Capsaicin attenuates Porphyromonas gingivalis-suppressed osteogenesis of periodontal ligament stem cells via regulating mitochondrial function and activating PI3K/AKT/mTOR pathway

Rapamycin ameliorates senescence of periodontal ligament stem cells and promotes their osteogenesis via the PI3K/AKT pathway

Periodontal ligament stem cells (PDLSCs) have been regarded as ideal candidates for tissue regeneration due to their excellent self-renewal and multipotent differentiation ability. Rapamycin (RAPA) is reported to play an important role in the regulation of biological properties of stem cells and a variety of physiological processes. This study investigates whether RAPA could ameliorate the senescence and accelerate the osteogenic differentiation of PDLSCs, particularly the regenerative potential in a rat calvarial bone defect model, and the underlying mechanisms involved. β-galactosidase staining, quantitative real-time polymerase chain reaction, and western blot analysis were performed to assess the effects of RAPA on senescent PDLSCs. The osteogenic differentiation ability of PDLSCs was detected by alkaline phosphatase staining and activity, Alizarin Red S staining, and gene and protein levels of osteogenesis-related markers. The underlying signaling pathways were investigated via RNA transcriptome sequencing analysis and WB tests. Calvarial bone defects in rat were treated with PDLSCs pre-incubated with or without RAPA and/or H2O2. The results showed that RAPA could enhance the osteogenic potentials of PDLSCs via PI3K/AKT signaling pathway, and reversed H2O2-induced senescence and osteogenic differentiation inhibition of PDLSCs. Moreover, calvarial defects transplanted with RAPA-treated PDLSCs showed significantly greater new bone formation compared with other groups, and also improved the H2O2-induced impairment of bone formation, whether by micro-computed tomography examination or by histological analysis. Collectively, RAPA was capable of promoting osteogenic differentiation of PDLSCs via PI3K/AKT signaling pathway in vitro, facilitating calvarial bone regeneration and reversing H2O2-induced impairment of osteogenic differentiation and cell senescence in PDLSCs.

Oxytocin-loaded hydrogel promotes cartilage regeneration and regulates microenvironment

Osteoarthritis is a common orthopedic condition, and traditional treatment methods often fail to regenerate cartilage effectively. Oxytocin (OXT) is a neuropeptide that plays a crucial role in the skeletal system. Hyaluronic acid (HAMA) hydrogel has emerged as a key carrier for cartilage repair due to its excellent biocompatibility and biodegradability. Combining OXT with HAMA hydrogel and implanting it at the site of cartilage defects can effectively promote cartilage regeneration. Cartilage damage often results in an altered microenvironment, characterized by macrophage polarization and high levels of reactive oxygen species (ROS). Oxidative stress can stimulate macrophages to produce more pro-inflammatory factors. OXT can inhibit the secretion of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1βby interacting with the STAT3/NF-κB signaling pathway, as well as the PI3K/Akt and mitogen-activated protein kinase pathways, thereby inducing the polarization of macrophages from the M1 phenotype to the M2 phenotype and alleviating the inflammatory response. OXT can also enhance the expression of NRF and HO-1, which helps eliminate ROS and suppress the expression of pro-inflammatory factors. Regulating the microenvironment of cartilage damage is beneficial for cartilage protection and repair. OXT activates the CFOS/AP-1 and STAT1/JAK2 pathways, which together act on MMP2 and MMP9 to alleviate cartilage degeneration. The STAT1/JAK2 pathway can further increase the expression of Col2, thereby protecting chondrocytes. Additionally, OXT can directly boost the protein levels of SOX9 and COMP, promoting chondrocyte proliferation and cartilage protection, ultimately achieving the therapeutic goal for arthritis. This study explores the potential of HAMA hydrogel as a delivery system for OXT and analyzes their impact on cartilage regeneration and anti-inflammatory properties. This research provides a novel strategy for the treatment of cartilage injuries.

Sirt3 Rescues Porphyromonas gingivalis-Impaired Cementogenesis via SOD2 Deacetylation

The keystone pathogen Porphyromonas gingivalis (P.g.) is responsible for cementum resorption in periodontitis; however, the mechanism involved in it remains unclear. Sirtuin 3 (Sirt3) is a NAD+-dependent protein deacetylase contributing to mitochondrial homeostasis and various cell functions. In this study, the expression of Sirt3 in cementoblasts was found to be increased during cementoblast mineralisation and cementum development, while it decreased gradually under P.g. infection in a multiplicity of infection-dependent manner. Compared with wild type mice, the Sirt3 knockout mice showed less cellular cementum and lower mineralisation capacity with decreased expression of Runx2 and OCN in cementoblasts. Sirt3 inhibition by 3-TYP or Sirt3 silencing by lentivirus infection both confirmed the impaired cementogenesis. Conversely, honokiol (HKL) was simulated to bind Sirt3 and was applied to activate Sirt3 in cementoblasts. HKL-mediated Sirt3 activation facilitated cementoblast mineralisation and rescued P.g.-suppressed cementoblast mineralisation markedly. Superoxide dismutase 2 (SOD2), the downstream molecule of Sirt3, showed a similar expression pattern to Sirt3 under different conditions. Silencing of SOD2 was demonstrated to restrain cementoblast mineralisation. The pan acetylation was detected to decrease under Sirt3-upregulating conditions and increase under Sirt3-downregulating conditions. The binding of Sirt3 and SOD2 in cementoblasts was also verified. Furthermore, SOD2 acetylation and specific SOD2-K68 acetylation were found to be upregulated under P.g. or Sirt3 silencing conditions and downregulated by HKL stimulation. Moreover, K68Q mutation simulating acetylation decreased cementoblast mineralisation, while K68R mutation simulating deacetylation increased it. Altogether, Sirt3 deacetylates SOD2 via K68 to orchestrate P.g.-perturbed cementogenesis, and HKL is a Sirt3-targeted treatment candidate.

Causal Relationship between Mitochondrial Biological Function and Periodontitis: Evidence from a Mendelian Randomization Study

A growing number of studies indicate that mitochondrial dysfunction serves as a pathological mechanism for periodontitis. Therefore, this two-sample Mendelian randomization (MR) study was carried out to explore the causal associations between mitochondrial biological function and periodontitis, because the specific nature of this causal relationship remains inconclusive in existing MR studies. Inverse variance weighting, Mendelian randomization-Egger, weighted mode, simple mode, and weighted median analyses were performed to assess the causal relationships between the exposure factors and periodontitis. The results of the present study revealed a causal association between periodontitis and medium-chain specific acyl-CoA dehydrogenase (MCAD), malonyl-CoA decarboxylase (MLYCD), glutaredoxin 2 (Grx2), oligoribonuclease (ORN), and pyruvate carboxylase (PC). Notably, MCAD and MLYCD are causally linked to periodontitis, and serve as protective factors. However, Grx2, ORN, and PC function as risk factors for periodontitis. Our study established a causal relationship between mitochondrial biological function and periodontitis, and such insights may provide a promising approach for treating periodontitis via mitochondrial regulation.