Physiological Remodelling of Mitral Valve Chordae Tendineae In The Maternal Bovine Heart

Abstract

Pregnancy is a cardiac volume-overload state that triggers heart valve remodelling. The bovine mitral valve anterior leaflet increases in area by ~35%, with a striking ~22% increase in the number of chordae tendineae attachments. It is hypothesized that the maternal increase in chordae number results from the splitting of existing tendons. Chordae from never-pregnant heifers and pregnant cows were harvested from a local abattoir. Differential scanning calorimetry was performed to assess collagen thermal stability, and histological sections were stained with Picrosirius Red and Movat Pentachrome, and immunostained for α-SMA and periostin. Collagen thermal stability, collagen crimp, the quantity of activated valvular interstitial cells, and periostin expression were unchanged between pregnancy groups. However, chordae bifurcations showed evidence of enhanced extracellular matrix remodelling compared to the surrounding tissue. This work suggests that chordae splitting may occur in both heifers and pregnant cows as a fundamental, routine tissue turnover mechanism.