Metabolism in synovial macrophages are reprogrammed by synovial fibroblasts under inflammatory condition

Macrophages have plasticity to adapt microenvironment. In joint tissue, synovial macrophages (SM) and synovial fibroblasts (SF) are maintained in the homeostasis. In Rheumatoid arthritis, crosstalk between SM and SF via inflammatory response induce abnormal activation in respective cells and contribute to disease progression. However, the activation mechanisms in SM which are encouraged by SF are largely unclear. Here, we demonstrated metabolic reprogramming and immunological activation in SM by secretary stimulations from SF using primary culture synovial cell derived from arthritis model mice. To analyze interaction between SM and SF, primary culture of murine synovial cells was performed, respectively. RNA-seq analysis showed SF express abundant secretion-related gene. Thus, we investigated whether conditioned medium from SF (SF-CM) affects biological activity in SM. As the results, SF-CM condition induced both glycolysis and mitochondrial respiration to SM with increased uptake of glucose and glutamine at least, accompanied with cell survival. In addition, several inflammation markers were also upregulated in SM by SF-CM condition. Taken together, these results suggest that metabolic reprogramming were induced in SM by secretory stimulations from SF, followed by activated inflammatory response and long-live. These indicate that such phenotypes of SM may contribute to chronic inflammation in Rheumatoid arthritis mRNA profiles of primary synovial macrophages and synovial fibroblasts obtained from swollen ankle in CAIA mice were generated by deep sequencing, in triplicate, using Illumina Miseq.