Skewness Angle of Interfibrillar Proteoglycan Increases with Applied Load on Chordae Tendineae

In highly aligned connective tissues, such as tendon, collagen fibrils are linked together by proteoglycans (PGs). We used transmission electron microscopy to observe the collagen fibril-proteoglycan interactions in porcine mitral valve chordae under loaded conditions. Comparison of fibril-proteoglycan configuration between stressed and load-free states showed that PGs mainly attached to collagen fibrils perpendicularly in the load-free situation, and became skewed when the chordae were loaded. The average skewness angle of PGs increased with the applied load. The observation of skewed proteoglycans demonstrated that interfibrillar slippage occurs in chordae, and that proteoglycans might play a role in the fibril-to-fibril interaction.