Histone deacetylase 1 is increased in rheumatoid arthritis synovium and promotes synovial cell hyperplasia and synovial inflammation in the collagen-induced arthritis mouse model via the microRNA-124-dependent MARCKS-JAK/STAT axis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease featured by synovial joint inflammation. Increasing evidence has highlighted microRNAs (miRNAs) and histone deacetylase 1 (HDAC1) as active participants in RA progression. Hence, the present study aims to explore the functions of HDAC1 and miR-124 on synovial cell hyperplasia and synovial inflammation in RA.The expression of HDAC1, miR-124 and MARCKS was determined in the synovial tissues collected from 25 RA patients by RT-qPCR and Western blot analysis. Next, a mouse model with collagen-induced arthritis (CIA) was established, from which fibroblast-like synovial cells (FLSs) were isolated. Then the effect of HDAC1, miR-124 and MARCKS on synovial cell hyperplasia and synovial inflammation in CIA mice was evaluated by HE staining, ELISA, and EdU assays. Afterwards, the interaction among HDAC1, miR-124, MARCKS and the JAK/STAT signalling pathway was assessed by ChIP and dual luciferase reporter assay. Finally, the effect of HDAC1 on RA was further verified by establishing a CIA mouse model.HDAC1 was highly expressed and miR-124 and MARCKS were poorly expressed in synovial tissues of CIA. Silencing HDAC1 inhibited synovial cell hyperplasia and synovial inflammation by elevating MARCKS and miR-124 both in vitro and in vivo. Deficiency of HDAC1 promoted H3 and H4 acetylation of miR-124 and MARCKS promoter region. miR-124 alleviated synovial cell hyperplasia and synovial inflammation by repressing the JAK/STAT signalling pathway in CIA.To sum up, silencing HDAC1 mitigates synovial cell hyperplasia and synovial inflammation in mice with CIA by elevating miR-124 and MARCKS expression, thus highlighting a promising competitive new target for RA treatment.