Search

In traditional Chinese medicine, propolis has been used for treating oral diseases for centuries, widely. Flavonoid extract is the main active ingredient in propolis, which has attracted extensive attention in recent years. The objective and novelty of the current study aims to identify the mechanism of total flavonoid extract of propolis (TFP) for the treatment of periodontitis, and evaluate the therapeutic effect of TFP-loaded liquid crystal hydrogel (TFP-LLC) in rats with periodontitis. In this study, we used lipopolysaccharide-stimulated periodontal ligament stem cells (PDLSCs) to construct in vitro inflammation model, and investigated the anti-inflammatory effect of TFP by expression levels of inflammatory factors. Osteogenic differentiation was assessed using alkaline phosphatase activity and alizarin red staining. Meanwhile, the expression of toll like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor-kappa B (NF- κ B), receptor activator of NF- κ B (RANK) etc, were quantitated to investigate the therapeutic mechanism of TFP. Finally, we constructed TFP-LLC using a self-emulsification method and administered it to rats with periodontitis via periodontal pocket injection to evaluate the therapeutic effects. The therapeutic index, microcomputed tomography (Micro-CT), H&E staining, TRAP staining, and Masson staining were used for this evaluation. TFP reduced the expression of TLR4, MyD88, NF- κ B and inflammatory factor in lipopolysaccharide-stimulated PDLSCs. Meanwhile, TFP simultaneously regulating alkaline phosphatase, RANK, runt-associated transcription factor-2 and matrix metalloproteinase production to accelerate osteogenic differentiation and collagen secretion. In addition, TFP-LLC can stably anchor to the periodontal lesion site and sustainably release TFP. After four weeks of treatment with TFP-LLC, we observed a decrease in the levels of NF- κ B and interleukin-1 β (IL-1β) in the periodontal tissues of rats, as well as a significant reduction in inflammation in HE staining. Similarly, Micro CT results showed that TFP-LLC could significantly inhibit alveolar bone resorption, increase bone mineral density (BMD) and reduce trabecular bone space (Tb.Sp) in rats with periodontitis. Collectively, we have firstly verified the therapeutic effects and mechanisms of TFP in PDLSCs for periodontitis treatment. Our results indicate that TFP perform anti-inflammatory and tissue repair activities through TLR4/MyD88/NF-κB and RANK/NF- κ B pathways in PDLSCs. Meanwhile, for the first time, we employed LLC delivery system to load TFP for periodontitis treatment. The results showed that TFP-LLC could be effectively retained in the periodontal pocket and exerted a crucial role in inflammation resolution and periodontal tissue regeneration. Scheme 1. Schematic diagram of TFP-LLC alleviating periodontitis via PDLSCs-dependent anti-inflammatory and periodontium regeneration mechanism. TFP–LLC was in situ injected into the periodontal pocket to ensure the sustained release of the active TFP ingredients at the periodontal lesion. TFP–LLC suppresses the expression of inflammatory factors and osteoclastogenesis by interfering with TLR4/MyD88/NF-κB and RANK/NF-κB signaling. In addition, TFP–LLC promotes osteogenic differentiation and collagen regeneration in PDLSCs, as demonstrated by the upregulation of ALP and RUNX2 and downregulation of MMP. The TFP–LLC-induced periodontal homeostasis alleviates acute periodontal inflammation and assists in the long-term tissue regeneration of the gingiva, cementum, periodontal ligament, and alveolar bone, thereby demonstrating comprehensive treatment efficacy in periodontitis. [Display omitted] • We demonstrated that TFP exerts an anti-inflammatory pathway through TLR4/MyD88/NF-κB pathway in PDLSCs. • We proved TFP boosting periodontium regeneration via RANK/NF- κ B pathway in PDLSCs. • We prepared lyotropic liquid crystals containing total flavonoid extract of propolis (TFP-LLC). • TFP-LLC was stably anchored to the periodontal lesion site to form a drug reservoir. • TFP-LLC demonstrated excellent periodontal protection in rats with periodontitis. [ABSTRACT FROM AUTHOR]