Shifting macrophage polarization with use of chondroitinase ABC in spinal cord injury

Abstract

In the local microenvironment of spinal cord injury, macrophages are mainly polarized to the M1 (pro-inflammatory) phenotype. This polarization contributes to secondary injury in the spinal cord. On-site treatment of the injured cord (rat model) with chondroitinase ABC (ChABC) led to improved prospects of axonal regrowth, and at the same time, a shift in macrophage polarization towards the M2 (anti-inflammatory) phenotype. We hypothesize that ChABC treatment mobilizes the cytokines that are normally sequestered by chondroitin sulphate (CS) moieties in the injured cord environment, and thus facilitates macrophage polarization to the M2 phenotype. In this study, we used naïve (M0) macrophages derived from adult rat bone marrow as a model. The macrophages were polarized to the M1 phenotype with use of lipopolysaccharide (LPS) induction. Following ChABC treatment, immunocytochemistry, Western blot and RT-PCR analyses revealed lowered expression of M1 markers and increased expression of M2 markers among the cells. Furthermore, by live cell-labelling of M1 pericellular proteins, M2 inducers (IL4 and IL10) were found in association with pericellular CS moieties. Altogether, results suggest that pericellular CS of M1 macrophages entrap M2 inducers which upon release, can act locally on signalling receptors to induce M2 polarization. The CS-cleaving activity of ChABC can conveniently be utilized to enhance M2 polarization as a treatment strategy in the secondary, progressive phase of cord injury.