A significant decrease in the canstatin concentration was observed in PAH rats (2 weeks: 24.4 ± 4.5 ng/mL, 3 weeks: 45.3 ± 1.7 ng/mL), which coincides with the decreased expression of canstatin in the organs including RV, lung and kidney but not LV and liver (Figure 2 and Figure S1). Here, COL4A2 is linked to pulmonary arterial hypertension.