Antimicrobial and anti-inflammatory thermo-reversible hydrogel for periodontal delivery.

In periodontal treatment, topical adjunctive therapy with antimicrobials or anti-inflammatory agents is frequently applied. However, currently available drug carrier biomaterials often exhibit poor perfusion into small crevices, such as the deep and irregular periodontal pockets, due to relatively high viscosity. Moreover, high polymer concentrations of the polymer can potentially be cytotoxic upon confined local administration. This study aimed to formulate an antimicrobial and anti-inflammatory treatment option, by incorporating doxycycline (DOX) and/or lipoxin A4 (LXA4) into 0.5 wt% thermo-reversible polyisocyanopeptide (PIC). PIC can form hydrogels upon low polymer concentration, and we hypothesized that the thermo-reversible nature of the material would allow for application into the periodontal pocket. The formulations were characterized in vitro and finally tested in dogs with naturally occurring periodontitis, which were not euthanized afterward. Results showed that PIC/DOX/LXA4 hydrogel could be easily prepared and injected into periodontal pockets. The PIC hydrogel facilitated the release of DOX or LXA4 for around 4 days in vitro. When applied in dogs, the hydrogel exerted no local or systemic adverse effects. Gels loaded with LXA4 and/or DOX reduced the subgingival bacterial load and pro-inflammatory interleukin-8 level. In addition, PIC-DOX and PIC-DOX+LXA4 improved gingival clinical attachment by 0.6 mm compared with conventional periodontal treatment alone (i.e. mechanical debridement). In conclusion, the thermo-reversible PIC hydrogel is a safe and effective vehicle for periodontal drug delivery.

The effect of dietary corn oil and fish oil supplementation in dogs with naturally occurring gingivitis.

The aim of this randomized, double-blinded, placebo-controlled study was to evaluate if downregulation of the inflammatory response due to ingestion of high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can slow down gingivitis development, and thus delay the progression of periodontal disease (PD) in dogs. To this aim, 44 client-owned adult dogs (>1 and <8 years old) with naturally occurring PD (stages 1 and 2) were submitted to a plaque, gingivitis and calculus scoring followed by a dental cleaning procedure and collection of blood samples. The animals were then fed a canine adult maintenance diet, supplemented with either corn oil (0.00 g EPA and 0.00 g DHA) or fish oil (1.53 g EPA and 0.86 g DHA, both per 1,000 kcal ME) over the following 5 months. At the end of this period, the PD scoring and the blood sampling were repeated. The animals consuming fish oil had higher plasma levels of the longer chain (C ≥ 20) omega 3 fatty acids (p < 0.01) and similar plasma levels of alpha-linolenic acid (p = 0.53), omega 6 fatty acids (p > 0.63) and C reactive protein (p = 0.28) then the ones consuming corn oil. There were no differences between fish oil and corn oil diet supplementation on plaque (18.2 vs. 17.8, p = 0.78), calculus (10.1 vs. 11.5, p = 0.18) or gingivitis (19.3 vs. 19.0, p = 0.77) indexes. The authors conclude that supplementation with EPA + DHA does not slow down progression of PD in dogs.

Increased vitamin D-driven signalling and expression of the vitamin D receptor, MSX2, and RANKL in tooth resorption in cats.

Tooth resorption occurs in 20-75% of cats (Felis catus). The aetiology is not known, but vitamin D is suggested to be involved. Vitamin D acts through a nuclear receptor (VDR) and increases the expression of receptor activator of nuclear factor-kappaB ligand (rankl) and muscle segment homeobox 2 (msx2) genes. Mice lacking the muscle segment homeobox 2 (msx2) gene show decreased levels of rankl, suggesting an interaction among VDR, MSX2, and RANKL. Here, we investigated the expression of VDR, MSX2, and RANKL proteins, and the activity of the VDR-mediated signalling pathway (using the quantitative polymerase chain reaction on VDR target genes), in tooth resorption, and measured the serum levels of vitamin D metabolites in cats. Tooth resorption was categorized into either resorptive or reparative stages. In the resorptive stage, odontoclasts expressed MSX2 and RANKL (100% and 88%, respectively) and fibroblasts expressed VDR and MSX2 (both at 100%), whereas fibroblasts expressed RANKL in only 29% of the sites analysed. In the reparative stage, cementoblasts expressed VDR, MSX2, and RANKL, whereas fibroblasts expressed VDR and MSX2, but not RANKL. The vitamin D status did not differ between the groups, based on the serum levels of 25-hydroxycholecalciferol. However, increased expression of VDR protein, and the relative gene expression levels of 1alpha-hydroxylase and the VDR-target gene, 24-hydroxylase, indicated the involvement of an active vitamin D signalling in the pathophysiology of tooth resorption in cats.

Inflammatory cytokines and the nuclear vitamin D receptor are implicated in the pathophysiology of dental resorptive lesions in cats.

Dental resorptive lesions (RL) are a common oral disease in cats (Felis catus) associated with pain and tooth destruction. The aetiology of RL in cats is unknown, but inflammation is often seen in conjunction with RL. Vitamin D involvement has been suggested because 1,25-dihydroxyvitamin D (1,25(OH)(2)D) stimulates osteoclastogenesis, through up-regulation of the nuclear vitamin D receptor (nVDR). The aim of this study is to determine the involvement of inflammatory cytokines and the possible role of vitamin D in the pathophysiology of RL using quantitative PCR. We measured the mRNA expression of cytokines with stimulatory (IL-1beta, IL-6, and TNF-alpha) and inhibitory effects (IL-10 and IFN-gamma) on osteoclastogenesis, and the mRNA expression of the receptor activator of nuclear factor-kappaB ligand (RANKL), osteoprotegerin (OPG), and nVDR in RL samples. We found increased expression of mRNA levels for inflammatory cytokines and nVDR, but not for RANKL and OPG, in tissue from RL-affected cats compared with tissue from radiological confirmed healthy controls. The mRNA levels of nVDR were positively correlated with mRNA levels of pro-inflammatory (IL-1beta, IL-6, TNF-alpha, and IFN-gamma), anti-inflammatory (IL-10), pro-resorptive (IL-1beta, IL-6, and TNF-alpha), and anti-resorptive (IFN-gamma and IL-10) cytokines in the course of resorptive lesions. These data are consistent with our view that both inflammation and an overexpression of the nVDR are likely to be involved in RL in cats.