STAT3 and rheumatoid arthritis: (1) In terms of the number of T cells, one research has demonstrated that lncRNA HOXA transcript at the distal tip was upregulated in rheumatoid arthritis (RA) synovial fibroblast cell-derived exosomes and promoted the expression of STAT3 by inhibiting the expression of miR-1908-5p, which increased the proportion of T-helper17(Th17) cells and decreased the proportion of Treg cells in the CD4+ T cell population, leading to increased synovial inflammation and cartilage erosion (20).