简介: |
As a potential interventional procedure, cell transplantation provides a novel strategy for the treatment of impaired organs. Compared to orthotopic organ transplantation, cell transplantation holds advantages of lower cost and risk as well as simpler manipulation. Autologous cell transplantation helps prevent immunological rejection, which is always a problem for orthotopic organ transplantation. However, there remain many important issues to be addressed for cell therapy. One of most important issues for clinical practice is monitoring migration, distribution and evolution of the transplanted cells. Recent research activities have focused on in vivo real-time tracking and detecting the fate of transplanted stem cells by using appropriate imaging technologies. Thus, radiologists may play an increasingly crucial role in the future experimentation and application.
Series of studies have been done which focused on above issues, including cell labeling with home-synthesized suparamagnetic iron oxide particles (SPIO) and prospectively track in vivo transplanted stem cells labeled with SPIO in the liver, kidney and atherosclerotic plaque by using MR imaging. Our studies show that various stem cells including bone mesenchymal stem cells (BMSCs) and endothelial progenitor cell (EPCs) could be effectively labeled with approximately 100% efficiency. Migration of transplanted labeled cells to the liver was successfully documented by in-vivo MR imaging. CNRs on T2*-weighted images decreased significantly in the liver 3 hours after injection of BMSCs (P<0.05) and returned gradually to the level achieved without labeled cell injection in 14 days. Histological analyses confirmed the presence of BMSCs in the liver. The magnetically labeled MSCs in the rat model of acute renal failure (ARF) were also successfully evaluated in vivo by MRI system as well, showing that the mechanisms of stem cell therapy have great potential for future ARF treatment recipients. Atherosclerosis at rabbit carotid artery was inhibited by SPIO-labeled EPCs, which was depicted with clinical MRI scanner and proven histologically, suggesting that EPCs may play a role in restoration of endothelial injury and prevention of atherosclerosis.
As well as iron-oxide-based MR ‘negative’ contrast agents, we synthesized multi-modality imaging nanoparticles prepared by conjugation with Gd and fluorophore for EPC labeling. Our preliminary data show that this conjugate can be successfully used for detecting cells with positive contrast in MR and optical imaging in vitro, and be promising as a multimodal imaging media in tracking the delivery and therapeutic response of EPCs in vivo. |
