A Tensioned Human Skin Explant Model Used for Preliminary Assessment of Chemexfoliant-Stimulated Bioeffects.

A tensioned ex vivo full-thickness human skin explant platform was used to assess the bioeffects arising from application of several commercial chemexfoliation agents. Although such treatments are well-established, and improved understanding of the underlying mechanistic processes continues to emerge, research into the optimum treatments for specific skin types/conditions is still needed for enhanced efficacy while minimizing recovery time. The 3 commercial chemexfoliation agents employed all contained trichloroacetic acid at well-defined concentrations (6, 10, and 20%) and were applied to the explants' stratum corneum.

Therapeutic Prospects of Exon Skipping for Epidermolysis Bullosa.

Epidermolysis bullosa is a group of genetic skin conditions characterized by abnormal skin (and mucosal) fragility caused by pathogenic variants in various genes. The disease severity ranges from early childhood mortality in the most severe types to occasional acral blistering in the mildest types. The subtype and severity of EB is linked to the gene involved and the specific variants in that gene, which also determine its mode of inheritance.

Development of a Corneal Bioluminescence Mouse for Real-Time In Vivo Evaluation of Gene Therapies.

Purpose: The purpose of this study was to develop and characterize a novel bioluminescence transgenic mouse model that facilitates rapid evaluation of genetic medicine delivery methods for inherited and acquired corneal diseases.

Methods: Corneal expression of the firefly luciferase transgene () was achieved via insertion into the locus, a type I intermediate filament keratin that is exclusively expressed in the cornea, to generate the mouse. The transgene includes a multiple target cassette with human pathogenic mutations in K3 and K12.

A Report of Three Cases from an Ongoing Prospective Clinical Study on a Novel Pink Biomimetic Implant System.

While, overall, dental implants are highly efficacious, consistently achieving predictable esthetic results can pose color-driven challenges at the implant/soft-tissue interface, particularly in the esthetic zone. An ongoing, 5-year, multicenter (eight sites) prospective study is following a total of 168 implants placed in 120 patients using a novel biomimetic (osteoconductive) implant system with pink collars and abutments that afford better gingival color matching, enhanced design variability, and streamlined fabrication and customization of the abutment/implant-tissue interface. The full results of this study will be published at the 3-year and 5-year timepoints; however, clinical analyses of the 18-month interim survival rates, marginal bone and soft-tissue level changes, and esthetics have been completed, showing an overall success rate among all of the implanted sites of 95.

Keratin 12 missense mutation induces the unfolded protein response and apoptosis in Meesmann epithelial corneal dystrophy.

Meesmann epithelial corneal dystrophy (MECD) is a rare autosomal dominant disorder caused by dominant-negative mutations within the KRT3 or KRT12 genes, which encode the cytoskeletal protein keratins K3 and K12, respectively. To investigate the pathomechanism of this disease, we generated and phenotypically characterized a novel knock-in humanized mouse model carrying the severe, MECD-associated, K12-Leu132Pro mutation. Although no overt changes in corneal opacity were detected by slit-lamp examination, the corneas of homozygous mutant mice exhibited histological and ultrastructural epithelial cell fragility phenotypes.

Imaging Functional Nucleic Acid Delivery to Skin.

Monogenic skin diseases arise from well-defined single gene mutations, and in some cases a single point mutation. As the target cells are superficial, these diseases are ideally suited for treatment by nucleic acid-based therapies as well as monitoring through a variety of noninvasive imaging technologies. Despite the accessibility of the skin, there remain formidable barriers for functional delivery of nucleic acids to the target cells within the dermis and epidermis.

Non-Invasive Intravital Imaging of siRNA-Mediated Mutant Keratin Gene Repression in Skin.

Purpose: Small interfering RNAs (siRNAs) specifically and potently inhibit target gene expression. Pachyonychia congenita (PC) is a skin disorder caused by mutations in genes encoding keratin (K) 6a/b, K16, and K17, resulting in faulty intermediate filaments. A siRNA targeting a single nucleotide, PC-relevant mutation inhibits K6a expression and has been evaluated in the clinic with encouraging results.

Gene expression profiling in pachyonychia congenita skin.

Background: Pachyonychia congenita (PC) is a skin disorder resulting from mutations in keratin (K) proteins including K6a, K6b, K16, and K17. One of the major symptoms is painful plantar keratoderma. The pathogenic sequelae resulting from the keratin mutations remain unclear.

In vivo gene silencing following non-invasive siRNA delivery into the skin using a novel topical formulation.

Therapeutics based on short interfering RNAs (siRNAs), which act by inhibiting the expression of target transcripts, represent a novel class of potent and highly specific next-generation treatments for human skin diseases. Unfortunately, the intrinsic barrier properties of the skin combined with the large size and negative charge of siRNAs make epidermal delivery of these macromolecules quite challenging. To help evaluate the in vivo activity of these therapeutics and refine delivery strategies we generated an innovative reporter mouse model that predominantly expresses firefly luciferase (luc2p) in the paw epidermis--the region of murine epidermis that most closely models the tissue architecture of human skin.

Keratin 16 regulates innate immunity in response to epidermal barrier breach.

Mutations in the type I keratin 16 (Krt16) and its partner type II keratin 6 (Krt6a, Krt6b) cause pachyonychia congenita (PC), a disorder typified by dystrophic nails, painful hyperkeratotic calluses in glabrous skin, and lesions involving other epithelial appendages. The pathophysiology of these symptoms and its relationship to settings in which Krt16 and Krt6 are induced in response to epidermal barrier stress are poorly understood. We report that hyperkeratotic calluses arising in the glabrous skin of individuals with PC and Krt16 null mice share a gene expression signature enriched in genes involved in inflammation and innate immunity, in particular damage-associated molecular patterns.

Gene Silencing in Skin After Deposition of Self-Delivery siRNA With a Motorized Microneedle Array Device.

Despite the development of potent siRNAs that effectively target genes responsible for skin disorders, translation to the clinic has been hampered by inefficient delivery through the stratum corneum barrier and into the live cells of the epidermis. Although hypodermic needles can be used to transport siRNA through the stratum corneum, this approach is limited by pain caused by the injection and the small volume of tissue that can be accessed by each injection. The use of microneedle arrays is a less painful method for siRNA delivery, but restricted payload capacity limits this approach to highly potent molecules.

Intravital fluorescence imaging of small interfering RNA-mediated gene repression in a dual reporter melanoma xenograft model.

Development of RNA interference (RNAi)-based therapeutics has been hampered by the lack of effective and efficient means of delivery. Reliable model systems for screening and optimizing delivery of RNAi-based agents in vivo are crucial for preclinical research aimed at advancing nucleic acid-based therapies. We describe here a dual fluorescent reporter xenograft melanoma model prepared by intradermal injection of human A375 melanoma cells expressing tandem tomato fluorescent protein (tdTFP) containing a small interfering RNA (siRNA) target site as well as enhanced green fluorescent protein (EGFP), which is used as a normalization control.

Designed guanidinium-rich amphipathic oligocarbonate molecular transporters complex, deliver and release siRNA in cells.

The polyanionic nature of oligonucleotides and their enzymatic degradation present challenges for the use of siRNA in research and therapy; among the most notable of these is clinically relevant delivery into cells. To address this problem, we designed and synthesized the first members of a new class of guanidinium-rich amphipathic oligocarbonates that noncovalently complex, deliver, and release siRNA in cells, resulting in robust knockdown of target protein synthesis in vitro as determined using a dual-reporter system. The organocatalytic oligomerization used to synthesize these co-oligomers is step-economical and broadly tunable, affording an exceptionally quick strategy to explore chemical space for optimal siRNA delivery in varied applications.

Inhibition of CD44 gene expression in human skin models, using self-delivery short interfering RNA administered by dissolvable microneedle arrays.

Treatment of skin disorders with short interfering RNA (siRNA)-based therapeutics requires the development of effective delivery methodologies that reach target cells in affected tissues. Successful delivery of functional siRNA to the epidermis requires (1) crossing the stratum corneum, (2) transfer across the keratinocyte membrane, followed by (3) incorporation into the RNA-induced silencing complex. We have previously demonstrated that treatment with microneedle arrays loaded with self-delivery siRNA (sd-siRNA) can achieve inhibition of reporter gene expression in a transgenic mouse model.

Visualization of plasmid delivery to keratinocytes in mouse and human epidermis.

The accessibility of skin makes it an ideal target organ for nucleic acid-based therapeutics; however, effective patient-friendly delivery remains a major obstacle to clinical utility. A variety of limited and inefficient methods of delivering nucleic acids to keratinocytes have been demonstrated; further advances will require well-characterized reagents, rapid noninvasive assays of delivery, and well-developed skin model systems. Using intravital fluorescence and bioluminescence imaging and a standard set of reporter plasmids we demonstrate transfection of cells in mouse and human xenograft skin using intradermal injection and two microneedle array delivery systems.

In vivo sustained release of siRNA from solid lipid nanoparticles.

Small interfering RNA (siRNA) is a highly potent drug in gene-based therapy with a challenge of being delivered in a sustained manner. Nanoparticle drug delivery systems allow for incorporating and controlled release of therapeutic payloads. We demonstrate that solid lipid nanoparticles can incorporate and provide sustained release of siRNA.

Use of self-delivery siRNAs to inhibit gene expression in an organotypic pachyonychia congenita model.

Although RNA interference offers therapeutic potential for treating skin disorders, delivery hurdles have hampered clinical translation. We have recently demonstrated that high pressure, resulting from intradermal injection of large liquid volumes, facilitated nucleic acid uptake by keratinocytes in mouse skin. Furthermore, similar intradermal injections of small interfering RNA (siRNA; TD101) into pachyonychia congenita (PC) patient foot lesions resulted in improvement.

Development of quantitative molecular clinical end points for siRNA clinical trials.

RNA interference (RNAi) is an evolutionarily conserved mechanism that results in specific gene inhibition at the mRNA level. The discovery that short interfering RNAs (siRNAs) are selective, potent, and can largely avoid immune surveillance has resulted in keen interest to develop these inhibitors as therapeutics. A single nucleotide-specific siRNA (K6a_513a.

Development of skin-humanized mouse models of pachyonychia congenita.

Molecular characterization and assessment of therapeutic outcomes for inherited cutaneous disorders requires faithful preclinical models. In this study we report the establishment of two different skin-humanized pachyonychia congenita (PC) model systems, based on permanent engraftment of bioengineered skin equivalents generated from patient skin cells onto immunodeficient mice. Using keratinocytes and fibroblasts isolated from unaffected skin biopsies of two PC patients carrying the p.

Silencing of reporter gene expression in skin using siRNAs and expression of plasmid DNA delivered by a soluble protrusion array device (PAD).

Despite rapid progress in the development of potent and selective small interfering RNA (siRNA) agents for skin disorders, translation to the clinic has been hampered by the lack of effective, patient-friendly delivery technologies. The stratum corneum poses a formidable barrier to efficient delivery of large and/or charged macromolecules including siRNAs. Intradermal siRNA injection results in effective knockdown of targeted gene expression but is painful and the effects are localized to the injection site.

Increased interstitial pressure improves nucleic acid delivery to skin enabling a comparative analysis of constitutive promoters.

Nucleic acid-based therapies hold great promise for treatment of skin disorders if delivery challenges can be overcome. To investigate one mechanism of nucleic acid delivery to keratinocytes, a fixed mass of expression plasmid was intradermally injected into mouse footpads in different volumes, and reporter expression was monitored by intravital imaging or skin sectioning. Reporter gene expression increased with higher delivery volumes, suggesting that pressure drives nucleic acid uptake into cells after intradermal injections similar to previously published studies for muscle and liver.

Nanoparticle formation of organic compounds with retained biological activity.

Many pharmaceuticals are formulated as powders to aid drug delivery. A major problem is how to produce powders having high purity, controlled morphology, and retained bioactivity. We demonstrate the use of supercritical carbon dioxide as an antisolvent for meeting this need for two model drug systems, quercetin, a sparingly soluble antioxidant, and short interfering RNA (siRNA), which can silence genes.