Virtual optical biopsy of human adipocytes with third harmonic generation microscopy

Area of Science:

• Medical imaging
• Histopathology
• Cardiovascular research

Background:

• Human adipocytes, particularly epicardial fat, play a role in cardiovascular health.
• Traditional methods for adipocyte analysis require fixation and labeling, potentially altering morphology.
• Non-invasive imaging techniques are needed for in-vivo assessment of adipocyte characteristics.

Purpose of the Study:

• To evaluate the morphologic features of human adipocytes using third harmonic generation (THG) microscopy.
• To compare adipocyte size distributions in patients with and without cardiovascular risk factors.
• To assess the utility of THG microscopy for virtual optical biopsy of adipocytes.

Main Methods:

• Third harmonic generation (THG) microscopy was employed for label-free, non-invasive imaging of human adipocytes.
• Sectioning capability of THG microscopy allowed for assessment of morphologic features at the largest cross-sectional area.
• Area-equivalent circular diameters (AECD) and perimeters were measured, and statistical distributions analyzed.

Main Results:

• In patients without cardiovascular risk factors, average epicardial adipocyte AECD was 70-90 μm with standard deviations of 11-17 μm.
• Patients with coronary artery disease exhibited increased amounts of small-sized adipocytes (AECD <40 µm).
• The standard deviation of AECD increased to 20-29 μm in patients with coronary artery disease, indicating greater size variability.

Conclusions:

• THG microscopy provides high-resolution imaging of adipocyte morphology without fixation or labeling.
• Distinct differences in epicardial adipocyte size distribution are observed between healthy individuals and those with coronary artery disease.
• The THG tomography platform shows promise for clinical histopathological evaluation of adipocytes via virtual optical biopsy.