Iloprost Affects Macrophage Activation and CCL2 Concentrations in a Microdialysis Model in Rats

The hypothesis that locally-released iloprost, a synthetic prostacyclin analog, affects macrophage phenotype at a microdialysis implant in the subcutaneous space of rats was tested. Macrophage activation towards alternatively-activated phenotypes using pharmaceutical release is of interest to improve integration of implants and direct the foreign body reaction toward a successful outcome.

Macrophage cell culture was used to test iloprost macrophage activation in vitro. Microdialysis sampling probes were implanted into the subcutaneous space of Sprague-Dawley rats to locally deliver iloprost in awake- and freely-moving rats. Monocyte chemoattractant protein -1 (CCL2) was quantified from collected dialysates using ELISA. Immunohistochemical staining was used to determine the presence of CD163⁺ macrophages in explanted tissues.

Iloprost reduced CCL2 concentrations in NR8383 macrophages stimulated with lipopolysaccharide. CCL2 concentrations in collected dialysates were similarly reduced in the presence of iloprost. Iloprost caused an increase in CD163⁺ cells in explanted tissue surrounding implanted microdialysis probes at two days post probe implantation.

Localized delivery of iloprost caused macrophage activation at the tissue interface of a microdialysis subcutaneous implant in rat. This model system may be useful for testing other potential macrophage modulators in vivo.