A novel hybrid baculovirus-adeno-associated viral vector-mediated radionuclide reporter gene imaging system for stem cells transplantation monitoring.

Hybrid baculovirus-adeno-associated virus (BV-AAV) containing enhanced green fluorescent protein (eGFP) reporter gene or human sodium-iodide symporter (hNIS) reporter gene flanked by inverted terminal repeats (ITRs) derived from AAV (BV-CMV-eGFP-ITR and BV-CMV-hNIS-ITR) were constructed and used to investigate the feasibility of using hybrid BV-AAV transgenic vector to mediate hNIS reporter gene imaging for monitoring bone marrow-derived mesenchymal stem cells (BM-MSCs) transplantation therapy as a novel biotechnological platform in radionuclide reporter gene imaging. The results showed that the infection efficiency of BV-CMV-eGFP-ITR in BM-MSCs reached 84.25 ± 1.38%, and there were no obvious adverse effects on BM-MSCs. The (125)I(-) and (99m)TcO₄(-) uptake assays showed that the radionuclide accumulation induced by BA-AAV-mediated hNIS was highly efficient in infected BM-MSCs. Furthermore, there was a robust correlation between the infected BM-MSCs cell number and the (125)I(-) accumulation amount (R(2) = 0.9026). The micro-SPECT/CT imaging showed that BV-CMV-hNIS-ITR-infected BM-MSCs accumulated radioiodine efficiently in vivo, exhibiting obvious radiotracer accumulation in transplantation sites. Further quantitative analysis revealed that 30 min might be the optimal imaging time point. Moreover, the revealed high target/individual organ background ratios also supported the feasibility of BV-AAV-mediated hNIS reporter gene imaging for monitoring BM-MSCs transplantation in most of commonly used transplantation sites, thus highlighting this promise biotechnological platform in radionuclide reporter gene imaging for stem cell transplantation therapy.