An Acid-Activatable Fluorescence Probe for Imaging Osteocytic Bone Resorption Activity in Deep Bone Cavities

Area of Science:

• Biomedical Engineering
• Skeletal Biology
• Fluorescent Probes

Background:

• Osteocytic lacunae are critical microenvironments within bone tissue.
• Understanding pH dynamics in these lacunae is vital for bone remodeling research.
• Existing methods lack the specificity and real-time capabilities for in vivo lacunae imaging.

Purpose of the Study:

• To develop and validate a pH-activatable fluorescent probe for measuring localized pH in osteocytic lacunae.
• To visualize the real-time bone mineralizing activities of osteocytes in vivo.
• To investigate the role of osteocytes in bone remodeling in healthy and diseased states.

Main Methods:

• Rational design of a pH-activatable BODIPY fluorophore conjugated with risedronate (pHocas-RIS).
• Administration of pHocas-RIS to bone tissue.
• Intravital two-photon excitation microscopy for in vivo imaging of osteocytic lacunae.
• Monitoring probe fluorescence in response to localized pH changes.

Main Results:

• The pHocas-RIS probe successfully penetrated osteocytic lacunae within the bone matrix.
• The probe exhibited fluorescence in vivo, correlating with localized pH changes caused by osteocyte activity.
• Real-time visualization of acid production by osteocytes and their role in bone matrix remodeling was achieved.

Conclusions:

• pHocas-RIS is an effective tool for measuring localized pH in osteocytic lacunae.
• The probe enables in vivo imaging of osteocyte-mediated bone remodeling.
• This technology offers new insights into skeletal biology and bone-related diseases.