The effect of nicotine on the mechanical properties of mesenchymal stem cells

Abstract

PURPOSE: To measure the elasticity of the nucleus and cytoplasm of human mesenchymal stem cells (MSCs) as well as changes brought about by exposure to nicotine in vitro. METHODS: MSCs were synchronized to the G(0) stage of the cell cycle through serum deprivation techniques. The cells were then treated with medium containing nicotine (0.1 µM, 0.5 µM, and 1 µM). Atomic force microscopy was then used to measure the Young's modulus of both the nucleus and cytoplasm of these cells. RESULTS: For both unsynchronized and synchronized cells, the nucleus was softer than the cytoplasm, although this difference was not found to be statistically significant. The nucleus of cells treated with nicotine was significantly stiffer than the control for all concentrations. The cytoplasm was significantly stiffer in nicotine-treated cells than in control cells for the 0.5 µM and 1.0 µM concentrations only. CONCLUSIONS: The results of this study could suggest that nicotine affects the biophysical properties of human MSCs in a dose-dependent manner, which may render the cells less responsive to mechanoinduction and other physical stimuli.

Figure 1

Phase-contrast images of mesenchymal stem cells in culture. Images were taken of the control cells as well as of those subjected to the highest concentration of nicotine (1 µM).

Figure 2

Image showing view (from bottom) of plate, with atomic force microscopy cantilever placed over the cytoplasm of the mesenchymal stem cell. The image is taken by a camera through a 20× objective positioned underneath the culture dish. The nucleus is signaled by the arrow.

Figure 3

Average values for the elasticity of cytoplasmic and nuclear regions of the mesenchymal stem cells. Note: ^#Variability was significantly decreased with synchronization, for cytoplasm measurements only.

Figure 4

Average values for the elasticity of cytoplasmic and nuclear regions of the mesenchymal stem cells treated with different concentrations of nicotine. For both regions of the cell, the elasticity decreases (Young’s modulus increases) with increasing nicotine concentration. Notes: *Statistical significance compared with cytoplasm control; **statistical significance compared with nucleus control.

Figure 5

Viability and cytoskeletal staining for mesenchymal stem cells across treatment. Top panel: cells were stained with fluorescent phalloidin and with DAPI stain. Bottom panel: cells were stained with calcein to measure viability and with ethidium homodimer to measure cell death.