Expression of heparan sulfate biosynthetic enzymes and proteoglycans in macrophages upon senescence and chronic inflammation

Introduction Heparan sulfate (HS) proteoglycans are ubiquitously expressed on the cell surface and in the extracellular matrix. They are also expressed by immune cells and can bind various proteins, such as chemokines, cytokines and growth factors due to their structural diversity. Structural diversity is achieved by the template‐independent synthesis by HS biosynthetic enzymes. A few studies have shown that individual HS biosynthetic enzymes affect immune cell function and in particular macrophage behaviour. To date, regulation of these HS biosynthetic enzymes in macrophages has not been systemically studied, and their regulation in chronic inflammation is not known. This study aims to define changes in expression of HS biosynthesis enzymes and proteoglycans in macrophages upon polarisation, in chronic inflammation (such as in rheumatoid arthritis), and with cellular senescence. Materials and Methods Primary murine macrophages were obtained by differentiation of bone marrow‐derived cells with M‐CSF. IFN‐γ/LPS or IL‐4/IL‐13 stimulation was used to polarize macrophages towards classically activated pro‐inflammatory or alternatively activated anti‐inflammatory macrophages. Senescence was induced in human GM‐CSF differentiated macrophages by treatment with the Mre11 inhibitor Mirin. Expression of heparan sulfate‐related genes was determined using quantitative real‐time PCR. Results Expression of several HS core proteins and biosynthetic enzymes was significantly altered by macrophage polarisation. We are validating induction of senescence phenotype upon mirin treatment, and will quantify expression of HS‐related genes following this treatment. Discussion This study suggests that HS core proteins and biosynthetic enzymes are differentially expressed in pro‐ and anti‐inflammatory primary murine macrophages.