Optical clearing in collagen- and proteoglycan-rich osteochondral tissues

Area of Science:

• Biomedical Engineering
• Tissue Optics
• Microscopy

Background:

• Optical clearing and microscopy enable 3D cellular characterization of intact tissues.
• Dense connective tissues like cartilage and bone remain largely unexplored due to opacity.
• This study investigates optical clearing's impact on musculoskeletal tissues.

Purpose of the Study:

• To quantify the effects of optical clearing on cell and tissue morphology in cartilage and bone.
• To assess the feasibility of deep-tissue imaging in musculoskeletal connective tissues.

Main Methods:

• Bovine osteochondral tissues were optically cleared using water-based fructose solutions.
• Transmission and confocal microscopy were used for imaging.
• Mechanical testing and cryo-scanning electron microscopy (cryo-SEM) confirmed structural integrity.

Main Results:

• Optical clearing enhanced light transmission in cartilage but not subchondral bone.
• Imaging depth in cartilage increased fivefold, preserving fluorescent staining.
• Chondrocyte volume remained unchanged, and mechanical properties temporarily altered due to fluid exchange.

Conclusions:

• Optical clearing is a viable method for deep imaging of cartilage, preserving cellular and ultrastructural details.
• This technique facilitates the study of intact 3D tissue interfaces like osteochondral tissues.
• Advanced imaging of connective tissues can advance understanding of development, disease, and regeneration.