M2 macrophages with inflammation tropism facilitate cementoblast mineralization

Extracellular Vesicles from Compression-Loaded Cementoblasts Promote the Tissue Repair Function of Macrophages

Treatment strategies for hard tissue defects aim to establish a mineralized microenvironment that facilitates tissue remodeling. As a mineralized tissue, cementum shares a similar structure with bone and exhibits an excellent capacity to resist resorption under compression. Macrophages are crucial for mineralized remodeling; however, their functional alterations in the microenvironment of cementum remain poorly understood. Therefore, this study explores the mechanisms by which cementum resists resorption under compression and the regulatory roles of cementoblasts in macrophage functions. As a result, extracellular vesicles from compression-loaded cementoblasts (Comp-EVs) promote macrophage M2 polarization and enhance the clearance of apoptotic cells (efferocytosis) by 2- to 3-fold. Local injection of Comp-EVs relieves cementum destruction in mouse root resorption model by activating the tissue repair function of macrophages. Moreover, Comp-EV-loaded hydrogels achieve significant bone healing in calvarial bone defect. Unexpectedly, under compression, EV secretion in cementoblasts is reduced by half. RNA-Seq analysis and verification reveal that Rab35 expression decreases by 60% under compression, thereby hampering the release of EVs. Rab35 overexpression is proposed as a modification of cementoblasts to boost the yield of Comp-EVs. Collectively, Comp-EVs activate the repair function of macrophages, which will be a potential therapeutic strategy for hard tissue repair and regeneration.

Tim4 deficiency reduces CD301b+ macrophage and aggravates periodontitis bone loss

Periodontitis is a common chronic inflammatory disease that causes the periodontal bone destruction and may ultimately result in tooth loss. With the progression of periodontitis, the osteoimmunology microenvironment in periodontitis is damaged and leads to the formation of pathological alveolar bone resorption. CD301b+ macrophages are specific to the osteoimmunology microenvironment, and are emerging as vital booster for conducting bone regeneration. However, the key upstream targets of CD301b+ macrophages and their potential mechanism in periodontitis remain elusive. In this study, we concentrated on the role of Tim4, a latent upstream regulator of CD301b+ macrophages. We first demonstrated that the transcription level of Timd4 (gene name of Tim4) in CD301b+ macrophages was significantly upregulated compared to CD301b- macrophages via high-throughput RNA sequencing. Moreover, several Tim4-related functions such as apoptotic cell clearance, phagocytosis and engulfment were positively regulated by CD301b+ macrophages. The single-cell RNA sequencing analysis subsequently discovered that Cd301b and Timd4 were specifically co-expressed in macrophages. The following flow cytometric analysis indicated that Tim4 positive expression rates in total macrophages shared highly synchronized dynamic changes with the proportions of CD301b+ macrophages as periodontitis progressed. Furthermore, the deficiency of Tim4 in mice decreased CD301b+ macrophages and eventually magnified alveolar bone resorption in periodontitis. Additionally, Tim4 controlled the p38 MAPK signaling pathway to ultimately mediate CD301b+ macrophages phenotype. In a word, Tim4 might regulate CD301b+ macrophages through p38 MAPK signaling pathway in periodontitis, which provided new insights into periodontitis immunoregulation as well as help to develop innovative therapeutic targets and treatment strategies for periodontitis.

Resveratrol modulates the inflammatory response in hPDLSCs via the NRF2/HO-1 and NF-κB pathways and promotes osteogenic differentiation

OBJECTIVE

The purpose of this study was to investigate resveratrol's specific role as an anti-inflammatory and osteogenic differentiation of hPDLSCs in periodontitis and to reveal the mechanisms involved.

BACKGROUND

Numerous studies have shown that inhibiting the inflammatory response of periodontal tissues and promoting the regeneration of alveolar bone are crucial treatments for periodontitis. Resveratrol has been found to have certain anti-inflammatory property. However, the anti-inflammatory mechanism and osteogenic effect of resveratrol in periodontitis are poorly understood.

MATERIALS AND METHODS

We constructed an in vitro periodontitis model by LPS stimulation of hPDLSCs and performed WB, RT-qPCR, and immunofluorescence to analyze inflammatory factors and related pathways. In addition, we explored the osteogenic ability of resveratrol in in vitro models.

RESULTS

In vitro, resveratrol ameliorated the inflammatory response associated with activation of the NF-κB pathway through activation of the NRF2/HO-1 pathway, characterized by inhibition of p65/p50 nuclear translocation and the proinflammatory cytokines interleukin-1β levels. Resveratrol also has a positive effect on osteogenic differentiation.

CONCLUSIONS

Observations suggest that resveratrol modulates the inflammatory response in hPDLSCs via the NRF2/HO-1 and NF-κB pathways and promotes osteogenic differentiation.

Genetically engineered M2-like macrophage-derived exosomes for P. gingivalis-suppressed cementum regeneration: From mechanism to therapy

Cementum, a thin layer of mineralized tissue covering tooth root surface, is recognized as the golden standard in periodontal regeneration. However, current efforts mainly focus on alveolar bone regeneration rather than cementum regeneration, and rarely take Porphyromonas gingivalis (Pg), the keystone pathogen responsible for periodontal tissue destruction, into consideration. Though M2 macrophage-derived exosomes (M2-EXO) show promise in tissue regeneration, the exosome-producing M2 macrophages are induced by exogenous cytokines with transitory and unstable effects, restricting the regeneration potential of M2-EXO. Here, exosomes derived from genetically engineered M2-like macrophages are constructed by silencing of casein kinase 2 interacting protein-1 (Ckip-1), a versatile player involved in various biological processes. Ckip-1 silencing is proved to be an effective gene regulation strategy to obtain permanent M2-like macrophages with mineralization-promoting effect. Further, exosomes derived from Ckip-1-silenced macrophages (sh-Ckip-1-EXO) rescue Pg-suppressed cementoblast mineralization and cementogenesis. Mechanismly, sh-Ckip-1-EXO delivers Let-7f-5p targeting and silencing Ckip-1, a negative regulator also for cementum formation and cementoblast mineralization. More deeply, downregulation of Ckip-1 in cementoblasts by exosomal Let-7f-5p activates PGC-1α-dependent mitochondrial biogenesis. In all, this study provides a new strategy of genetically engineered M2-like macrophage-derived exosomes for cementum regeneration under Pg-dominated inflammation.

Mitochondrial Dysfunction in Periodontitis and Associated Systemic Diseases: Implications for Pathomechanisms and Therapeutic Strategies

Periodontitis is a chronic infectious disorder damaging periodontal tissues, including the gingiva, periodontal ligament, cementum, and alveolar bone. It arises from the complex interplay between pathogenic oral bacteria and host immune response. Contrary to the previous view of "energy factories", mitochondria have recently been recognized as semi-autonomous organelles that fine-tune cell survival, death, metabolism, and other functions. Under physiological conditions, periodontal tissue cells participate in dynamic processes, including differentiation, mineralization, and regeneration. These fundamental activities depend on properly functioning mitochondria, which play a crucial role through bioenergetics, dynamics, mitophagy, and quality control. However, during the initiation and progression of periodontitis, mitochondrial quality control is compromised due to a range of challenges, such as bacterial-host interactions, inflammation, and oxidative stress. Currently, mounting evidence suggests that mitochondria dysfunction serves as a common pathological mechanism linking periodontitis with systemic conditions like type II diabetes, obesity, and cardiovascular diseases. Therefore, targeting mitochondria to intervene in periodontitis and multiple associated systemic diseases holds great therapeutic potential. This review provides advanced insights into the interplay between mitochondria, periodontitis, and associated systemic diseases. Moreover, we emphasize the significance of diverse therapeutic modulators and signaling pathways that regulate mitochondrial function in periodontal and systemic cells.

The Applications and Potentials of Extracellular Vesicles from Different Cell Sources in Periodontal Regeneration

Periodontitis is a chronic infectious disease worldwide that can cause damage to periodontal supporting tissues including gingiva, bone, cementum and periodontal ligament (PDL). The principle for the treatment of periodontitis is to control the inflammatory process. Achieving structural and functional regeneration of periodontal tissues is also essential and remains a major challenge. Though many technologies, products, and ingredients were applied in periodontal regeneration, most of the strategies have limited outcomes. Extracellular vesicles (EVs) are membranous particles with a lipid structure secreted by cells, containing a large number of biomolecules for the communication between cells. Numerous studies have demonstrated the beneficial effects of stem cell-derived EVs (SCEVs) and immune cell-derived EVs (ICEVs) on periodontal regeneration, which may be an alternative strategy for cell-based periodontal regeneration. The production of EVs is highly conserved among humans, bacteria and plants. In addition to eukaryocyte-derived EVs (CEVs), a growing body of literature suggests that bacterial/plant-derived EVs (BEVs/PEVs) also play an important role in periodontal homeostasis and regeneration. The purpose of this review is to introduce and summarize the potential therapeutic values of BEVs, CEVs and PEVs in periodontal regeneration, and discuss the current challenges and prospects for EV-based periodontal regeneration.