Increased oxygen exposure alters collagen expression and tissue architecture during ligature-induced periodontitis

Hyperoxia: Effective Mechanism of Hyperbaric Treatment at Mild-Pressure

HBOT increases the proportion of dissolved oxygen in the blood, generating hyperoxia. This increased oxygen diffuses into the mitochondria, which consume the majority of inhaled oxygen and constitute the epicenter of HBOT effects. In this way, the oxygen entering the mitochondria can reverse tissue hypoxia, activating the electron transport chain to generate energy. Furthermore, intermittent HBOT is sensed by the cell as relative hypoxia, inducing cellular responses such as the activation of the HIF-1α pathway, which in turn, activates numerous cellular processes, including angiogenesis and inflammation, among others. These effects are harnessed for the treatment of various pathologies. This review summarizes the evidence indicating that the use of medium-pressure HBOT generates hyperoxia and activates cellular pathways capable of producing the mentioned effects. The possibility of using medium-pressure HBOT as a direct or adjunctive treatment in different pathologies may yield benefits, potentially leading to transformative therapeutic advancements in the future.

Effect of Hyperbaric Oxygen and Inflammation on Human Gingival Mesenchymal Stem/Progenitor Cells

The present study explores for the first time the effect of hyperbaric oxygen (HBO) on gingival mesenchymal stem cells' (G-MSCs) gene expression profile, intracellular pathway activation, pluripotency, and differentiation potential under an experimental inflammatory setup. G-MSCs were isolated from five healthy individuals (n = 5) and characterized. Single (24 h) or double (72 h) HBO stimulation (100% O2, 3 bar, 90 min) was performed under experimental inflammatory [IL-1β (1 ng/mL)/TNF-α (10 ng/mL)/IFN-γ (100 ng/mL)] and non-inflammatory micro-environment. Next Generation Sequencing and KEGG pathway enrichment analysis, G-MSCs' pluripotency gene expression, Wnt-/β-catenin pathway activation, proliferation, colony formation, and differentiation were investigated. G-MSCs demonstrated all mesenchymal stem/progenitor cells' characteristics. The beneficial effect of a single HBO stimulation was evident, with anti-inflammatory effects and induction of differentiation (TLL1, ID3, BHLHE40), proliferation/cell survival (BMF, ID3, TXNIP, PDK4, ABL2), migration (ABL2) and osteogenic differentiation (p < 0.05). A second HBO stimulation at 72 h had a detrimental effect, significantly increasing the inflammation-induced cellular stress and ROS accumulation through HMOX1, BHLHE40, and ARL4C amplification and pathway enrichment (p < 0.05). Results outline a positive short-term single HBO anti-inflammatory, regenerative, and differentiation stimulatory effect on G-MSCs. A second (72 h) stimulation is detrimental to the same properties. The current results could open new perspectives in the clinical application of short-termed HBO induction in G-MSCs-mediated periodontal reparative/regenerative mechanisms.

Topical sodium alendronate combined or not with photodynamic therapy as an adjunct to scaling and root planing: Histochemical and immunohistochemical study in rats

OBJECTIVE

The purpose of this study was to evaluate influence of topical sodium alendronate (ALN), photodynamic therapy (aPDT), or a combination thereof as adjuvant to scaling and root planing (SRP) in the treatment of experimental periodontitis in rats.

BACKGROUND

Therapeutic protocols to control periodontitis progression that aim to equalize bacterial action and load with tissue immune response are well addressed in current scientific research.

METHODS

Experimental periodontitis was induced in 96 rats with a ligature around the mandibular left first molar. After 7 days, ligature was removed and animals were treated according to the following experimental groups (n = 8): control-SRP plus saline solution; ALN-SRP plus ALN; aPDT-SRP plus methylene blue irrigation, followed by low-level laser therapy (LLLT); and ALN/aPDT-SRP plus ALN and methylene blue irrigation followed by LLLT. The animals were euthanized at 7, 15, and 30 days after treatments. Collagen maturation (picrosirius red staining) and immunohistochemical analyses (TRAP, RANKL and osteoprotegerin [OPG]) were performed. Data were submitted to statistical analysis (P < .05).

RESULTS

At 7 days, group ALN presented a significantly higher number of TRAP-positive cells and percentage of immature collagen fibers than group ALN/aPDT, while group ALN/aPDT presented a significantly higher percentage of mature collagen fibers than group ALN. At 30 days, group ALN presented significantly lower percentage of immature collagen fibers and higher percentage of mature collagen fibers than control.

CONCLUSION

It can be concluded that topical use of ALN coadjutant to SRP, alone or combined with aPDT, enhanced collagen maturation and reduced osteoclastogenesis during the healing of experimental periodontitis.

Deconvolution of RNA-Seq Analysis of Hyperbaric Oxygen-Treated Mice Lungs Reveals Mesenchymal Cell Subtype Changes

Hyperbaric oxygen (HBO) is widely applied to treat several hypoxia-related diseases. Previous studies have focused on the immediate effect of HBO-exposure induced oxidative stress on the lungs, but knowledge regarding the chronic effects from repetitive HBO exposure is limited, especially at the gene expression level. We found that repetitive HBO exposure did not alter the morphology of murine lungs. However, by deconvolution of RNA-seq from those mice lungs using CIBERSORTx and the expression profile matrices of 8 mesenchymal cell subtypes obtained from bleomycin-treated mouse lungs, we identify several mesenchymal cell subtype changes. These include increases in Col13a1 matrix fibroblasts, mesenchymal progenitors and mesothelial cell populations and decreases in lipofibroblasts, endothelial and Pdgfrb high cell populations. Our data suggest that repetitive HBO exposure may affect biological processes in the lungs such as response to wounding, extracellular matrix, vasculature development and immune response.

Cellular and collagen reference values of gingival and periodontal ligament tissues in rats: a pilot study

Reference data are lacking on the periodontal ligament and the gingival tissue of the rat model, which would be useful for studies of new medical or biomaterial periodontal treatments. The objective of the current study was to propose cellular and collagen reference values of gingival and periodontal ligament tissues in rat, using a simple and reliable quantitative method after decalcification. Mandibular samples of ten adult Sprague-Dawley rats were used. Mild decalcification was carried out using ethylenediaminetetraacetic acid (EDTA) to preserve the morphology of tissues. Half of the samples were decalcified and the other half were not. The gingiva and the periodontal ligament were analyzed. Descriptive histology and computer-assisted image analysis were performed. The data showed that qualitatively, cellular and extracellular matrix morphologies were well preserved compared to non-decalcified periodontal soft tissue biopsies. Histomorphometrically, constitutive cellularity and the total amount of native collagen, collagen directionality and collagen anisotropy in both experimental conditions did not significantly differ. Taken together, these results suggested that EDTA decalcification did not negatively affect the studied endpoints. Moreover, this mild decalcification method allowed in situ maintenance of the periodontal soft and hard tissue integrity. The structural and compositional computerized assessment performed in the healthy periodontal soft tissue could provide reference values that will be required for future assessment on the effects of pathological, reparative and regenerative processes in rat periodontal soft tissues.