Comparative reviews of PAH models and translational limitations underscore that model choice and timing profoundly shape observed fibrotic and inflammatory phenotypes, and therefore can account for discrepant reports linking IGFBP-5 to fibrosis in pulmonary vascular disease (Voelkel and Bogaard, 2021; Maarman et al., 2013). The gene discussed is IGFBP5; the disease is pulmonary arterial hypertension.