Background: Mitral valve chordae tendinae are an essential component for proper functioning of the human heart. The microstructural make-up of the chordae is responsible for their tensile properties and gradually changes with age. However, little is known about the maturation of chordae and their microstructure.
Objective and Methods: To examine the maturation of the mitral valve chordae tendinae, we studied the structural changes in chordae tendinae in rats at 1, 3, 7, 15, 30 days of postnatal life and of adult. The differences in microstructure of the chordae of each age group were observed using light microscopy. Collagen fibril crimp period was measured using polarized light microscopy.
Results: At day 1 after birth the chordae have yet to develop and the lateral sides of the mitral valve leaflets were completely attached to the papillary muscles. Chordae developed through the formation of gaps in the leaflet tissue. From day 7 on, numerous chordae were seen. No organized collagen fibrils were seen at day 1 after birth. As the chordae matured, crimped collagen fibrils were formed and started to align in a longitudinally packed core with increasing density. Collagen crimp period increased significantly with age (P < 0,001). No differences were found between average crimp period and chordae diameter.
Conclusion: Rat chordae tendinae have yet to develop 1 day after birth. Morphological development and microstructural maturation of the chordae are not completed until adulthood. A better understanding of normal chordal maturation may help improve methods for the development of tissue-engineered chordae.