Modulation of inflammatory process and tissue regeneration in calvaria mouse models
Al-Hashemi, Jacob Yousef
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MicroRNAs (miRNAs) are short, non-coding RNAs involved in the regulation of several processes associated with inflammatory diseases and infection. Bacterial infection modulates miRNA expression to subvert innate immune response. In this study, we analyzed bacterial modulation of miRNAs in bone-marrow-derived macrophages (BMMs), in which activity was induced by infection with Porphyromonas gingivalis (Pg) through a microarray analysis. Several miRNA expressions levels were modulated 3 hours post infection (at a multiplicity of infection (MOI) of 25). A bioinformatics analysis was performed to further identify pathways related to the innate immune host-response pathways that are under the influence of the selected miRNAs. To assess the effects of the identified miRNAs on cytokines secretion (pro inflammatory TNF-α and anti-inflammatory IL-10), BMMs were transfected with selected miRNAs mimics or inhibitors. Transfection with mmu-miR-155 and mmu-miR- 2137 did not modify TNF-α secretion while their inhibitors increased it. Inhibitors of mmumiR-2137 and mmu-miR-7674 increased the secretion of the anti-inflammatory IL-10. In Pginfected BMMs, mmu-miR-155-5p significantly decreased TNF-α secretion while inhibitor of mmu-miR-2137 increased IL-10 secretion. In vivo, in a Pg-induced calvarial bone resorption mouse model, injection of mmu-miR-155-5p or anti-mmu-miR-2137 reduced the size of the lesion significantly. Furthermore, anti-mmu-miR-2137 significantly reduced inflammatorycell infiltration, osteoclast activity and bone loss. Bioinformatics analysis demonstrated that pathways related to cytokines and chemokines related pathways but also osteoclast differentiation may be involved in the observed effects. The study highlights the potential therapeutic merits of targeting mmu-miR-155-5p and mmu-miR-2137 to control inflammation induced by Pg infection. To assess the regenerative process in the same animal model, we aimed to compare the effect of Bone Morphogenic Protien 2 (BMP2), Platelets Rich Plasma (PRP), Leukocyte-Platelets Rich Fibrin (L-PRF), and Polygucosamine (PGIcNAc) on bone formation in critical size bone defects in mice. One-hundred-thirty-eight mice were divided into 23 groups (n=6), negative control, different combinations of the PGIcNAc with or without of BMP2, Collagen Sponge (SurgiFoam), PRP, and L-PRF. The 5mm defect, then, was allowed to heal. After six weeks, samples were analyzed for bone formation utilizing radiographs, H&E staining, alkaline phosphatase staining. Our results show that BMP2 were able to produce 90-95% healing of critical size defects after six weeks histologically and radiographically. However, SurgiFoam, PRP and L-PRF with or without PGIcNAc were able to close 60% of the original defect. This study supports that BMP2 is more effective for bone regeneration than SurgiFoam, PRP, L-PRF and PGIcNAc.