OR08 - The Role of MMP-9-Induced Inflammation on Multicellular Functions and its Sensitivity to N-acetylcysteine

Matrix metalloproteinase-9 (MMP-9) is a pro-inflammatory molecule implicated in the development of pulpal inflammation. This study aimed to investigate MMP-9’s effects on key cells involved in pulpal healing—dental pulp stem cells (DPSCs), human umbilical vein endothelial cells (HUVECs), and macrophages—and to explore the modification of the effects of MMP-9 by N-acetylcysteine (NAC)-encapsulated GelMA hydrogel. DPSCs, HUVECs, and THP-1 macrophages were cultured and treated with 1000 ng/ml of MMP-9 for 1-3 days for cell viability, angiogenesis, and inflammatory response and up to 21 days for mineralization. Statistical analyses were performed using t-tests, ANOVA, or Kruskal Wallis tests with pair-wise comparisons at the significance level at p<0.05. Results showed that MMP-9 increased DPSC vitality and reduced alkaline phosphatase activity as an early mineralization marker while enhancing late-stage mineralization. In HUVECs, MMP-9 downregulated von Willebrand factor (vWF) expression without altering vascular density. MMP-9 also upregulated macrophage secretion of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1 β (IL-1β). Notably, NAC (1, 5, and 10 mM) reduced early inflammatory cytokine expression, including TNF-α and transforming growth factor-β (TGF-β), in MMP-9-treated macrophages without impacting pulpal or angiogenic functions. These findings highlight MMP-9’s involvement in early pulpal inflammation and suggest NAC’s potential for therapeutic use in mitigating inflammation without disrupting cellular activities.