Preparation and evaluation of a novel 99mTc-cys-annexin A5 as radiotracer in the cycloheximide induced liver apoptosis model

Objectives A novel cys-annexin A5 with a single cysteine-residue at its C-terminal has been developed. This study was designed to evaluate 99mTc labeled cys-annexin A5 as a SPCET tracer in a rat model of cycloheximide (CHX) induced liver apoptosis.

Methods Using SnCl2 as reducing agent, and in the presence of sodium glucoheptonate, a series of studies were performed to optimize labeling efficiency of 99mTc-cys-annexin A5. The radiolabeling yield (RLY) and radiochemical purity (RCP) of 99mTc-cys-annexin A5 were determined by high performance liquid chromatography (HPLC) with a TSK GEL column. In this study, male SD rats were treated IV with 5 mg/kg CHX to induce liver apoptosis. 3 h after the treatment, rats were injected via the tail vein with 0.5mCi 99mTc-cys- annexin A5 and 3h later imaged with SPECT for 10min. The organs of interest (liver, spleen and kidney) were dissected and weighed at the end of the scan. The livers were harvested for terminal deoxynucleotide end-labeling (TUNEL) staining.

Results RLY and RCP of 99mTc-cys- annexin A5 were over 95% at selected condition. HPLC retention time of 99mTc-cys- annexin A5 was about 9.8min with the flow rate was 0.8mL/min. 99mTc-cys- annexin A5 tracer uptake in the liver and spleen were increased with CHX treatment. Liver, spleen and kidney uptake ratios (treated/control) were 2.83, 4.94 and 0.95 respectively. There were no differences in the blood pool activity between treated and control rats. TUNEL staining showed good correlation of 99mTc-cys- annexin A5 uptake with TUNEL-positive cells.

Conclusions SPECT studies combined with TUNEL staining showed that uptake of 99mTc-cys- annexin A5 correlates well with the level of apoptotic cells in this CHX induced liver apoptosis model.

Research Support Supported by Ministry of Health Foundation of China (W201207).