Transcription Levels of Endothelin‐1 and Endothelin Receptors are Associated with Age and Leaflet Location in Porcine Mitral Valves

Summary The aim of the study was to investigate the expression levels of endothelin-1 (ET-1) and ETA and ETB receptors (ETA-R and ETB-R) in porcine mitral valves and associate the transcription levels to age, leaflet location and deposition of mucopolysaccharides (MPS). Tissue samples from the chordal and inter-chordal insertion area of the anterior mitral valve leaflet from 11 sows (≥2 years of age) and 10 slaughter pigs (approximately 6 months old) were obtained and the relative gene expression levels of ET-1, ETA-R and ETB-R measured by semi-quantitative real-time PCR. A separate tissue sample was taken for histopathological grading of MPS deposition. The transcription levels of ET-1 (P < 0.0001) and ETA-R (P < 0.0004) were significantly higher in leaflets from the sows compared with slaughter pigs. The gene expression of ETB-R was not associated to age (P = 0.38), but increased in chordal insertion areas compared with inter-chordal areas (P = 0.01). The expression of ET-1 and ETA-R mRNA did not differ significantly between the two leaflet locations. The valve leaflets from sows had a significantly increased degree of MPS deposition compared with slaughter pigs upon histological examination (P = 0.04). In conclusion, an age-related valvular degeneration is observed in porcine mitral valve leaflets and ET-1 is suggested to be involved through action of both ETA and ETB receptors.