Crucial role of extra-domain A containing fibronectin for the development of pulmonary hypertension and associated right heart failure
Authors: Singerer I , Gruen K , Schrepper A , Baez L , Schwarzer M , Bauer R , Jung C , Berndt A , Schulze P C , Franz M 
Published: October 2021

Abstract

Background
Pulmonary vascular and right ventricular myocardial remodelling are unique phenomena in PH progression. Both processes are accompanied by an abundant re-expression of the extra-domain A of fibronectin (ED-A+ Fn) therefore qualifying as promising biomarker or even therapeutic target. Nevertheless, its functional role in PH pathogenesis remains unclear until now. Objective: The purpose of our study was to analyse the development of PH and RHF in a mouse model of monocrotaline (MCT)-induced PH comparing C57BL/6 ED-A+ Fn knockout (KO) and wild-type (WT) mice.

Methods
PH was induced by subcutaneous injection of a single dose of MCT (60 mg/kg body weight). Subgroups were additionally treated with the dual endothelin receptor antagonist Macitentan (MAC, 15mg/kg body weight per day from day 14 to 28). There were 6 experimental groups: sham-treated control WT mice (WTco, n=4); MCT induced PH WT mice (WTPH, n=6); MCT induced PH WT mice treated with MAC (WTPH_MAC, n=6); sham-treated control KO mice (KOco, n=4); MCT induced PH KO mice (KOPH, n=6); MCT induced PH KO mice treated with MAC (KOPH_MAC, n=6). Between day 26 and 28, transthoracic echocardiography and right heart catheterization were performed. Both, lung and cardiac tissue samples were subjected to histological analyses.

Results
Right heart catheterization revealed significantly increased RVPsys values in WTPH (87.0±16.4mmHg) compared to WTco (36.1±9.4mmHg; p=0.034) animals, which showed, at least in trend, a diminution in the WTPH_MAC group (67.1±20.9mmHg; p=n.s.). There was a non-significant increase in RVPsys in the KOPH (55.6±14.9mmHg) compared to KOco mice (37.2±5.6mmHg; p=n.s.) without any differences compared to the KOPH_MAC group (60.9±14.0mmHg; p=n.s.). When comparing the WTPH and the KOPH group, RVPsys was significantly lower in the KO animals (p=0.014), while there were no differences between the WTPH_MAC and the KOPH_MAC group (p=n.s.). Echocardiographic evaluation including surrogate parameters of right ventricular (RV) overload and failure were significantly altered in WTPH compared to WTco animals (p&lt;0.05) and could not be shown to be relevantly improved in the WTPH_MAC group (p=n.s.). The majority of echocardiographic parameters did not significantly differ between the KOPH and the KOco group (p=n.s.). Lung tissue analysis revealed significant alterations in both, the WTPH and the KOPH group, each compared to the corresponding control (p&lt;0.05). The level of lung tissue damage was significantly decreased in KOPH compared to WTPH mice (p&lt;0.05). In RV, the amount of interstitial fibrosis was increased in the WTPH (p=0.009) but not in the KOPH group (p=n.s.), each compared to the corresponding controls.

Conclusions
The findings of the current study underline the hypothesis that ED-A+ Fn is a key player in the pathogenesis of PH and associated RHF. Thus, it might represent a promising therapeutic target, e.g., by the administration of neutralizing antibodies.

Funding Acknowledgement
Type of funding sources: Public hospital(s). Main funding source(s): University Hospital Jena