SDC1 and pulmonary arterial hypertension: Although no direct evidence supports a role of eGCX in PAH pathogenesis, a recent study showed that the plasma levels of heparin sulfate proteoglycan (HSPG), hyaluronan (HA), and syndecan-1 (SDC-1) were elevated in monocrotaline-induced PAH rats in comparison with control group (46).