ATR and rheumatoid arthritis: qRT‐PCR and Western blot analysis were used to detect the expression of p53, ATM and ATR in RA‐FLSs, and the results demonstrated that silencing miR‐34a in BM‐MSC‐derived Evs led to reduced p53, ATM and ATR expression both in rat synovial tissues and RA‐FLSs (Figure 7E‐H).