SPIO-Annexin V, a potential probe for MRI detection of radiation induced apoptosis

Finding a suitable method for rapid, accurate and reliable estimation of absorbed dose has high priority in management of the radiation exposed persons. Shortly after radiation exposure, apoptosis is a major detriment in proliferative tissues such as the hematopoietic system. Therefore, quantification of apoptosis in these tissues could be useful for rapid estimation of radiation exposure. Annexin V (ANX) is considered as a biological probe for detection of apoptotic cells. The aim of the present study is to investigate the potential suitability of apoptosis quantification for estimation of radiation exposure. In order to determine the biological distribution of ANX within the mice body after radiation exposure, mice whole body irradiated with 2, 4, 6 and 8 Gy (60Co gamma rays). Ten hours later, ANX conjugated with super paramagnetic iron oxide nanoparticles (SPIO-ANX) was administered intravenously and magnetic resonance imaging was conducted 3 hours later. Average signal intensities in the regions of interest (ROIs) of the femur bone marrow, liver and testis were calculated and normalized to parafemoral muscle signals. SPIO-ANX accumulated in bone marrow of irradiated groups and significantly decreased the normalized mean of signal intensity for bone marrow in comparison with control group (p< 0.01). Tracing and quantification of SPIO-ANX in bone marrow can be used as an indicator for radiation exposure. However, development and optimization of the assay are necessary for discrimination between different radiation doses.