Neuronal Precursor Cell Expressed Developmentally Down Regulated 4 (NEDD4) Gene Polymorphism Contributes to Keloid Development in Egyptian Population

Update on the Pathogenesis of Keloid Formation

Keloids are abnormal skin growths occurring in a significant portion of the global population. Despite their pervasiveness, the underlying pathophysiology of this scarring process is yet to be fully understood. In this review article, we delve into the current literature on the pathophysiological mechanisms of keloids. We take a top-down approach, first looking at host factors such as genetics and endocrine factors and then taking a more granular approach describing specific control factors such as germline keloid predisposition variants, epigenetics and transcriptomics, inflammatory and immune dysregulation, and the role of profibrotic and angiogenic cell signaling pathways. We then discuss current knowledge gaps, propose further research avenues, and explore potential future treatment options considering our increased understanding of keloid pathogenesis.

Global insights into keloid formation: An international systematic review of regional genetic risk factors and commonalities

Keloid disorder is a morbid and disfiguring benign fibroproliferative disease with a higher incidence in groups with darker skin pigmentation. Predicting keloidogenesis in patients is difficult with treatment primarily aimed at preventing further scar expansion and improving aesthetics without addressing their unknown underlying pathophysiology. We aimed to identify potential genetic predispositions to keloid scarring in the literature. A search was conducted on 21 August 2023, by the first and second authors independently from 1985 to August 2023 using PubMed, MEDLINE, Embase, Web of Science, Scopus and CINAHL. The following MeSH terms were used: 'Keloid', 'Risk' and 'Genetic'. Two researchers independently searched for studies based on titles and abstracts and screened filtered articles by reviewing full text. If no agreement could be reached, a third senior author designated whether the article should be included. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement as the basis of our organisation. Human studies with genetic analysis to determine an association of a protein or gene to keloidogenesis were selected for inclusion. Studies in languages other than English, reviews, conference articles, and book chapters were excluded. Fifty studies met inclusion criteria. The human leukocyte antigen (HLA) system was broadly implicated, and the DRB1*15 allele was associated with an increased risk of keloid in three separate ethnic groups. Some HLA Class I alleles were associated with keloid in one population but not in others. Additionally, polymorphisms in the E3 ubiquitin-protein ligase (NEDD4) signal cascade and vitamin D receptor (VDR) have been implicated in diverse groups. No current genetic test can predict keloid risk. Our review identified candidate predisposing genes, including NEDD4, VDR and components of the HLA system. Further studies in heterogeneous populations are needed to identify reliable screening targets.

Discovery of Nedd4 auto-ubiquitination inhibitors

E3 ubiquitin ligases are critical to the protein degradation pathway by catalyzing the final step in protein ubiquitination by mediating ubiquitin transfer from E2 enzymes to target proteins. Nedd4 is a HECT domain-containing E3 ubiquitin ligase with a wide range of protein targets, the dysregulation of which has been implicated in myriad pathologies, including cancer and Parkinson's disease. Towards the discovery of compounds disrupting the auto-ubiquitination activity of Nedd4, we developed and optimized a TR-FRET assay for high-throughput screening. Through selective screening of a library of potentially covalent compounds, compounds 25 and 81 demonstrated apparent IC50 values of 52 µM and 31 µM, respectively. Tandem mass spectrometry (MS/MS) analysis confirmed that 25 and 81 were covalently bound to Nedd4 cysteine residues (Cys182 and Cys867). In addition, 81 also adducted to Cys627. Auto-ubiquitination assays of Nedd4 mutants featuring alanine substitutions for each of these cysteines suggested that the mode of inhibition of these compounds occurs through blocking the catalytic Cys867. The discovery of these inhibitors could enable the development of therapeutics for various diseases caused by Nedd4 E3 ligase dysregulation.

Characterization of the skin keloid microenvironment

Keloids are a fibroproliferative skin disorder that develops in people of all ages. Keloids exhibit some cancer-like behaviors, with similar genetic and epigenetic modifications in the keloid microenvironment. The keloid microenvironment is composed of keratinocytes, fibroblasts, myofibroblasts, vascular endothelial cells, immune cells, stem cells and collagen fibers. Recent advances in the study of keloids have led to novel insights into cellular communication among components of the keloid microenvironment as well as potential therapeutic targets for treating keloids. In this review, we summarized the nature of genetic and epigenetic regulation in keloid-derived fibroblasts, epithelial-to-mesenchymal transition of keratinocytes, immune cell infiltration into keloids, the differentiation of keloid-derived stem cells, endothelial-to-mesenchymal transition of vascular endothelial cells, extracellular matrix synthesis and remodeling, and uncontrolled angiogenesis in keloids with the aim of identifying new targets for therapeutic benefit. Video Abstract.

An updated review of the immunological mechanisms of keloid scars

Keloid is a type of disfiguring pathological scarring unique to human skin. The disorder is characterized by excessive collagen deposition. Immune cell infiltration is a hallmark of both normal and pathological tissue repair. However, the immunopathological mechanisms of keloid remain unclear. Recent studies have uncovered the pivotal role of both innate and adaptive immunity in modulating the aberrant behavior of keloid fibroblasts. Several novel therapeutics attempting to restore regulation of the immune microenvironment have shown variable efficacy. We review the current understanding of keloid immunopathogenesis and highlight the potential roles of immune pathway-specific therapeutics.

Keloid: Genetic susceptibility and contributions of genetics and epigenetics to its pathogenesis

Keloid, characterized by fibroproliferative disorders of the skin, can be developed in people of different genders, ages, and ethnicities. Keloid can appear in any part of the body but are especially common on the earlobe, upper torso, and triangular muscle. The genetic heterogeneity and susceptibility of KD (keloid) vary among different races and ethnicities. Studies have found that multiple loci on multiple chromosomes are associated with the pathogenesis of KD, and specific gene variants may also be involved. Despite multiple investigations attempting to uncover the etiology of keloid formation, the genetic mechanism of keloid formation remains unknown. To establish a foundation for a better understanding of the genetics and epigenetics of keloids, we have evaluated and summarized current studies which are mostly related to heredity, genetic polymorphisms, predisposing gene, DNA methylation, and non-coding RNA. We also discussed the problems and potential of genetic and epigenetic investigations of keloids, with the goal of developing new therapeutic approaches to enhance the prognosis of keloid patients.