Dw. Haas et Mf. Holick, ENHANCED OSTEONECTIN EXPRESSION IN THE CHONDROID MATRIX OF THE UNLOADED MANDIBULAR CONDYLE, Calcified tissue international, 59(3), 1996, pp. 200-206
Osteonectin provided a spatial and temporal marker for proliferating a
nd differentiating chondrocytes, and during the chondroid matrix forma
tion. The goal of this investigation was to examine early cellular and
molecular regulation of mandibular growth. Unloading was induced by a
nterior functional mastication. The proliferative activity measured by
tritiated thymidine incorporation increased 8.3-fold at 24 hours comp
ared with the corresponding control group. Mandibular unloading for 24
hours increased osteonectin mRNA expression 60% in the condyle over t
he corresponding control group. Microscopic inspection of the condyle
demonstrated osteonectin immunostaining of proliferating, early hypert
rophic chondrocytes, and the chondroid matrix across the sagittal sect
ion in an anterior-posterior direction. An increasing gradient intensi
ty from a medial-superior to posterior direction was produced with tre
atment in direct contrast to the control group. The posterior chondroi
d matrix immunostaining increased 11.7-fold (P = 0.038) after 24 hours
treatment over a corresponding control group. Unloading of the mouse
mandible caused an increased cellular proliferation, a coincident incr
ease of osteonectin mRNA, and a subsequent increased secretion of the
osteonectin protein in the chondroid matrix formation.