Determining whether observed eukaryotic cell migration indicates chemotactic responsiveness or random chemokinetic...

Area of Science:

• Cellular and Molecular Biology
• Biophysics
• Cancer Research

Background:

• Chemotaxis, or directed cell migration along chemoattractant gradients, is crucial for biological processes like immune response and cancer metastasis.
• Distinguishing true chemotaxis from chemokinesis (stimulated random cell motion) in standard assays can be challenging.
• Common chemotaxis assays infer directed motion by quantifying cells crossing a boundary or entering a defined region.

Purpose of the Study:

• To develop a mathematical model to accurately assess whether observed cell migration in chemotaxis assays indicates true directed motion.
• To quantify the extent to which gradient sensing enhances cell migration rates compared to random motility.
• To evaluate the reliability of common chemotaxis assay methods and the necessity for appropriate controls.

Main Methods:

• Development of a novel mathematical model to analyze chemoattractant gradients and resulting cell motion.
• Application of the model to experimental data from various cell types (e.g., MDA-MB-231 breast cancer cells, neutrophils) and assays (filter, under-agarose, agarose spot).
• Comparison of cell migration rates under gradient conditions versus random motility controls.

Main Results:

• MDA-MB-231 cells exhibit significantly lower sensitivity to EGF or CXCL12 gradients compared to neutrophils' sensitivity to formyl peptides.
• Neutrophils showed a 2-4 fold increase in filter assay boundary crossing with a gradient, while other cell/assay combinations showed only 10-20% increases.
• Chemotaxis is frequently over-reported, particularly for slow-moving, gradient-insensitive cells like MDA-MB-231, due to inadequate controls and assay limitations.

Conclusions:

• The developed mathematical model provides a more rigorous method for interpreting chemotaxis assay data.
• Standard chemotaxis assays may overestimate directed cell migration, especially for certain cell types and experimental setups.
• Careful consideration of assay design and controls is essential for accurate quantification of chemotaxis and understanding cell migration in biological contexts.