TLR4 and rheumatoid arthritis: Other circRNAs, such as circ_0088194 (167), circ-AFF2 (168), circ-Sirt1 (170), circ-PTTG1IP (171), and circASH2L (173), also acted as miRNA sponge in RA; they regulated FLS proliferation, inflammation, and migration via circ_0088194/miR-766-3p/MMP2 axis, circ-AFF2/miR-650/CNP axis, circ-Sirt1/miR-132/Sirt1 pathway, circ-PTTG1IP/miR-671-5p/TLR4 axis, and circASH2L/miR-129-5p/HIPK2 axis, respectively.