Background: Previous studies have reported the association between the disease activity of systemic inflammatory diseases and circulating exosomal microRNAs (miRNAs) which were previously known to be associated with hyperproliferation of keratinocytes and abnormal immune activation in psoriasis. Currently, when evaluating disease severity of psoriasis, such as psoriasis area and severity index (PASI) and body surface area (BSA), are widely used in clinical practice. However, PASI and BSA are subjective tools that do not reflect co-morbidities and may have relatively high inter-rater variability. There is a need for a tool that can objectively evaluate psoriatic lesions.
Objective: This study aimed to reveal the possible relationship between circulating exosomal miRNAs and the disease severity of psoriasis and to discover miRNAs as potential biomarkers to measure the severity objectively.
Material and methods: 41 psoriasis patients who visited Ajou University Hospital from May 2016 to March 2021 and 12 Behçet's disease (BD) patients who visited Ajou University Hospital from July 2013 to May 2020 participated in the study, respectively. We classified psoriasis patients based on PASI scores. Plasmas were collected from 10 patients in the discovery phase and 33 patients in the validation phase, and two patients were included in both phases. Also, skin samples were obtained only from 18 psoriasis patients who consented to additional tissue collection at the time of biopsy. Next, we performed next-generation RNA sequencing (NGS) to identify differentially expressed exosomal miRNAs and ran the RT-PCR to validate these exosomal miRNAs.
Results: Five upregulated and 10 downregulated exosomal miRNAs were found to be differentially expressed based on NGS method. Among the three upregulated and downregulated miRNAs found in NGS, candidate miRNAs were considered by both fold change and p-value and verified by RT-qPCR. Also, we were able to identify miR-625-3p, miR-4488 and miR-342-3p expression levels were significantly proportional to the disease severity. Disease activity in BD patients did not show any association with miR-625-3p in plasma samples. Especially, the expression levels of miR-625-3p in both plasma and skin tissue samples and miR-4488 in plasma significantly correlated with PASI scores and showed good predictive values.
Conclusion: We believe that miR-625-3p and miR-4488 could be used as an objective biomarker for the disease severity of psoriasis.
