2.3. Isolation, culture and treatment of human atrial fibroblasts (HAFs)

Human atrial fibroblasts (HAFs) were isolated from atrial appendage tissue of patients with SR. The atrial appendage tissue was digested using 0.25% trypsin plus 20 IU/mL DNase. HAFs were separated from cardiomyocytes using gravity separation and then grown to confluency in 10‐cm cell culture dishes in the growth media (DMEM/LG 10% FBS, 1% penicillin and 1% streptomycin) at 37°C in humid air with 5% CO₂. HAFs from the fourth to sixth passage were used for the experiments. The miR‐23b‐3p mimic, miR‐27b‐3p mimic and TGFBR3 siRNA (50 nmol/L each, RiboBio, Guangzhou, China) were transfected into HAFs using oligofectamine reagent (Invitrogen, Carlsbad, CA, USA). HAFs were then incubated with DMEM/LG 1% FBS overnight before treatment with 10 μmol/L Ang‐II (Sigma‐Aldrich, St. Louis, MO, USA). As indicated, HAFs were infected with the following recombinant adenovirus respectively: rAd‐GFP, rAd‐TGFBR3 adenovirus (MOI 5).