Page 15 - Cellular Imaging in Regenerative Medicine, Cancer and Osteoarthritis
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                                well. The first clinical data showed encouraging results: in fifty percent of the patients the lesions were visualized (28, 29). During surgical excision of such tumours the surgeon may prefer to visualise the tumour pre-operatively with SPECT and also detect the tumour intra-operatively (30). This can be achieved when a radionuclide is coupled to the tracer which emits gamma photons, like Indium-111 (31). Here we investigated the potential of [111In]In-SB3 as a radiotracer for pre-operative SPECT/MRI and sub sequentially improved tumour targeting.
Macrophage imaging
Macrophages are abundantly present immune cells characterized by phagocytic activity. When macrophages become activated, upon receiving signals from their microenvironment, they secrete cytokines that influence matrix remodelling and other cells in close proximity. Macrophages are then polarized towards different phenotypes (M1=pro-inflammatory, M2=anti- inflammatory) expressing a characteristic repertoire of surface markers. M1 macrophages constitute the first line of defence against intracellular pathogens and occur in an inflammatory environment. They are able to produce pro- inflammatory cytokines (e.g. TNF-α, type I IFN) and several chemokines. M2 macrophages are particularly involved during parasitic, helminthic and fungal infections. They down regulate pro-inflammatory cytokines and induce production of anti-inflammatory mediators (32, 33). The original polarization can be reversed upon environmental changes (34).
To emphasise the importance of in vivo macrophage visualisation, one should realize that macrophages play a role in many diseases. Activated macrophages are e.g. found in the brain of patients with schizophrenia (35, 36) and pulmonary macrophages are associated with tissue fibrosis (37). In the vasculature macrophages contribute to the formation of atherosclerotic plaques (38, 39). Macrophages also play a role in inflammatory diseases such as inflammatory bowel disease (40) and rheumatoid arthritis (41). Depending on the type of activation, macrophages can facilitate or prevent disease. So, knowing which kind of macrophage is present during the development of a disease is important for interference in disease development. In collaboration with the Orthopaedics Department we focused on macrophage involvement in the development of osteoarthritis (OA). OA affects many persons worldwide
Introduction
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