David T. Woodley

The classification of inherited epidermolysis bullosa (EB): Report of the Third International Consensus Meeting on Diagnosis and Classification of EB

BACKGROUND Since publication in 2000 of the Second International Consensus Report on Diagnosis and Classification of Epidermolysis Bullosa, many advances have been made to our understanding of this group of diseases, both clinically and molecularly. At the same time, new epidermolysis bullosa (EB) subtypes have been described and similarities with some other diseases have been identified. OBJECTIVE We sought to arrive at a new consensus of the classification of EB subtypes. RESULTS We now present a revised classification system that takes into account the new advances, as well as encompassing other inherited diseases that should also be included within the EB spectrum, based on the presence of blistering and mechanical fragility. Current recommendations are made on the use of specific diagnostic tests, with updates on the findings known to occur within each of the major EB subtypes. Electronic links are also provided to informational and laboratory resources of particular benefit to clinicians and their patients. LIMITATIONS As more becomes known about this disease, future modifications may be needed. The classification system has been designed with sufficient flexibility for these modifications. CONCLUSION This revised classification system should assist clinicians in accurately diagnosing and subclassifying patients with EB.

TANGO1 Facilitates Cargo Loading at Endoplasmic Reticulum Exit Sites

A genome-wide screen revealed previously unidentified components required for transport and Golgi organization (TANGO). We now provide evidence that one of these proteins, TANGO1, is an integral membrane protein localized to endoplasmic reticulum (ER) exit sites, with a luminal SH3 domain and a cytoplasmic proline-rich domain (PRD). Knockdown of TANGO1 inhibits export of bulky collagen VII from the ER. The SH3 domain of TANGO1 binds to collagen VII; the PRD binds to the COPII coat subunits, Sec23/24. In this scenario, PRD binding to Sec23/24 subunits could stall COPII carrier biogenesis to permit the luminal domain of TANGO1 to guide SH3-bound cargo into a growing carrier. All cells except those of hematopoietic origin express TANGO1. We propose that TANGO1 exports other cargoes in cells that do not secrete collagen VII. However, TANGO1 does not enter the budding carrier, which represents a unique mechanism to load cargo into COPII carriers.

Extracellular heat shock protein‐90α: linking hypoxia to skin cell motility and wound healing

Hypoxia is a microenvironmental stress in wounded skin, where it supports wound healing by promoting cell motility. The mechanism of the hypoxia action remained speculative. Here, we provide evidence that hypoxia promotes human dermal fibroblast (HDF) migration by inducing secretion of heat shock protein‐90alpha (hsp90α) into the extracellular environment through hypoxia‐inducible factor‐1alpha (HIF‐1α). The secreted hsp90α in turn executes hypoxias pro‐motility effect. Expression of an activated HIF‐1α mimicked, whereas expression of an inactive HIF‐1α or suppression of endogenous HIF‐1α blocked, hypoxia‐induced hsp90α secretion and HDF migration. Interestingly, the hypoxia–HIF‐1 pathway‐induced hsp90α secretion required neither changes in the steady‐state mRNA level nor in the promoter activity of hsp90α. Recombinant hsp90α fully duplicated the hypoxia effect on HDFs. Inhibition of extracellular hsp90α function completely blocked the hypoxia–HIF‐1 pathway‐stimulated HDF migration. More intriguingly, topical application of hsp90α accelerated wound healing in mice. This study has demonstrated a novel mechanism of hypoxia>HIF‐1>hsp90α secretion>skin cell migration>wound healing, and identified extracellular hsp90α as a potential therapeutic agent for skin wounds.

Restoration of type VII collagen expression and function in dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa (DEB) is a family of inherited mechano-bullous disorders caused by mutations in the human type VII collagen gene (COL7A1). Individuals with DEB lack type VII collagen and anchoring fibrils, structures that attach epidermis and dermis. The current lack of treatment for DEB is an impetus to develop gene therapy strategies that efficiently transfer and stably express genes delivered to skin cells in vivo. In this study, we delivered and expressed full-length type VII collagen using a self-inactivating minimal lentivirus-based vector. Transduction of lentiviral vectors containing the COL7A1 transgene into recessive DEB (RDEB) keratinocytes and fibroblasts (in which type VII collagen was absent) resulted in persistent synthesis and secretion of type VII collagen. Unlike RDEB parent cells, the gene-corrected cells had normal morphology, proliferative potential, matrix attachment and motility. We used these gene-corrected cells to regenerate human skin on immune-deficient mice. Human skin regenerated by gene-corrected RDEB cells had restored expression of type VII collagen and formation of anchoring fibrils at the dermal–epidermal junction in vivo. These studies demonstrate that it is possible to restore type VII collagen gene expression in RDEB skin in vivo.

Nck/Dock: an adapter between cell surface receptors and the actin cytoskeleton.

In response to extracellular signals, cell surface receptors engage in connections with multiple intracellular signaling pathways, leading to the cellular responses such as survival, migration, proliferation and differentiation. The ‘pY→SH2/SH3→effector’ connection is a frequently used scheme by many cell surface receptors, in which SH2/SH3-containing adapters connect protein tyrosine phosphorylation to a variety of downstream effector pathways. Following the initial landmark finding that Grb2 adapter links the receptors to the Ras pathway leading to DNA synthesis, recent studies have revealed that the biological function of the SH2/SH3 adapter Nck/Dock is to link cell surface receptors to the actin cytoskeleton. For example, in the evolutionarily-conserved signaling network, GEF-Rac-Nck-Pak, Nck ‘fixes up’ the interaction of Pak with its upstream activator, Rac. The activated Pak then regulates the cytoskeletal dynamics. The fact that the majority of the more than 20 Nck-SH3-associated effectors are regulators of the actin cytoskeleton suggests that Nck/Dock regulates, via binding to distinct effectors, various cell type-specific motogenic responses. This review focuses on our current understanding of Nck/Dock function. Due to the number and complexity of the terminologies used in this review, a ‘Glossary of Terms’ is provided to help reduce confusions.

The Role of Oxygen in Wound Healing: A Review of the Literature

BACKGROUND The presence of oxygen is necessary for normal wound healing. Oxygen has been given as a therapeutic modality to assist and speed wound healing. OBJECTIVE The objective was to summarize the role of oxygen in wound healing. MATERIALS AND METHODS A literature review of clinical and basic science studies regarding oxygen and wound healing was conducted. RESULTS Hypoxia appears to jump start wound healing via hypoxia-inducible factor 1α and reepithelialization. Nonetheless, oxygen is often required to start or sustain other wound healing processes. CONCLUSION Both the absence and the presence of oxygen have effects on wound healing; however, its role is not completely understood. Although hyperbaric oxygen and topical oxygen therapy have been described in aiding wound healing, case-controlled prospective studies are lacking and evidence for their efficacy is inconsistent.

Epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a rare, acquired, chronic subepidermal bullous disease of the skin and mucosa characterized by autoantibodies to type VII collagen (C7) structures, a major component of anchoring fibrils, which attach the epidermis to the dermis. EBA patients have tissue-bound and circulating antitype C7 autoantibodies that attack type C7 and result in a reduction or perturbation of normally functioning anchoring fibrils. Patients with EBA have skin fragility, blisters, erosions, scars, milia, and nail loss, all features reminiscent of genetic dystrophic epidermolysis bullosa. These immunoglobulin G antitype C7 antibodies are pathogenic, because when they are injected into mice, the mice develop an EBA-like blistering disease. In addition to the classical mechanobullous presentation, EBA also has several other distinct clinical syndromes similar to bullous pemphigoid, Brunsting-Perry pemphigoid, or cicatricial pemphigoid. Although treatment for EBA is often unsatisfactory, some therapeutic success has been achieved with colchicine, dapsone, plasmapheresis, photopheresis, infliximab, and intravenous immunoglobulin.

Definitions and outcome measures for bullous pemphigoid: recommendations by an international panel of experts

Our scientific knowledge of bullous pemphigoid (BP) has dramatically progressed in recent years. However, despite the availability of various therapeutic options for the treatment of inflammatory diseases, only a few multicenter controlled trials have helped to define effective therapies in BP. A major obstacle in sharing multicenter-based evidences for therapeutic efforts is the lack of generally accepted definitions for the clinical evaluation of patients with BP. Common terms and end points of BP are needed so that experts in the field can accurately measure and assess disease extent, activity, severity, and therapeutic response, and thus facilitate and advance clinical trials. These recommendations from the International Pemphigoid Committee represent 2 years of collaborative efforts to attain mutually acceptable common definitions for BP and proposes a disease extent score, the BP Disease Area Index. These items should assist in the development of consistent reporting of outcomes in future BP reports and studies.

Transforming Growth Factor α (TGFα)-Stimulated Secretion of HSP90α: Using the Receptor LRP-1/CD91 To Promote Human Skin Cell Migration against a TGFβ-Rich Environment during Wound Healing

ABSTRACT Jump-starting and subsequently maintaining epidermal and dermal cell migration are essential processes for skin wound healing. These events are often disrupted in nonhealing wounds, causing patient morbidity and even fatality. Currently available treatments are unsatisfactory. To identify novel wound-healing targets, we investigated secreted molecules from transforming growth factor α (TGFα)-stimulated human keratinoytes, which contained strong motogenic, but not mitogenic, activity. Protein purification allowed us to identify the heat shock protein 90α (hsp90α) as the factor fully responsible for the motogenic activity in keratinocyte secretion. TGFα causes rapid membrane translocation and subsequent secretion of hsp90α via the unconventional exosome pathway in the cells. Secreted hsp90α promotes both epidermal and dermal cell migration through the surface receptor LRP-1 (LDL receptor-related protein 1)/CD91. The promotility activity resides in the middle domain plus the charged sequence of hsp90α but is independent of the ATPase activity. Neutralizing the extracellular function of hsp90α blocks TGFα-induced keratinicyte migration. Most intriguingly, unlike the effects of canonical growth factors, the hsp90α signaling overrides the inhibition of TGFβ, an abundant inhibitor of dermal cell migration in skin wounds. This finding provides a long-sought answer to the question of how dermal cells migrate into the wound environment to build new connective tissues and blood vessels. Thus, secreted hsp90α is potentially a new agent for wound healing.

Hypoxia increases human keratinocyte motility on connective tissue.

Re-epithelialization of skin wounds depends upon the migration of keratinocytes from the cut margins of the wound and is enhanced when human keratinocytes are covered with occlusive dressings that induce hypoxia. In this study, two independent migration assays were used to compare cellular motility on connective tissue components under normoxic or hypoxic conditions. Human keratinocytes apposed to collagens or fibronectin exhibited increased motility when subjected to hypoxic (0.2 or 2% oxygen) conditions compared with normoxic (9 or 20% oxygen) conditions. When compared with normoxic cells, hypoxic keratinocytes exhibited increased expression and redistribution of the lamellipodia-associated proteins (ezrin, radixin, and moesin). Furthermore, hypoxic keratinocytes demonstrated decreased secretion of laminin-5, a laminin isoform known to inhibit keratinocyte motility. Hypoxia did not alter the number of integrin receptors on the cell surface, but did induce enhanced secretion of the 92-kD type IV collagenase. These data demonstrate that hypoxia promotes human keratinocyte motility on connective tissue. Hypoxia-driven motility is associated with increased expression of lamellipodia proteins, increased expression of collagenase and decreased expression of laminin-5, the locomotion brake for keratinocytes.