The expression of Acta2 and Loxl1 was significantly higher on cells grown on 3 kPa matrices but not significantly higher on cells grown on 10 kPa matrices, while Col1a1, Col3a1, Eln, and Fn1 were significantly upregulated on 10 kPa substrates (comparable to arterial stiffness in advanced PAH [14]), compared with PAAFs cultured on 0.5 kPa matrices (Figure 3A). This evidence concerns the gene COL3A1 and pulmonary arterial hypertension.