Therapeutic gene delivery to the skin

Highly branched poly(β-amino ester)s for gene delivery in hereditary skin diseases

Non-viral gene therapy for hereditary skin diseases is an attractive prospect. However, research efforts dedicated to this area are rare. Taking advantage of the branched structural possibilities of polymeric vectors, we have developed a gene delivery platform for the treatment of an incurable monogenic skin disease - recessive dystrophic epidermolysis bullosa (RDEB) - based on highly branched poly(β-amino ester)s (HPAEs). The screening of HPAEs and optimization of therapeutic gene constructs, together with evaluation of the combined system for gene transfection, were comprehensively reviewed. The successful restoration of type VII collagen (C7) expression both in vitro and in vivo highlights HPAEs as a promising generation of polymeric vectors for RDEB gene therapy into the clinic. Considering that the treatment of patients with genetic cutaneous disorders, such as other subtypes of epidermolysis bullosa, pachyonychia congenita, ichthyosis and Netherton syndrome, remains challenging, the success of HPAEs in RDEB treatment indicates that the development of viable polymeric gene delivery vectors could potentially expedite the translation of gene therapy for these diseases from bench to bedside.

Effects of chemical and physical enhancement techniques on transdermal delivery of 3-fluoroamphetamine hydrochloride

The present study investigated the passive transdermal delivery of 3-fluoroamphetamine hydrochloride (PAL-353) and evaluated the effects of chemical and physical enhancement techniques on its permeation through human skin. In vitro drug permeation studies through dermatomed human skin were performed using Franz diffusion cells. Passive permeation of PAL-353 from propylene glycol and phosphate buffered saline as vehicles was studied. Effect of oleic acid, maltose microneedles, ablative laser, and anodal iontophoresis on its transdermal permeation was investigated. Infrared spectroscopy, scanning electron microscopy, calcein imaging, confocal laser microscopy, and histology studies were used to characterize the effects of chemical and physical treatments on skin integrity. Passive permeation of PAL-353 (propylene glycol) after 24h was found to be 1.03±0.17μg/cm². Microneedles, oleic acid, and laser significantly increased the permeation to 7.35±4.87μg/cm², 38.26±5.56μg/cm², and 523.24±86.79μg/cm² (p<0.05), respectively. A 548-fold increase in drug permeation was observed using iontophoresis as compared to its passive permeation from phosphate buffered saline (p<0.05). The characterization studies depicted disruption of the stratum corneum by microneedles and laser treatment. Overall, transdermal permeation of PAL-353 was significantly enhanced by the use of chemical and physical enhancement techniques.

Non-viral gene therapy: Gains and challenges of non-invasive administration methods

Gene therapy is becoming an influential part of the rapidly increasing armamentarium of biopharmaceuticals for improving health and combating diseases. Currently, three gene therapy treatments are approved by regulatory agencies. While these treatments utilize viral vectors, non-viral alternative technologies are also being developed to improve the safety profile and manufacturability of gene carrier formulations. We present an overview of gene-based therapies focusing on non-viral gene delivery systems and the genetic therapeutic tools that will further revolutionize medical treatment with primary focus on the range and development of non-invasive delivery systems for dermal, transdermal, ocular and pulmonary administrations and perspectives on other administration methods such as intranasal, oral, buccal, vaginal, rectal and otic delivery.

Induced pluripotent stem cells in dermatology: potentials, advances, and limitations

The discovery of methods for reprogramming adult somatic cells into induced pluripotent stem cells (iPSCs) has raised the possibility of producing truly personalized treatment options for numerous diseases. Similar to embryonic stem cells (ESCs), iPSCs can give rise to any cell type in the body and are amenable to genetic correction by homologous recombination. These ESC properties of iPSCs allow for the development of permanent corrective therapies for many currently incurable disorders, including inherited skin diseases, without using embryonic tissues or oocytes. Here, we review recent progress and limitations of iPSC research with a focus on clinical applications of iPSCs and using iPSCs to model human diseases for drug discovery in the field of dermatology.

Non-invasive, epicutaneous immunisation with toxoid in deformable vesicles protects mice against tetanus, chiefly owing to a Th2 response

A non-invasive, intra/transcutaneous immunisation of mice with a suitable combination of tetanus toxoid, ultradeformable vesicle (Transfersome®) carrier, and monophosphoryl lipid A adjuvant targets immuno-competent cells in a body and can protect 100% of the tested mice against an otherwise lethal (50×LD50) parenteral tetanus toxin challenge. The late immune response to the epicutaneously applied tetanus toxoid in such vesicles consists chiefly of circulating IgG1 and IgG2b antibody isotypes, indicative of a specific Th2 cellular response bias. Immunisations by subcutaneous injections moreover protect 100% of mice against a similar, otherwise lethal, dose of tetanus toxin. However, the immune response to transcutaneous and invasive immunisation differs. The latter elicits mainly IgG1 and IgG2b as well as IgG2a antibody isotypes, indicative of a mixed Th1/Th2 response. The cytokine response of the intra/transcutaneously and subcutaneously immunised mice reflects the difference in the organ-specific manner. IFN-γ concentration is appreciably increased in the draining lymph nodes and IL-10 in spleen. Since tetanus is a neutral antigen, both the Th1-specific IFN-γ and the Th-2 specific-IL-10 are observable.

Topical gene electrotransfer to the epidermis of hairless guinea pig by non-invasive multielectrode array

Topical gene delivery to the epidermis has the potential to be an effective therapy for skin disorders, cutaneous cancers, vaccinations and systemic metabolic diseases. Previously, we reported on a non-invasive multielectrode array (MEA) that efficiently delivered plasmid DNA and enhanced expression to the skin of several animal models by in vivo gene electrotransfer. Here, we characterized plasmid DNA delivery with the MEA in a hairless guinea pig model, which has a similar histology and structure to human skin. Significant elevation of gene expression up to 4 logs was achieved with intradermal DNA administration followed by topical non-invasive skin gene electrotransfer. This delivery produced gene expression in the skin of hairless guinea pig up to 12 to 15 days. Gene expression was observed exclusively in the epidermis. Skin gene electrotransfer with the MEA resulted in only minimal and mild skin changes. A low level of human Factor IX was detected in the plasma of hairless guinea pig after gene electrotransfer with the MEA, although a significant increase of Factor IX was obtained in the skin of animals. These results suggest gene electrotransfer with the MEA can be a safe, efficient, non-invasive skin delivery method for skin disorders, vaccinations and potential systemic diseases where low levels of gene products are sufficient.

Differentiation of human induced pluripotent stem cells into a keratinocyte lineage

Direct reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) provides an opportunity to develop novel personalized treatment options for numerous diseases and to advance current approaches for cell-based drug discoveries and disease modeling. The ability to differentiate iPSCs into relevant cell types is an important prerequisite for the successful development of iPSC-based treatment and modeling strategies. Here, we describe a protocol for the efficient differentiation of human iPSCs into functional keratinocytes. The protocol employs treating iPSCs with retinoic acid and bone-morphogenetic protein-4 to induce differentiation toward a keratinocyte lineage, which is then followed by the growth of differentiated iPSCs on collagen type I- and collagen type IV-coated dishes to enrich for iPSC-derived keratinocytes.

Nucleofection: a new method for cutaneous gene transfer?

Background. Transfection efficacy after nonviral gene transfer in primary epithelial cells is limited. The aim of this study was to compare transfection efficacy of the recently available method of nucleofection with the established transfection reagent FuGENE6. Methods. Primary human keratinocytes (HKC), primary human fibroblasts (HFB), and a human keratinocyte cell line (HaCaT) were transfected with reporter gene construct by FuGENE6 or Amaxa Nucleofector device. At corresponding time points, β-galactosidase expression, cell proliferation (MTT-Test), transduction efficiency (X-gal staining), cell morphology, and cytotoxicity (CASY) were determined. Results. Transgene expression after nucleofection was significantly higher in HKC and HFB and detected earlier (3 h vs. 24 h) than in FuGENE6. After lipofection 80%–90% of the cells remained proliferative without any influence on cell morphology. In contrast, nucleofection led to a decrease in keratinocyte cell size, with only 20%–42% proliferative cells. Conclusion. Related to the method-dependent increase of cytotoxicity, transgene expression after nucleofection was earlier and higher than after lipofection.

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.

Skin targeted DNA vaccine delivery using electroporation in rabbits II. Safety

The Achilles heel of gene-based therapy is gene delivery into the target cells efficiently with minimal toxic effects. Viral vectors for gene/DNA vaccine delivery are limited by the safety and immunological problems. Recently, nonviral gene delivery mediated by electroporation has been shown to be efficient in different tissues including skin. There are no detailed reports about the effects of electroporation on skin tissue, when used for gene/DNA vaccine delivery. In a previous study we demonstrated the efficacy of skin targeted DNA vaccine delivery using electroporation in rabbits [Medi, B.M., Hoselton, S., Marepalli, B.R., Singh, J., 2005. Skin targeted DNA vaccine delivery using electroporation in rabbits. I. Efficacy. Int. J. Pharm. 294, 53-63]. In the present study, we investigated the safety aspects of the electroporation technique in vivo in rabbits. Different electroporation parameters (100-300 V) were tested for their effects on skin viability, macroscopic barrier property, irritation and microscopic changes in the skin. Skin viability was not affected by the electroporation protocols tested. The electroporation pulses induced skin barrier perturbation and irritation as indicated by elevated transepidermal water loss (TEWL) and erythema/edema, respectively. Microscopic studies revealed inflammatory responses in the epidermis following electroporation using 200 and 300 V pulses. However, these changes due to electroporation were reversible within a week. The results suggest that the electroporation does not induce any irreversible changes in the skin and can be a useful technique for skin targeted DNA vaccine delivery.

New technologies for burn wound closure and healing--review of the literature

Methods for handling burn wounds have changed in recent decades. Increasingly, aggressive surgical approach with early tangential excision and wound closure is being applied leading to improvement in mortality rates of burn victims. Autografts from uninjured skin remain the mainstay of treatment. Autologous skin graft, however, has limited availability and is associated with additional morbidity and scarring. Severe burn patients invariably lack sufficient adequate skin donor sites requiring alternative methods of skin replacement. The present review summarizes available replacement technologies.

Gene transfer in tissue repair: status, challenges and future directions

Wound repair involves a complex interaction of various cell types, extracellular matrix molecules and soluble mediators. Details on signals controlling wound cell activities are beginning to emerge. In recent years this knowledge has been applied to a number of therapeutic strategies in soft tissue repair. Key challenges include re-adjusting the adult repair process in order to augment diseased healing processes, and providing the basis for a regenerative rather than a reparative wound environment. 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 trials indicates that an important aspect of the growth factor wound-healing paradigm is the effective delivery of these polypeptides to the wound site. A molecular genetic approach in which genetically modified cells synthesise and deliver the desired growth factor in a time-regulated manner is a powerful means to overcome the limitations associated with the (topical) application of recombinant growth factor proteins. This article summarises repair mechanisms and their failure, and gives an overview of techniques and studies applied to gene transfer in tissue repair. It also provides perspectives on potential targets for gene transfer technology.

State of the Art in Burn Treatment

Optimal treatment of burn victims requires deep understanding of the profound pathophysiological changes occurring locally and systemically after injury. Accurate estimation of burn size and depth, as well as early resuscitation, is essential. Good burn care includes also cleansing, debridement, and prevention of sepsis. Wound healing, is of major importance to the survival and clinical outcome of burn patients. An ideal therapy would not only promote rapid healing but would also act as an antiscarring therapy. The present article is a literature review of the most up-to-date modalities applied to burn treatment without overlooking the numerous controversies that still persist.

Topical colchicine selection of keratinocytes transduced with the multidrug resistance gene (MDR1) can sustain and enhance transgene expression in vivo

For skin gene therapy, achieving prolonged high-level gene expression in a significant percentage of keratinocytes (KC) is difficult because we cannot selectively target KC stem cells. We now demonstrate that topical colchicine treatment can be used to select, in vivo, KC progenitor cells transduced with the multidrug resistance gene (MDR1). When human skin equivalents containing MDR1-transduced KC were grafted onto immunocompromised mice, topical colchicine treatments significantly increased (7-fold) the percentage of KC expressing MDR1, compared to vehicle-treated controls, for up to 24 wk. Topical colchicine treatment also significantly enhanced the amount of MDR1 protein expressed in individual KC. Furthermore, quantitative real-time PCR analysis of MDR1 transgene copy number demonstrates that topical colchicine treatment selects and enriches for KC progenitor cells in the skin that contain and express MDR1. For clinical skin gene therapy applications, this in vivo selection approach promises to enhance both the duration and expression level of a desired therapeutic gene in KC, by linking its expression to the MDR1 selectable marker gene.

Cutaneous gene transfer for skin and systemic diseases

Recent progress in molecular genetics has illuminated the basis for a wide variety of inherited and acquired diseases. Gene therapy offers an attractive therapeutic approach capitalizing upon these new mechanistic insights. The skin is a uniquely attractive tissue site for development of new genetic therapeutic approaches both for its accessibility as well as for the large number of diseases that are amenable in principle to cutaneous gene transfer. Amongst these opportunities are primary monogenic skin diseases, chronic wounds and systemic disorders characterized by low or absent levels of circulating polypeptides. For cutaneous gene therapy to be effective, however, significant progress is required in a number of domains. Recent advances in vector design, administration, immune modulation, and regulation of gene expression have brought the field much nearer to clinical utility.

Gene therapy in plastic surgery

Recent developments in gene therapy have shown promise in the treatment of soft-tissue repair, bone formation, nerve regeneration, and cranial suture development. This special topic article reviews commonly used methods of gene therapy and discusses their various advantages and disadvantages. In addition, an overview of new developments in gene therapy as they relate to plastic surgery is provided.

Advances in skin gene therapy

Specific anatomical and biological properties make the skin a very interesting target organ for gene therapy approaches. Different cell types of the epidermis, such as keratinocytes, melanocytes, or dendritic cells, can be genetically modified to treat a broad spectrum of diseases, including genetically inherited skin disorders, tumour diseases, metabolic disorders and infectious diseases. The easy accessibility of skin suggests that different methods for gene delivery can be pursued, depending on the desired application. The approach used to deliver DNA to the skin will influence not only the efficiency of DNA delivery, but also the level and duration of transgene expression. Furthermore, the desired biological effect will also influence the decision of which gene transfer method is the best choice. Among the current challenges of cutaneous gene therapy are: optimising the efficiency of direct in vivo gene delivery; targeting specific epidermal cells, including keratinocyte stem cells; achieving sustained gene expression and regulating gene expression in vivo. This review summarises recent advances in the field of skin gene therapy and evaluates possible strategies to overcome obstacles and achieve successful clinical applications of skin gene therapy.

Transdermal drug delivery: overcoming the skin's barrier function

The skin represents an extraordinary evolutionary feat. Not only does it physically encapsulate the organism and provide a multifunctional interface between us and our surroundings, but it is perpetually engaged in the assembly of a highly efficient homeostatic barrier to the outward loss of water(1). In so doing, it furnishes a membrane that is equally adept at limiting molecular transport both from and into the body. Overcoming this barrier function then, for the purpose of transdermal drug delivery, has been a necessarily challenging task for the pharmaceutical scientist, and one that boasts significant progress.