The polymer poly-trimethylenecarbonate (pTMC) is readily degradable by macrophages both in vitro and in vivo, without a significant degradation by water1. This makes pTMC an ideal model polymer to investigate which conditions influence the degradation activity of macrophages. This includes the possibility to assess the mutual influence of macrophages and fibroblasts2, the influence of a broad range of molecules that mediate inflammation, and also the environment in which the degradation takes place. J774 macrophages in their non-activated mode readily degrade pTMC. In this study the macrophages were activated towards their M1 and M2 phenotypes, while degrading pTMC.
pTMC polymer discs were prepared from solution. J774 mouse macrophages were used. Incubations were done for 6 days with medium changes at day 2 and day 4. Supernatants of days 2, 4 and 6 were stored for cytokine determination. At day 6 samples were fixed. Cells were stained with phalloidin (actin cytoskeleton) and DAPI (nuclei) and imaged with confocal microscopy. Afterwards, the end weights of the pTMC were determined and the percent degradation calculated. Cytokine release was measured using ELISA.
RESULTS AND DISCUSSION
J774 mouse macrophages readily degrade pTMC without further stimulation or activation. Pushing the macrophages towards M1 drastically reduces their potential for degradation. On the other hand a shift towards the M2 phenotype does not increase the degradation either. In this case a slight reduction in degradation potential has been observed. When the cell behavior is compared between the three different modes, it appears that the non-stimulated macrophages are closer to the M2 phenotype than the M1 phenotype.
Detailed confocal microscopy image stacks are available that shed more light on the behavior of the cells while degrading pTMC.
J774 mouse macrophages driven into a M1 phenotype show a reduced potential in degrading pTMC.
1. Bat et al. Biomaterials 2009, 30:3652
2. Ploeger et al. Cell Communication and Signaling 2013, 11:29.
The author would like to thank bachelor students Medicine and also Life Sciences & Technology (both University of Groningen) for performing part of the study in their science elective and research projects.