The use of live-animal micro-computed tomography to determine the effect of a novel phospholipase A2inhibitor on alveolar bone loss in anin vivomouse model of periodontitis

Porphyromonas gingivalis, a periodontal pathogen, impairs post-infarcted myocardium by inhibiting autophagosome-lysosome fusion

While several previous studies have indicated the link between periodontal disease (PD) and myocardial infarction (MI), the underlying mechanisms remain unclear. Autophagy, a cellular quality control process that is activated in several diseases, including heart failure, can be suppressed by Porphyromonas gingivalis (P.g.). However, it is uncertain whether autophagy impairment by periodontal pathogens stimulates the development of cardiac dysfunction after MI. Thus, this study aimed to investigate the relationship between PD and the development of MI while focusing on the role of autophagy. Neonatal rat cardiomyocytes (NRCMs) and MI model mice were inoculated with wild-type P.g. or gingipain-deficient P.g. to assess the effect of autophagy inhibition by P.g. Wild-type P.g.-inoculated NRCMs had lower cell viability than those inoculated with gingipain-deficient P.g. This study also revealed that gingipains can cleave vesicle-associated membrane protein 8 (VAMP8), a protein involved in lysosomal sensitive factor attachment protein receptors (SNAREs), at the 47th lysine residue, thereby inhibiting autophagy. Wild-type P.g.-inoculated MI model mice were more susceptible to cardiac rupture, with lower survival rates and autophagy activity than gingipain-deficient P.g.-inoculated MI model mice. After inoculating genetically modified MI model mice (VAMP8-K47A) with wild-type P.g., they exhibited significantly increased autophagy activation compared with the MI model mice inoculated with wild-type P.g., which suppressed cardiac rupture and enhanced overall survival rates. These findings suggest that gingipains, which are virulence factors of P.g., impair the infarcted myocardium by cleaving VAMP8 and disrupting autophagy. This study confirms the strong association between PD and MI and provides new insights into the potential role of autophagy in this relationship.

Simulation Study of Radio Frequency Safety and the Optimal Size of a Single-Channel Surface Radio Frequency Coil for Mice at 9.4 T Magnetic Resonance Imaging

The optimized size of a single-channel surface radio frequency (RF) coil for mouse body images in a 9.4 T magnetic resonance imaging (MRI) system was determined via electromagnetic-field analysis of the signal depth according to the size of a single-channel coil. The single-channel surface RF coils used in electromagnetic field simulations were configured to operate in transmission/reception mode at a frequency of 9.4 T–400 MHz. Computational analysis using the finite-difference time-domain method was used to assess the single-channel surface RF coil by comparing single-channel surface RF coils of varying sizes in terms of |B₁|-, |B₁⁺|-, |B₁⁻|- and |E|-field distribution. RF safety for the prevention of burn injuries to small animals was assessed using an analysis of the specific absorption rate. A single-channel surface RF coil with a 20 mm diameter provided optimal B₁-field distribution and RF safety, thus confirming that single-channel surface RF coils with ≥25 mm diameter could not provide typical B₁-field distribution. A single-channel surface RF coil with a 20 mm diameter for mouse body imaging at 9.4 T MRI was recommended to preserve the characteristics of single-channel surface RF coils, and ensured that RF signals were applied correctly to the target point within RF safety guidelines.

Metagenomic Analysis Reveals a Mitigating Role for Lactobacillus paracasei and Bifidobacterium animalis in Experimental Periodontitis

Probiotics have aroused increasing concern as an intervention strategy for periodontitis (PD), but their underlying mechanism of action remains poorly characterized. Regarding the significance of oral microbiota dysbiosis related to PD, we predicted that the preventive activity of probiotics may be influenced by suppressing the bacterial pathogenicity. Herein, we investigated the effects of Lactobacillus paracasei L9 (L9) and Bifidobacterium animalis A6 (A6) on PD using a rat model, and demonstrated a regulatory effect of probiotics on oral flora from a metagenomics perspective. Oral administration of A6 or L9 effectively relieved gingival bleeding, periodontal inflammatory infiltration, and alveolar bone resorption. In addition, A6 or L9 treatment reduced the inflammatory response and increased the expression of anti-inflammatory cytokines, which we expected to ameliorate alveolar bone resorption as mediated by the receptor activator of the nuclear factor-κB ligand/OPG signaling pathway. More importantly, using metagenomic sequencing, we showed that probiotics significantly altered the taxonomic composition of the subgingival microbiome, and reduced the relative proportions of pathogenic bacterial genera such as Streptococcus, Fusobacterium, Veillonella, and Escherichia. Both probiotics significantly inhibited levels of bacterial virulence factors related to adherence, invasion, exoenzyme, and complement protease functions that are strongly correlated with the pathogenesis of PD. Our overall results suggest that A6 and L9 may constitute promising prophylactic agents for PD, and should thus be further explored in the future.

Metagenomic Analysis Reveals a Mitigating Role for Lactobacillus paracasei and Bifidobacterium animalis in Experimental Periodontitis

Probiotics have aroused increasing concern as an intervention strategy for periodontitis (PD), but their underlying mechanism of action remains poorly characterized. Regarding the significance of oral microbiota dysbiosis related to PD, we predicted that the preventive activity of probiotics may be influenced by suppressing the bacterial pathogenicity. Herein, we investigated the effects of Lactobacillus paracasei L9 (L9) and Bifidobacterium animalis A6 (A6) on PD using a rat model, and demonstrated a regulatory effect of probiotics on oral flora from a metagenomics perspective. Oral administration of A6 or L9 effectively relieved gingival bleeding, periodontal inflammatory infiltration, and alveolar bone resorption. In addition, A6 or L9 treatment reduced the inflammatory response and increased the expression of anti-inflammatory cytokines, which we expected to ameliorate alveolar bone resorption as mediated by the receptor activator of the nuclear factor-κB ligand/OPG signaling pathway. More importantly, using metagenomic sequencing, we showed that probiotics significantly altered the taxonomic composition of the subgingival microbiome, and reduced the relative proportions of pathogenic bacterial genera such as Streptococcus, Fusobacterium, Veillonella, and Escherichia. Both probiotics significantly inhibited levels of bacterial virulence factors related to adherence, invasion, exoenzyme, and complement protease functions that are strongly correlated with the pathogenesis of PD. Our overall results suggest that A6 and L9 may constitute promising prophylactic agents for PD, and should thus be further explored in the future.

Metagenomic Analysis Reveals a Mitigating Role for Lactobacillus paracasei and Bifidobacterium animalis in Experimental Periodontitis

Probiotics have aroused increasing concern as an intervention strategy for periodontitis (PD), but their underlying mechanism of action remains poorly characterized. Regarding the significance of oral microbiota dysbiosis related to PD, we predicted that the preventive activity of probiotics may be influenced by suppressing the bacterial pathogenicity. Herein, we investigated the effects of Lactobacillus paracasei L9 (L9) and Bifidobacterium animalis A6 (A6) on PD using a rat model, and demonstrated a regulatory effect of probiotics on oral flora from a metagenomics perspective. Oral administration of A6 or L9 effectively relieved gingival bleeding, periodontal inflammatory infiltration, and alveolar bone resorption. In addition, A6 or L9 treatment reduced the inflammatory response and increased the expression of anti-inflammatory cytokines, which we expected to ameliorate alveolar bone resorption as mediated by the receptor activator of the nuclear factor-κB ligand/OPG signaling pathway. More importantly, using metagenomic sequencing, we showed that probiotics significantly altered the taxonomic composition of the subgingival microbiome, and reduced the relative proportions of pathogenic bacterial genera such as Streptococcus, Fusobacterium, Veillonella, and Escherichia. Both probiotics significantly inhibited levels of bacterial virulence factors related to adherence, invasion, exoenzyme, and complement protease functions that are strongly correlated with the pathogenesis of PD. Our overall results suggest that A6 and L9 may constitute promising prophylactic agents for PD, and should thus be further explored in the future.

Development and characterization of an oral microbiome transplant among Australians for the treatment of dental caries and periodontal disease: A study protocol

BACKGROUND

Oral microbiome transplantation (OMT) is a novel concept of introducing health-associated oral microbiota into the oral cavity of a diseased patient. The premise is to reverse the state of oral dysbiosis, and restore the ecological balance to maintain a stable homeostasis with the host immune system. This study will assess the effectiveness, feasibility, and safety of OMT using an interdisciplinary approach.

METHODS/DESIGN

To find donors suitable for microbial transplantation, supragingival plaque samples will be collected from 600 healthy participants. Each sample (200μL) will subsequently be examined in two ways: 1) 100μL of the sample will undergo high-throughput 16S rRNA gene amplicon sequencing and shotgun sequencing to identify the composition and characterisation of a healthy supragingival microbiome, 2) the remaining 100μL of the plaque sample will be mixed with 25% artificial saliva medium and inoculated into a specialised in-vitro flow cell model containing a hydroxyapatite disk. To obtain sufficient donor plaque, the samples would be grown for 14 days and further analysed microscopically and sequenced to examine and confirm the growth and survival of the microbiota. Samples with the healthiest microbiota would then be incorporated in a hydrogel delivery vehicle to enable transplantation of the donor oral microbiota. The third step would be to test the effectiveness of OMT in caries and periodontitis animal models for efficacy and safety for the treatment of oral diseases.

DISCUSSION

If OMTs are found to be successful, it can form a new treatment method for common oral diseases such as dental caries and periodontitis. OMTs may have the potential to modulate the oral microbiota and shift the ecological imbalances to a healthier state.

Guidelines for Micro-Computed Tomography Analysis of Rodent Dentoalveolar Tissues

Micro–computed tomography (μCT) has become essential for analysis of mineralized as well as nonmineralized tissues and is therefore widely applicable in the life sciences. However, lack of standardized approaches and protocols for scanning, analyzing, and reporting data often makes it difficult to understand exactly how analyses were performed, how to interpret results, and if findings can be broadly compared with other models and studies. This problem is compounded in analysis of the dentoalveolar complex by the presence of four distinct mineralized tissues: enamel, dentin, cementum, and alveolar bone. Furthermore, these hard tissues interface with adjacent soft tissues, the dental pulp and periodontal ligament (PDL), making for a complex organ. Drawing on others' and our own experience analyzing rodent dentoalveolar tissues by μCT, we introduce techniques to successfully analyze dentoalveolar tissues with similar or disparate compositions, densities, and morphological characteristics. Our goal is to provide practical guidelines for μCT analysis of rodent dentoalveolar tissues, including approaches to optimize scan parameters (filters, voltage, voxel size, and integration time), reproducibly orient samples, define regions and volumes of interest, segment and subdivide tissues, interpret findings, and report methods and results. We include illustrative examples of analyses performed on genetically engineered mouse models with phenotypes in enamel, dentin, cementum, and alveolar bone. The recommendations are designed to increase transparency and reproducibility, promote best practices, and provide a basic framework to apply μCT analysis to the dentoalveolar complex that can also be extrapolated to a variety of other tissues of the body. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Hypericin-glucamine antimicrobial photodynamic therapy in the progression of experimentally induced periodontal disease in rats

OBJECTIVE

To evaluate the effect of antimicrobial photodynamic therapy (aPDT) using the photosensitizer hypericin-glucamine in the progression of experimentally induced periodontal disease (PD) in rats.

MATERIAL AND METHODS

Subgingival ligatures were inserted around the upper second molars of 30 rats. After 7 days (Baseline), the animals were randomly distributed into 3 experimental (n = 5) groups: Hypericin-glucamine; LED (amber LED, 700 mA, 590 nm, 90 mW, 34.10 J/cm²); and aPDT (Hypericin-glucamine + LED). The treated hemimaxillae were randomly chosen. The periodontal disease progression was monitored without treatment interference in the opposite hemimaxillaes, which were used as the negative control of each animal. The euthanasia was programmed according to each experimental period, 7 or 15 days after the Baseline. Microtomographic, histometric and Tartrate Resistant Acid Phosphatase (TRAP) immunohistochemistry analyses were carried out.

RESULTS

Computerized microtomography analyses indicated that the aPDT group had a significantly higher percentage of bone tissue when compared to the other 7 days experimental groups. This result was corroborated by the histometric evaluations of the furcal area. The LED-treated group presented the highest percentages of bone volume for the 15 days experimental groups, which is remarkably higher than the groups treated with Hy-g and aPDT. The histometric analyses demonstrated the control groups had greater bone loss in the proximal regions when compared to the treated groups. The aPDT led to a lower osteoclast activity at both 7 and 15 days. Thus, we can conclude that aPDT exhibits positive effects in PD treatment by promoting favorable conditions for periodontal repair.

Potential of iPSC-Derived Mesenchymal Stromal Cells for Treating Periodontal Disease

Mesenchymal stromal cell-like populations have been derived from mouse-induced pluripotent stem cells (miPSC-MSC) with the capability for tissue regeneration. In this study, murine iPSC underwent differentiation towards an MSC-like immunophenotype. Stable miPSC-MSC cultures expressed the MSC-associated markers, CD73, CD105, and Sca-1, but lacked expression of the pluripotency marker, SSEA1, and hematopoietic markers, CD34 and CD45. Functionally, miPSC-MSC exhibited the potential for trilineage differentiation into osteoblasts, adipocytes, and chondrocytes and the capacity to suppress the proliferation of mitogen-activated splenocytes. The efficacy of miPSC-MSC was assessed in an acute inflammation model following systemic or local delivery into mice with subcutaneous implants containing heat-inactivated P. gingivalis. Histological analysis revealed less inflammatory cellular infiltrate within the sponges in mice treated with miPSC-MSC cells delivered locally rather than systemically. Assessment of proinflammatory cytokines in mouse spleens found that CXCL1 transcripts and protein were reduced in mice treated with miPSC-MSC. In a periodontitis model, mice subjected to oral inoculation with P. gingivalis revealed less bone tissue destruction and inflammation within the jaws when treated with miPSC-MSC compared to PBS alone. Our results demonstrated that miPSC-MSC derived from iPSC have the capacity to control acute and chronic inflammatory responses associated with the destruction of periodontal tissue. Therefore, miPSC-MSC present a promising novel source of stromal cells which could be used in the treatment of periodontal disease and other inflammatory systemic diseases such as rheumatoid arthritis.

Evidence that osteocyte perilacunar remodelling contributes to polyethylene wear particle induced osteolysis

Periprosthetic osteolysis (PO) leading to aseptic loosening, is the most common cause of failure of total hip replacement (THR) in the mid- to long-term. Polyethylene (PE) particulates from the wear of prosthesis liners are bioactive and are implicated in the initiation and or progression of osteolysis. Evidence exists that cells of the osteoblast/osteocyte lineage are affected by PE particles and contribute to the catabolic response by promoting osteoclastic bone resorption. In this study, we hypothesised that osteocytes contribute directly to PO by removing bone from their perilacunar matrix. Osteocyte responses to ultra-high molecular weight PE (UHMWPE) particles were examined in vitro in human primary osteocyte-like cultures, in vivo in the mouse calvarial osteolysis model, and in the acetabulum of patients undergoing revision total hip replacement (THR) surgery for PO. Osteocytes exposed to UHMWPE particles showed upregulated expression of catabolic markers, MMP-13, carbonic anhydrase 2 (CA2), cathepsin K (CTSK) and tartrate resistant acid phosphatase (TRAP), with no effect on cell viability, as assessed by Caspase 3 activity. Consistent with this catabolic activity causing perilacunar bone loss, histological analysis of calvarial sections from mice exposed to UHMWPE revealed a significant (p<0.001) increase in osteocyte lacunar area (Lac.Ar) compared to sham-operated animals. Furthermore, acetabular biopsies from patients with PO also showed significantly (p<0.001) increased osteocyte lacunar size in trabecular bone adjacent to PE particles, compared with osteocyte lacunar size in bone from primary THR patients. Together, these findings suggest a previously unrecognised action of UHMWPE wear particles on osteocytes, which directly results in a loss of osteocyte perilacunar bone. This action may exacerbate the indirect pro-osteoclastic action of UHMWPE-affected osteocytes, previously shown to contribute to aseptic loosening of orthopaedic implants.

STATEMENT OF SIGNIFICANCE

This study addresses the clinical problem of periprosthetic osteolysis, bone loss in response to polyethylene wear particles derived from materials used in orthopaedic implants. Periprosthetic osteolysis has been thought to be due largely to wear particles stimulating the activity of bone resorbing osteoclasts. However, in this study we demonstrate for the first time that polyethylene particles stimulate another type of bone loss, mediated by the direct activity of bone mineral embedded osteocytes, termed osteocytic osteolysis or osteocyte perilacunar remodelling. This study provides new mechanistic insight into wear-particle mediated bone loss and represents a new paradigm for the way in which bone cells, namely osteocytes, the key controlling cell type in bone, react to biomaterials.

Ethical guidelines, animal profile, various animal models used in periodontal research with alternatives and future perspectives

Laboratory animal models serve as a facilitator to investigate the etiopathogenesis of periodontal disease, are used to know the efficacy of reconstructive and regenerative procedures, and are also helpful in evaluation of newer therapeutic techniques including laser and implant therapies prior to application in the human beings. The aim of this review is to know the different animal models used in various specialties of dental research and to know the ethical guidelines prior to the usage of experimental models with main emphasis on how to refine, replace, and reduce the number of animal models usage in the laboratory. An online search for experimental animal models used in dental research was performed using MEDLINE/PubMed database. Publications from 2009 to May 2013 in the specialty of periodontics were included in writing this review. A total of 652 references were published in PubMed/MEDLINE databases based on the search terms used. Out of 245 studies, 241 were related to the periodontal research published in English from 2009 to 2013. Relevant papers were chosen according to the inclusion and exclusion criteria. After extensive electronic and hand search on animal models, it has been observed that various animal models were used in dental research. Search on animal models used for dental research purpose revealed that various animals such as rats, mice, guinea pigs, rabbit, beagle dogs, goats, and nonhuman primates were extensively used. However, with the new advancement of ex vivo animal models, it has become easy to investigate disease pathogenesis and to test the efficacy of newer therapeutic modalities with the reduced usage of animal models. This review summarized the large amount of literature on animal models used in periodontal research with main emphasis on ethical guidelines and on reducing the animal model usage in future perspective.

Long-term evaluation of oral gavage with periodontopathogens or ligature induction of experimental periodontal disease in mice

OBJECTIVE

To evaluate in long-term periods the destruction of periodontal tissues and bacterial colonization induced by oral gavage with periodontopathogens or ligature experimental periodontal disease models.

MATERIAL AND METHODS

Forty-eight C57BL/6 J mice were divided into four groups: group C: negative control; group L: ligature; group G-Pg: oral gavage with Porphyromonas gingivalis; and group G-PgFn: oral gavage with Porphyromonas gingivalis associated with Fusobacterium nucleatum. Mice were infected by oral gavage five times in 2-day intervals. After 45 and 60 days, animals were sacrificed and the immune-inflammatory response in the periodontal tissue was assessed by stereometric analysis. The alveolar bone loss was evaluated by live microcomputed tomography and histometric analysis. qPCR was used to confirm the bacterial colonization in all the groups. Data were analyzed using the Kruskal-Wallis, Wilcoxon, and ANOVA tests, at 5 % of significance level.

RESULTS

Ligature model induced inflammation and bone resorption characterized by increased number of inflammatory cells and decreased number of fibroblasts, followed by advanced alveolar bone loss at 45 and 60 days (p < 0.05). Bacterial colonization in groups G-Pg and G-PgFn was confirmed by qPCR but inflammation and bone resorption were not observed (p < 0.05).

CONCLUSIONS

The ligature model but not the oral gavage models were effective to induce inflammation and bone loss in long-term periods. Pg colonization was observed in all models of experimental periodontal disease induction, independent of tissue alterations. These mice models of periodontitis validates, compliments, and enhances published PD models that utilize ligature or oral gavage and supports the importance of a successful colonization of a susceptible host, a bacterial invasion into vulnerable tissue, and host-bacterial interactions that lead to tissue destruction.

CLINICAL RELEVANCE

The ligature model was an effective approach to induce inflammation and bone loss similar to human periodontitis, but the oral gavage models were not efficient in inducing periodontal inflammation and tissue destruction in the conditions studied. Ligature models can provide a basis for future interventional studies that contribute to the understanding of the disease pathogenesis and the complex host response to microbial challenge.

Caffeic acid phenethyl ester abrogates bone resorption in a murine calvarial model of polyethylene particle-induced osteolysis

Particle-induced bone loss by osteoclasts is a common cause of aseptic loosening around implants. This study investigates whether caffeic acid phenethyl ester (CAPE), a potent and specific inhibitor of nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1 and nuclear factor kappa B, at a low dose reduces bone resorption in a murine calvarial model of polyethylene (PE) particle-induced osteolysis. The effects of particles and CAPE treatment on gastrointestinal tract (GIT) histopathology were also evaluated. Mice were scanned using in vivo animal micro-computed tomography (μCT) as a baseline measurement. PE particles (2.82 × 10(9) particles/mL) were implanted over the calvariae on day 0. CAPE was administered subcutaneously (1 mg/kg/day) at days 0, 4, 7 and 10. Mice were killed at day 14 and serum was analysed for Type-1 carboxyterminal collagen crosslinks (CTX)-1 and osteoclast-associated receptor (OSCAR) levels. Ex vivo μCT scans were conducted to assess bone volume (BV) change and percentage area of calvarial surface resorbed. Calvarial and GIT tissue was processed for histopathology. By day 14, PE particles significantly induced calvarial bone loss compared with control animals as evidenced by resorption areas adjacent to the implanted PE in three-dimensional μCT images, an increase in percentage of resorbed area (p = 0.0022), reduction in BV (p = 0.0012) and increased Tartrate-resistant acid phosphatase positive cells. Serum CTX-1 (p = 0.0495) and OSCAR levels (p = 0.0006) significantly increased in the PE implant group. CAPE significantly inhibited PE particle-induced calvarial osteolysis, as evidenced by a significant reduction in surface bone resorption (p = 0.0012) and volumetric change (p = 0.0154) compared with PE only, but had no effect on systemic CTX-1. Neither particles nor CAPE had an effect on GIT histopathology.

Parthenolide reduces empty lacunae and osteoclastic bone surface resorption induced by polyethylene particles in a murine calvarial model of peri-implant osteolysis

The study aimed to determine the effects of parthenolide (PAR) on bone volume (BV) and bone surface resorption as assessed by live-animal microcomputed tomography (μCT) and possible osteocyte death as indicated by empty lacunae histologically in polyethylene (PE) particle-induced calvarial osteolysis in mice. Baseline μCT scans were conducted 7 days preimplantation of 2 × 10(8) PE particles/mL over the calvariae (day 0). PAR at 1 mg/kg/day was subcutaneously injected on days 0, 4, 7, and 10. At day 14, BV and surface resorption was analyzed with μCT. Calvarial tissue was processed for histomorphometric osteocyte evaluation. Serum was analyzed for type-1 carboxy-terminal collagen crosslinks (CTX-1) and osteoclast associated receptor (OSCAR) levels by ELISA. PE significantly decreased BV (p = 0.0368), increased surface bone resorption area (p = 0.0022), and increased the percentage of empty lacunae (p = 0.0043). Interestingly, PAR significantly reduced the resorption surface area (p = 0.0022) and the percentage of empty osteocyte lacunae (p = 0.0087) in the PE-calvariae, but it did not affect BV, serum CTX-1 or OSCAR levels. The ability of PAR to inhibit PE-induced surface bone erosion may better reflect the in vivo situation, where bone resorption occurs on the surface at the bone-implant interface and may also be related to the role of osteocytes in this pathology.

Porphyromonas gingivalis peptidylarginine deiminase, a key contributor in the pathogenesis of experimental periodontal disease and experimental arthritis

OBJECTIVES

To investigate the suggested role of Porphyromonas gingivalis peptidylarginine deiminase (PAD) in the relationship between the aetiology of periodontal disease and experimentally induced arthritis and the possible association between these two conditions.

METHODS

A genetically modified PAD-deficient strain of P. gingivalis W50 was produced. The effect of this strain, compared to the wild type, in an established murine model for experimental periodontitis and experimental arthritis was assessed. Experimental periodontitis was induced following oral inoculation with the PAD-deficient and wild type strains of P. gingivalis. Experimental arthritis was induced via the collagen antibody induction process and was monitored by assessment of paw swelling and micro-CT analysis of the radio-carpal joints. Experimental periodontitis was monitored by micro CT scans of the mandible and histological assessment of the periodontal tissues around the mandibular molars. Serum levels of anti-citrullinated protein antibodies (ACPA) and P. gingivalis were assessed by ELISA.

RESULTS

The development of experimental periodontitis was significantly reduced in the presence of the PAD-deficient P. gingivalis strain. When experimental arthritis was induced in the presence of the PAD-deficient strain there was less paw swelling, less erosive bone damage to the joints and reduced serum ACPA levels when compared to the wild type P. gingivalis inoculated group.

CONCLUSION

This study has demonstrated that a PAD-deficient strain of P. gingivalis was associated with significantly reduced periodontal inflammation. In addition the extent of experimental arthritis was significantly reduced in animals exposed to prior induction of periodontal disease through oral inoculation of the PAD-deficient strain versus the wild type. This adds further evidence to the potential role for P. gingivalis and its PAD in the pathogenesis of periodontitis and exacerbation of arthritis. Further studies are now needed to elucidate the mechanisms which drive these processes.

Glucocorticoids reduce alveolar and trabecular bone in mice

Glucocorticoid (GC) treatment is the main cause of secondary osteoporosis. There are some controversies about the relationships between alveolar bone loss and bone loss at the appendicular and axial skeleton.

OBJECTIVE

To assess, in parallel, the effects of GCs on alveolar bone and on the tibia in a mice model.

METHODS

Five-month-old male Swiss-Webster mice were randomized into two groups. Pellets releasing 5 mg/kg/day of prednisolone or control pellets were subcutaneously implanted for 28 days. After euthanasia, the right tibia and the right hemimandible of each mouse were analyzed by histomorphometry and microcomputed tomography. Alveolar bone consists of a thin slab between the incisor and the molar roots connected with the alveolar processes. A 2D-frontal section was done through the pulp chamber of the first molar and was used to measure the thickness of the alveolar bone slab. A 2D-sagittal section was done through the pulp chamber of the three molars and was used to measure bone volume in the alveolar processes.

RESULTS

At day 28, thickness and bone volume of alveolar bone were significantly decreased in the GC group (P<0.05). At the tibia, GCs decreased bone formation with a reduced mineral apposition rate and bone formation rate and a significant decrease in BV/TV and Tb.Th (P<0.05).

CONCLUSION

Although the amount of alveolar bone is very low in the mouse, this study shows that GCs can induce an alveolar bone loss in long-term treated animals.

Histone deacetylase inhibitors as suppressors of bone destruction in inflammatory diseases

OBJECTIVES

Despite progress in developing many new anti-inflammatory treatments in the last decade, there has been little progress in finding treatments for bone loss associated with inflammatory diseases, such as rheumatoid arthritis and periodontitis. For instance, treatment of rheumatic diseases with anti-tumour necrosis factor-alpha agents has been largely successful in reducing inflammation, but there have been varying reports regarding its effectiveness at inhibiting bone loss. In addition, there is often a delay in finding the appropriate anti-inflammatory therapy for individual patients, and some therapies, such as disease modifying drugs, take time to have an effect. In order to protect the bone, adjunct therapies targeting bone resorption are being developed. This review focuses on new treatments based on using histone deacetylase inhibitors (HDACi) to suppress bone loss in these chronic inflammatory diseases.

KEY FINDINGS

A number of selected HDACi have been shown to suppress bone resorption by osteoclasts in vitro and in animal models of chronic inflammatory diseases. Recent reports indicate that these small molecules, which can be administered orally, could protect the bone and might be used in combination with current anti-inflammatory treatments.

SUMMARY

HDACi do have potential to suppress bone destruction in chronic inflammatory diseases including periodontitis and rheumatoid arthritis.

Histone deacetylase inhibitors and periodontal bone loss

BACKGROUND AND OBJECTIVE

Bone loss caused by enhanced osteoclast activity is a significant feature of periodontitis. Histone deacetylase inhibitors (HDACi) can suppress osteoclast-mediated bone loss in vitro and in vivo. This study investigated whether HDACi can suppress bone loss in experimental periodontitis.

MATERIAL AND METHODS

Experimental periodontitis was induced in mice by oral inoculation with Porphyromonas gingivalis bacteria. Mice were treated orally with olive oil alone, with olive oil and a novel compound - 1179.4b - which targets both Class I and Class II histone deacetylases (HDACs) or with olive oil and MS-275, which targets Class I HDACs. Micro-computed tomography scans of live mice, stereo imaging and histological analyses were used to detect changes in bone.

RESULTS

In the absence of treatment there was a 13.2% increase in bone volume in controls compared with a 7.4% decrease in P. gingivalis-inoculated mice. 1179.4b significantly reduced bone loss, with a 3.4% increase in bone volume (p < 0.01). MS-275 did not have a significant effect on P. gingivalis-induced bone loss. Histological analysis revealed that 1179.4b reduced bone loss despite having no effect on inflammation.

CONCLUSION

HDACi were found to effectively suppress bone loss in the mouse model of periodontitis. 1179.4b - the inhibitor of Class I and Class II HDACs - was more effective at suppressing bone loss than MS-275, which targets Class I HDACs only. These compounds may therefore have the potential to be used for the management of periodontitis.