A Mitosis Block Links Active Cell Cycle with Human Epidermal Differentiation and Results in Endoreplication

How human self-renewal tissues co-ordinate proliferation with differentiation is unclear. Human epidermis undergoes continuous cell growth and differentiation and is permanently exposed to mutagenic hazard. Keratinocytes are thought to arrest cell growth and cell cycle prior to terminal differentiation. However, a growing body of evidence does not satisfy this model. For instance, it does not explain how skin maintains tissue structure in hyperproliferative benign lesions. We have developed and applied novel cell cycle techniques to human skin in situ and determined the dynamics of key cell cycle regulators of DNA replication or mitosis, such as cyclins E, A and B, or members of the anaphase promoting complex pathway: cdc14A, Ndc80/Hec1 and Aurora kinase B. The results show that actively cycling keratinocytes initiate terminal differentiation, arrest in mitosis, continue DNA replication in a special G2/M state, and become polyploid by mitotic slippage. They unambiguously demonstrate that cell cycle progression coexists with terminal differentiation, thus explaining how differentiating cells increase in size. Epidermal differentiating cells arrest in mitosis and a genotoxic-induced mitosis block rapidly pushes epidermal basal cells into differentiation and polyploidy. These observations unravel a novel mitosis-differentiation link that provides new insight into skin homeostasis and cancer. It might constitute a self-defence mechanism against oncogenic alterations such as Myc deregulation

Measuring oral health literacy: A scoping review of existing tools

Background This article presents findings from a scoping review of tools used to measure oral health literacy. Internationally, interest in oral health literacy is driven by oral health disparities, particularly for disadvantaged groups, with conditions such as dental caries and periodontal disease contributing substantially to the global burden of disease. The increasing focus on measuring oral health literacy aligns with reasons for measuring broader health literacy, that is, by assessing oral health literacy, decisions can be made about instigating interventions at policy and practice level to improve individual and population level oral health. There are numerous tools available that measure oral health literacy using a range of indicators. Methods A scoping review was designed to map the existing tools designed to measure oral health literacy (OHL). Key search terms were developed and mapped. Selected databases were used that identified 32 relevant studies reporting a range of OHL tools. Results We identified 32 articles that reported a range of oral health literacy tools. Many of the studies used the Rapid Estimate of Adult Literacy in Dentistry (REALD) and/or the Test of Functional Health Literacy in Dentistry (ToFHLiD) that were developed from earlier tools designed to measure broader health literacy. These tools have been widely criticised for providing only an approximate measure of OHL based mainly on word recognition. A number of newer tools have included new measures of oral health literacy including numeracy and oral health conceptual knowledge however tools that measure important indicators of oral health literacy such as service navigation are rare. Conclusions Findings from this scoping exercise confirm our findings from preliminary scans that the majority of tools are heavily biased towards word recognition, numeracy and reading skills, rather than what this means in terms of health behaviours and service utilisation. More recent developments have attempted to incorporate other aspects considered important, including decision making and service navigation. The incorporation of these aspects into newer tools will provide oral health researchers and policy makers with further evidence of the importance of oral health literacy when designing interventions to improve oral health