Investigation of the ultrastructure of dental pulp odontoblasts in a patient following a COVID-19 viral infection

Abstract

Relevance. Recent studies on odontoblast ultrastructure have indicated that these cells possess immune functions. Unfortunately, both domestic and international sources lack transmission electron microscopy research data that characterise the ultrastructure of odontoblasts. This gap in the literature limits the expansion of knowledge about these specific cells of the human dental pulp and their practical applications. An analysis of existing literature and our own research suggests that the organs of the oral cavity may become targets for the coronavirus. Odontoblasts, as specialized cells of the dental pulp, perform multiple functions. Their primary role is in dentinogenesis, but equally important is their participation in immune functions, evidenced by the presence of pattern recognition receptors (PRRs) on their surface. These include Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain-like receptors (NOD-like receptors, NLRs), some of which can mount an immune response to the entry of SARS-CoV-2 into the cell.Materials and methods. This study involved a comprehensive clinical-laboratory investigation of the pulp from an intact tooth 2.8, extracted for orthodontic reasons from a patient who had recovered from a COVID-19 infection a few weeks prior to the tooth extirpation. The ultrastructure of the dental pulp was examined using transmission electron microscopy.Results. In the ultrathin sections of the pulp specimens from the extirpated tooth, specific odontoblast cells with clearly traceable ultrastructure were identified. The electron micrographs visualized features characteristic of viral entry into the cell: initial apoptotic changes in the nucleus of the odontoblast, the presence of clathrin-coated vesicles in the cytoplasmic membrane of the odontoblast process. Additionally, clathrin-coated invaginations of the cytolemma in the terminal parts of the odontoblasts were observed.Conclusion. The electron micrographs revealed ultrastructural changes indicative of a viral infection, suggesting the involvement of odontoblasts, equipped with the TLR3 and TLR4 system, in the antiviral defence against SARS-CoV-2.