Psoriasis is a chronic inflammatory skin disease, the pathogenesis of which is more complicated and often requires long-term treatment. In particular, moderate to severe psoriasis usually requires systemic treatment. Psoriasis is also associated with many diseases, such as cardiometabolic diseases, malignant tumors, infections, and mood disorders. Psoriasis can appear at any age, and lead to a substantial burden for individuals and society. At present, psoriasis is still a treatable, but incurable, disease. Previous studies have found that microRNAs (miRNAs) play an important regulatory role in the progression of various diseases. Currently, miRNAs studies in psoriasis and dermatology are relatively new. Therefore, the identification of key miRNAs in psoriasis is helpful to elucidate the molecular mechanism of psoriasis.

To identify key molecular markers and signaling pathways to provide potential basis for the treatment and management of psoriasis.

The miRNA and mRNA data were obtained from the Gene Expression Omnibus database. Then, differentially expressed mRNAs (DEmRNAs) and differentially expressed miRNAs (DEmiRNAs) were screened out by limma R package. Subsequently, DEmRNAs were analyzed for Gene Ontology and Kyoto Encyclopedia of Genes and Genomics functional enrichment. The “WGCNA” R package was used to analyze the co-expression network of all miRNAs. In addition, we constructed miRNA-mRNA regulatory networks based on identified hub miRNAs. Finally, in vitro validation was performed. All experimental procedures were approved by the ethics committee of Chinese PLA General Hospital (S2021-012-01).

A total of 639 DEmRNAs and 84 DEmiRNAs were identified. DEmRNAs screening criteria were adjusted P (adj. P) value < 0.01 and |logFoldChange| (|logFC|) > 1. DEmiRNAs screening criteria were adj. P value < 0.01 and |logFC| > 1.5. KEGG functional analysis demonstrated that DEmRNAs were significantly enriched in immune-related biological functions, for example, toll-like receptor signaling pathway, cytokine-cytokine receptor interaction, and chemokine signaling pathway. In weighted gene co-expression network analysis, turquoise module was the hub module. Moreover, 10 hub miRNAs were identified. Among these 10 hub miRNAs, only 8 hub miRNAs predicted the corresponding target mRNAs. 97 negatively regulated miRNA-mRNA pairs were involved in the miRNA-mRNA regulatory network, for example, hsa-miR-21-5p-claudin 8 (CLDN8), hsa-miR-30a-3p-interleukin-1B (IL-1B), and hsa-miR-181a-5p/hsa-miR-30c-2-3p-C-X-C motif chemokine ligand 9 (CXCL9). Real-time polymerase chain reaction results showed that IL-1B and CXCL9 were up-regulated and CLDN8 was down-regulated in psoriasis with statistically significant differences.

The identification of potential key molecular markers and signaling pathways provides potential research directions for further understanding the molecular mechanisms of psoriasis. This may also provide new research ideas for the prevention and treatment of psoriasis in the future.

Psoriasis is a common chronic, recurrent, immune-regulatory skin and joint disease. It has a variety of clinical skin manifestations, but the most common clinical manifestations are erythematous, scaling papules, and plaques[1]. Previous studies have found that psoriasis is affected by family history and age[2]. Mechanical stress, air pollutants, sun exposure, infection, lifestyle, obesity, dyslipidemia, and mental stress are associated with the progression of psoriasis[3]. The pathogenesis of psoriasis is more complicated and often requires long-term treatment. Mild to moderate psoriasis can be treated topically with a combination of glucocorticoids, vitamin D analogues, and phototherapy. Moderate to severe psoriasis usually requires systemic treatment[4]. Psoriasis is also associated with many diseases, for example cardiometabolic diseases, malignant tumors, infections and mood disorders[5]. So far, psoriasis is still a treatable, but incurable, disease. Therefore, identification of key genes and signaling pathways are of great significance for understanding the molecular mechanism of psoriasis and provides potential basis for the treatment and management of psoriasis.

MicroRNAs (miRNAs) are a class of small non-coding single-stranded RNAs that regulate gene expression[6]. MiRNAs play a vital role in the progression of diseases, for example cancer, infectious diseases, and immune diseases[7]. MiRNAs can regulate cell proliferation, keratinocyte differentiation, apoptosis, and atypical immune activation in psoriasis[8]. Previous studies have found that miR-187 can inhibit the proliferation of keratinocytes by targeting B7 homolog 3 protein. In addition, in the mouse model of psoriasis, overexpression of miR-187 can reduce acanthosis and reduce the severity of the disease[9]. MiR-183-3p can inhibit the proliferation and migration of keratinocytes in psoriasis by inhibiting growth factor receptor binding 2-associated binding protein 1[10]. MiR-320b negatively regulates keratinocyte proliferation in psoriasis by targeting AKT serine/threonine kinase 3[11]. The low expression of miR-31 in dermal mesenchymal stem cells (DMSCs) in patients with psoriasis results in the increased expression of some of its target genes, which in turn promotes the activation of T lymphocyte by inhibiting the proliferation of DMSCs, thereby contributing to the pathogenesis of psoriasis[12]. Previous studies have found that miR-146 regulates inflammatory responses in keratinocytes and skin fibroblasts, which may affect the pathogenesis of psoriasis[13]. Furthermore, in human keratinocytes, the expression of miR-146a is induced by pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1B (IL-1B), and IL-17a, and the expression of miR-146b is induced by interferon-γ (IFN-γ) and IL-22. MiR-203 promotes keratinocyte proliferation by targeting liver X receptor-α and peroxisome proliferator-activated receptor-γ in psoriasis[14]. MiR-125 regulates keratinocytes proliferation by regulating targeted genes[15,16]. MiR-197 over expression inhibits keratinocytes proliferation induced by IL-22 and keratinocytes migration[17]. In addition, miR-99 also plays an important role in regulating the abnormal proliferation and differentiation of keratinocytes in psoriasis[18]. These studies demonstrate that miRNAs play a vital role in the pathogenesis of psoriasis. Currently, miRNAs studies in psoriasis and dermatology are relatively new. Therefore, the identification of key miRNAs in psoriasis is helpful to elucidate the molecular mechanism of psoriasis.

Weighted gene co-expression network analysis (WGCNA) can be used for finding clusters (modules) of highly correlated genes[19]. WGCNA has been used to identify key genes for many diseases, including cancer[20], cardiovascular disease[21], and immunological diseases[22]. In addition, WGCNA has also been used to identify key mRNAs and long noncoding RNAs in psoriasis. So far, we have not found studies that use WGCNA to identify key miRNAs in psoriasis. Therefore, we use WGCNA to identify key modules and miRNAs related to psoriasis and explore potential key pathways related to psoriasis through the targeting relationship of miRNA-mRNA.

Although psoriasis is widespread and has significant negative impact on patients’ quality of life, it has not yet been fully diagnosed and treated. In the research, we used the WGCNA method to identify 10 hub miRNAs that may be related to the pathogenesis of psoriasis. Then, target mRNAs of hub miRNAs were predicted by using miRDB database. Only 8 hub miRNAs were predicted to the corresponding target mRNAs. Subsequently, to understand the key biological functions involved in DEmRNAs and target DEmRNAs, we performed GO and KEGG functional analysis. Results demonstrated that they were significantly enriched in immune-related biological functions, for example, immune response, cell chemotaxis, and chemokine signaling pathway.

Hsa-miR-21-5p is abnormally expressed in psoriasis, but the specific molecular mechanism remains unclear[29]. In this study, results demonstrated that hsa-miR-21-5p expression was up-regulated and negatively regulated with CLDN8. CLDN8 is down-regulated in psoriasis and has an important molecular regulatory role[30]. CLDN8 has also been identified as a key downstream component of the IL-9 and IL-23 inflammatory cascade[31,32]. In addition, KEGG functional enrichment analysis showed that CLDN8 was enriched in hepatitis C. Cohen et al[33] found that psoriasis is associated with hepatitis C[33]. Cathelicidin, toll like receptor 9 (TLR9), IFN-γ, and TNF-α are inflammatory cytokines. Hepatitis C may increase susceptibility to psoriasis by up-regulating these inflammatory factors[34,35]. Thus, we hypothesized that hsa-miR-21-5p may play a vital regulatory role in hepatitis C through regulating CLDN8 and, thus, affect the pathogenesis of psoriasis.

Hsa-miR-30a-3p can affect the migration and proliferation of cancer cells by targeting related genes[36,37]. Hsa-miR-30a-3p is also contacted with platelet apoptosis and adhesion in immune thrombocytopenia[38]. However, we have not found any report about hsa-miR-30a-3p in psoriasis. In this study, we found that hsa-miR-30a-3p was up-regulated and negatively regulated with multiple DEmRNAs in psoriasis. It may play a vital regulatory role in psoriasis by targeting these DEmRNAs. We found the pro-inflammatory factor IL-1B in target DEmRNAs of hsa-miR-30a-3p. IL-1B has been found to play an important role in autoimmune or autoinflammatory conditions[39]. IL-1B is abundant in the tissue fluid of psoriasis and participates in the disease progression through dual effects[40]. First, it induces insulin resistance through p38 mitogen-activated protein kinase (p38MAPK), preventing insulin-dependent differentiation of keratinocytes, while IL-1B promotes keratinocyte proliferation, both hallmarks of psoriasis. Through KEGG functional enrichment analysis, we also found that IL-1B participates in multiple signal pathways, for example, measles, toll-like receptor signaling pathway, and cytokine-cytokine receptor interaction. Measles can relieve psoriasis through an immunosuppressive effect[41]. Toll-like receptor signaling pathway play an important role in psoriasis by affecting keratinocyte production[42]. The cytokine-cytokine receptor interaction is related to the occurrence and progression of psoriasis through combined transcriptomic analysis[43], which is consistent with our analysis. Thus, we hypothesized that hsa-miR-30a-3p may play a vital molecular role in the progression of psoriasis by targeting DEmRNAs to regulate multiple biological signaling pathways.

Hsa-miR-181a-5p is involved in the catabolic pathway of chondrocytes and oxidative stress in osteoarthritis[44]. Hsa-miR-181a-5p can also regulate the pathogenesis of sepsis-related inflammation through CRNDE/hsa-miR-181a-5p/TLR4 pathway[45]. In a case-control study, hsa-miR-181a-5p was significantly down-regulated in psoriasis[29]. The miRNA-mRNA regulatory network results demonstrated that hsa-miR-181a-5p was negatively regulated with multiple DEmRNAs. Among these DEmRNAs, we found inflammatory mediators CXCL9 and CCL8. CXCL9 is an important chemokine involved in T cell recruitment and is up-regulated in the plasma of patients with psoriasis[46,47]. Increased CXCL9 expression can aggravate the progression of psoriasis[48]. CXCL9 and hsa-miR-30c-2-3p were also negatively regulated in the miRNA-mRNA regulatory network. Oncology studies have shown that hsa-miR-30c-2-3p play a vital role in tumor pathogenesis by regulating the proliferation, apoptosis, migration, and invasion of cancer cells[49,50]. So far, we have not found any studies on hsa-miR-30c-2-3p in psoriasis. This article may be the first to report that hsa-miR-30c-2-3p plays a role in the pathogenesis of psoriasis. As a chemokine, CCL8 is involved in immune regulation and inflammatory processes in a variety of diseases[51-53]. Although no relevant studies on CCL8 have been found in psoriasis, the expression of CCL8 is up-regulated in atopic dermatitis[54]. In addition, CXCL9 and CCL8 were found to be enriched in chemokine signaling pathway and cytokine-cytokine receptor interaction by functional analysis. Therefore, this further suggests that hsa-miR-181a-5p and hsa-miR-30c-2-3p may play a regulatory role in psoriasis by targeting DEmRNAs to mediate multiple biological signaling pathways.

Current research results highlighted that silencing hsa-miR-181a-2-3p could enhance cadmium-induced inflammatory response and activation of inflammasome[55]. In the research, we found that hsa-miR-181a-2-3p was negatively regulated with multiple DEmRNAs. Among these DEmRNAs, OAS3 was found to be involved in hepatitis C and measles in KEGG functional enrichment. Some researchers have found that the OAS3 is concerned with the occurrence and progression of psoriasis through transcriptomic analysis, which is consistent with our analysis[56,57]. Thus, we hypothesized that hsa-miR-181a-2-3p may play a regulatory role in the progression of psoriasis by targeting OAS3 to mediate hepatitis C and measles. This provides potential molecular research directions for further research on the pathogenesis of psoriasis.

The expression of hsa-miR-21-3p in psoriasis was significantly increased[58]. Moreover, hsa-miR-21-3p plays a pro-inflammatory role in keratinocytes, and high expression in the skin is concerned with psoriasis[59]. So far, we have not found relevant reports about hsa-miR-18a-5p in psoriasis. However, hsa-miR-18a-5p promotes the proliferation and migration of pulmonary smooth muscle cells by targeting notch receptor 2[60]. Oncology studies have shown that hsa-miR-18a-5p promotes melanoma cell proliferation by targeting EPH receptor A7 signaling[61]. Hsa-miR-18a-5p can affect keratinocytes apoptosis by targeting B-cell lymphoma/leukemia-2-like protein 10 in patients with toxic epidermal necrolysis and is related to the skin erythema or erosion area of drug eruptions[62]. The miRNA-mRNA regulatory network regulatory network result demonstrates that hsa-miR-21-3p and hsa-miR-18a-5p jointly negatively regulate coagulation factor III, tissue factor (F3). This finding provides new research ideas for the pathogenesis of psoriasis in the future.

Results of previous studies demonstrate that down-regulation of interleukin 1 receptor associated kinase 3 by hsa-miR-33b-3p can alleviate the inflammation and apoptosis induced by IL-1B in CHON-001 cells[63]. As a key miRNA of major depression disorder and Kawasaki disease, hsa-miR-33b-3p play an important role in their pathogenesis[64,65]. Hsa-miR-33b-3p has also been reported in cancer[66]. In the miRNA-mRNA regulatory network, phospholipase C beta 4 (PLCB4) is the only negatively regulated target DEmRNA of hsa-miR-33b-3p. Neutrophils are an important part of the innate immune system and an early line of defense against microbial invasion. PLCB4 can regulate the number of neutrophils[67]. In addition, KEGG functional analysis result demonstrated that PLCB4 was enriched in chemokine signaling pathway. Thus, we hypothesized that hsa-miR-33b-3p may play a vital molecular role in psoriasis by targeting PLCB4 to regulate chemokine signaling pathway.

This study has some limitations. First, sample size of in vitro validation was small, leading to a certain degree of error between RT-PCR validation results and bioinformatics analysis results. Further studies with a larger sample size are needed. Secondly, the specific regulatory mechanism of the identified genes and signaling pathways in psoriasis remain unclear, so further research is needed.

In conclusion, identification of potential key molecular markers and signaling pathways provides potential molecular research directions for further understanding the pathological mechanisms of psoriasis. This may also provide new research ideas for the prevention and treatment of psoriasis in the future.