Extra domain A-containing fibronectin in pulmonary hypertension and treatment effects of a function-blocking antibody.

Aims: Pulmonary vascular and right ventricular (RV) remodelling processes are important for development and progression of pulmonary hypertension (PH). The current study analysed the functional role of the extra domain A-containing fibronectin (ED-A+ Fn) for the development of PH by comparing ED-A+ Fn knockout (KO) and wild-type (WT) mice as well as the effects of an antibody-based therapeutic approach in a model of monocrotaline (MCT)-induced PH, which will be validated in a model of Sugen 5416/hypoxia-induced PH.

Methods and results: PH was induced using MCT (PH mice). Sixty-nine mice were divided into the following groups: sham-treated controls (WT: n = 7; KO: n = 7), PH mice without specific treatment (WT: n = 12; KO: n = 10), PH mice treated with a dual endothelin receptor antagonist (macitentan; WT: n = 6; KO: n = 11), WT PH mice treated with the F8 antibody, specifically recognizing ED-A+ Fn, (n = 8), and WT PH mice treated with an antibody of irrelevant antigen specificity (KSF, n = 8). Compared to controls, WT_PH mice showed a significant elevation of the RV systolic pressure (P = 0.04) and RV functional impairment including increased basal RV (P = 0.016) diameter or tricuspid annular plane systolic excursion (P = 0.008). In contrast, KO PH did not show such effects compared to controls (P = n.s.). In WT_PH mice treated with F8, haemodynamic and echocardiographic parameters were significantly improved compared to untreated WT_PH mice or those treated with the KSF antibody (P < 0.05). On the microscopic level, KO_PH mice showed significantly less tissue damage compared to the WT_PH mice (P = 0.008). Furthermore, lung tissue damage could significantly be reduced after F8 treatment (P = 0.04). Additionally, these findings could be verified in the Sugen 5416/hypoxia mouse model, in which F8 significantly improved echocardiographic, haemodynamic, and histologic parameters.

Conclusion: ED-A+ Fn is of crucial importance for PH pathogenesis representing a promising therapeutic target in PH. We here show a novel therapeutic approach using antibody-mediated functional blockade of ED-A+ Fn capable of attenuating and partially reversing PH-associated tissue remodelling.