Oswald Elizabeth S, Chao Pen-Hsiu Grace, Bulinski J Chloe, Ateshian Gerard A, Hung Clark T
Department of Biomedical Engineering, Columbia University, New York, NY 10027.
Cell Mol Bioeng. 2008 Dec 1;1(4):339-348. doi: 10.1007/s12195-008-0026-6.
The increasing concentration of proteoglycans from the surface to the deep zone of articular cartilage produces a depth-dependent gradient in fixed charge density, and therefore extracellular osmolarity, which may vary with loading conditions, growth and development, or disease. In this study we examine the relationship between in situ variations in osmolarity on chondrocyte water transport properties. Chondrocytes from the depth-dependent zones of cartilage, effectively preconditioned in varying osmolarities, were used to probe this relationship. DESIGN: First, depth variation in osmolarity of juvenile bovine cartilage under resting and loaded conditions was characterized using a combined experimental/theoretical approach. Zonal chondrocytes were isolated into two representative "baseline" osmolarities chosen from this analysis to reflect in situ conditions. Osmotic challenge was then used as a tool for determination of water transport properties at each of these baselines. Cell calcium signaling was monitored simultaneously as a preliminary examination of osmotic baseline effects on cell signaling pathways. RESULTS: Osmotic baseline exhibits a significant effect on the cell membrane hydraulic permeability of certain zonal subpopulations but not on cell water content or incidence of calcium signaling. CONCLUSIONS: Chondrocyte properties can be sensitive to changes in baseline osmolarity, such as those occurring during OA progression (decrease) and de novo tissue synthesis (increase). Care should be taken in comparing chondrocyte properties across zones when cells are tested in vitro in non-physiologic culture media.
从关节软骨表面到深层区域蛋白聚糖浓度不断增加，会产生与深度相关的固定电荷密度梯度，进而导致细胞外渗透压梯度，而该梯度可能会随负荷条件、生长发育或疾病而变化。在本研究中，我们探讨了渗透压的原位变化与软骨细胞水转运特性之间的关系。使用在不同渗透压下有效预处理的来自软骨深度依赖区的软骨细胞来探究这种关系。设计：首先，采用实验与理论相结合的方法，对幼年牛软骨在静息和负荷条件下的渗透压深度变化进行表征。从该分析中选择两种具有代表性的“基线”渗透压来分离区域软骨细胞，以反映原位条件。然后将渗透压挑战用作测定每个基线水转运特性的工具。同时监测细胞钙信号，作为对渗透压基线对细胞信号通路影响的初步检查。结果：渗透压基线对某些区域亚群的细胞膜水力通透性有显著影响，但对细胞含水量或钙信号发生率没有影响。结论：软骨细胞特性可能对基线渗透压的变化敏感，例如在骨关节炎进展过程中发生的变化（降低）和新生组织合成过程中发生的变化（增加）。当在体外非生理培养基中测试细胞时，在比较不同区域的软骨细胞特性时应谨慎。
