Apoptotic vesicles activate autophagy in recipient cells to induce angiogenesis and dental pulp regeneration.

Extracellular vesicles (EVs) derived from living cells play important roles in donor cell-induced recipient tissue regeneration. Although numerous studies have found that cells undergo apoptosis after implantation in an ischemic-hypoxic environment, the roles played by the EVs released by apoptotic cells are largely unknown. In this study, we obtained apoptotic vesicles (apoVs) derived from human deciduous pulp stem cells and explored their effects on the dental pulp regeneration process. Our work showed that apoVs were ingested by endothelial cells (ECs) and elevated the expression of angiogenesis-related genes, leading to pulp revascularization and tissue regeneration. Furthermore, we found that, at the molecular level, apoV-carried mitochondrial Tu translation elongation factor was transported and regulated the angiogenic activation of ECs via the transcription factor EB-autophagy pathway. In a beagle model of dental pulp regeneration in situ, apoVs recruited endogenous ECs and facilitated the formation of dental-pulp-like tissue rich in blood vessels. These findings revealed the significance of apoptosis in tissue regeneration and demonstrated the potential of using apoVs to promote angiogenesis in clinical applications.

The effect of 3D-printed plastic teeth on scores in a tooth morphology course in a Chinese university.

BACKGROUND: The tooth morphology course is an important basic dental course. However, it is difficult to fully reflect the three-dimensional (3D) morphological characteristics of tooth structure in two-dimensional pictures in traditional textbooks. The aim of this study was to assess the effect of 3D-printed plastic model teeth in the teaching of tooth morphology. METHODS: Twenty-two undergraduate students who matriculated at the School of Stomatology, the Fourth Medical University, in 2014 and 23 who matriculated in 2016 participated in the study. Each student who matriculated in 2016 was given a full set of fourteen standard 3D-printed plastic model teeth for use during the learning process, and an anonymous questionnaire was used to evaluate the usefulness of the 3D-printed plastic model teeth from the perspective of the students. RESULTS: There was no significant difference between the two groups in the scores of the theoretical examination or the total score. However, for the score of the sculpted gypsum teeth, the students who used the 3D-printed plastic model teeth in their studies scored significantly higher (P = 0.002). More than 90% of the students thought that the 3D-printed plastic model teeth were of great help or were very helpful for mastering the anatomy of teeth and for carving the gypsum teeth. CONCLUSION: Standard 3D-printed plastic teeth can effectively assist students in learning tooth morphology by transforming two-dimensional pictures and descriptions in the textbook into a 3D conformation, effectively promoting students' learning and mastery of tooth morphology and structure. Additionally, the results suggest that 3D-printed plastic model teeth are of great help to the students in mastering and improving their carving skills.

Apoptotic extracellular vesicles alleviate Pg-LPS induced inflammatory responses of macrophages via AMPK/SIRT1/NF-κB pathway and inhibit osteoclast formation.

BACKGROUND: Periodontitis is caused by the imbalance of anti-bacteria immune response and excessive inflammation whereas macrophages play an important role in inflammation. Thus, it is critical for finding efficient anti-inflammatory strategies to alleviate periodontal inflammation and prevent bone destruction. Apoptosis of mesenchymal stem cells (MSCs) exerts immune silencing effects, however, using these effects to develop anti-inflammatory strategies remains unknown. In our study, we extracted apoptotic extracellular vesicles (ApoEVs) from bone marrow MSCs (BMMSCs) and found ApoEVs inhibited macrophages polarizing into proinflammatory condition via AMPK/SIRT1/NF-κB pathway. Besides that, we also found ApoEVs inhibited adjacent osteoclast formation by suppressing the secretion of TNF-α of proinflammatory macrophages. METHODS: BMMSCs derived ApoEVs were extracted by gradient centrifugation. Protein expression level and secreted cytokines of ApoEVs treated macrophages were examined by western blot and ELISA, respectively. Besides, the change of NF-κB pathway and related molecules were examined by immunofluorescence and western blot. The osteoclast formation under the different conditioned mediums from macrophages was measured by TRAP staining, MMP-9 expression, and pit assay. RESULTS: ApoEVs were extracted from staurosporine-induced apoptotic BMMSCs and were in sphere shapes whose diameters are between 100 and 1000 nm. ApoEVs could be phagocyted by macrophages and in turn reduce the expression of COX2 in proinflammatory macrophages. Besides that, ApoEVs suppressed the secretions of TNF-α and IL-6 while elevating the secretion of IL-10 in a dose-dependent manner. Further studies revealed that ApoEVs inhibited macrophages polarizing into proinflammatory phenotypes via AMPK/SIRT1/NF-κB pathway. In addition, ApoEVs inhibited osteoclasts differentiation and bone resorption measured by TRAP staining, MMP-9 expression, and pit resorption area by downregulating the secretion of TNF-α of proinflammatory macrophages. CONCLUSIONS: The results suggest that ApoEVs inhibited macrophages to skew into proinflammatory phenotypes via AMPK/SIRT1/NF-κB pathway and suppress adjacent osteoclasts formation by reducing the secretion of TNF-α. Our findings shed a light on the treatment for periodontitis based on EVs therapy.

Hybrid Biomaterial Initiates Refractory Wound Healing via Inducing Transiently Heightened Inflammatory Responses.

Inflammation plays a crucial role in triggering regeneration, while inadequate or chronic inflammation hinders the regenerative process, resulting in refractory wounds. Inspired by the ideal regeneration mode in lower vertebrates and the human oral mucosa, realigning dysregulated inflammation to a heightened and acute response provides a promising option for refractory wound therapy. Neutrophils play important roles in inflammation initiation and resolution. Here, a hybrid biomaterial is used to stimulate transiently heightened inflammatory responses by precise tempospatial regulation of neutrophil recruitment and apoptosis. The hybrid biomaterial (Gel@fMLP/SiO2 -FasL) is constructed by loading of formyl-met-leu-phe (fMLP) and FasL-conjugated silica nanoparticles (SiO2 -FasL) into a pH-responsive hydrogel matrix. This composition enables burst release of fMLP to rapidly recruit neutrophils for heightened inflammation initiation. After neutrophils act to produce acids, the pH-responsive hydrogel degrades to expose SiO2 -FasL, which induces activated neutrophils apoptosis via FasL-Fas signaling triggering timely inflammation resolution. Apoptotic neutrophils are subsequently cleared by macrophages, and this efferocytosis activates key signalings to promote macrophage anti-inflammatory phenotypic transformation to drive regeneration. Ultimately, Gel@fMLP/SiO2 -FasL successfully promotes tissue regeneration by manipulating inflammation in critical-sized calvarial bone defects and diabetic cutaneous wound models. This work provides a new strategy for refractory wound therapy via inducing transiently heightened inflammatory responses.

Chondrocyte apoptosis in rat mandibular condyles induced by dental occlusion due to mitochondrial damage caused by nitric oxide.

OBJECTIVE: Chondrocyte apoptosis is a pathological manifestation of osteoarthritis. The goal of this report was to explore the role of nitric oxide in chondrocyte apoptosis in osteoarthritic mandibular condylar cartilage. DESIGN: This study used our reported experimental unilateral anterior crossbite in vivo rat model and chondrocyte fluid flow shear stress in vitro model. In the in vivo model, apoptosis in the mandibular condylar cartilage was assessed by detection of the TUNEL-positive cells, the expression levels of inducible nitric oxide synthase (iNOS), caspase-9, and caspase-3. In the in vitro model, mitochondrial injury was evaluated, the nitric oxide and superoxide dismutase (SOD) production levels were measured, and the cytochrome C (Cyt C) expression level was detected. The expression levels of apoptosis-related proteins B cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, and poly-ADP-ribose polymerase 1 (PARP1) were analyzed in both in vivo and in vitro models. The effects of iNOS inhibitor on chondrocyte apoptosis were also investigated. RESULTS: The data indicated that the unilateral anterior crossbite induced cartilage degeneration with enhanced cell apoptosis and stimulated the expression of caspase-3/-9 and iNOS. The fluid flow shear stress upregulated the expression of iNOS, SOD, and nitric oxide, reduced mitochondrial membrane potential, and promoted Cyt C to enter the cytoplasm. All of these changes were reversed by iNOS inhibitors. CONCLUSION: The abnormal occlusion stimulated mitochondrial damage and apoptosis of the chondrocytes in the mandibular condylar cartilage mediated by nitric oxide. Inhibiting nitric oxide production could be a therapeutic strategy.