Fibronectin-Binding Integrins Distribution in the Rat Condylar Cartilage during Puberty

Objective: Fibronectin is an abundant extracellular matrix protein that regulates proliferation and differentiation of different cell types. Considering that it is an important component of cartilage and that its expression is altered in some articular diseases, we aimed to study the distribution of the integrin subunits alpha 5 and alpha v, which join different b subunits to form fibronectin receptors, in the condyle of young rats, from puberty to adulthood. Methods: Wistar rats were sacrificed at 30, 32, 34, 36, 38, 42, 47, 57 and 62 days of age. Sagital sections of decalcified and Paraplast-embedded condyles were submitted to immunohistochemistry using the avidin-biotin-peroxidase technique. Results: Expression of the alpha 5 subunit was stronger in the proliferative compartment, composed by undifferentiated, chondroblast and chondrocyte layers. It was pronounced up to 36 days of age, corresponding to puberty, gradually decreasing in the adult, with upward fluctuations in 47 and 57 days-old rats. The alpha v subunit was observed mainly in the well-differentiated hypertrophic layer. Its expression showed a cyclical pattern, with increases at 36 and 57 days of age, followed by a gradual reduction. Conclusion: The high expression of alpha 5 in the proliferative layers during puberty suggests its involvement in the condylar cartilage growth and potential regulation by different hormones