The therapeutic role of bone marrow stem cell local injection in rat experimental periodontitis

TGF-β1 promotes osteogenesis of mesenchymal stem cells via integrin mediated mechanical positive autoregulation

Positive autoregulation (PAR), one type of network motifs, provides a high phenotypic heterogeneity for cells to better adapt to their microenvironments. Typical mechanosensitive proteins can also form PAR, e.g., integrin mediated PAR, but the role of such mechanical PAR in physiological development and pathological process remains elusive. In this study, we found that transforming growth factor β1 (TGF-β1) and integrin levels decrease with tissue softening after the development of paradentium in vivo in rat model of periodontitis (an inflammatory disease with bone defect). Interestingly, TGF-β1 could induce the formation of mechanical PAR involving the integrin-FAK-YAP axis in mesenchymal stem cells (MSCs) by both in vitro experiments and in silico computational model. The computational model predicted a mechanical PAR involving the bimodal distribution of focus adhesions, which enables cells to accurately perceive extracellular mechanical cues. Thus, our analysis of TGF-β1 mediated mechanosensing mechanism on MSCs may help to better understand the molecular process underlying bone regeneration.

Mesenchymal stem cells and their extracellular vesicles in bone and joint diseases: targeting the NLRP3 inflammasome

The nucleotide-binding oligomerization domain-like-receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a cytosolic multi-subunit protein complex, and recent studies have demonstrated the vital role of the NLRP3 inflammasome in the pathological and physiological conditions, which cleaves gasdermin D to induce inflammatory cell death called pyroptosis and mediates the release of interleukin-1 beta and interleukin-18 in response to microbial infection or cellular injury. Over-activation of the NLRP3 inflammasome is associated with the pathogenesis of many disorders affecting bone and joints, including gouty arthritis, osteoarthritis, rheumatoid arthritis, osteoporosis, and periodontitis. Moreover, mesenchymal stem cells (MSCs) have been discovered to facilitate the inhibition of NLRP3 and maybe ideal for treating bone and joint diseases. In this review, we implicate the structure and activation of the NLRP3 inflammasome along with the detail on the involvement of NLRP3 inflammasome in bone and joint diseases pathology. In addition, we focused on MSCs and MSC-extracellular vesicles targeting NLRP3 inflammasomes in bone and joint diseases. Finally, the existing problems and future direction are also discussed.

Local application of gingiva-derived mesenchymal stem cells on experimental periodontitis in rats

BACKGROUND

Stem cell-based approaches in regenerative periodontal therapy have been used in different experimental models. In this study, the effect of local application of gingival mesenchymal stem cells (GMSC) in fibroin/chitosan oligosaccharide lactate hydrogel (F/COS) on periodontal regeneration was evaluated using experimental periodontitis model in rats.

METHODS

Mesenchymal stem cells were isolated from the gingiva of rats and characterized. Viability tests and confocal imaging of GMSC in hydrogels were performed. Healthy control without periodontitis (Health; H; n=10), control with periodontitis but no application (Periodontitis; P; n=10), only hydrogel application (F/COS; n=10), and GMSC+F/COS (n=10) four groups were formed for in vivo studies. Experimental periodontitis was created with silk sutures around the maxillary second molars. GMSC labeled with green fluorescent protein (GFP) (250,000 cells/50 μL) in F/COS were applied to the defect. Animals were sacrificed at 2nd and 8th weeks and maxillae of the animals were evaluated by micro-computed tomography (micro-CT) and histologically. The presence of GFP-labeled GMSC was confirmed at the end of 8 weeks.

RESULTS

Micro-CT analysis showed statistically significant new bone formation in the F/COS+GMSC treated group compared with the P group at the end of 8 weeks (p < 0.05). New bone formation was also observed in the F/COS group, but the statistical analysis revealed that this difference was not significant when compared with the P group (p > 0.05). Long junctional epithelium formation was less in the F/COS+GMSC group compared with the P group. Periodontal ligament and connective tissue were well-organized in F/COS+GMSC group.

CONCLUSION

The results showed that local GMSC application in hydrogel contributed to the formation of new periodontal ligament and alveolar bone in rats with experimental periodontitis. Since gingiva is easly accessible tissue, it is promising for autologous cell-based treatments in clinical applications.

The Genetic Aspects of Periodontitis Pathogenesis and the Regenerative Properties of Stem Cells

Periodontitis (PD) is a prevalent and chronic inflammatory disease with a complex pathogenesis, and it is associated with the presence of specific pathogens, such as Porphyromonas gingivalis. Dysbiosis and dysregulated immune responses ultimately lead to chronic inflammation as well as tooth and alveolar bone loss. Multiple studies have demonstrated that genetic polymorphisms may increase the susceptibility to PD. Furthermore, gene expression is modulated by various epigenetic mechanisms, such as DNA methylation, histone modifications, or the activity of non-coding RNA. These processes can also be induced by PD-associated pathogens. In this review, we try to summarize the genetic processes that are implicated in the pathogenesis of PD. Furthermore, we discuss the use of these mechanisms in diagnosis and therapeutic purposes. Importantly, novel treatment methods that could promote tissue regeneration are greatly needed in PD. In this paper, we also demonstrate current evidence on the potential use of stem cells and extracellular vesicles to stimulate tissue regeneration and suppress inflammation. The understanding of the molecular mechanisms involved in the pathogenesis of PD, as well as the impact of PD-associated bacteria and stem cells in these processes, may enhance future research and ultimately improve long-term treatment outcomes.

New insights into nanotherapeutics for periodontitis: a triple concerto of antimicrobial activity, immunomodulation and periodontium regeneration

Periodontitis is a chronic inflammatory disease caused by the local microbiome and the host immune response, resulting in periodontal structure damage and even tooth loss. Scaling and root planning combined with antibiotics are the conventional means of nonsurgical treatment of periodontitis, but they are insufficient to fully heal periodontitis due to intractable bacterial attachment and drug resistance. Novel and effective therapeutic options in clinical drug therapy remain scarce. Nanotherapeutics achieve stable cell targeting, oral retention and smart release by great flexibility in changing the chemical composition or physical characteristics of nanoparticles. Meanwhile, the protectiveness and high surface area to volume ratio of nanoparticles enable high drug loading, ensuring a remarkable therapeutic efficacy. Currently, the combination of advanced nanoparticles and novel therapeutic strategies is the most active research area in periodontitis treatment. In this review, we first introduce the pathogenesis of periodontitis, and then summarize the state-of-the-art nanotherapeutic strategies based on the triple concerto of antibacterial activity, immunomodulation and periodontium regeneration, particularly focusing on the therapeutic mechanism and ingenious design of nanomedicines. Finally, the challenges and prospects of nano therapy for periodontitis are discussed from the perspective of current treatment problems and future development trends.

An altered oral microbiota induced by injections of superparamagnetic iron oxide nanoparticle-labeled periodontal ligament stem cells helps periodontal bone regeneration in rats

Stem cell injection is good for periodontal regeneration due to the capacity of stem cells to differentiate toward osteogenic direction and to regulate the production of pro- and anti-inflammatory cytokines. However, injected cells are difficult to track in vivo. And there is microbiota in oral cavity, the dysbiosis of which leads to the damage and loss of periodontal tissue. Here, we demonstrated an enhanced periodontal repair was due to an altered oral microbiota. Periodontal defects were surgically prepared in rats, and periodontal ligament stem cells (PDLSCs) labeled by superparamagnetic iron oxide (SPIO) nanoparticles (PC-SPIO) were injected, with PDLSCs and saline treatments as controls. Detected by magnetic resonance imaging (MRI) and histological staining, PC-SPIO was major at limited areas in regenerated periodontal tissues. PC-SPIO-treated rats achieved better periodontal regeneration than the other two groups. Concurrently, the oral microbiota of PC-SPIO-treated rats was changed, presenting SPIO-Lac as a biomarker. SPIO-Lac assisted periodontal repair in vivo, inhibited the inflammation of macrophages induced by lipopolysaccharide (LPS) and antibacterial in vitro. Therefore, our study proved that SPIO-labeled cells can be tracked in periodontal defect and highlighted a potential positive role of an oral microbiota in periodontal regeneration, suggesting the possibility of periodontal repair promotion by manipulating oral microbiota.

Galangin inhibits lipopolysaccharide-induced inflammation and stimulates osteogenic differentiation of bone marrow mesenchymal stem cells via regulation of AKT/mTOR signaling

BACKGROUND

Bone marrow mesenchymal stem cells (BMSCs), with the abilities of multidirectional differentiation and self-renewal, have been widely used in bone repair and regeneration of inflammation-stimulated oral diseases. Galangin is a flavonoid isolated from Alpinia officinarum, exerts anti-obesity, antitumor, and anti-inflammation pharmacological effects. The roles of galangin in lipopolysaccharide-induced inflammation and osteogenic differentiation of BMSCs were investigated.

METHODS

BMSCs were isolated from rat bone marrow and identified by flow cytometry. The isolated BMSCs were treated with 1 μg/mL lipopolysaccharides or cotreated with lipopolysaccharides and different concentrations of galangin. Cell viability and apoptosis were detected by MTT (tetrazolium component) and flow cytometry. ELISA was used to detect inflammation. Alizarin red staining was used to investigate osteogenic differentiation.

RESULTS

The rat BMSCs showed negative rate of CD34, and positive rate of CD29 and CD44. Lipopolysaccharides treatment reduced cell viability of BMSCs, and promoted the cell apoptosis. Incubation with galangin enhanced cell viability of lipopolysaccharide-stimulated BMSCs, and suppressed the cell apoptosis. Galangin decreased levels of TNF-α, IL-1β, and IL-6 in lipopolysaccharide-stimulated BMSCs through down-regulation of NF-κB phosphorylation (p-NF-κB). Galangin up-regulated expression of osteo-specific proteins, collagen type I alpha 1 (COL1A1), osteopontin (OPN), and runt-related transcription factor 2 (RUNX2), to promote the osteogenic differentiation of lipopolysaccharide-stimulated BMSCs. Protein expression of p-AKT and p-mTOR in lipopolysaccharide-stimulated BMSCs were increased by galangin treatment.

CONCLUSION

Galangin exerted an anti-inflammatory effect against lipopolysaccharide- stimulated BMSCs and promoted osteogenic differentiation through the activation of AKT/ mTOR signaling.

Advances in novel therapeutic approaches for periodontal diseases

Periodontal diseases are pathological processes resulting from infections and inflammation affecting the periodontium or the tissue surrounding and supporting the teeth. Pathogenic bacteria living in complex biofilms initiate and perpetuate this disease in susceptible hosts. In some cases, broad-spectrum antibiotic therapy has been a treatment of choice to control bacterial infection. However, increasing antibiotic resistance among periodontal pathogens has become a significant challenge when treating periodontal diseases. Thanks to the improved understanding of the pathogenesis of periodontal disease, which involves the host immune response, and the importance of the human microbiome, the primary goal of periodontal therapy has shifted, in recent years, to the restoration of homeostasis in oral microbiota and its harmonious balance with the host periodontal tissues. This shift in therapeutic goals and the drug resistance challenge call for alternative approaches to antibiotic therapy that indiscriminately eliminate harmful or beneficial bacteria. In this review, we summarize the recent advancement of alternative methods and new compounds that offer promising potential for the treatment and prevention of periodontal disease. Agents that target biofilm formation, bacterial quorum-sensing systems and other virulence factors have been reviewed. New and exciting microbiome approaches, such as oral microbiota replacement therapy and probiotic therapy for periodontal disease, are also discussed.

Immunomodulation in the Treatment of Periodontitis: Progress and Perspectives

Periodontitis is one of the most common dental diseases. Compared with healthy periodontal tissues, the immune microenvironment plays the key role in periodontitis by allowing the invasion of pathogens. It is possible that modulating the immune microenvironment can supplement traditional treatments and may even promote periodontal regeneration by using stem cells, bacteria, etc. New anti-inflammatory therapies can enhance the generation of a viable local immune microenvironment and promote cell homing and tissue formation, thereby achieving higher levels of immune regulation and tissue repair. We screened recent studies to summarize the advances of the immunomodulatory treatments for periodontitis in the aspects of drug therapy, microbial therapy, stem cell therapy, gene therapy and other therapies. In addition, we included the changes of immune cells and cytokines in the immune microenvironment of periodontitis in the section of drug therapy so as to make it clearer how the treatments took effects accordingly. In the future, more research needs to be done to improve immunotherapy methods and understand the risks and long-term efficacy of these methods in periodontitis.

The Gingiva from the Tissue Surrounding the Bone to the Tissue Regenerating the Bone: A Systematic Review of the Osteogenic Capacity of Gingival Mesenchymal Stem Cells in Preclinical Studies

The current review aims to systematically assess the osteogenic capacity of gingiva-derived mesenchymal stem cells (GMSCs) in preclinical studies. A comprehensive electronic search of PubMed, Embase, Web of Science, and Scopus databases, as well as a manual search of relevant references, was performed in June 2020 without date or language restrictions. Eligibility criteria were the following: studies that compared mesenchymal stem cells (MSCs) derived from the gingiva with other MSC sources (in vitro or in vivo) or cell-free scaffold (in vivo) and studies that reported at least one of the following outcomes: osteogenic potential and new bone formation for in vitro and in vivo, respectively. Moreover, the assessment of included studies was conducted using appropriate guidelines. From 646 initial retrieved studies, 35 full-text articles were subjected to further screening and 26 studies were selected (20 in vitro studies and 6 in vivo studies). GMSCs showed great proliferation capacity and expressed recognized mesenchymal stem cell markers, particularly CD90. In vitro, MSC sources including GMSCs were capable of undergoing osteogenic differentiation with less ability in GMSCs, while most in vivo studies confirmed the capacity of GMSCs to regenerate bony defects. Concerning the assessment of methodological quality, in vitro studies met the relevant guideline except in five areas: the sample size calculation, randomization, allocation concealment, implementation, and blinding, and in vivo publications had probably low risk of bias in most domains except in three areas: allocation concealment, attrition, and blinding items.

Advanced technologies in periodontal tissue regeneration based on stem cells: Current status and future perspectives

Periodontitis is a progressive inflammation disease, the clinical management of which remains a challenge. The traditional management may control periodontal inflammation, but failed to regenerate functional periodontium. This review summarizes the most advancing regenerative techniques regarding stem cell culture and scaffold fabrication, such as cell sheeting, spheroid culture, electrospinning and 3D printing. The applications of different techniques manifest tremendous potential of regenerating the complete and functional periodontium. Albeit promising, new technologies have met with their own drawbacks such as insufficient vascularization and precision, which necessitate deeper modification. Thus, this review also points out the potential perspectives and methods aiming at their disadvantages, illuminating the directions of future researches to successful clinical scenarios.

N‑acetyl cysteine inhibits the lipopolysaccharide‑induced inflammatory response in bone marrow mesenchymal stem cells by suppressing the TXNIP/NLRP3/IL‑1β signaling pathway

N-acetyl cysteine (NAC) has been used to inhibit lipopolysaccharide (LPS)-induced inflammation. However, the molecular mechanism underlying its anti-inflammatory effects remains to be elucidated. The present study aimed to determine the effect of NAC on the LPS-induced inflammatory response in bone marrow mesenchymal stem cells (BMSCs) and elucidate the underlying molecular mechanism. First, BMSCs were stimulated by LPS following pretreatment with NAC (0, 0.1, 0.5, 1 or 2 mM). A Cell Counting Kit 8 assay was used to determine the number of viable cells and 1 mM NAC was selected as the experimental concentration. Then, the secretion of inflammatory factors, including interleukin (IL)-1β, IL-6 and tumor necrosis factor-α was evaluated by enzyme-linked immunosorbent assay. Finally, the expression levels of mRNA and proteins, including apoptosis-associated speck-like protein containing a CARD (ASC), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), caspase-1, thioredoxin-interacting protein (TXNIP), and thioredoxin (TRX), were evaluated by reverse transcription-quantitative PCR and western blot analysis, respectively. The results demonstrated that the secretion of inflammatory factors, which was increased by the administration of LPS, was reduced by pretreatment with NAC. Furthermore, NAC reduced the expression of ASC, NLRP3, caspase-1 and TXNIP, but enhanced that of TRX. To conclude, NAC had anti-inflammatory effects on LPS-stimulated BMSCs, which was closely associated with the TXNIP/NLRP3/IL-1β signaling pathway. Thus, NAC may be a promising treatment to attenuate the inflammatory response in LPS-induced BMSCs.

Is maxillary diastema an appropriate site for implantation in rats?

Background

Implantology or implant dentistry is growing fast during last four decades. Facing the growing demand of implant treatment, there are extreme challenges to clinicians and researchers. First is peri-implantitis with remarkable prevalence. Though investigators have revealed that the etiology of the peri-implant infection is similar to periodontitis, clinically there is no effective treatment. Second, implantation in patients with severe systemic conditions, i.e., severe diabetes, lupus, osteoporosis, organ transplant, and cancer with intensive radiotherapy and/or chemotherapy, is another challenge to implant treatment for lack of scientific research data. Animal models are crucial to help investigators reveal the mechanisms underlying these disorders. Murine models are used most commonly. Rats are the better subject in dental implant research, due to mice could not provide clinical compatible and macro-level measurable data for implant osseointegration and peri-implantitis in oral cavity for lacking enough cancellous bone to support an implant more than 1 mm in length.

Objective

Our aim of this research is to find a clinical comparable rat dental implant model.

Methods

Six male Sprague-Dawley rats with body weight more than 500 g were used in the experiment. Each rat received two implants. One implant was placed at maxillary diastema in each side. Seven weeks after the implantation, only one implant successfully osseointegrated without movement and inflammation. Implant success and failure rate is analyzed by using Clopper-Pearson’s exact method at 95% confidence interval.

Results

The present data indicate that the true success rate of implantation in maxillary natural diastema in rat is less than 38.4% at a confident level of 95%. Meanwhile, Micro-CT indicates maxillary first molar position will be a promising site for implantation.

Conclusion

Maxillary nature diastema may not be an appropriate site for implantation research for its low successful rate, but maxillary first molar position could be a candidate for implantation research. Further researches are required to illustrate the details.