Nodule formation and calcification of mandibular condylar cartilage cell cultures mimic in vivo ultrastructure.
Mandibular condylar cartilage (MCC) of growing mammals contains four layers of cells which display a series of increasingly differentiated phenotypes and which culminate in a terminally differentiated cell that produces a calcified matrix. In this study, MCC cells were placed into culture in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum and 50 micrograms/ml ascorbic acid. After 12 h in culture, transmission electron microscopy revealed the presence of multiple cell types that underwent differentiation with additional time in culture. By 7 days, fusiform-shaped cells were seen that contained numerous actin-like cytofilaments and micropinocytotic vesicles characteristic of myofibroblasts. Chondroblast-like cells were also observed. By 10 days, without addition of beta-glycerophosphate or dexamethasone, these cellular events culminated in the formation of mineralized nodules containing matrix vesicles. The nodular surface at day 13 consisted of two or more layers of myofibroblast-like cells, while the deeper zones of the nodule contained cells displaying a morphology typical of calcified hypertrophic chondroblasts. These ultrastructural observations are consistent with the hypothesis that cells from the MCC are capable of recapitulating in culture the maturational events seen in vivo. This cell culture model may be useful for investigating cell-mediated cartilage calcification without the addition of exogenous phosphate or other regulatory factors.
Engel
F E
FE
Department of Orthopaedics, University of Texas Health Science Center at San Antonio 78284-7774.
Swain
L D
LD
Dean
D D
DD
Boyan
B D
BD
D000818:Animals; D001857:Bone Matrix / Q000648:ultrastructure; D002113:Calcification, Physiologic; D002114:Calcinosis / Q000378:metabolism / Q000473:pathology*; D002358:Cartilage, Articular / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D002454:Cell Differentiation; D002478:Cells, Cultured; D008335:Mandibular Condyle / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D010641:Phenotype; D011817:Rabbits