Objective: We undertook an integrated analysis of genomic and epidemiological data to investigate a large healthcare-associated COVID-19 outbreak and to better understand the epidemiology of all COVID-19 cases in Tasmania, Australia. Methods: Epidemiological data collected on COVID-19 cases notified in Tasmania between 2 March and 15 May 2020, and positive SARS-CoV-2 samples or extracted RNA from those cases, were included. Sequencing was conducted by tiled amplicon PCR using ARTIC v1 or v3 primers and Illumina sequencing. Consensus sequences were generated, sequences were aligned to a reference sequence, and phylogenetic analysis performed. Genomic clusters were determined and integrated with epidemiologic data to assess any additional insights. Results: All COVID-19 cases notified in Tasmania during the study period (n=231) and 266 SARS-CoV-2 positive samples, representing 217/231 (94%) of notified cases, were included in the study; 182/217 (84%) were clustered, 21/217 (10%) were unique, 12/217 (6%) could not be sequenced. Genomics confirmed the presence of seven epidemiological clusters, clarified transmission networks where epidemiology was unclear and additionally identified another genomic cluster which had not been identified by epidemiology alone. Discussion

Ameloblasts are specialized cells derived from the dental epithelium that produce enamel, a hierarchically structured tissue comprised of highly elongated hydroxylapatite (OHAp) crystallites. The unique function of the epithelial cells synthesizing crystallites and assembling them in a mechanically robust structure is not fully elucidated yet, partly due to limitations with in vitro experimental models. Herein, we demonstrate the ability to generate mineralizing dental epithelial organoids (DEOs) from adult dental epithelial stem cells (aDESCs) isolated from mouse incisor tissues. DEOs expressed ameloblast markers, could be maintained for more than five months (11 passages) in vitro in media containing modulators of Wnt, Egf, Bmp, Fgf and Notch signaling pathways, and were amenable to cryostorage. When transplanted underneath murine kidney capsules, organoids produced OHAp crystallites similar in composition, size, and shape to mineralized dental tissues, including some enamel-like elongated crystals. DEOs are thus a powerful in vitro model to study mineralization process by dental epithelium, which can pave the way to understanding amelogenesis and developing regenerative therapy of enamel.
Mice ; Animals ; Durapatite/metabolism* ; Dental Enamel/metabolism* ; Ameloblasts/metabolism* ; Amelogenesis ; Stem Cells ; Organoids