Structural characterization of the chordae tendineae in native porcine mitral valves.

Background: This study was aimed to characterize the different mitral valve chordae tendineae to provide additional understanding of their function.

Methods: Mitral valve chordae tendineae from fresh porcine hearts were stained for collagen and elastin using either a Verhoeff and van Gieson stain or Verhoeff light green stain. Cellular distribution was determined using a hematoxylin and eosin stain. Immunohistochemistry was used to verify the findings of vasculature. Biochemical assays were performed to quantify DNA, collagen, and elastin content of each of the six different types of chordae tendineae.

Results: Blood vessels were observed in the longitudinal and circumferential directions of the chordae. The strut chordae on the anterior leaflet of the mitral valve showed an increased degree of vascularization compared with the other chordae. All chordae had an inner layer characterized by a high concentration of collagen and an outer layer that was mostly elastin with interwoven collagen fibers. The collagen microstructure was characterized by directional crimping. Hematoxylin and eosin staining showed fibroblasts evenly distributed throughout the inner and outer layer of the chordae tendineae. Quantitative analysis showed significantly higher levels of DNA and collagen content in the anterior and posterior marginal chordae compared with the other chordae.

Conclusions: The chordae tendineae were seen to have different microstructures according to chordal type. The presence of vessels characterized the chordae tendineae as complex living components that work in coordination with the papillary muscles and mitral valve leaflets to prevent mitral valve prolapse and regurgitation. They may also function to supply nutrients to the valve leaflets.