Efficacy and safety of a new heterologous fibrin biopolymer on socket bone healing after tooth extraction: An experimental pre-clinical study.

AIM: To assess the efficacy of heterologous fibrin biopolymer (HFB) in promoting alveolar bone healing after tooth extraction in rats. MATERIALS AND METHODS: The upper right incisors of 48 Wistar rats were extracted. Toothless sockets were filled with HFB (HFBG, n = 24) or blood clot (BCG, n = 24). The tooth extraction sites were subjected to micro-computed tomography (micro-CT), histological, histomorphometric and immunohistochemical (for Runt-related transcription factor 2/Runx2 and tartrate-resistant acid phosphatase/TRAP) analyses on days 0, 7, 14 and 42 after extraction. RESULTS: Socket volume remained similar between days 0 and 14 (69 ± 5.4 mm3), except in the BCG on day 14, when it was 10% lower (p = .043). Although the number of Runx2+ osteoblasts was high and similar in both groups (34 × 102 cells/mm2), the HFBG showed lower inflammatory process and osteoclast activity than BCG at 7 days. On day 14, the number of Runx2+ osteoblasts remained high and similar to the previous period in both groups. However, osteoclast activity increased. This increase was 55% lower in the HFBG than BCG. In the BCG, the presence of an inflammatory process and larger and numerous osteoclasts on day 14 led to resorption of the alveolar bone ridge and newly formed bone. On day 42, numbers of Runx2+ osteoblast and TRAP+ osteoclasts decreased dramatically in both groups. Although the BCG exhibited a more mature cortical bone formation, it exhibited a higher socket reduction (28.3 ± 6.67%) and smaller bone volume (37 ± 5.8 mm3) compared with HFBG (socket reduction of 14.8 ± 7.14% and total bone volume of 46 ± 5.4 mm3). CONCLUSIONS: HFB effectively suppresses osteoclast activity and reduces alveolar bone resorption compared with blood clot, thus preventing three-dimensional bone loss, particularly during the early healing period. HFB emerges as a promising biopharmaceutical material for enhancing healing processes after tooth extraction.

Regulatory T cells attenuate experimental periodontitis progression in mice.

AIMS: The aim of this study was to identify the presence and characterize the function of regulatory T cells (Tregs) in experimental periodontitis in mice. MATERIAL AND METHODS: C57Bl/6 mice infected with Actinobacillus actinomycetemcomitans, treated or not with anti-glucocorticoid-inducible tumour necrosis factor receptor (anti-GITR) to inhibit Tregs function, were analysed regarding inflammatory cell and Tregs influx, alveolar bone loss and cytokine expression/production (analysed by real-time polymerase chain reaction and ELISA) throughout experimental periodontitis. RESULTS: A. actinomycetemcomitans inoculation in mice resulted in periodontal disease characterized by marked alveolar bone loss and an influx of inflammatory cells. Flow cytometry evaluation of inflammatory cells demonstrated an increased number of CD4(+)CD25(+) and CD4(+)FOXp3(+) cells, characterizing the presence of Tregs in the periodontal environment in a late stage after infection. Tregs-associated cytokines interleukin-10 (IL-10), cytotoxic T lymphocyte-associated molecule 4 (CTLA-4) and transforming growth factor-beta (TGF-beta) were found to be expressed/produced in a kinetics that resembles Tregs migration. Treatment with anti-GITR, which inhibits Tregs function, showed increased alveolar bone loss and inflammatory cell migration. A reduction in IL-10, CTLA-4 and TGF-beta levels was also observed, while interferon-gamma, tumour necrosis factor-alpha and receptor activator for nuclear factor kappaB ligand levels were increased. However, bacterial load and C-reactive protein serum did not show any differences. CONCLUSION: Taken together, our results showed that the presence of Treg cells attenuates the severity of experimental periodontitis without impairment in the control of infection.

Down-regulation of expression of osteoblast and osteocyte markers in periodontal tissues associated with the spontaneous alveolar bone loss of interleukin-10 knockout mice.

The aim of this study was to unravel the mechanisms by which interleukin (IL)-10, a potent pleiotropic cytokine, modulates alveolar bone homeostasis in C57BL/6 wild-type (WT) and IL-10 knockout (IL-10 KO) mice, evaluated at 8, 24, and 48 wk of age. Interleukin-10 KO mice presented significant alveolar bone loss when compared with WT mice, and this was not associated with changes in leukocyte counts or bacterial load. The levels of expression of messenger RNA (mRNA) for tumor necrosis factor-alpha (TNF-alpha), IL-1beta, IL-6, transforming growth factor-beta (TGF-beta), receptor activator of nuclear factor kappaB ligand (RANKL), osteoprotegerin (OPG), and matrix metalloproteinase 13 (MMP13) were similar between both strains, whereas a significant decrease of tissue inhibitor of metalloproteinase 1 (TIMP1) mRNA expression was found at 48 wk in IL-10 KO mice. The osteoblast markers core binding factor alpha1 (CBFA1) and type I collagen (COL-I) were expressed at similar levels in both strains, whereas the levels of alkaline phosphatase (ALP) and osteocalcin (OCN), and those of the osteocyte markers phosphate-regulating gene endopeptidases (PHEX) and dentin matrix protein 1 (DMP1) were significantly lower in IL-10 KO mice. Our results demonstrate that the alveolar bone loss in the absence of IL-10 was associated with a reduced expression of osteoblast and osteocyte markers, an effect independent of microbial, inflammatory or bone-resorptive pathways.