Ultrastructure of porcine mitral valve chordae tendineae.
OBJECTIVE
The chordae tendineae, which form an important component of the mitral valve apparatus, experience continuous cyclic loading and are thus well-adapted for effectively storing and dissipating energy. An understanding of their microstructure would be expected to shed light on the mechanism of their remarkable durability.


METHODS
In these studies, porcine mitral valve chordae from freshly slaughtered pigs were used. Histological samples of Picrosirius Red-stained and Movat's pentachrome-stained chordae were examined with optical microscopy and laser scanning confocal microscopy. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the ultrastructure at high magnification.


RESULTS
Both, optical microscopy and SEM revealed that the waviness of collagen fibers was uniform across the thickness of the chordae, with no straight fibers in the core. Wavy fibers and fiber bundles were found to be in skewed-register, rather than transverse. Collagen fiber bundles were found to undulate in a three-dimensional path, rather than the planar waveform, as reported previously. TEM showed that different types of chordae had different fibril configurations. Marginal chordae had smaller diameters but a higher fibril density than did basal and strut chordae.


CONCLUSIONS
The configuration of collagen fibrils in the mitral valve chordae is more complex than initially thought, and different chordae have morphologies that are likely specific to their mechanical role in the mitral apparatus. These findings provide insight into possible improvements for chordal repair surgery, and form a structural basis for accurate computational modeling.
Liao
Jun
J
Cardiovascular Tissue Biomechanics Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, 130 Creelman Street, Room 222, Mississippi State, MS 39762, USA. jliao@abe.msstate.edu
Priddy
Lauren B
LB
Wang
Bo
B
Chen
Joseph
J
Vesely
Ivan
I
D000818:Animals; D001696:Biomechanical Phenomena; D002815:Chordae Tendineae / Q000648:ultrastructure*; D003094:Collagen / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008943:Mitral Valve / Q000648:ultrastructure*; D013552:Swine
D003094:Collagen