Knockdown of circular RNA hsa_circ_0003307 inhibits synovial inflammation in ankylosing spondylitis by regulating the PI3K/AKT pathway

Background: Ankylosing spondylitis (AS) has a high disability rate, and an early diagnosis is difficult.

Objectives: To explore the possible functions and underlying mechanism of circular RNAs Homo sapiens (hsa)_circ_0003307 in ankylosing spondylitis.

Material and methods: The hsa_circ_0003307 expression levels were investigated in the peripheral blood mononuclear cells (PBMCs) of 30 AS patients and 30 healthy controls (HC) using quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis. Primary fibroblast-like synoviocytes (FLS) were separated from synovial tissues, established as cell lines and cultured for subsequent cell experiments involving transfection with different vectors. The qRT-PCR analysis was used for evaluating the levels of hsa_circ_0003307 in AS-FLS. Phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway-related protein levels were measured using western blotting and immunofluorescence. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of inflammatory cytokines. Spearman's correlation analysis was used to assess the correlation between hsa_circ_0003307 and clinical characteristics.

Results: The expression level of hsa_circ_0003307 was significantly high in AS patients and was positively associated with erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and Bath Ankylosing Spondylitis Functional Index (BASFI). We found that hsa_circ_0003307 overexpression could promote the activation of the PI3K/AKT pathway and expression of inflammatory cytokines - tumor necrosis factor alpha (TNF-α) and TNF-α-induced protein 2 (TNFAIP2). However, hsa_circ_0003307 knockdown reduced the expression of TNF-α and TNFAIP2.

Conclusions: The expression level of hsa_circ_0003307 was associated with inflammatory response, and it was revealed that hsa_circ_0003307 knockdown could reduce the inflammatory response of AS by regulating the PI3K/AKT pathway.