Clonal hematopoiesis driven by mutated DNMT3A promotes inflammatory bone loss.

Clonal hematopoiesis of indeterminate potential (CHIP) arises from aging-associated acquired mutations in hematopoietic progenitors, which display clonal expansion and produce phenotypically altered leukocytes. We associated CHIP-DNMT3A mutations with a higher prevalence of periodontitis and gingival inflammation among 4,946 community-dwelling adults. To model DNMT3A-driven CHIP, we used mice with the heterozygous loss-of-function mutation R878H, equivalent to the human hotspot mutation R882H. Partial transplantation with Dnmt3aR878H/+ bone marrow (BM) cells resulted in clonal expansion of mutant cells into both myeloid and lymphoid lineages and an elevated abundance of osteoclast precursors in the BM and osteoclastogenic macrophages in the periphery. DNMT3A-driven clonal hematopoiesis in recipient mice promoted naturally occurring periodontitis and aggravated experimentally induced periodontitis and arthritis, associated with enhanced osteoclastogenesis, IL-17-dependent inflammation and neutrophil responses, and impaired regulatory T cell immunosuppressive activity. DNMT3A-driven clonal hematopoiesis and, subsequently, periodontitis were suppressed by rapamycin treatment. DNMT3A-driven CHIP represents a treatable state of maladaptive hematopoiesis promoting inflammatory bone loss.

A randomized, double-blind pilot study of analgesic and anti-inflammatory effects of naproxen sodium and acetaminophen following dental implant placement surgery.

Introduction: Post-surgical pain following dental implant placement surgery is typically managed with non-opioid analgesics, including non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen. However, the comparative analgesic efficacy of over-the-counter doses of non-steroidal anti-inflammatory drugs and acetaminophen in implant patients is unknown. Therefore, we compared the analgesic and anti-inflammatory effects of naproxen sodium and acetaminophen after surgical placement of one or two dental implants. Methods: Adult patients were treated with naproxen sodium (440 mg loading dose +220 mg q8h, n = 15) or acetaminophen (1,000 mg q6h-max daily dose 3,000 mg, n = 15) for 3 days after implant placement in a randomized, double-blind design. Pain was assessed on a 0-10 scale every 20 min for 6 h after study medication treatment. Tramadol (50 mg) was available as a rescue medication. Plasma and gingival crevicular fluid (GCF) were collected prior to the surgery and 0, 1, 2, 4, 6, 24, and 72 h after surgery for quantification of interleukin (IL)-6, IL-8, and IL-1ß levels. Results: Pain scores were significantly lower in patients treated with naproxen sodium compared to those treated with acetaminophen. Inflammatory mediator levels in plasma and gingival crevicular fluid increased after surgery and returned to near baseline levels by 72 h. Plasma IL-6 levels were significantly lower 6 h after surgery in patients treated with naproxen sodium compared to acetaminophen. No differences in inflammatory mediator concentrations in gingival crevicular fluid were observed between the treatment groups. The number of implants placed and body mass index (BMI) influenced inflammatory mediator concentrations in plasma and gingival crevicular fluid, respectively. Discussion: Naproxen sodium was more effective than acetaminophen in reducing post-operative pain and systemic inflammation following surgical placement of one or two dental implants. Further studies are needed to determine whether these findings are applicable to more complex implant cases and how they affect clinical outcomes following implant placement. Clinical Trial Registration: ClinicalTrials.gov, identifier NCT04694300.

Distinct fibroblast progenitor subpopulation expedites regenerative mucosal healing by immunomodulation.

Injuries that heal by fibrosis can compromise organ function and increase patient morbidity. The oral mucosal barrier has a high regenerative capacity with minimal scarring, but the cellular mechanisms remain elusive. Here, we identify distinct postnatal paired-related homeobox-1+ (Prx1+) cells as a critical fibroblast subpopulation that expedites mucosal healing by facilitating early immune response. Using transplantation and genetic ablation model in mice, we show that oral mucosa enriched with Prx1+ cells heals faster than those that lack Prx1+ cells. Lineage tracing and scRNA-seq reveal that Prx1+ fibroblasts exhibit progenitor signatures in physiologic and injured conditions. Mechanistically, Prx1+ progenitors accelerate wound healing by differentiating into immunomodulatory SCA1+ fibroblasts, which prime macrophage recruitment through CCL2 as a key part of pro-wound healing response. Furthermore, human Prx1+ fibroblasts share similar gene and spatial profiles compared to their murine counterpart. Thus, our data suggest that Prx1+ fibroblasts may provide a valuable source in regenerative procedures for the treatment of corneal wounds and enteropathic fibrosis.

Stromal cell-derived DEL-1 inhibits Tfh cell activation and inflammatory arthritis.

The secreted protein developmental endothelial locus 1 (DEL-1) regulates inflammatory cell recruitment and protects against inflammatory pathologies in animal models. Here, we investigated DEL-1 in inflammatory arthritis using collagen-induced arthritis (CIA) and collagen Ab-induced arthritis (CAIA) models. In both models, mice with endothelium-specific overexpression of DEL-1 were protected from arthritis relative to WT controls, whereas arthritis was exacerbated in DEL-1-deficient mice. Compared with WT controls, mice with collagen VI promoter-driven overexpression of DEL-1 in mesenchymal cells were protected against CIA but not CAIA, suggesting a role for DEL-1 in the induction of the arthritogenic Ab response. Indeed, DEL-1 was expressed in perivascular stromal cells of the lymph nodes and inhibited Tfh and germinal center B cell responses. Mechanistically, DEL-1 inhibited DC-dependent induction of Tfh cells by targeting the LFA-1 integrin on T cells. Overall, DEL-1 restrained arthritis through a dual mechanism, one acting locally in the joints and associated with the anti-recruitment function of endothelial cell-derived DEL-1; the other mechanism acting systemically in the lymph nodes and associated with the ability of stromal cell-derived DEL-1 to restrain Tfh responses. DEL-1 may therefore be a promising therapeutic for the treatment of inflammatory arthritis.

DEL-1 promotes macrophage efferocytosis and clearance of inflammation.

Resolution of inflammation is essential for tissue homeostasis and represents a promising approach to inflammatory disorders. Here we found that developmental endothelial locus-1 (DEL-1), a secreted protein that inhibits leukocyte-endothelial adhesion and inflammation initiation, also functions as a non-redundant downstream effector in inflammation clearance. In human and mouse periodontitis, waning of inflammation was correlated with DEL-1 upregulation, whereas resolution of experimental periodontitis failed in DEL-1 deficiency. This concept was mechanistically substantiated in acute monosodium-urate-crystal-induced inflammation, where the pro-resolution function of DEL-1 was attributed to effective apoptotic neutrophil clearance (efferocytosis). DEL-1-mediated efferocytosis induced liver X receptor-dependent macrophage reprogramming to a pro-resolving phenotype and was required for optimal production of at least certain specific pro-resolving mediators. Experiments in transgenic mice with cell-specific overexpression of DEL-1 linked its anti-leukocyte-recruitment action to endothelial cell-derived DEL-1 and its efferocytic/pro-resolving action to macrophage-derived DEL-1. Thus, the compartmentalized expression of DEL-1 facilitates distinct homeostatic functions in an appropriate context that can be harnessed therapeutically.

Revisiting the Page & Schroeder model: the good, the bad and the unknowns in the periodontal host response 40 years later.

In their classic 1976 paper, Page & Schroeder described the histopathologic events and the types of myeloid cells and lymphocytes involved in the initiation and progression of inflammatory periodontal disease. The staging of periodontal disease pathogenesis as 'initial', 'early', 'established' and 'advanced' lesions productively guided subsequent research in the field and remains fundamentally valid. However, major advances regarding the cellular and molecular mechanisms underlying the induction, regulation and effector functions of immune and inflammatory responses necessitate a reassessment of their work and its integration with emerging new concepts. We now know that each type of leukocyte is actually represented by functionally distinct subsets with different, or even conflicting, roles in immunity and inflammation. Unexpectedly, neutrophils, traditionally regarded as merely antimicrobial effectors in acute conditions and protagonists of the 'initial' lesion, are currently appreciated for their functional versatility and critical roles in chronic inflammation. Moreover, an entirely new field of study, osteoimmunology, has emerged and sheds light on the impact of immunoinflammatory events on the skeletal system. These developments and the molecular dissection of crosstalk interactions between innate and adaptive leukocytes, as well as between the immune system and local homeostatic mechanisms, offer a more nuanced understanding of the host response in periodontitis, with profound implications for treatment. At the same time, deeper insights have generated new questions, many of which remain unanswered. In this review, 40 years after Page & Schroeder proposed their model, we summarize enduring and emerging advances in periodontal disease pathogenesis.

The B Cell-Stimulatory Cytokines BLyS and APRIL Are Elevated in Human Periodontitis and Are Required for B Cell-Dependent Bone Loss in Experimental Murine Periodontitis.

B-lineage cells (B lymphocytes and plasma cells) predominate in the inflammatory infiltrate of human chronic periodontitis. However, their role in disease pathogenesis and the factors responsible for their persistence in chronic lesions are poorly understood. In this regard, two cytokines of the TNF ligand superfamily, a proliferation-inducing ligand (APRIL) and B-lymphocyte stimulator (BLyS), are important for the survival, proliferation, and maturation of B cells. Thus, we hypothesized that APRIL and/or BLyS are upregulated in periodontitis and contribute to induction of periodontal bone loss. This hypothesis was addressed in both human and mouse experimental systems. We show that, relative to healthy controls, the expression of APRIL and BLyS mRNA and protein was upregulated in natural and experimental periodontitis in humans and mice, respectively. The elevated expression of these cytokines correlated with increased numbers of B cells/plasma cells in both species. Moreover, APRIL and BLyS partially colocalized with κ L chain-expressing B-lineage cells at the epithelial-connective tissue interface. Ligature-induced periodontitis resulted in significantly less bone loss in B cell-deficient mice compared with wild-type controls. Ab-mediated neutralization of APRIL or BLyS diminished the number of B cells in the gingival tissue and inhibited bone loss in wild-type, but not in B cell-deficient, mice. In conclusion, B cells and specific cytokines involved in their growth and differentiation contribute to periodontal bone loss. Moreover, APRIL and BLyS have been identified as potential therapeutic targets in periodontitis.

Clinical and histologic assessment of lateral alveolar ridge augmentation using a synthetic long-term bioabsorbable membrane and an allograft.

BACKGROUND: Guided bone regeneration (GBR) is a widely used procedure for augmenting alveolar ridge width prior to placement of endosseous implants. Various graft materials and barrier membranes (non-resorbable and bioabsorbable) have been used in GBR. The aim of this study was to assess the performance of a new bioabsorbable, synthetic polyglycolic acid/trimethylene carbonate (PGA/TMC) barrier membrane with an increased absorption time in conjunction with a combination of assayed demineralized bone matrix and cortical cancellous chips uniformly dispersed in a thermoplastic biologic carrier. METHODS: At 72 potential implant sites in 38 subjects, ridge width at the crest and 4 mm apical to the crest was measured before and 6 months after a GBR procedure using the long-term (LT) PGA/TMC membrane and an allograft in a thermoplastic carrier. Before placement of endosseous implants, 48 biopsy specimens were obtained from the augmentation sites and analyzed histomorphometrically. RESULTS: The GBR procedure increased the mean ridge width at the crest from 2.4 to 5.2 mm. This 216% change from baseline was significant (P <0.001). The mean width 4 mm apical to the crest increased from 4.4 to 7.5 mm, a significant (P <0.001) 174% change. The histomorphometric analysis showed that the biopsy specimens consisted, on average, of 57% bone (36% graft material and 21% new bone) and 43% soft tissue and space. CONCLUSION: Our findings suggest that the LT PGA/TMC barrier membrane, used in conjunction with an allograft, provides lateral alveolar ridge augmentation comparable to that achieved with other materials without the necessity for bone-graft harvesting or a second procedure to remove the barrier membrane.

Compression and tension: differential effects on matrix accumulation by periodontal ligament fibroblasts in vitro.

Human periodontal ligament fibroblasts were subjected to 10% cyclic equibiaxial tensional and compressive forces in vitro. Media supernatants were analyzed for changes in total protein, extracellular matrix proteins type I collagen and fibronectin, as well as MMP expression by gelatin zymography and Western blot. RNA analyses for changes in collagen, MMP-2, and TIMP-2 were carried out by either Real-time PCR and/or Northern blot. Application of compressional forces resulted in decreases in type I collagen and fibronectin protein, Col1A1 RNA, and increases in total protein, MMP-2 protein (latent and active), and MMP-2 RNA. TIMP-2 RNA was unchanged by compressive forces. In contrast, tensional forces increased total protein, type I collagen, Col1A1 RNA, as well as MMP-2 and TIMP-2 RNA. These studies show that cells can perceive two different forms of mechanical stimuli and respond in a differential manner relative to extracellular matrix synthesis and degradation.

Fc gamma receptor genes as risk markers for localized aggressive periodontitis in African-Americans.

BACKGROUND: Receptors for the Fc fragment of immunoglobulin G (Fc gammaRs) play a crucial role in host defense against bacterial infection by linking humoral and cell-mediated immune responses. Allelic variants of certain Fc gammaRs have been shown to differ relative to their biologic activity. Thus, genes encoding allotypes with diminished activity have been suggested as potential risk factors for infectious diseases. The goal of this study was to determine whether specific Fc gammaRIIa, Fc gammaRIIIa, and Fc gammaRIIIb alleles and/or genotypes could be used to predict susceptibility to localized aggressive periodontitis (LAgP) in an African-American population. METHODS: Whole blood or saliva was obtained from 48 LAgP and 67 periodontally-healthy African-American subjects. DNA was prepared from each sample. Fc gammaRIIa and Fc gammaRIIIa genotyping was analyzed by polymerase chain reaction (PCR) amplification of DNA with allele-specific primers followed by allele-specific restriction digestion of the products. Fc gammaRIIIb genotyping was done by allele-specific PCR. RESULTS: There was a statistically significant over-representation of the Fc gammaRIIIb-NA2 allele in LAgP patients compared to controls (P = 0.024). Relative to the Fc gammaRIIIb-NA1/NA2 and homozygous NA1/NA1 genotypes, the prevalence of the Fc gammaRIIIb NA2/NA2 genotype was higher in the LAgP group relative to the control population. Individuals expressing this genotype appeared at greater risk for developing LAgP (odds ratio 2.271, 95% confidence interval: 1.005 to 5.132). There were no significant differences in the distribution of the Fc gammaRIIa H/R or Fc gammaRIIIa-158 F/V genotypes nor their allelic frequencies between the LAgP patients and controls. CONCLUSIONS: These data suggest that the Fc gammaRIIIb NA2 allele and/or NA2/NA2 genotype may represent risk markers for susceptibility to LAgP in African-Americans.