RETNLB and pulmonary arterial hypertension: Moreover, by knocking out or overexpressing the Fizz1 gene in the rodent PAH model, Lin et al. (50) recently validated that Fizz1 mediated the crosstalk between PAECs and PASMCs, which promoted the alteration of PASMCs to a proliferative phenotype and pulmonary vascular remodeling in PAH.