ABSTRACT
To assess a novel cell manipulation technique of tissue engineering with respect to its ability to augment superparamagnetic iron oxide particles (SPIO) labeled mesenchymal stem cells (MSCs) density at a localized cartilage defect site in an in vitro phantom by applying magnetic force.Meanwhile,non-invasive imaging techniques were use to track SPIO-labeled MSCs by magnetic resonance imaging (MRI).Human bone marrow MSCs were cultured and labeled with SPIO.Fresh degenerated human osteochondral fragments were obtained during total knee arthroplasty and a cartilage defect was created at the center.Then,the osteochondral fragments were attached to the sidewalls of culture flasks filled with phosphate-buffered saline (PBS) to mimic the human joint cavity.The SPIO-labeled MSCs were injected into the culture flasks in the presence of a 0.57 Tesla (T) magnetic force.Before and 90 min after cell targeting,the specimens underwent T2-weighted turbo spin-echo (SET2WI) sequence of 3.0 T MRI.MRI results were compared with histological findings.Macroscopic observation showed that SPIO-labeled MSCs were steered to the target region of cartilage defect.MRI revealed significantchanges in signal intensity (P＜0.01).HE staining exibited that a great number of MSCs formed a three-dimensional (3D) cell "sheet" structure at the chondral defect site.It was concluded that 0.57 T magnetic force permits spatial delivery of magnetically labeled MSCs to the target region in vitro.High-field MRI can serve as an very sensitive non-invasive technique for the visualization of SPIO-labeled MSCs.