Imaging of normal and pathologic joint synovium using nonlinear optical microscopy as a potential diagnostic tool

Area of Science:

• Biomedical Optics
• Rheumatology
• Microscopy

Background:

• Rheumatoid arthritis (RA) affects 1.3 million Americans, causing joint damage.
• Early RA diagnosis and intervention are crucial to prevent permanent joint alterations.

Purpose of the Study:

• To determine if nonlinear optical microscopy (NLOM) can image fresh, unfixed synovial tissue.
• To visualize the structural and cellular composition of normal and pathologic synovial tissue using intrinsic fluorescence.

Main Methods:

• NLOM was performed on rabbit knee joint synovial samples.
• Excitation wavelengths of 730- and 800-nm were used with a 40×, 0.8-NA water immersion objective.
• Low excitation power (<30 mW) allowed imaging up to 70 microm depth without tissue damage.

Main Results:

• NLOM successfully visualized cellular structures, including synoviocytes and adipocytes.
• Collagen, vascular structures, and inflammatory infiltrates were identified in synovial tissue.
• Imaging was achieved without the need for tissue processing or staining.

Conclusions:

• NLOM can visualize the cellular and structural composition of fresh synovial tissue.
• The technique holds potential for assessing rheumatoid arthritis (RA) pathology.
• Further research is warranted to explore NLOM's role in RA disease management.