Label-free imaging of atherosclerotic plaques using third-harmonic generation microscopy

Area of Science:

• Biomedical Optics
• Cardiovascular Research
• Microscopy

Background:

• Atherosclerotic plaques are complex structures involving cellular and extracellular lipid deposits.
• Current diagnostic methods for cardiovascular disease may lack detailed morphological information.
• Nonlinear optical microscopy offers label-free imaging capabilities for biological tissues.

Purpose of the Study:

• To investigate the utility of multiphoton microscopy with mid-infrared laser sources for imaging atherosclerotic plaques.
• To evaluate the potential of Third Harmonic Generation (THG) as an endogenous contrast mechanism for plaque visualization.
• To explore the application of label-free nonlinear optical signals for detailed imaging of diseased vessel walls.

Main Methods:

• Multiphoton microscopy utilizing mid-infrared (MIR) laser sources (1,300 nm and 1,700 nm).
• Imaging of atherosclerotic plaques from both murine and human samples.
• Detection of Third Harmonic Generation (THG), Second Harmonic Generation (SHG), and endogenous fluorescence signals.

Main Results:

• THG microscopy effectively revealed morphological details of cellular and extracellular lipid deposits within atherosclerotic plaques.
• Simultaneous nonlinear optical signals provided label-free images of different layers in the diseased vessel wall.
• THG demonstrated specificity for atherosclerotic plaques, complementing existing nonlinear optical methods.

Conclusions:

• THG microscopy using MIR lasers is a valuable tool for label-free imaging of atherosclerotic plaque morphology.
• The combination of THG with other nonlinear optical signals enhances the characterization of cardiovascular disease.
• The use of whole-mount tissue imaging and epi-detection suggests THG's potential as a future clinical diagnostic tool for atherosclerosis.