Functional therapies for cutaneous wound repair in epidermolysis bullosa

Mechanotransduction through hemidesmosomes during aging and longevity

Hemidesmosomes are structural protein complexes localized at the interface of tissues with high mechanical demand and shear forces. Beyond tissue anchoring, hemidesmosomes have emerged as force-modulating structures important for translating mechanical cues into biochemical and transcriptional adaptation (i.e. mechanotransduction) across tissues. Here, we discuss the recent insights into the roles of hemidesmosomes in age-related tissue regeneration and aging in C. elegans, mice and humans. We highlight the emerging concept of preserved dynamic mechanoregulation of hemidesmosomes in tissue maintenance and healthy aging.

Intradermally delivered mRNA-encapsulating extracellular vesicles for collagen-replacement therapy

The success of messenger RNA therapeutics largely depends on the availability of delivery systems that enable the safe, effective and stable translation of genetic material into functional proteins. Here we show that extracellular vesicles (EVs) produced via cellular nanoporation from human dermal fibroblasts, and encapsulating mRNA encoding for extracellular-matrix α1 type-I collagen (COL1A1) induced the formation of collagen-protein grafts and reduced wrinkle formation in the collagen-depleted dermal tissue of mice with photoaged skin. We also show that the intradermal delivery of the mRNA-loaded EVs via a microneedle array led to the prolonged and more uniform synthesis and replacement of collagen in the dermis of the animals. The intradermal delivery of EV-based COL1A1 mRNA may make for an effective protein-replacement therapy for the treatment of photoaged skin.

EGFR-mediated epidermal stem cell motility drives skin regeneration through COL17A1 proteolysis

Skin regenerative capacity declines with age, but the underlying mechanisms are largely unknown. Here we demonstrate a functional link between epidermal growth factor receptor (EGFR) signaling and type XVII collagen (COL17A1) proteolysis on age-associated alteration of keratinocyte stem cell dynamics in skin regeneration. Live-imaging and computer simulation experiments predicted that human keratinocyte stem cell motility is coupled with self-renewal and epidermal regeneration. Receptor tyrosine kinase array identified the age-associated decline of EGFR signaling in mouse skin wound healing. Culture experiments proved that EGFR activation drives human keratinocyte stem cell motility with increase of COL17A1 by inhibiting its proteolysis through the secretion of tissue inhibitor of metalloproteinases 1 (TIMP1). Intriguingly, COL17A1 directly regulated keratinocyte stem cell motility and collective cell migration by coordinating actin and keratin filament networks. We conclude that EGFR-COL17A1 axis-mediated keratinocyte stem cell motility drives epidermal regeneration, which provides a novel therapeutic approach for age-associated impaired skin regeneration.

Self-assembly of differentiated progenitor cells facilitates spheroid human skin organoid formation and planar skin regeneration

Self-assembly of solid organs from single cells would greatly expand applicability of regenerative medicine. Stem/progenitor cells can self-organize into micro-sized organ units, termed organoids, partially modelling tissue function and regeneration. Here we demonstrated 3D self-assembly of adult and induced pluripotent stem cell (iPSC)-derived fibroblasts, keratinocytes and endothelial progenitors into both, planar human skin in vivo and a novel type of spheroid-shaped skin organoids in vitro, under the aegis of human platelet lysate. Methods: Primary endothelial colony forming cells (ECFCs), skin fibroblasts (FBs) and keratinocytes (KCs) were isolated from human tissues and polyclonally propagated under 2D xeno-free conditions. Human tissue-derived iPSCs were differentiated into endothelial cells (hiPSC-ECs), fibroblasts (hiPSC-FBs) and keratinocytes (hiPSC-KCs) according to efficiency-optimized protocols. Cell identity and purity were confirmed by flow cytometry and clonogenicity indicated their stem/progenitor potential. Triple cell type floating spheroids formation was promoted by human platelet-derived growth factors containing culture conditions, using nanoparticle cell labelling for monitoring the organization process. Planar human skin regeneration was assessed in full-thickness wounds of immune-deficient mice upon transplantation of hiPSC-derived single cell suspensions. Results: Organoids displayed a distinct architecture with surface-anchored keratinocytes surrounding a stromal core, and specific signaling patterns in response to inflammatory stimuli. FGF-7 mRNA transfection was required to accelerate keratinocyte long-term fitness. Stratified human skin also self-assembled within two weeks after either adult- or iPSC-derived skin cell-suspension liquid-transplantation, healing deep wounds of mice. Transplant vascularization significantly accelerated in the presence of co-transplanted endothelial progenitors. Mechanistically, extracellular vesicles mediated the multifactorial platelet-derived trophic effects. No tumorigenesis occurred upon xenografting. Conclusion: This illustrates the superordinate progenitor self-organization principle and permits novel rapid 3D skin-related pharmaceutical high-content testing opportunities with floating spheroid skin organoids. Multi-cell transplant self-organization facilitates development of iPSC-based organ regeneration strategies using cell suspension transplantation supported by human platelet factors.

Pathogenetic Therapy of Epidermolysis Bullosa: Current State and Prospects

Epidermolysis bullosa is a severe hereditary disease caused by mutations in genes encoding cutaneous basement membrane proteins. These mutations lead to dermal-epidermal junction failure and, as a result, to disturbances in the morphological integrity of the skin. Clinically, it manifests in the formation of blisters on the skin or mucosa that in some cases can turn into non-healing chronic wounds, which not only impairs patient's quality of life, but also is a live-threatening condition. Now, the main approaches in the treatment of epidermolysis bullosa are symptomatic therapy and palliative care, though they are little effective and are aimed at reducing the pain, but not to complete recovery. In light of this, the development of new treatment approaches aimed at correction of genetic defects is in progress. Various methods based on genetic engineering technologies, transplantation of autologous skin cells, progenitor skin cells, as well as hematopoietic and mesenchymal stem cells are studied. This review analyzes the pathogenetic methods developed for epidermolysis bullosa treatment based on the latest achievements of molecular genetics and cellular technologies, and discusses the prospects for the use of these technologies for the therapy of epidermolysis bullosa.

Epidermolysis bullosa

Epidermolysis bullosa (EB) is an inherited, heterogeneous group of rare genetic dermatoses characterized by mucocutaneous fragility and blister formation, inducible by often minimal trauma. A broad phenotypic spectrum has been described, with potentially severe extracutaneous manifestations, morbidity and mortality. Over 30 subtypes are recognized, grouped into four major categories, based predominantly on the plane of cleavage within the skin and reflecting the underlying molecular abnormality: EB simplex, junctional EB, dystrophic EB and Kindler EB. The study of EB has led to seminal advances in our understanding of cutaneous biology. To date, pathogenetic mutations in 16 distinct genes have been implicated in EB, encoding proteins influencing cellular integrity and adhesion. Precise diagnosis is reliant on correlating clinical, electron microscopic and immunohistological features with mutational analyses. In the absence of curative treatment, multidisciplinary care is targeted towards minimizing the risk of blister formation, wound care, symptom relief and specific complications, the most feared of which - and also the leading cause of mortality - is squamous cell carcinoma. Preclinical advances in cell-based, protein replacement and gene therapies are paving the way for clinical successes with gene correction, raising hopes amongst patients and clinicians worldwide.

Improved Double-Nicking Strategies for COL7A1-Editing by Homologous Recombination

Current gene-editing approaches for treatment of recessive dystrophic epidermolysis bullosa (RDEB), an inherited, severe form of blistering skin disease, suffer from low efficiencies and safety concerns that complicate implementation in clinical settings. We present a strategy for efficient and precise repair of RDEB-associated mutations in the COL7A1 gene. We compared the efficacy of double-strand breaks (induced by CRISPR/Cas9), single nicks, or double nicks (induced by Cas9n) in mediating repair of a COL7A1 splice-site mutation in exon 3 by homologous recombination (HR). We accomplished remarkably high HR frequencies of 89% with double nicking while at the same time keeping unwanted repair outcomes, such as non-homologous end joining (NHEJ), at a minimum (11%). We also investigated the effects of subtle differences in repair template design on HR rates and found that strategic template-nicking can enhance COL7A1-editing efficiency. In RDEB patient keratinocytes, application of double-nicking led to restoration and subsequent secretion of type VII collagen at high efficiency. Comprehensive analysis of 25 putative off-target sites revealed no off-target activity for double-nicking, while usage of Cas9 resulted in 54% modified alleles at one site. Taken together, our work provides a framework for efficient, precise, and safe repair of COL7A1, which lies at the heart of a future curative therapy of RDEB.

Patent landscape of molecular and cellular targeted therapies for recessive dystrophic epidermolysis bullosa

INTRODUCTION

Recessive Dystrophic Epidermolysis Bullosa (RDEB) is a monogenetic inherited genodermatosis associated with deleterious mutations in the gene encoding type VII collagen (COL7A1). COL7A1 is essential for promoting attachment of the epidermis to the dermis, and its dysfunction may lead to generalized mucosal and cutaneous blistering associated to severe deformities. Currently, management of RDEB patients is limited to supportive care, being aimed at treating and preventing common complications associated with this condition. There is a great demand to develop targeted therapies for this devastating disease and RDEB research advances are currently being translated into clinical trials.

AREAS COVERED

Based on the literature and patent search, the authors have grouped the RDEB targeted therapies into five categories: a) cell-based therapies; b) gene therapy; c) protein replacement therapy; d) molecular therapy based on exon skipping; and e) drug-mediated premature termination codon read-through. The patent searching strategy involved inquiring Google and USPTO patent databases to reveal companies and institutions that are active in the area of RDEB targeted therapies.

EXPERT OPINION

The patent landscape related to targeted therapies for RDEB is quite heterogeneous, with each targeted therapeutic approach being associated with its own challenges in achieving robust patent protection and identifying opportunities for future development.