Structural organization of interphase 3T3 fibroblasts studied by total internal reflection fluorescence microscopy

Area of Science:

• Cell Biology
• Biophysics
• Microscopy Techniques

Background:

• Understanding cell-substrate interactions is crucial for cell adhesion and migration.
• Total internal reflection fluorescence (TIRF) microscopy offers high resolution near the cell surface.
• Quantifying cell-substrate separation and intracellular component distribution is challenging.

Purpose of the Study:

• To investigate the laminar organization of 3T3 fibroblast cells at the cell-substrate interface.
• To utilize TIRF microscopy for precise measurements of cell-substrate separation.
• To map the distribution of actin and other cellular components within contact regions.

Main Methods:

• Employing TIRF microscopy with various fluorescent stains (dil-C3-(3), Hoechst dye 33342, dil-C18-(3), fluoresceinyl-dextran, carboxyfluorescein, fluorescein-labeled actin).
• Analyzing reflection interference images alongside TIRF images to correlate cell structures with contact zones.
• Performing TIRF photometry on selected contact regions to compute absolute cell-substrate separation.

Main Results:

• Computed cytoplasmic refractive index (1.358-1.374) based on critical angle measurements.
• Demonstrated high correlation between low-reflectance zones and TIRF images of plasma membrane and cytoplasm.
• Identified intense TIRF signal patches at focal contact points, corresponding to stress fiber endpoints in adherent cells.

Conclusions:

• TIRF microscopy can accurately measure the proximity of cellular components to the substrate.
• The technique allows for detailed analysis of cell-substrate contact dynamics and intracellular organization.
• TIRF microscopy is a powerful tool for studying the physical interactions between cells and their environment.