Dynamic changes in traction forces with DC electric field in osteoblast-like cells

Area of Science:

• Cell biology
• Biophysics
• Mechanobiology

Background:

• Electric fields influence cell behavior and alignment.
• Osteoblasts and osteosarcoma cells are relevant models for studying cellular responses to stimuli.

Purpose of the Study:

• To investigate the cellular reorientation and force generation of bovine osteoblasts and human osteosarcoma cells in response to direct-current electric fields.
• To determine the relationship between electric field strength and reorientation time.
• To analyze changes in cellular force output and intracellular calcium levels during reorientation.

Main Methods:

• Exposure of primary bovine osteoblasts and human osteosarcoma cells to direct-current electric fields.
• Traction force microscopy to measure cellular force output.
• Phase-contrast microscopy to observe cell morphology.
• Fluorescent dye Fura-2 AM to measure intracellular free calcium levels.

Main Results:

• Cells reoriented their long axis perpendicular to the electric field.
• Reorientation time was inversely correlated with electric field strength.
• An initial increase in average traction force was observed within 10-30 seconds, followed by a decrease in forces at tangential margins.
• Elongating protrusions formed at tangential margins several minutes after field exposure.
• No correlation was found between initial traction changes and intracellular calcium levels.

Conclusions:

• Direct-current electric fields induce a distinct reorientation response in osteoblasts and osteosarcoma cells.
• Cellular force dynamics change significantly during electric field-induced reorientation.
• The observed cellular responses are not mediated by rapid changes in intracellular calcium levels.