Page 148 - Cellular Imaging in Regenerative Medicine, Cancer and Osteoarthritis

Chapter 7
are attracted to the synovial lining (24, 25) and are pivotal in promoting the production of inflammatory and degradative mediators in the OA synovium, maintaining an inflammatory state in the joint. Human synovial explants were used to perform tracer binding tests in pro-inflammatory circumstances. In this study we evaluated targeting of SSTR2 as a tool for longitudinal imaging of pro-inflammatory macrophages in an experimental mouse model of OA.
Materials and Methods
Ethics approval
All animal experiments were performed in accordance with the ARRIVE guidelines for reporting on Animal Research (26), the Dutch law on animal experimentation, and were approved on March 12th 2014 by the committee on animal experimentation of the Erasmus MC, with protocol number EMC 3246. We chose male mice because sex hormones play a critical role in the progression of OA in the murine DMM surgical model, with males having more severe OA than females (27). Mice were housed at the Experimental Animal Facility of the Erasmus MC with a 12-h light–dark regimen, in individually ventilated cages including extensive cage enrichment. The mice received acidified tap water and standard chow ad libitum.
Synovial tissue was obtained with implicit consent from the patients, meaning that they had the right to refuse. The protocol was approved by the medical ethical committee of the Erasmus MC on November 12th 2004 with protocol number MEC-2004-322.
Somatostatin receptor subtype 2 expression
To verify the expression of SSTR2 on monocyte-derived macrophages, primary human monocytes were isolated from five buffy coats of male donor blood samples (58±8Y; Sanquin Blood bank, Amsterdam, the Netherlands) by Ficoll density gradient separation (GE Healthcare, Little Chalfont, UK) and CD14+ magneticactivated- cell sorting (MACS; Miltenyi, Bergisch Gladbach, Germany), as previously described (15). To acquire pro-inflammatory macrophages in vitro (15, 28), the monocytes were stimulated 1h after plating with 10 ng/mL IFN-γ (PeproTech, New Jersey, USA) and 10 ng/mL TNF-α (PeproTech, New Jersey,
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