Department of Genetics, Cell Biology, and Anatomy and the Mary and Dick Holland Regenerative Medicine Program, University of Nebraska Medical Center, 985965 Nebraska Medical Center, Omaha, NE 68198-5965, USA.
Development. 2014 May;141(10):2085-95. doi: 10.1242/dev.105452. Epub 2014 Apr 24.
The architecture and morphogenetic properties of tissues are founded in the tissue-specific regulation of cell behaviors. In endochondral bones, the growth plate cartilage promotes bone elongation via regulated chondrocyte maturation within an ordered, three-dimensional cell array. A key event in the process that generates this cell array is the transformation of disordered resting chondrocytes into clonal columns of discoid proliferative cells aligned with the primary growth vector. Previous analysis showed that column-forming chondrocytes display planar cell divisions, and the resulting daughter cells rearrange by ∼90° to align with the lengthening column. However, these previous studies provided limited information about the mechanisms underlying this dynamic process. Here we present new mechanistic insights generated by application of a novel time-lapse confocal microscopy method along with immunofluorescence and electron microscopy. We show that, during cell division, daughter chondrocytes establish a cell-cell adhesion surface enriched in cadherins and β-catenin. Rearrangement into columns occurs concomitant with expansion of this adhesion surface in a process more similar to cell spreading than to migration. Column formation requires cell-cell adhesion, as reducing cadherin binding via chelation of extracellular calcium inhibits chondrocyte rearrangement. Importantly, physical indicators of cell polarity, such as cell body alignment, are not prerequisites for oriented cell behavior. Our results support a model in which regulation of adhesive surface dynamics and cortical tension by extrinsic signaling modifies the thermodynamic landscape to promote organization of daughter cells in the context of the three-dimensional growth plate tissue.
组织的结构和形态发生特性基于细胞行为的组织特异性调节。在软骨内骨中，生长板软骨通过在有序的三维细胞阵列中调节软骨细胞成熟来促进骨骼伸长。在生成该细胞阵列的过程中，一个关键事件是将无序的静止软骨细胞转化为与主要生长轴对齐的圆盘状增殖细胞的克隆柱。先前的分析表明，形成柱状的软骨细胞表现出平面细胞分裂，并且由此产生的子细胞通过大约 90°的重排与伸长的柱状物对齐。然而，这些先前的研究仅提供了有关该动态过程背后的机制的有限信息。在这里，我们通过应用新的延时共聚焦显微镜方法以及免疫荧光和电子显微镜提供了新的机制见解。我们表明，在细胞分裂期间，子软骨细胞建立富含钙粘蛋白和β-连环蛋白的细胞-细胞粘附表面。在该过程中，伴随着这个粘附表面的扩展，细胞排列成柱状，这更类似于细胞铺展而不是迁移。柱状形成需要细胞-细胞粘附，因为通过螯合细胞外钙来减少钙粘蛋白结合会抑制软骨细胞重排。重要的是，细胞极性的物理指标，如细胞体对齐，不是定向细胞行为的先决条件。我们的结果支持这样一种模型，即通过外在信号调节粘附表面动力学和皮层张力来改变热力学景观，从而促进三维生长板组织中子细胞的组织。
