suggested that circ-AFF2 was up-regulated in synovial tissues and FLS of RA; circ-AFF2 could bind to the miRNA miR-650; it enhances the expression level of downstream target 2’,3’-cyclic nucleotide phosphodiesterase (CNP) and promotes fibroblast−like synoviocyte proliferation, inflammatory response, migration, and invasion (168). Here, CNP is linked to rheumatoid arthritis.