Total RNA was extracted using the miRNeasy kit (Qiagen), according to the manufacturer’s instructions. For RNA extraction from solid tissues (ascending thoracic aorta and right atrial appendage), about 50 mg of tissue was first homogenized in 1 mL QIAzol (Qiagen) in a gentleMACS M tube using the gentleMACS dissociator (both from Miltenyi Biotec). For RNA extraction from PF and plasma, 200 μl of sample was used with 1 mL of QIAzol. A synthetic analog of the non-human Caenorhabditis elegans microRNA-39 (cel-miRNA-39; Qiagen) was spiked in (10 μl of a 5 fmol/μl stock) to normalize RNA extraction efficiency. Reverse transcription of individual miRNAs was performed using the TaqMan miRNA Reverse Transcription Kit and miRNA-specific stem-loop primers (see Table S3; Thermo Fisher Scientific). qPCR was performed in triplicate using 2x Universal PCR Master Mix with No AmpErase UNG (Thermo Fisher Scientific) using the QuantStudio 6 Flex Real-Time PCR System (Thermo Fisher Scientific). miRNA expression was normalized with either cel-miRNA-39 (for biological fluids) or with the small nuclear U6 small nuclear RNA (snRNA) (ID: 001973) (for solid tissues). For mRNA analysis, cDNA obtained using the High-Capacity RNA-to-cDNA Kit (Thermo Fisher Scientific) was amplified by real-time qPCR. TaqMan Gene Expression Assays (Thermo Fisher Scientific) and 2x Universal PCR Master Mix with No AmpErase UNG (Thermo Fisher Scientific) were used to analyze the gene expression of TGFBR1 (ID: Hs00610320_m1), CASPASE3 (ID: Hs00234387_m1), LOX (ID: Hs00942480_m1), and UBC (ID: Hs00824723_m1) (all from Thermo Fisher Scientific). Real-time quantification to measure gene expression for human DICER and mouse TGFBR1 was performed using Power SYBR Green PCR Master Mix (Thermo Fisher Scientific) and normalized against human or mouse GAPDH.