Diagnosis of abnormal biliary copper excretion by positron emission tomography with targeting of⁶⁴Copper-asialofetuin complex in LEC rat model of Wilson’s disease

Identification by molecular imaging of key processes in handling of transition state metals, such as copper (Cu), will be of considerable clinical value. For instance, the ability to diagnose Wilson’s disease with molecular imaging by identifying copper excretion in an ATP7B-dependent manner will be very significant. To develop highly effective diagnostic approaches, we hypothesized that targeting of radiocopper via the asialoglycoprotein receptor will be appropriate for positron emission tomography, and examined this approach in a rat model of Wilson’s disease. After complexing⁶⁴Cu to asialofetuin we studied handling of this complex compared with⁶⁴Cu in healthy LEA rats and diseased homozygous LEC rats lacking ATP7B and exhibiting hepatic copper toxicosis. We analyzed radiotracer clearance from blood, organ uptake, and biliary excretion, including sixty minute dynamic positron emission tomography recordings. In LEA rats,⁶⁴Cu-asialofetuin was better cleared from blood followed by liver uptake and greater biliary excretion than⁶⁴Cu. In LEC rats,⁶⁴Cu-asialofetuin activity cleared even more rapidly from blood followed by greater uptake in liver, but neither⁶⁴Cu-asialofetuin nor⁶⁴Cu appeared in bile. Image analysis demonstrated rapid visualization of liver after⁶⁴Cu-asialofetuin administration followed by decreased liver activity in LEA rats while liver activity progressively increased in LEC rats. Image analysis resolved this difference in hepatic activity within one hour. We concluded that⁶⁴Cu-asialofetuin complex was successfully targeted to the liver and radiocopper was then excreted into bile in an ATP7B-dependent manner. Therefore, hepatic targeting of radiocopper will be appropriate for improving molecular diagnosis and for developing drug/cell/gene therapies in Wilson’s disease.