whether the adenovirus capsid elicited an unfavorable inflammatory response and whether fibrin's beneficial properties were altered by addition of adenovirus. The fibrin adenovirus group showed a wound-healing response similar to fibrin alone, showing maximum cellularity and angiogenesis at 7 days. By 14 days, cellularity and angiogenesis subsided, and this effect was not inhibited by the presence of adenovirus. Adenovirus alone did not cause an unfavorable inflammatory response. It is concluded the fibrin aids in the delivery of a low-dose viral vector, thereby avoiding a chronic inflammatory response, and allowing superior transfection than viral vector alone. This has wide-ranging implications on the use of viral vectors in tissue engineering.

Fibroblast Growth Factor-2 regulates proliferation of cardiac myocytes in normal and hypoplastic left ventricles in the developing chick

The developing heart increases its mass predominantly by increasing the number of contained cells through proliferation. We hypothesized that addition of fibroblast growth factor-2, a factor previously shown to stimulate division of the embryonic myocytes, to the left ventricular myocardium in an experimental model of left heart hypoplasia created in the chicken would attenuate phenotypic severity by increasing cellular proliferation. We have established an effective mode of delivery of fibroblast growth factor-2 to the chick embryonic left ventricular myocardium by using adenovirus vectors, which was more efficient and better tolerated than direct injection of recombinant fibroblast growth factor-2 protein. Injection of control adenovirus expressing green fluorescent protein did not result in significant alterations in myocytic proliferation or cell death compared with intact, uninjected, controls. Co-injection of adenoviruses expressing green fluorescent protein and fibroblast growth factor-2 was used for verification of positive injection, and induction of proliferation, respectively. Treatment of both normal and hypoplastic left ventricles with fibroblast growth factor-2 expressing adenovirus resulted in to 2 to 3-fold overexpression of fibroblast growth factor-2, as verified by immunostaining. An increase by 45% in myocytic proliferation was observed following injection of normal hearts, and an increase of 39% was observed in hypoplastic hearts. There was a significant increase in anti-myosin immunostaining in the hypoplastic, but not the normal hearts. We have shown, therefore, that expression of exogenous fibroblast growth factor-2 in the late embryonic heart can exert direct effects on cardiac myocytes, inducing both their proliferation and differentiation. These data suggest potential for a novel therapeutic option in selected cases of congenital cardiac disease, such as hypoplastic left heart syndrome.

Characterization of a preclinical model of chronic ischemic wound

Chronic ischemic wounds presenting at wound clinics are heterogeneous with respect to etiology, age of the wound, and other factors complicating wound healing. In addition, there are ethical challenges associated with collecting repeated biopsies from a patient to develop an understanding of the temporal dynamics of the mechanisms underlying chronic wounds. The need for a preclinical model of ischemic wound is therefore compelling. The porcine model is widely accepted as an excellent preclinical model for human wounds. A full-thickness bipedicle flap approach was adopted to cause skin ischemia. Closure of excisional wounds placed on ischemic tissue was severely impaired resulting in chronic wounds. Histologically, ischemic wounds suffered from impaired re-epithelialization, delayed macrophage recruitment and poorer endothelial cell abundance and organization. Compared with the pair-matched nonischemic wound, unique aspects of the ischemic wound biology were examined on days 3, 7, 14, and 28 by systematic screening of the wound tissue transcriptome using high-density porcine GeneChips. Ischemia markedly potentiated the expression of arginase-1, a cytosolic enzyme that metabolizes the precursor of nitric oxide l-arginine. Ischemia also induced the SOD2 in the wound tissue perhaps as survival response of the challenged tissue. Human chronic wounds also demonstrated elevated expression of SOD2 and arginase-1. This study provides a thorough database that may serve as a valuable reference tool to develop novel hypotheses aiming to elucidate the biology of ischemic chronic wounds in a preclinical setting.

Promotion of incisional wound repair by human mesenchymal stem cell transplantation

The purpose of this study was to determine the effect of transplanted human mesenchymal stem cells (hMSCs) on wound healing. In this model, full-thickness cutaneous wounds were created by incision in the skin of adult New Zealand white rabbits and treated by transplanted hMSCs into the wounds. Wound healing was evaluated by histological analysis and tensiometry over time. A total of 15 New Zealand white rabbits with 10 wounds per animal were examined in this study. Animals were treated with hMSCs and euthanised at 3, 7, 14, 21 and 80 days after manipulation. The hMSCs were labelled with a fluorescent dye (CM-DiI), suspended in phosphate-buffered saline and used to treat full-thickness incisional wounds in rabbit skin. Tensiometry and histology were used to characterise the wound-healing rate of the incisional wounds. These results showed that transplanted hMSCs significantly inhibited scar formation and increased the tensile strength of the wounds. Importantly, MSCs from genetically unrelated donors did not appear to induce an immunologic response. In conclusion, human mesenchymal stem cell therapy is a viable approach to significantly affect the course of normal cutaneous wound healing and significantly increase the tensile strength.

A review of gene and stem cell therapy in cutaneous wound healing

Different therapies that effect wound repair have been proposed over the last few decades. This article reviews the emerging fields of gene and stem cell therapy in wound healing. Gene therapy, initially developed for treatment of congenital defects, is a new option for enhancing wound repair. In order to accelerate wound closure, genes encoding for growth factors or cytokines showed the greatest potential. The majority of gene delivery systems are based on viral transfection, naked DNA application, high pressure injection, or liposomal vectors. Embryonic and adult stem cells have a prolonged self-renewal capacity with the ability to differentiate into various tissue types. A variety of sources, such as bone marrow, peripheral blood, umbilical cord blood, adipose tissue, skin and hair follicles, have been utilized to isolate stem cells to accelerate the healing response of acute and chronic wounds. Recently, the combination of gene and stem cell therapy has emerged as a promising approach for treatment of chronic and acute wounds.

Stromal progenitor cell therapy corrects the wound-healing defect in the ischemic rabbit ear model of chronic wound repair

Chronic wounds create a formidable clinical problem resulting in considerable morbidity and healthcare expenditure. The etiology for wound healing impairment appears to be multifactorial; however, ischemia is a common factor in most types of chronic wounds. Ideal therapy for such wounds would be to correct deficiencies in growth factors and matrix components and provide cellular precursors required for timely wound closure. We hypothesized that stromal progenitor cell (SPC) therapy could correct the ischemic wound-healing defect through both direct and indirect mechanisms. To test this hypothesis, we used the ischemic rabbit ear model of chronic wound healing. We found that treatment of the wounds with SPCs was able to reverse the ischemic wound-healing impairment, with improved granulation tissue formation and reepithelialization compared with vehicle or bone marrow mononuclear cell controls. In vitro, SPCs were found to produce factors involved in angiogenesis and reepithelialization, and extracellular matrix components, providing evidence for both direct and indirect mechanisms for the observed correction of the healing impairment in these wounds. Treatment of ischemic wounds with SPCs can dramatically improve wound healing and provides a rationale for further studies focused on SPCs as a potential cellular therapy in impaired wound healing.

IL-10 overexpression decreases inflammatory mediators and promotes regenerative healing in an adult model of scar formation

Adult wound healing is characterized by an exuberant inflammatory response and scar formation. In contrast, scarless fetal wound healing has diminished inflammation, a lack of fibroplasia, and restoration of normal architecture. We have previously shown that fetal wounds produce less inflammatory cytokines, and the absence of IL-10, an anti-inflammatory cytokine, results in fetal scar formation. We hypothesized that increased IL-10 would decrease inflammation and create an environment conducive for regenerative healing in the adult. To test this hypothesis, a lentiviral vector expressing IL-10 and green fluorescent protein (GFP) (Lenti-IL-10) or GFP alone (Lenti-GFP) was injected at the wound site 48 hours before wounding. We found that both Lenti-IL-10 and Lenti-GFP were expressed in the wounds at 1 and 3 days post wounding. At 3 days, Lenti-IL-10-treated wounds demonstrated decreased inflammation and decreased quantities of all proinflammatory mediators analyzed with statistically different levels of IL-6, monocyte chemoattractant protein-1, and heat-shock protein 47. At 3 weeks, Lenti-GFP wounds demonstrated scar formation. In contrast, wounds injected with Lenti-IL-10 demonstrated decreased inflammation, a lack of abnormal collagen deposition, and restoration of normal dermal architecture. We conclude that lentivirus-mediated overexpression of IL-10 decreases the inflammatory response to injury, creating an environment conducive for regenerative adult wound healing.

Becaplermin gel in the treatment of diabetic neuropathic foot ulcers

Diabetic foot ulcers remain a major cause of morbidity. Significant progress has been accomplished in ulcer healing by improved management of both ischemia and neuropathy in the diabetic foot. Nevertheless, there is a vital need for further improvement. Becaplermin gel represents an important therapeutic advance for diabetic neuropathic foot ulcers with adequate blood supply. Randomized controlled trials have shown that it is effective in increasing healing rates. However, this efficacy has not translated to positive clinical experience, and the drug is not widely used. Moreover, becaplermin is an expensive medication. Even though it has repeatedly been estimated as cost-effective, its high cost may be prohibitive for some clinicians, especially in developing countries. Clearly, further work is needed to clarify whether use of becaplermin is justified in everyday clinical practice. Future research also needs to assess the potential room for improvement with becaplermin, for instance by combination with other growth factors or by exploring alternative modes of drug delivery.

Collagen membranes loaded with collagen-binding human PDGF-BB accelerate wound healing in a rabbit dermal ischemic ulcer model

Studies have shown that exogenous platelet-derived growth factor-BB (PDGF-BB) could accelerate the ulcer healing, but the lack of efficient growth factor delivery system limits its clinical application. Our previous work has demonstrated that the native human PDGF-BB was added a collagen-binding domain (CBD), TKKTLRT, to develop a collagen-based PDGF targeting delivery system. Here, we showed that this CBD-fused PDGF-BB (CBD-PDGF) could bind to collagen membrane efficiently. We used the rabbit dermal ischemic ulcer model to study the effects of CBD-PDGF loaded on collagen membranes. Results revealed that this system maintained a higher concentration and stronger bioactivity of PDGF-BB on the collagen membranes and promoted the re-epithelialization of dermal ulcer wounds, the collagen deposition, and the formation of capillary lumens within the newly formed tissue area. It demonstrated that collagen membranes loaded with collagen-targeting human PDGF-BB could effectively promote ulcer healing.

Growth factors in the treatment of diabetic foot ulcers: new technologies, any promises?

Foot ulcers remain a common problem, leading to increased morbidity in patients with diabetes. Despite the progress that has been achieved in revascularization techniques as well as in off-loading to relieve high-pressure areas, diabetic foot wounds remain a clinical challenge. Growth factors are a major technological advance that promised to change the face of wound healing. The most important of growth factors are recombinant human platelet-derived growth factor-BB and granulocyte colony-stimulating factor. The former has been approved by the FDA for the treatment of neuropathic ulcers when there is adequate blood supply. The latter is less demonstrably useful. Advances include methods of delivering growth factors.

Preparation and evaluation of gene-transfected cultured skin as a novel drug delivery system for severely burned skin

PURPOSE

The purpose of this study is to prepare and evaluate gene-transfected cultured skin to establish a dermal patch consisting of cultured skin as a new and novel delivery system for severely burned skin.

MATERIALS AND METHODS

Plasmid DNA encoding the green fluorescent protein (GFP) gene was used as a model gene and transfected to rat and human cultured dermis models (CDMs) using the hemagglutinating virus of Japan envelope vector (HVJ-E) to prepare gene-transfected CDM and evaluate GFP expression in the CDM. Two kinds of transfection methods were evaluated. In pre-transfection, the gene was first transfected into fibroblasts and then CDM was prepared using these gene-transfected cells. In post-transfection, the gene was transfected directly into CDM.

RESULTS

GFP expression was observed in both the pre- and post-transfected CDMs. The post-transfection method showed higher GFP expression in the CDM than pre-transfection, although no statistically significant difference was observed. The cell viability of these transfected CDMs was also examined with MTT assay. Slight decrease in viability was observed in these transfected CDMs. These methods could be useful in preparing gene-transfected cultured skins with low cell damage.

CONCLUSION

Gene transfection to cultured skin may produce several dermal patches that release potent endogenous bioactive peptides.

Effect of adenoviral mediated overexpression of fibromodulin on human dermal fibroblasts and scar formation in full-thickness incisional wounds

Fibromodulin, a member of the small leucine-rich proteoglycan family, has been recently suggested as a biologically significant mediator of fetal scarless repair. To assess the role of fibromodulin in the tissue remodeling, we constructed an adenoviral vector expressing human fibromodulin cDNA. We evaluated the effect of adenovirus-mediated overexpression of fibromodulin in vitro on transforming growth factors and metalloproteinases in fibroblasts and in vivo on full-thickness incisional wounds in a rabbit model. In vitro, we found that Ad-Fibromodulin induced a decrease of expression of TGF-beta(1) and TGF-beta(2) precursor proteins, but an increase in expression of TGF-beta(3) precursor protein and TGF-beta type II receptor. In addition, fibromodulin overexpression resulted in decreased MMP-1 and MMP-3 protein secretion but increased MMP-2, TIMP-1, and TIMP-2 secretion, whereas MMP-9 and MMP-13 were not influenced by fibromodulin overexpression. In vivo evaluation by histopathology and tensile strength demonstrated that Ad-Fibromodulin administration could ameliorate wound healing in incisional wounds. In conclusion, although the mechanism of scar formation in adult wounds remains incompletely understood, we found that fibromodulin overexpression improves wound healing in vivo, suggesting that fibromodulin may be a key mediator in reduced scarring.

Gene therapy and wound healing

Wound repair involves the sequential interaction of various cell types, extracellular matrix molecules, and soluble mediators. During the past 10 years, much new information on signals controlling wound cell behavior has emerged. This knowledge has led to a number of novel therapeutic strategies. In particular, the local delivery of pluripotent growth factor molecules to the injured tissue has been intensively investigated over the past decade. Limited success of clinical trails indicates that a crucial aspect of the growth factor wound healing strategy is the effective delivery of these polypeptides to the wound site. A molecular approach in which genetically modified cells synthesize and deliver the desired growth factor in regulated fashion has been used to overcome the limitations associated with the (topical) application of recombinant growth factor proteins. We have summarized the molecular and cellular basis of repair mechanisms and their failure, and we give an overview of techniques and studies applied to gene transfer in tissue repair.

Gene-modified tissue-engineered skin: the next generation of skin substitutes

Tissue engineering combines the principles of cell biology, engineering and materials science to develop three-dimensional tissues to replace or restore tissue function. Tissue engineered skin is one of most advanced tissue constructs, yet it lacks several important functions including those provided by hair follicles, sebaceous glands, sweat glands and dendritic cells. Although the complexity of skin may be difficult to recapitulate entirely, new or improved functions can be provided by genetic modification of the cells that make up the tissues. Gene therapy can also be used in wound healing to promote tissue regeneration or prevent healing abnormalities such as formation of scars and keloids. Finally, gene-enhanced skin substitutes have great potential as cell-based devices to deliver therapeutics locally or systemically. Although significant progress has been made in the development of gene transfer technologies, several challenges have to be met before clinical application of genetically modified skin tissue. Engineering challenges include methods for improved efficiency and targeted gene delivery; efficient gene transfer to the stem cells that constantly regenerate the dynamic epidermal tissue; and development of novel biomaterials for controlled gene delivery. In addition, advances in regulatable vectors to achieve spatially and temporally controlled gene expression by physiological or exogenous signals may facilitate pharmacological administration of therapeutics through genetically engineered skin. Gene modified skin substitutes are also employed as biological models to understand tissue development or disease progression in a realistic three-dimensional context. In summary, gene therapy has the potential to generate the next generation of skin substitutes with enhanced capacity for treatment of burns, chronic wounds and even systemic diseases.

Gene therapy in wound healing: present status and future directions

Gene therapy was traditionally considered a treatment modality for patients with congenital defects of key metabolic functions or late-stage malignancies. The realization that gene therapy applications were much vaster has opened up endless opportunities for therapeutic genetic manipulations, especially in the skin and external wounds. Cutaneous wound healing is a complicated, multistep process with numerous mediators that act in a network of activation and inhibition processes. Gene delivery in this environment poses a particular challenge. Numerous models of gene delivery have been developed, including naked DNA application, viral transfection, high-pressure injection, liposomal delivery, and more. Of the various methods for gene transfer, cationic cholesterol-containing liposomal constructs are emerging as a method with great potential for non-viral gene transfer in the wound. This article aims to review the research on gene therapy in wound healing and possible future directions in this exciting field.

[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.

Biomimetic approaches to protein and gene delivery for tissue regeneration

Novel therapeutic strategies that promote wound healing seek to mimic the response of the body to wounding, to regenerate rather than repair injured tissues. Many synthetic or natural biomaterials have been developed for this purpose and are used to deliver wound therapeutics in a controlled manner that prevents unwanted and potentially harmful side-effects. Here, we review the natural and synthetic biomaterials that have been developed for protein and gene delivery to enhance tissue regeneration. Particular emphasis is placed on novel biomimetic materials that respond to environmental stimuli or release their cargo according to cellular demand. Engineering biomaterials to release therapeutic agents in response to physiologic signals mimics the natural healing process and can promote faster tissue regeneration and reduce scarring in severe acute or chronic wounds.

PDGF Gene Therapy Enhances Expression of VEGF and bFGF Genes and Activates the NF-??B Gene in Signal Pathways in Ischemic Flaps

BACKGROUND

Gene therapy is a novel approach for enhancing the viability of ischemic flaps. Expression of growth factor genes pertinent to angiogenesis and activation of genes of relevant signal pathways are imperative for improving flap viability. The authors investigated the gene expression profiles of growth factors and signal transduction pathways in ischemic flaps after PDGF gene therapy.

METHODS

Twenty Sprague-Dawley rats were divided into two groups. The experimental group (n = 10) received the plasmid vector containing the PDGF cDNA injected into the dermis of the flap area, whereas the control group (n = 10) received the physiologic saline. Seven days later, a dorsal random flap was raised. Seven days after surgery, flap viability was assessed, and expression of VEGF, bFGF, TGF-beta1, NF-kappaB, Erk2, Stat1, and Smad2 genes of the NF-kappaB, MAPK, JAK-STAT, and Smad pathways was assessed by quantitative analysis of the products of reverse-transcriptase polymerase chain reaction.

RESULTS

Transfer of exogenous PDGF gene significantly improved flap viability (p = 0.011). Levels of expression of VEGF and bFGF genes in the flap were significantly elevated after PDGF gene transfer (p = 0.0001 and p = 0.001, respectively). Expression of the NF-kappaB gene was significantly elevated (p = 0.041). In contrast, expression of TGF-beta1, and Erk2, Stat1, and Smad2 genes was not changed.

CONCLUSIONS

Transfer of exogenous PDGF gene to ischemic flaps promotes expression of VEGF and bFGF genes and activation of NF-kappaB gene in addition to its effects on the PDGF gene. The finding implies that transfer of the gene of one growth factor ultimately improves the expression of the genes of multiple growth factors. Activation of the NF-kappaB gene suggests that the NF-kappaB pathway may be important in enhancement of flap viability and will likely be a target of future efforts of regulation of signaling process in treatment of ischemic flaps.

The cell based dressing with living allogenic keratinocytes in the treatment of foot ulcers: a case study

In this study, we aimed to investigate the efficacy of cell based dressing with living allogenic keratinocytes in diabetic foot patients. To address this issue, the cultured keratinocytes were attached to the microcarriers produced from polyethylene and silica. The microcarriers were then applied to the wounds at 3-day intervals. Forty patients with grade II and III diabetic foot ulcers were included into the study. The patients were randomised into two groups (n=20). The treatment and control groups received cell based dressing and microcarriers kept in culture medium overnight, respectively. The wound size was recorded at 3 days intervals. The wounds were also categorised by a specific scoring system considering the wound contraction, granulation tissue formation, epithelisation and discharge from the wounds. The high score indicates better condition. The mean reduction of the wound area was 92% in the treatment group and 32% in the control group at the end of the 30 days treatment (p<0.001). When considered the complete healing, the mean number of dressings was 9.2+/-3.2 in the treatment group whereas it was 16.5+/-2.3 in the control group (p<0.001). The initial mean score of the treatment and control groups were 2.5 and 2.35, respectively. At the end of the 30th day, the mean score of the treatment group was 17.15+/-2.7 and of control group was 9.05+/-3. Allogenic keratinocyte treatment delivered with microcarriers can make significant contributions to wound healing in diabetic foot patients.