As a crucial mechanobiological regulator, the tension of the cell membrane plays a vital role in governing cellular adhesion, proliferation, and differentiation processes. Additionally, it displayed a dynamic response to mechanical microenvironmental changes. This research systematically examines the mechanoresponsive behaviors of mouse bone marrow mesenchymal stem cells (mBMSCs) that are cultured on poly(dimethylsiloxane) (PDMS) substrates which are functionalized with methyl (-CH 3 ), amino (-NH 2 ), and carboxyl (-COOH) groups. Under both static and stretching conditions, it is found that compared with the -CH 3 surface, static culture on the -NH 2 and -COOH functionalized surfaces significantly promotes the proliferation of mBMSCs and upregulates the expression of extracellular matrix adhesion-related genes, especially focal adhesion kinase (FAK) and integrin β1. Morphometric analysis reveals that there are concomitant increases in the cell spreading area and the number of pseudopods on these modified surfaces. Mechanical stretching stimulation not only amplifies these cellular responses but also leads to more uniform FAK distribution. The assessment by atomic force microscopy (AFM) shows that both chemical functionalization (-NH 2 /-COOH) and stretch stimulation reduce the deformability of the cell membrane, and the -NH 2 modification exhibits a greater membrane-stiffening effect than -COOH.
Hai-Yan Wen,Yusi Hu,You-Yang Duo,Liang Zhao,Zhi-Gang Wang,Shu-Lin Liu
Membrane tension is an important physical parameter of describing cellular homeostasis, and it is widely used in the study of cellular processes involving membrane deformation and reorganization, such as cell migration, cell spreading, and cell division. Despite the importance of membrane tension, direct measurement remains difficult. In this work, we developed a ratiometric fluorescent probe sensitive to membrane tension by adjusting the carbon chain structure based on polarity-sensitive fluorophores. The probe is sensitive to changes in membrane tension after cells were subjected to physical or chemical stimuli, such as osmotic shock, lipid peroxidation, and mechanical stress. When the polarity of the plasma membrane increases (the green/red ratio decreases) and the membrane tension increases, the relative magnitude of the membrane tension can be quantitatively calculated by fluorescence ratio imaging. Thus, the probe proved to be an efficient and sensitive membrane tension probe.
Kai Ni,Bo Che,Rong Gu,Chunhong Wang,Yan Pan,Jingjing Li,Lei Liu,Mingzhi Luo,Linhong Deng
Severe asthma is characterized by increased cell volume (hypertrophy) and enhanced contractile function (hyperresponsiveness) of the airway smooth muscle cells (ASMCs). The causative relationship and underlying regulatory mechanisms between them, however, have remained unclear. Here, we manipulated the single-cell volume of in vitro cultured human ASMCs to increase from 2.7 to 5.2 and 8.2 × 103μm3as a simulated ASMC hypertrophy by culturing the cells on micropatterned rectangular substrates with a width of 25 μm and length from 50 to 100 and 200 μm, respectively. We found that as the cell volume increased, ASMCs exhibited a pro-contractile function with increased mRNA expression of contractile proteins, increased cell stiffness and traction force, and enhanced response to contractile stimulation. We also uncovered a concomitant increase in membrane tension and Piezo1 mRNA expression with increasing cell volume. Perhaps more importantly, we found that the enhanced contractile function due to cell volume increase was largely attenuated when membrane tension and Piezo1 mRNA expression were downregulated, and an auto-regulatory loop between Piezo1 and YAP mRNA expression was also involved in perpetuating the contractile function. These findings, thus, provide convincing evidence of a direct link between hypertrophy and enhanced contractile function of ASMCs that was mediated via Piezo1 mRNA expression, which may be specifically targeted as a novel therapeutic strategy to treat pulmonary diseases associated with ASMC hypertrophy such as severe asthma.
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