Matrix Metalloproteinases 2 and 9 are Concentrated in the Luminal Aspect of the Cricoid Cartilage, Diminish with Loss of Perichondrium, and are Reinstated by Transforming Growth Factor Beta 3

Objectives: We determined the location of matrix metalloproteinases (MMP) 2 and 9, and whether the luminal perichondrium or transforming growth factor (TGF) β3 influences the presence of MMP-2 and/or −9 within the chondrocytes of the cricoid cartilage. Methods: Subglottises from 15 neonatal mice were divided into group A (N = 5; luminal epithelium intact, grown in basic medium), group B (N = 5; epithelium-free, with sections of luminal perichondrium removed, grown in basic medium), and group C (N = 5; epithelium-free, with sections of luminal perichondrium removed, grown in basic medium with supplemental TGF-β3). Immunohistochemical analysis was done to identify MMP-2 and −9 distributions. Results: Group A demonstrated concentrations of MMP-2 and −9 in the luminal perichondrial and adjacent chondrocytes with a gradual decrease in signal intensity toward the outer perichondrium. Group B showed findings similar to those in group A, but in the region of removed perichondrium, the adjacent chondrocytes lost MMP-2 and −9 signal. The group C rings demonstrated reestablishment of MMP-2 and −9 signal in regions of luminal perichondrial loss. Conclusions: Localization of MMP-2 and −9 is predominantly in the luminal perichondrium and gradually decreases toward the outer perichondrium. The luminal perichondrium maintains expression of MMP-2 and −9 within the adjacent chondrocytes. Exogenous TGF-β3 reestablishes production of at least MMP-9, and probably MMP-2, in cricoid cartilages missing luminal perichondrium.