Abstract 2196: A Novel Annexin A5 Probe to Detect Cell Death In Vivo Non Invasively using PET/CT
Introduction Imaging of apoptosis with Annexin A5 is mostly done using fluorescent techniques making it less suitable for clinical applications. For clinical research different imaging modalities are necessary. We report the development of a new Annexin construct that can be labeled with a nuclear label allowing us to use it in combination with PET technology.
Methods A cys-annexin A5 variant was generated by genetically modifying annexin A5 to introduce a cysteine residue at the concave side of the molecule. This side is apical to the convex side that harbours the binding sites through which it binds to apoptotic cells. The cys-annexin A5 variant can be coupled to compounds via thiolchemistry without affecting this biological activity. A maleimide derivatized DOTA was synthesized and coupled directly to cys-annexin A5 yielding a cys-annexin A5-DOTA complex with 1:1 stoichiometry. This complex was labeled with Ga68 and injected into a rat with ischemia/reperfusion (I/R) injury of the heart. The rats were subjected to PET/CT imaging. After the scan the animals were sacrificed and both absolute quantitative and immunohistochemical analysis were performed.
Results We were able to detect apoptosis in our model of I/R injury non invasively using of Ga68 labeled A5-DOTA. Immunohistochemical staining and absolute quantitative analysis demonstrated that the areas seen on PET/CT correlated with the actual infarct.
Conclusion With this new Annexin construct we are able to visualize apoptosis non invasively using a clinical PET/CT scanner. This makes apoptosis imaging with Annexin more suitable for (clinical) research, combining the anatomical and biological information from PET/CT.