Project description:Background. Hematopoietic cell transplantation (HCT) is a potentially curative therapy for a wide range of pediatric malignant and nonmalignant diseases. However, complications, including blood stream infection (BSI) remain a major cause of morbidity and mortality. While certain bacteria that are abundant in the oral microbiome, such as S. mitis, can cause BSI, the role of the oral microbial community in the etiology of BSI is not well understood. The finding that the use of xylitol wipes, which specifically targets the cariogenic bacteria S. mutans is associated with reduced BSI in pediatric patients, lead us to investigate dental caries as a risk factor for BSI. Methods. A total of 41 pediatric patients admitted for allogenic or autologous HCT, age 8 months to 25 years, were enrolled. Subjects with high dental caries risk were identified as those who had dental restorations completed within 2 months of admission for transplant, or who had untreated decay. Fisher’s exact test was used to determine if there was a significant association between caries risk and BSI. Dental plaque and saliva were collected on a cotton swab from a subset of 4 high caries risk (HCR) and 4 low caries risk (LCR) children following pretransplant conditioning. 16SrRNA sequencing was used to compare the microbiome of HCR and LCR subjects and to identify microbes that were significantly different between the 2 groups. Results. There was a statistically significant association between caries risk and BSI (p<0.035) (Fisher’s exact test). Multivariate logistic regression analysis showed children in the high dental caries risk group were 21.39 times more likely to have BSI, with no significant effect of age or mucositis severity. HCR subjects showed significantly reduced microbial alpha diversity as compared to LCR subjects. LEfse metagenomic analyses, showed the oral microbiome in HCR children enriched in order Lactobacillales. This order includes Streptococcus and Lactobacillus, both which contain bacteria primarily associated with dental caries. Discussion. These findings support the possibility that the cariogenic microbiome can enhance the risk of BSI in pediatric populations. Future metagenomic analyses to measure microbial differences at, before, and after conditioning related to caries risk, may further unravel the complex relationship between the oral microbiome, and whether it affects health outcomes such as BSI.

Project description:Rationale：Poor peri-implant osseointegration of dental implants in patients with type II diabetes has become a major clinical challenge in recent years. MSC (Mesenchymal stem cell)-derived exosomes may play an important role in peri-implant osseointegration, but the mechanism remains unclear. Enhancing the therapeutic effect of MSC-derived exosomes and exploring the potential mechanism can help provide a new therapeutic strategy to improve the clinical outcome of dental implant restorations in patients with type II diabetes. Methods：The exosomes derived from hypoxia (Hypo-exos) or normoxia (Nor-exos) preconditioned bone marrow mesenchymal stem cells (BMSCs) were co-cultured with BMSCs and human umbilical vein endothelial cells (HUVECs). The effect of exosomes on BMSCs cell proliferation was detected by CCK-8 assay and EdU assay, and the effect on angiogenesis ability of HUVECs was detected by wound healing assay, transwell migration assay, tube formation assay, enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. A diabetic rat dental implant model was also established and the effect of exosomes on implant osseointegration was evaluated through micro-CT scanning and histological analysis. The differentially expressed miRNAs between Hypo-exos and Nor-exos were identified by high-throughput miRNA sequencing. Subsequently, the target genes and their roles in regulating angiogenesis were predicted and analyzed by bioinformatics analysis and dual luciferase reporter assay. Results：In vitro experiments indicated that hypoxia preconditioning could elevate exosome production and promote cell proliferation of BMSCs and angiogenesis of HUVECs. Moreover, Hypo-exos promoted peri-implant osteogenesis in rats with diabetes. Further investigation revealed the vital involvement of the miR-106b-5p/HIF-1α axis in promoting peri-implant osseointegration. Conclusion: Exosomes derived from hypoxia-preconditioned BMSCs could improve the peri-implant osseointegration in rats with diabetes by promoting cell proliferation and angiogenesis, and the miR-106b-5p/ HIF-1α axis could be the underlying mechanism.

Project description:Oral health is associated with a symbiotic microbial community and host-microbe homeostasis is maintained by the controlled immune response. Various factors can disrupt this homeostasis. Dysbiosis, which is characterized by increased immune response and a shift in the microbiome, contributes the pathogenesis of peri-implantitis. Peri-implant mucosa and commensal bacteria play important roles in the maintenance of host-microbe homeostasis, but little is known about how they interact. We have therefore investigated the early host-microbe interaction between a commensal multispecies biofilm (Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar, Porphyromonas gingivalis) and peri-implant mucosa at 24 and 48 h. Our in vitro peri-implant mucosa-biofilm model contained organotypic oral mucosa, implant material and biofilm. After 24 h, the biofilm induced a modest innate immune response in the peri-implant mucosa by the upregulation of 5 genes related to immune and inflammatory response and the increased secretion of IL-6 and CCL20. This controlled immune response protected tissue integrity and the peri-implant mucosa remained intact. The secreted antibacterial proteins human β-Defensins-1, -2, and CCL20 controlled the overgrowth of the biofilm by reducing its volume - without affecting the live/dead ratio or bacterial distribution. Thus, host-microbe homeostasis was established within the first 24 h. In contrast, host-microbe homeostasis was disrupted after 48 h. The mucosa was damaged and detached from the implant, due to the induced downregulation of cell adhesion related genes. The immune response was enhanced by upregulation of additional genes related to the immune and inflammatory response and increased secretion of IL-1β, TNF-α, and CCL20. Moreover, bacterial distribution was altered, with an increased proportion of V. dispar. The disrupted host-microbe homeostasis could lead to incipient dysbiosis. This deeper understanding of the early host-microbe interaction at the peri-implant site may provide the basis for new strategies to improve the prevention and therapy of peri-implant diseases.

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