Nexus between COVID-19 and periodontal disease.

Over the past several decades, studies have demonstrated the existence of bi-directional relationships between periodontal disease and systemic conditions. Periodontitis is a polymicrobial and multifactorial disease involving both host and environmental factors. Tissue destruction is primarily associated with hyperresponsiveness of the host resulting in release of inflammatory mediators. Pro-inflammatory cytokines play a major role in bacterial stimulation and tissue destruction. In addition, these cytokines are thought to underlie the associations between periodontitis and systemic conditions. Current research suggests that increased release of cytokines from host cells, referred to as the cytokine storm, is associated with disease progression in patients with coronavirus disease 2019 (COVID-19). An intersection between periodontitis and pulmonary disease is biologically plausible. Hence, we reviewed the evidence linking COVID-19, cytokines, and periodontal disease. Plaque control is essential to prevent exchange of bacteria between the mouth and the lungs, reducing the risk of lung disease. Understanding these associations may help identify individuals at high risk and deliver appropriate care at early stages.

Bargain with the tooth fairy - The savings accounts for dental stem cells.

Despite the hard times COVID-19 has imposed on us, the Biomedical Journal strives to provide fresh and compelling reading material - to be enjoyed safely from home. In this issue, we glance behind the scenes of dental stem cell preservation for potential therapeutic use, and discover that cancer cells hijack podoplanin expression to induce thrombosis. Moreover, we learn how the helicase DDX17 promotes tumour stemness, how genetic defects in meiosis and DNA repair cause premature ovarian insufficiency, and that the brain-derived neurotrophic factor is associated with several psychiatric diseases. Further accounts relate the role of miR-95-3p in colorectal cancer, the protective power of eggplants against mercury poisoning, and the predictive value of inhibin A for premature delivery. Finally, the very rare case of adenoid cystic carcinoma in the external auditory canal receives some attention, and we get to read up on how 3D imaging and modelling combines functional and aesthetic repair of cleft lip and palate cases.

Identification of viral DNA (Anelloviridae) in a 200-year-old dental pulp sample (Napoleon's Great Army, Kaliningrad, 1812).

Ancient human remains are potential sources of biological information including traces of past infections, since previous studies have demonstrated the effective detection of several bacterial agents or host-integrated viruses in old biological remnants like tissues or teeth. Studies of skeletal dental pulp samples are of particular interest since this location is potentially exposed to bloodborne agents during life through its vascularization, and could be considered as well preserved from environment after death of the host. DNA viruses belonging to the family Anelloviridae are highly present in human populations where they harbor an extreme genetic diversity but a yet undefined implication in hosts' health. We hypothesized that anelloviruses would be detected in ancient remains and that they may also serve as tracer viruses for the study of other viral agents. We analyzed 200-year-old dental pulp samples from remains of soldiers of Napoleon's Great Army during the Russian Retreat. Successful detection of Anelloviridae DNA by PCR was obtained for 1/21 ancient samples tested. The sequence identified showed 23% nucleotide divergence with the closest group of modern isolates (genus Gammatorquevirus), and was confirmed as phylogenetically distinct from those identified in saliva samples from the two investigators in charge of the study (genera Alphatorquevirus and Betatorquevirus). PCR directed toward the human beta globin gene was also performed. Negative controls were negative. Our results demonstrate that an ubiquitary, non-integrated, DNA virus is detectable from ancient biological material, with potential developments in terms of evolution studies or subsequent molecular investigations involving further viral agents.

Application of lentivirus-mediated RNAi in studying gene function in mammalian tooth development.

RNA interference (RNAi) has recently become a powerful tool to silence gene expression in mammalian cells, but its application in assessing gene function in mammalian developing organs remains highly limited. Here we describe several unique developmental properties of the mouse molar germ. Embryonic molar mesenchyme, but not the incisor mesenchyme, once dissociated into single cell suspension and re-aggregated, retains its odontogenic potential, the capability of a tissue to instruct an adjacent tissue to initiate tooth formation. Dissociated molar mesenchymal cells, even after being plated in cell culture, retain odontogenic competence, the capability of a tissue to respond to odontogenic signals and to support tooth formation. Most interestingly, while dissociated epithelial and mesenchymal cells of molar tooth germ are mixed and re-aggregated, the epithelial cells are able to sort out from the mesenchymal cells and organize into a well-defined dental epithelial structure, leading to the formation of a well-differentiated tooth organ after sub-renal culture. These unique molar developmental properties allow us to develop a strategy using a lentivirus-mediated RNAi approach to silence gene expression in dental mesenchymal cells and assess gene function in tooth development. We show that knockdown of Msx1 or Dlx2 expression in the dental mesenchyme faithfully recapitulates the tooth phenotype of their targeted mutant mice. Silencing of Barx1 expression in the dental mesenchyme causes an arrest of tooth development at the bud stage, demonstrating a crucial role for Barx1 in tooth formation. Our studies have established a reliable and rapid assay that would permit large-scale analysis of gene function in mammalian tooth development.