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UBC Theses and Dissertations

Regulation of raw264.7 macrophage polarization on smooth and rough topographies by galectin-3 Kianoush , Fariba


Surface topography can modulate cytokine gene expression and protein secretion in macrophages. Although phosphoinositide 3-kinase (PI3K) has been found to have a key role in the induction of the alternatively activated phenotype (M2) by interleukin 4 (IL-4), the pathways involved in topographic modulation of phenotype are largely unknown. This study examined the effect of polished (PO) and three rough surfaces, SLA (Sandblasted Large-grit Acid-etched surface which is a well-documented and widely used implant surface) and two novel grooved topographies G1 and G2 produced by anisotropic etching of Si <110> for their effects on RAW 264.7 macrophage gene expression and morphology using real time quantitative polymerase chain reaction (RT-qPCR). We hypothesized that the galectin-3/ CD98/ integrin β1 complex was involved in phenotype regulation. The hypothesis was tested by blocking attachment of galectin- 3 (gal-3) to CD98 by lactose. The G1 and G2 surfaces caused the macrophages to adopt an elongated M2-like morphology. In the presence of lactose the M2 markers were downregulated but the M1 marker was upregulated on smooth and rough surfaces. Thus the inhibition of gal-3 binding to integrin skewed macrophages phenotype towards the M1 phenotype and the effects of topography were thus abrogated. To test if PI3K is involved in regulation of macrophage phenotype on rough and smooth topographies (without any exogenously added IL-4/IL-13), we studied the effects of the PI3K inhibitor, LY294002, on phenotype markers. As expected from the results with IL-4 induced polarization, an M2 marker (the mannose receptor) was downregulated on both PO and G1 surfaces. Our data suggest that galectin-3 dependent CD98 interaction with integrin β1 skewed RAW264.7 cells toward an M2-like phenotype on both smooth and rough surface topographies through CD98-activated PI3K. Furthermore, we report that rough surface topography plays a substantive role in directing macrophages towards the M2 phenotype. This was reflected in both M2 marker expression and cellular morphology.

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