Garcia A M, Gray M L
Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge 02139, USA.
J Orthop Res. 1995 Mar;13(2):208-19. doi: 10.1002/jor.1100130209.
Mandibular condyles in organ culture commonly have been used as a model system for examination of the factors that influence skeletal growth and development. The work reported here complements previously published histological studies by providing quantitative temporal information on growth and matrix accumulation. Condyles maintained for as long as 5 weeks in serum-free and 1% serum-supplemented culture media were found to remain viable and metabolically active as demonstrated by continued dimensional growth as well as cell and matrix accumulation. Growth occurred by a combination of cell proliferation, matrix synthesis and accumulation, and cell hypertrophy (with the latter two mechanisms dominating). Increases in tissue volume correlated directly with increased glycosaminoglycan content; both increased 7-fold over 5 weeks. In comparison with serum-free culture, after 35 days in medium containing 1% serum, glycosaminoglycan content was 24% lower and collagen content was 36% higher, whereas dry weight, condyle length, and DNA content were not significantly different; in addition, histological observation suggested that, for samples cultured with serum, chondrogenic phenotype had been lost from some regions. The temporal behavior for all growth parameters exhibited a transient phase 1-2 weeks in duration followed by a steady-state period in which dimensions and tissue constituents or content increased at a constant or near constant rate. Comparison of the rates of incorporation of [35S]sulfate with glycosaminoglycan content in serum-free cultures suggests that the loss of glycosaminoglycan occurs only initially or is negligible; therefore, under these baseline conditions, cartilage glycosaminoglycan content reflects the biosynthetic rate. The high degree of reproducibility seen during steady-state growth suggests that these data provide reliable baseline information and further supports the notion that this model system is useful for investigation of the effects of specific physical factors on in vitro growth and development.
器官培养中的下颌髁突通常被用作一个模型系统，用于研究影响骨骼生长发育的因素。本文报道的工作通过提供关于生长和基质积累的定量时间信息，对先前发表的组织学研究进行了补充。在无血清和添加1%血清的培养基中培养长达5周的髁突被发现保持存活且代谢活跃，持续的尺寸生长以及细胞和基质积累证明了这一点。生长是通过细胞增殖、基质合成与积累以及细胞肥大（后两种机制占主导）的组合发生的。组织体积的增加与糖胺聚糖含量的增加直接相关；两者在5周内均增加了7倍。与无血清培养相比，在含有1%血清的培养基中培养35天后，糖胺聚糖含量低24%，胶原蛋白含量高36%，而干重、髁突长度和DNA含量无显著差异；此外，组织学观察表明，对于用血清培养的样本，某些区域已失去软骨形成表型。所有生长参数的时间行为表现出一个持续1 - 2周的短暂阶段，随后是一个稳定期，在此期间尺寸和组织成分或含量以恒定或接近恒定的速率增加。在无血清培养中[35S]硫酸盐掺入率与糖胺聚糖含量的比较表明，糖胺聚糖的损失仅在最初发生或可忽略不计；因此，在这些基线条件下，软骨糖胺聚糖含量反映了生物合成速率。稳态生长期间所见的高度可重复性表明这些数据提供了可靠的基线信息，并进一步支持了该模型系统可用于研究特定物理因素对体外生长发育影响的观点。
