Jordanova Albena, Stefanova Nadezhda, Staneva Galya, Pankov Roumen, Momchilova Albena, Lalchev Zdravko
Department of Lipid-Protein Interactions, Institute of Biophysics, Bulgarian Academy of Sciences, 1113, Sofia, Bulgaria.
Cell Biochem Biophys. 2009;54(1-3):47-55. doi: 10.1007/s12013-009-9050-y. Epub 2009 May 30.
The differences in the surface active properties of native lipids extracted from plasma membranes of cells cultured as a monolayer and in three-dimensional (3D) matrix were investigated. This experimental model was chosen because most of the current knowledge on cellular physiological processes is based on studies performed with conventional monolayer two-dimensional (2D) cell cultures, where cells are forced to adjust to unnaturally rigid surfaces that differ significantly from the natural matrix surrounding cells in living organisms. Differences between monolayer and 3D cells were observed in the lipid composition of plasma membranes and especially in the level of the two major microdomain-forming lipids--sphingomyelin (SM) and cholesterol, which were significantly elevated in 3D cells. The obtained results showed that culturing of cells in in vivo-like environment affected the surface active properties of plasma membrane lipids at interfaces which might influence certain membrane-associated interface processes. The detected differences in the lipid levels in 2D and 3D cell extracts affected significantly the behavior of the model lipid monolayers at the air-water interface (Langmuir monolayers) which resulted in different values of the monolayer equilibrium (gamma(eq)) and dynamic (gamma(max), gamma(min)) surface tension and surface potential. Compensation of the SM content in extracts of 2D cell cultures up to a level close to the one measured in 3D cells approximated the monolayer properties to the values observed for 3D cells. These results implied that the interactions between the cells and the surrounding medium affected the level of plasma membrane SM and other lipids, which had a strong impact on the surface properties of lipid monolayers, such as gamma(eq), gamma(max), and gamma(min), the compression/decompression curve shape, the hysteresis area during cycling of the monolayers, etc. We suggest that the elevated content of SM observed in plasma membranes of 3D fibroblasts could be responsible for an increased rigidity and possibly reduced permeability of cells cultured in 3D environment. The current results provide useful information that should be taken into account in the interpretation of the membrane physico-chemical properties of cells cultured under different conditions.
研究了从单层培养细胞和三维（3D）基质培养细胞的质膜中提取的天然脂质的表面活性特性差异。选择该实验模型是因为目前关于细胞生理过程的大多数知识基于传统单层二维（2D）细胞培养的研究，在这种培养中，细胞被迫适应与活生物体中细胞周围天然基质有显著差异的非自然刚性表面。在质膜的脂质组成中观察到单层细胞和3D细胞之间的差异，特别是在两种主要的微区形成脂质——鞘磷脂（SM）和胆固醇的水平上，它们在3D细胞中显著升高。所得结果表明，在类似体内的环境中培养细胞会影响质膜脂质在界面处的表面活性特性，这可能会影响某些与膜相关的界面过程。在2D和3D细胞提取物中检测到的脂质水平差异显著影响了模型脂质单层在气-水界面（朗缪尔单层）的行为，导致单层平衡（γ(eq)）和动态（γ(max)，γ(min)）表面张力以及表面电位的不同值。将2D细胞培养提取物中的SM含量补偿到接近在3D细胞中测得的水平，可使单层特性接近在3D细胞中观察到的值。这些结果表明，细胞与周围介质之间的相互作用影响了质膜SM和其他脂质的水平，这对脂质单层的表面特性有很大影响，如γ(eq)、γ(max)和γ(min)、压缩/解压曲线形状、单层循环期间的滞后面积等。我们认为，在3D成纤维细胞质膜中观察到的SM含量升高可能导致在3D环境中培养的细胞刚性增加以及通透性可能降低。目前的结果提供了有用的信息，在解释不同条件下培养的细胞的膜物理化学性质时应予以考虑。
