Farnum C E, Wilsman N J
Department of Anatomy, Cornell University, Ithaca, NY 14853.
Anat Rec. 1987 Nov;219(3):221-32. doi: 10.1002/ar.1092190303.
Recent biochemical and morphologic evidence supports the concept that hypertrophic chondrocytes of growth plate cartilage are fully viable cells that play a major functional role in controlling endochondral ossification. However, events associated with chondrocyte death remain unknown. In this study we assess the viability of terminal hypertrophic chondrocytes in situ in an organ culture system viewed simultaneously with rectified Nomarski interference contrast optics and with vital staining under fluorescence optics. Second, we use two methods of optimal chemical fixation at the ultrastructural level to define morphologically distinct stages of the terminal hypertrophic chondrocyte, which we interpret as the stages preceding chondrocyte death. An analysis of serial sections at the light microscope level showed that terminal chondrocytes were found, with different probabilities, in three morphologically distinguishable stages. Seventy-five percent of all profiles were fully hydrated cells with an intact plasma membrane making direct contact with the pericellular matrix, a morphology identical to that of living terminal chondrocytes viewed in Nomarski optics. Approximately 1% of terminal chondrocytes, while still in a fully hydrated state, consistently made a direct asymmetrical contact of the plasma membrane with the last transverse septum. In 24% of the profiles, terminal chondrocytes were found as condensed cells that retained their attachment to the last transverse septum. The stages were not characteristic of chondrocytes positioned more proximally in the growth plate. We hypothesize that a condensed morphology eventually characterizes each hypertrophic chondrocyte, and we relate these observations to current hypotheses concerning the mechanism of death of hypertrophic chondrocytes.
最近的生化和形态学证据支持这样一种概念，即生长板软骨的肥大软骨细胞是完全有活力的细胞，在控制软骨内骨化过程中发挥主要功能作用。然而，与软骨细胞死亡相关的事件仍然未知。在本研究中，我们在器官培养系统中，利用矫正的诺马斯基干涉对比光学显微镜和荧光光学显微镜下的活体染色，同时观察原位终末肥大软骨细胞的活力。其次，我们在超微结构水平上使用两种最佳化学固定方法，来定义终末肥大软骨细胞形态上不同的阶段，我们将其解释为软骨细胞死亡之前的阶段。光镜水平的连续切片分析表明，终末软骨细胞以不同概率处于三个形态上可区分的阶段。所有细胞轮廓中有75%是完全水化的细胞，其质膜完整，与细胞周基质直接接触，这种形态与在诺马斯基光学显微镜下观察到的活终末软骨细胞相同。约1%的终末软骨细胞，虽然仍处于完全水化状态，但始终使其质膜与最后一个横向隔膜直接不对称接触。在24%的细胞轮廓中，终末软骨细胞呈浓缩状，仍附着于最后一个横向隔膜。这些阶段并非生长板中位置更靠近近端的软骨细胞所具有的特征。我们假设浓缩形态最终是每个肥大软骨细胞的特征，并且我们将这些观察结果与当前关于肥大软骨细胞死亡机制的假设联系起来。
