Psoriasis is a common, chronic, noncommunicable skin disease, with no clear cause or cure. Recent advances in psoriasis pathogenesis improved the understanding of disease mechanisms and resulted in the development of new immunobiologics and small molecules that help to control the chronic inflammation. However, long-term adverse effects of treatments and loss of drug efficacy are still major concerns for patients who need systemic therapy. During the last decade, the non-coding microRNAs (miRNAs) have emerged as key mediators of post-transcriptional gene silencing in several skin disorders, including psoriasis. In particular, several studies documented a differential expression of about a hundred of miRNAs in psoriatic skin compared with healthy skin, and the most highly changed miRNAs are related to inflammation and hyperproliferation pathways. However, the exact pathogenic roles of miRNAs have not been fully elucidated, and there is very little information regarding the genes involved in miRNAs biogenesis in psoriatic skin.Therefore, the present research proposal is aimed at investigating, on in vitro 2D and 3D psoriasis models, the expression of panel of selected miRNAs, their precursors, and the main protein-coding genes involved in miRNA processing and function. The latter will be also evaluated at the post-transcriptional and post-translational levels, by analyzing protein abundance, phosphorylation status (related to protein activity), and subcellular localization. We believe that the results obtainable with this work could fill important gaps on current knowledge about psoriasis, and represent a prerequisite for further preclinical research.
In 2014, a resolution of the World Health Organization highlighted that many people in the world suffer needlessly from psoriasis due to incorrect or delayed diagnosis, inadequate treatment options and insufficient access to care, and because of social stigmatization. Individuals with psoriasis are also reported to be at increased risk of developing other serious clinical conditions such as cardiovascular and other non-communicable diseases (Global report on psoriasis, WHO 2016). Psoriasis does not have a cure, and available treatments are still limited to symptoms control. About 70-80% of patients have mild forms that can be controlled using topical drugs alone, while others require systemic therapies and/or phototherapy. In practice, a combination of these methods is often used and the cure is usually lifelong. However, despite the variety of treatment options, it is not possible to predict which patients will respond adequately to a certain drug, and there is a significant number of primary or secondary non-responders, and patients intolerant to therapy. In recent years, transcriptomics revealed a profoundly altered expression profile of miRNAs in psoriatic whole skin as well as in individual resident cell types (PMID: 27783430). Furthermore, independent studies agree in indicating a marked dysregulation of specific miRNAs in lesions and/or blood of psoriatic patients, which are presently regarded as either candidate disease markers or therapeutic targets. Nonetheless, the miRNA regulatory networks and relevant mechanisms that come into play in psoriasis are far from being understood. The experimental plan of the present project was conceived to explore, in a simplified and controlled system, the effects of a psoriatic-like environment on miRNA expression profile in the cell type responsible for the cutaneous manifestations of the disease, i.e. the keratinocyte. Given that regulation of miRNA processing has emerged as a crucial step in defining the spatiotemporal pattern of miRNA expression, it was essential to include in the study the examination of the main proteins involved in miRNA biogenesis and functions.
To the best of our knowledge, there is no study in which the main genes linked to miRNA biogenesis have been characterized at the same time, both in terms of gene expression, post-transcriptional modifications and subcellular localization. Therefore, untreated control keratinocytes will provide valuable information also from a physiological point of view. Moreover, in order to work with a psoriasis model as similar as possible to the human psoriatic skin while maintaining the advantages of acting in strictly controlled experimental conditions, we chose to verify the results obtained in monolayer cultures on skin equivalents.
Improved understanding the role of miRNAs in psoriasis may lead to future insights into disease pathogenesis, diagnosis, and treatment. Because of the easy accessibility of the skin, it is plausible that, once efficient and safe methods for the topical delivery of substances mimicking or modulating miRNA activity become available, skin diseases will be among the first to be approached with miRNA-based therapies.