In vivo oxygen imaging using green fluorescent protein

Area of Science:

• Physiology
• Biophysics
• Medical Imaging

Background:

• In vivo oxygen measurement is critical for understanding biological system adaptation to reduced oxygen supply.
• High spatial resolution oxygen imaging is important for studying oxygen heterogeneities in health and disease.

Purpose of the Study:

• To develop a new technique for in vivo molecular imaging of oxygen in organs using green fluorescent protein (GFP).
• To assess the utility of GFP's red-shifted fluorescence as a stable indicator of hypoxia in biological tissues.

Main Methods:

• Utilized GFP-expressing COS-7 cells and cardiomyocytes from GFP knock-in mice.
• Photoactivated GFP with blue light under decreasing oxygen concentrations (10% to <0.001%).
• Observed red fluorescence shift indicative of hypoxia, which reversed upon reoxygenation.

Main Results:

• A stable red shift in GFP fluorescence was observed at oxygen concentrations below 2%, indicating hypoxia.
• This red shift was successfully imaged in vivo in ischemic liver and kidney tissues of mice.
• Significant spatial heterogeneities in the red shift were detected in the epicardium of a mouse heart model of ischemia.

Conclusions:

• The developed technique using GFP as an oxygen indicator enables in vivo molecular imaging of oxygen levels in organs.
• This method has the potential to visualize hypoxic regions within tissues with high spatial resolution.
• The findings highlight the importance of spatial oxygen heterogeneities in physiological and pathological conditions.