Department of Biomedical Engineering , University of North Texas , Denton , Texas 76207 , United States.
Department of Biomedical Engineering , Worcester Polytechnic Institute , Worcester , Massachusetts 01609 , United States.
Nano Lett. 2019 Aug 14;19(8):5443-5451. doi: 10.1021/acs.nanolett.9b01943. Epub 2019 Aug 5.
Most living tissues exhibit the specific stiffness, which has been known to have profound influence on cell behaviors, yet how the stiffness affects cellular responses to engineered nanomaterials has not been elucidated. Particularly, discrepancies exist between and nanotoxicological studies. Here, we investigated the effects of substrate stiffness on the fibrogenic responses of normal human lung fibroblasts (NHLFs) to multiwalled carbon nanotubes (MWCNTs). NHLFs were grown on polyacrylamide (PAAm) hydrogels with the stiffness comparable to that of human normal and fibrotic lung tissues, and treated with MWCNTs for various time. The fibrogenic responses, including cell proliferation, reactive oxygen species production, and collagen I expression, of NHLFs to MWCNTs were observed to be regulated by substrate stiffness in a time-dependent manner. NHLFs generally were rounded on soft hydrogels and required a long treatment time to exhibit fibrogenic responses, while on stiff hydrogels the cells were well-spread with defined stress fibers and short-time MWCNTs treatment sufficiently induced the fibrogenic responses. Mechanistic studies showed that MWCNTs induced fibrogenesis of NHLFs through promoting expression and phosphorylation of focal adhesion kinase (FAK), while attenuating intracellular tension in the cells on stiff gels could increase MWCNTs uptake and thus elevate the induced fibrogenic responses. Moreover, we proposed a time-stiffness superposition principle to describe the equivalent effects of treatment time and substrate stiffness on nanomaterials-induced fibrogenesis, which suggested that increasing substrate stiffness expedited fibrogenesis and shed light on the rational design of models for nanotoxicological study.
大多数活组织都表现出特定的刚度，这已被证明对细胞行为有深远的影响，但刚度如何影响细胞对工程纳米材料的反应尚未阐明。特别是， 和 纳米毒理学研究之间存在差异。在这里，我们研究了基底刚度对正常人类肺成纤维细胞（NHLFs）对多壁碳纳米管（MWCNTs）的纤维化反应的影响。NHLFs 生长在与人类正常和纤维化肺组织相当的聚丙烯酰胺（PAAm）水凝胶上，并在不同时间用 MWCNTs 处理。观察到 NHLFs 对 MWCNTs 的纤维化反应，包括细胞增殖、活性氧产生和胶原 I 表达，受基底刚度的时间依赖性调节。NHLFs 通常在软水凝胶上呈圆形，需要较长的处理时间才能表现出纤维化反应，而在硬水凝胶上，细胞铺展良好，具有明确的应力纤维，短时间的 MWCNTs 处理足以诱导纤维化反应。机制研究表明，MWCNTs 通过促进粘着斑激酶（FAK）的表达和磷酸化来诱导 NHLFs 的纤维化，而在刚性凝胶中降低细胞内张力可以增加 MWCNTs 的摄取，从而提高诱导的纤维化反应。此外，我们提出了一个时间-刚度叠加原理来描述处理时间和基底刚度对纳米材料诱导的纤维化的等效影响，这表明增加基底刚度可以加速纤维化，并为纳米毒理学研究的 模型的合理设计提供了启示。
