MMP1 and rheumatoid arthritis: In addition to its widely reported proinflammatory role in immune cells, miR-155 also upregulates the secretion of inflammatory factors from RA-FLSs.81,82 Of interest, miR-155 is assumed to protect against acquisition of a destructive phenotype by RA-FLSs by repressing the expression of MMP3 and MMP1.80,83 In this regard, further research is warranted to dissect the precise role of miR-155 in RA-FLSs and identify its direct target genes and pathways.