Towards a comprehensive resource for elucidating the pathogenesis of inherited keratodermas

Keratoderma – pathological hyperkeratosis of palms and soles - is a cause of disability in many clinical situations, including the rare and heterogeneous group of inherited palmoplantar keratodermas (PPKs). The aim of this study was to work towards better understanding of molecular mechanisms active in the pathogenesis of PPK by the creation of a cell and tissue culture resource and its initial application to laboratory studies. My study was based on a diverse group of autosomal dominant disorders, previously ascertained in families from Scotland, in whom the precise genetic aetiology was known. I established a tissue and cell culture resource of inherited keratodermas of known single-gene aetiology from patients with proven keratin 1, 9, 17, loricrin and mitochondrial mutations. An additional pedigree with striate keratoderma with an unknown mutation was recruited, and the causative mutation identified as a novel heterozygous A-to-T transversion in exon 5 (c.430A>T) of the desmoglein 1 gene, converting an arginine residue to a premature termination codon (p.Arg144stop). The keratinocyte culture resource was established from patients with keratin 1, 9, 17 and loricrin mutations, as well as controls. Due to the pain associated with direct infiltration of plantar skin, biopsies were obtained using peripheral nerve block for plantar biopsy. The effectiveness of this approach, which may be useful for future administration of treatment, was made the subject of an open clinical trial. Histological and immunocytochemical studies were carried out on affected plantar skin obtained from PPK patients and compared to control tissue, in an attempt to identify common and distinct pathways resulting in hyperkeratosis. Histological changes, e.g. hypergranulosis, extent of hyperkeratosis, acanthosis or acantholysis, were not uniform across different subtypes of inherited PPK and varied even between individuals within subtypes. Prominent eosin staining of spinous cells was a common feature in inherited PPK due to underlying K1 and K17 mutations. Electron microscopy showed abnormal keratin filaments in PPK with underlying keratin mutations only but was not a uniform finding within subtypes, and other electron microscopic features also varied between individuals. Immunocytochemical study did not demonstrate significant differences in expression of a selection of markers of differentiation (keratins 1, 9, 14 and 17), and cornified envelope protein filaggrin. Abnormal involucrin expression was observed, with premature expression in basal and lower spinous layers in all PPK subtypes raising the possibility of a common underlying mechanism in the development of hyperkeratosis. Prominent loricrin staining was noted in areas of acantholysis in K1 and K9 subtypes, but was uniform across other subtypes. Markers of proliferation and apoptosis demonstrated no overt change in epidermal turnover, although it is possible that only small changes in proliferative index are required to produce plantar hyperkeratosis. Overall, using morphological criteria, plantar hyperkeratosis was not readily distinguishable between inherited PPK of different underlying genetic causes. This raises the possibility that many of the reported structural features of inherited PPK are secondary phenomena as opposed to critical steps in the pathogenesis of hyperkeratosis. Initial attempts at RNA extraction using laser and manual microdissection have to date been unsuccessful in generating RNA of the quality and concentration to run a pilot microarray experiment, using standard RNA extraction kits. Plans for future projects include the further development of a possible microarray experiment in the Pachyonychia Congenita type 2 pedigree with the McLean laboratory in Dundee. The tissue resource has been made available for collaborative study via the GENESKIN project, as well as through the McLean and Lane laboratories, Dundee for both functional studies and immortalisation of cell lines

Dysregulation of Connexin expression plays a pivotal role in psoriasis

Background: Psoriasis, a chronic inflammatory disease affecting 2–3% of the population, is characterised by epidermal hyperplasia, a sustained pro-inflammatory immune response and is primarily a T-cell driven disease. Previous work determined that Connexin26 is upregulated in psoriatic tissue. This study extends these findings. Methods: Biopsies spanning psoriatic plaque (PP) and non-involved tissue (PN) were compared to normal controls (NN). RNA was isolated and subject to real-time PCR to determine gene expression profiles, including GJB2/CX26, GJB6/CX30 and GJA1/CX43. Protein expression was assessed by immunohistochemistry. Keratinocytes and fibroblasts were isolated and used in 3D organotypic models. The pro-inflammatory status of fibroblasts and 3D cultures was assessed via ELISA and RnD cytokine arrays in the presence or absence of the connexin channel blocker Gap27. Results: Connexin26 expression is dramatically enhanced at both transcriptional and translational level in PP and PN tissue compared to NN (>100x). In contrast, CX43 gene expression is not affected, but the protein is post-translationally modified and accumulates in psoriatic tissue. Fibroblasts isolated from psoriatic patients had a higher inflammatory index than normal fibroblasts and drove normal keratinocytes to adopt a “psoriatic phenotype” in a 3D-organotypic model. Exposure of normal fibroblasts to the pro-inflammatory mediator peptidoglycan, isolated from Staphylococcus aureus enhanced cytokine release, an event protected by Gap27. Conclusion: dysregulation of the connexin26:43 expression profile in psoriatic tissue contributes to an imbalance of cellular events. Inhibition of connexin signalling reduces pro-inflammatory events and may hold therapeutic benefit

Towards a comprehensive resource for elucidating the pathogenesis of inherited keratodermas

Keratoderma – pathological hyperkeratosis of palms and soles - is a cause of disability in many clinical situations, including the rare and heterogeneous group of inherited palmoplantar keratodermas (PPKs). The aim of this study was to work towards better understanding of molecular mechanisms active in the pathogenesis of PPK by the creation of a cell and tissue culture resource and its initial application to laboratory studies. My study was based on a diverse group of autosomal dominant disorders, previously ascertained in families from Scotland, in whom the precise genetic aetiology was known. I established a tissue and cell culture resource of inherited keratodermas of known single-gene aetiology from patients with proven keratin 1, 9, 17, loricrin and mitochondrial mutations. An additional pedigree with striate keratoderma with an unknown mutation was recruited, and the causative mutation identified as a novel heterozygous A-to-T transversion in exon 5 (c.430A>T) of the desmoglein 1 gene, converting an arginine residue to a premature termination codon (p. Arg144stop). The keratinocyte culture resource was established from patients with keratin 1, 9, 17 and loricrin mutations, as well as controls. Due to the pain associated with direct infiltration of plantar skin, biopsies were obtained using peripheral nerve block for plantar biopsy. The effectiveness of this approach, which may be useful for future administration of treatment, was made the subject of an open clinical trial. Histological and immunocytochemical studies were carried out on affected plantar skin obtained from PPK patients and compared to control tissue, in an attempt to identify common and distinct pathways resulting in hyperkeratosis. Histological changes, e.g. hypergranulosis, extent of hyperkeratosis, acanthosis or acantholysis, were not uniform across different subtypes of inherited PPK and varied even between individuals within subtypes. Prominent eosin staining of spinous cells was a common feature in inherited PPK due to underlying K1 and K17 mutations. Electron microscopy showed abnormal keratin filaments in PPK with underlying keratin mutations only but was not a uniform finding within subtypes, and other electron microscopic features also varied between individuals. Immunocytochemical study did not demonstrate significant differences in expression of a selection of markers of differentiation (keratins 1, 9, 14 and 17), and cornified envelope protein filaggrin. Abnormal involucrin expression was observed, with premature expression in basal and lower spinous layers in all PPK subtypes raising the possibility of a common underlying mechanism in the development of hyperkeratosis. Prominent loricrin staining was noted in areas of acantholysis in K1 and K9 subtypes, but was uniform across other subtypes. Markers of proliferation and apoptosis demonstrated no overt change in epidermal turnover, although it is possible that only small changes in proliferative index are required to produce plantar hyperkeratosis. Overall, using morphological criteria, plantar hyperkeratosis was not readily distinguishable between inherited PPK of different underlying genetic causes. This raises the possibility that many of the reported structural features of inherited PPK are secondary phenomena as opposed to critical steps in the pathogenesis of hyperkeratosis. Initial attempts at RNA extraction using laser and manual microdissection have to date been unsuccessful in generating RNA of the quality and concentration to run a pilot microarray experiment, using standard RNA extraction kits. Plans for future projects include the further development of a possible microarray experiment in the Pachyonychia Congenita type 2 pedigree with the McLean laboratory in Dundee. The tissue resource has been made available for collaborative study via the GENESKIN project, as well as through the McLean and Lane laboratories, Dundee for both functional studies and immortalisation of cell lines.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Generation and Clinical Application of Gene-Modified Autologous Epidermal Sheets in Netherton Syndrome:Lessons Learned from a Phase 1 Trial

Netherton Syndrome (NS) is a rare autosomal recessive skin disorder caused by mutations in SPINK5. It is a debilitating condition with notable mortality in the early years of life. There is no curative treatment. We undertook a non-randomized, open-label, feasibility and safety study using autologous keratinocytes transduced with a lentiviral vector encoding SPINK5 under the control of the human involucrin promoter. Six NS subjects were recruited and gene-modified epithelial sheets were successfully generated in three out of five subjects. The sheets exhibited expression of correctly sized LEKTI protein after modification. One subject was grafted with a 20cm2 gene-modified graft on the left anterior thigh without any adverse complications and was monitored by serial sampling for 12 months. Recovery within the graft area were compared against an area outside by morphology, pro-viral copy number and expression of the SPINK5 encoded protein, LEKTI, and its down-stream target kallikrein 5, which exhibited transient functional correction. The study confirmed the feasibility of generating lentiviral gene-modified epidermal sheets for inherited skin diseases such as NS, but sustained LEKTI expression is likely to require the identification, targeting and engraftment of long-lived keratinocyte stem cell populations for durable therapeutic effects. Important learning points for the application of gene modified epidermal sheets are discussed

Haploinsufficiency for AAGAB causes clinically heterogeneous forms of punctate palmoplantar keratoderma

Palmoplantar keratodermas (PPKs) are a group of disorders that are diagnostically and therapeutically problematic in dermatogenetics(1-3). Punctate PPKs are characterized by circumscribed hyperkeratotic lesions on palms and soles with considerable heterogeneity. In 18 families with autosomal dominant punctate PPK (OMIM #148600), we report heterozygous loss-of-function mutations in AAGAB, encoding alpha- and gamma-adaptin binding protein p34, at a previously linked locus on 15q22. p34, a cytosolic protein with a Rab-like GTPase domain, was shown to bind both clathrin adaptor protein complexes, indicative of a role in membrane traffic. Ultrastucturally, lesional epidermis showed abnormalities in intracellular vesicle biology. Immunohistochemistry showed hyperproliferation within the punctate lesions. Knockdown of p34 in keratinocytes led to increased cell division, which was linked to greatly increased epidermal growth factor receptor (EGFR) protein expression and tyrosine phosphorylation. We hypothesize that p34 deficiency may impair endocytic recycling of growth factor receptors such as EGFR, leading to increased signaling and proliferation