Benya P D, Brown P D, Padilla S R
Department of Orthopedics, Orthopedic Hospital, University of Southern California, Los Angeles 90007-2697.
J Cell Biol. 1988 Jan;106(1):161-70. doi: 10.1083/jcb.106.1.161.
Primary monolayers of rabbit articular chondrocytes synthesize high levels of type II collagen and proteoglycan. This capacity was used as a marker for the expression of the differentiated phenotype. Such cells were treated with 1 microgram/ml retinoic acid (RA) for 10 d to produce a modulated collagen phenotype devoid of type II and consisting of predominantly type I trimer and type III collagen. After transfer to secondary culture in the presence of RA, the stability of the RA-modulated phenotype was investigated by culture in the absence of RA. Little reexpression of type II collagen synthesis occurred in this period unless cultures were treated with 3 X 10(-6) M dihydrocytochalasin B to modify microfilament structures. Reexpression of the differentiated phenotype began between days 6-8 and was essentially complete by day 14. Substantial reexpression occurred by day 8 without a detectable increase in cell rounding. Colony formation, characteristic of primary chondrocytes, was infrequent even after reexpression was complete. These data suggest that the integrity of microfilament cytoskeletal structures can be a source of regulatory signals that mechanistically appear to be more proximal to phenotypic change than the overt changes in cell shape that accompany reexpression of subculture-modulated chondrocytes in agarose culture.
兔关节软骨细胞的原代单层细胞合成高水平的II型胶原蛋白和蛋白聚糖。这种能力被用作分化表型表达的标志物。用1微克/毫升视黄酸（RA）处理这些细胞10天，以产生一种缺乏II型且主要由I型三聚体和III型胶原蛋白组成的调节型胶原蛋白表型。在RA存在的情况下转移至传代培养后，通过在无RA的条件下培养来研究RA调节表型的稳定性。在此期间，除非用3×10⁻⁶ M双氢细胞松弛素B处理培养物以改变微丝结构，否则很少发生II型胶原蛋白合成的重新表达。分化表型的重新表达在第6 - 8天开始，并在第14天基本完成。即使在重新表达完成后，原代软骨细胞特有的集落形成也很少见。这些数据表明，微丝细胞骨架结构的完整性可能是调节信号的一个来源，从机制上看，它似乎比在琼脂糖培养中传代培养调节的软骨细胞重新表达时伴随的细胞形状明显变化更接近表型变化。
