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Objective: To investigate and compare the feasibility of rat sodium iodide symporter (rNIS) and human NIS (hNIS) as reporter genes for noninvasive monitoring of rat bone marrow mesenchymal stem cells (rBMSCs) transplanted into infarcted rat myocardium.Methods: rBMSCs were isolated from rat bone marrow.Adenovirus was reconstructed to contain both rNIS and enhanced green fluorescence protein (eGFP) reporter genes or hNIS-eGFP.The transfection efficiency of Ad/eGFP/rNIS and Ad/eGFP/rNIS to rBMSCs was measured by real-time PCR, flow cytometry, Western blot and immunofluorescence staining.The transfected rBMSCs were transplanted into infarcted rat myocardium followed by single-photon emission computed tomography (SPECT) imaging study with 99mTc-pertechnetate as the radiotracer and by autoradiography.Results: The isolated rBMSCs were CD29, CD45 and CD90 positive, and CD34, CD44 and CD11b negative.The toxic effect of Ad/eGFP/rNIS and Ad/eGFP/rNIS to rBMSCs was not significant when the multiplicity of infection (MOI) was less than 2000.The expression of rNIS and hNIS in the transfected rBMSCs at both gene and protein levels were obviously higher than those without transfection.Immunofluorescence staining found that the two NIS were highly expressed on both cell membrane and cytoplasm of transfected rBMSCs.The uptake of 99mTc-pertechnetate in transfected rBMSCs was much higher than that in the non-transfected rBMSCs, which can be inhibited by sodium perchlorate.The transfection efficiency of rNIS was higher than hNIS.The myocardium of rats transplanted with transfected rBMSCs could be visualized by SPECT due to the accumulation of 99mTc-pertechnetate in rBMSCs mediated by exogenous NIS genes.The accumulation of 99mTc-pertechnetate in myocardium mediated by rNIS was higher than that by hNIS, which was also confirmed by autoradiography.The homing of transfected rBMSCs was further confirmed by the detection of the two NIS reporter genes ex vivo.Conclusions: Both rNIS and hNIS are useful reporter genes to monitor BMSCs transplanted into infarcted myocardium in vivo with rNIS being superior to hNIS as the reporter gene.