Page 168 - Cellular Imaging in Regenerative Medicine, Cancer and Osteoarthritis

Chapter 8
Summary, Discussion, Concluding remarks
For this thesis we have performed preclinical studies in different models and at different levels of complexity with the ultimate aim to optimize cellular imaging in regenerative medicine, cancer and osteoarthritis. Single and multi- modal imaging was performed using MRI, SPECT and CT.
In Chapter 1 a general introduction to molecular imaging is given. We describe the imaging devices used in molecular imaging and cell labelling strategies that can be employed.
Cellular imaging in regenerative medicine
Regenerative medicine focuses on repair, replacement or regeneration of damaged tissue to restore functions. Impaired functions can be caused by congenital defects, by disease, trauma, and ageing. A variety of technologies and approaches such as gene therapy, stem cell therapy and progenitor cell therapy, as well as tissue engineering can be used for function repair (1).
In case of cell therapy it is essential to know if accurate delivery of the cell graft occurs (2). Monitoring the fate of the transplanted cells and measuring their therapeutic effect (e.g. improved cardiac output) is crucial to establish efficacy of cell therapy. Various methods have been studied for cell labelling and imaging. One method that has been considered as highly efficient and translatable is labelling of the cells with iron oxide nanoparticles. Such particles result in a local change in MRI signal and offer the possibility of highly sensitive detection of labelled cells at high spatial resolution within anatomical and/or functional context as imaged by MRI. As described in Chapters 2, 3 and 4 various types of iron oxide particles can be used. In these studies two types of particles were applied; 1) Ferumoxide which are super paramagnetic iron oxide particles (SPIO) having a particle diameter between 80 and 150nm and an iron oxide core (3-5) and 2) the larger micron-sized paramagnetic iron oxide particles (MPIO) composed of polystyrene–divinyl benzene polymer micro spheres containing a magnetite core and tagged with the fluorescent dye Dragon green (480/520 nm). MPIO particles have an average size of 1630 nm and have been shown to be functionally inert (6, 7). The iron oxide core of both SPIO and MPIO has a strong magnetic moment, causing a disturbance of the local magnetic field in
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