Inflammation and Periodontal Regeneration

Extracellular Vesicles From LPS-Treated PDLSCs Induce NLRP3 Inflammasome Activation in Periodontitis

OBJECTIVE

This study aimed to investigate the effects of lipopolysaccharide (LPS)-pretreated primary periodontal ligament stem cell (PDLSC)-derived extracellular vesicles (EVs) (L-PDLSC-EVs) on periodontitis.

MATERIALS AND METHODS

PDLSCs were obtained from mouse periodontal ligaments via enzymatic digestion. An in vitro inflammatory microenvironment for PDLSCs was established using LPS, and L-PDLSC-EVs were isolated through ultracentrifugation and identified. EVs from different treatments were co-incubated with RAW264.7 macrophages (Mφs) or periodontal ligament fibroblasts (PLFs) and their co-cultures, whereafter the biological behaviors in Mφs and PLFs were evaluated. Periodontitis mouse models were established to verify the role of L-PDLSC-EVs and the mechanisms involved.

RESULTS

There were no significant changes in the characteristics of L-PDLSC-EVs compared with control EVs. L-PDLSC-EVs promoted M1-type Mφ polarization and activated the nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing protein 3 (NLRP3) inflammasome. Furthermore, L-PDLSC-EVs promoted PLF cytotoxicity and apoptosis by enhancing the M1 polarization of Mφs. In periodontitis mouse models, L-PDLSC-EVs facilitated alveolar bone loss, PLF injury, and inflammatory responses, accompanied by an increased proportion of M1-type Mφs and reinforced NLRP3 inflammasome activation.

CONCLUSIONS

L-PDLSC-EVs promoted PLF injury and exacerbated periodontitis through activating the NLRP3 inflammasome and promoting the polarization of M1-type Mφs, providing novel insights for the periodontitis progression.

Metronidazole may display anti-inflammatory features in periodontitis treatment: A scoping review

AIM

Metronidazole (MTZ) is an antimicrobial agent used to treat anaerobic infections. It has been hypothesized that MTZ may also have anti-inflammatory properties, but the evidence is limited and has not been previously reviewed. Thus, this scoping review aimed to answer the following question: "What is the evidence supporting anti-inflammatory properties of metronidazole that are not mediated by its antimicrobial effects?"

METHODS

A scoping review was conducted according to the PRISMA-ScR statement. Five databases were searched up to January 2023 for studies evaluating the anti-inflammatory properties of MTZ used as monotherapy for treating infectious and inflammatory diseases.

RESULTS

A total of 719 records were identified, and 27 studies (21 in vivo and 6 in vitro) were included. The studies reported experimental evidence of MTZ anti-inflammatory effects on (1) innate immunity (barrier permeability, leukocyte adhesion, immune cell populations), (2) acquired immunity (lymphocyte proliferation, T-cell function, cytokine profile), and (3) wound healing/resolution of inflammation.

CONCLUSION

Taken together, this scoping review supported a potential anti-inflammatory effect of MTZ in periodontitis treatment. We recommend that future clinical studies should be conducted to evaluate specific MTZ anti-inflammatory pathways in the treatment of periodontitis.

Targeting chronic inflammation as a potential adjuvant therapy for osteoporosis

Systemic, chronic, low-grade inflammation (SCLGI) underlies the pathogenesis of various widespread diseases. It is often associated with bone loss, thus connecting chronic inflammation to the pathogenesis of osteoporosis. In postmenopausal women, osteoporosis is accompanied by SCLGI development, likely owing to estrogen deficiency. We propose that SCGLI persistence in osteoporosis results from failed inflammation resolution, which is mainly mediated by specialized, pro-resolving mediators (SPMs). In corroboration, SPMs demonstrate encouraging therapeutic effects in various preclinical models of inflammatory disorders, including bone pathology. Since numerous data implicate gut dysbiosis in osteoporosis-associated chronic inflammation, restoring balanced microbiota by supplementing probiotics and prebiotics could contribute to the efficient resolution of SCGLI. In the present review, we provide evidence for this hypothesis and argue that efficient SCGLI resolution may serve as a novel approach for treating osteoporosis, complementary to traditional anti-osteoporotic medications.

Advances in periodontal stem cells and the regulating niche: From in vitro to in vivo

Periodontium possesses stem cell populations for its self-maintenance and regeneration, and has been proved to be an optimal stem cell source for tissue engineering. In vitro studies have shown that stem cells can be isolated from periodontal ligament, alveolar bone marrow and gingiva. In recent years, more studies have focused on identification of periodontal stem cells in vivo. Multiple genetic markers, including Gli1, Prx1, Axin2, αSMA, and LepR, were identified with the lineage tracing approaches. Characteristics, functions, and regulatory mechanisms of specific populations expressing one of these markers have been investigated. In vivo studies also revealed that periodontal stem cells can be regulafrted by different niche and mechanisms including intercellular interactions, ECM and multiple secreted factors. In this review, we summarized the current knowledge of in vitro characteristics and in vivo markers of periodontal stem cells, and discussed the specific regulating niche.