Differential gene expression of leaflet tissue in chronic ovine functional tricuspid regurgitation

Abstract

Abstract OBJECTIVES Severe functional tricuspid regurgitation (FTR) is associated with subvalvular remodelling, but leaflet tissue alterations may also contribute. We set out to investigate molecular mechanisms driving leaflet remodelling in chronic ovine FTR. METHODS Thirteen adult sheep (55 ± 4 kg) underwent left thoracotomy, epicardial echocardiography and pulmonary artery banding to induce right heart failure and FTR. After 16 weeks, 13 banded (FTR) and 12 control animals underwent median sternotomy for epicardial echocardiography and were subsequently sacrificed with each tricuspid leaflet tissue harvested for RNA-seq and histology. RESULTS After 16 weeks, 7 animals developed severe, 2 moderate and 4 mild tricuspid regurgitation. Relative to control, FTR animals had increased pulmonary artery pressure, tricuspid regurgitation, tricuspid annular diameter and right atrial volume, while tricuspid annular plane systolic excursion and right ventricle fractional area change decreased. FTR leaflets exhibited altered constituents and an increase in cellularity. RNA-seq identified 85 significantly differentially expressed genes with 17, 53 and 127 within the anterior, posterior and septal leaflets, respectively. RRM2, PRG4 and CXCL8 (IL-8) were identified as differentially expressed genes across all leaflets and CXCL8 was differentially expressed between FTR severity grades. RRM2, PRG4 and CXCL8 significantly correlated with tricuspid annular plane systolic excursion, and this correlation was consistent regardless of the anatomical location of the leaflet. CONCLUSIONS Pulmonary artery banding in our ovine model resulted in right ventricle failure and FTR. Leaflet RNA-seq identified several differentially expressed genes, specifically RRM2, PRG4 and CXCL8, with known roles in tissue remodelling. These data, along with an overall increase in leaflet cellularity, suggest tricuspid leaflets actively remodel in FTR.