Objective assessment of intra-oral suturing for certification of competency.

INTRODUCTION: Suturing is an essential skill for dental surgeons, yet there is limited evidence for objective measures of competence in this field, which can be applied to licensing or certification processes for dental surgeons to ensure patient safety. METHODS: In an objective structured clinical examination (OSCE), participants placed two simple interrupted sutures across a lower molar socket in different suturing environments: [A] commercial simulator, [B] suturing sponge mounted in a 3D printed model, [C] suturing sponge and [D] pig's jaw. Simulators [A] and [B] were mounted into phantom heads in dental chairs, and [C] and [D] were placed on bench tops. Performance indicators, overall task success, quality of sutures placed, length of suture remaining and time taken, were analysed against participants' characteristics such as previous suturing experience. RESULTS: Participants (n = 38) took significantly longer to successfully complete the sutures on models mounted in a phantom head. Time points at which each model differentiated between competent (n = 11) and novice (n = 27) participants were as follows: model A (3:26 min), B (2:41), C (2:05) and D (2:06). Model A showed a significant association between task completion and previous suturing experience (p = .006). CONCLUSION: Suturing simulators can be used to objectively differentiate between novice and competent dental surgeons. Model A demonstrated construct validity, as it reliably identified competence using time and task completion as objectively measurable parameters. Utilising model A, the candidate of unknown ability could be identified as appropriately skilled at intra-oral suturing. To ensure patient safety, further research is needed to identify other objective measures of competence in simulation environments.

Serum lipids, retinoic acid and phenol red differentially regulate expression of keratins K1, K10 and K2 in cultured keratinocytes.

Abnormal keratinocyte differentiation is fundamental to pathologies such as skin cancer and mucosal inflammatory diseases. The ability to grow keratinocytes in vitro allows the study of differentiation however any translational value is limited if keratinocytes get altered by the culture method. Although serum lipids (SLPs) and phenol red (PR) are ubiquitous components of culture media their effect on differentiation is largely unknown. We show for the first time that PR and SLP themselves suppress expression of differentiation-specific keratins K1, K10 and K2 in normal human epidermal keratinocytes (NHEK) and two important cell lines, HaCaT and N/TERT-1. Removal of SLP increased expression of K1, K10 and K2 in 2D and 3D cultures, which was further enhanced in the absence of PR. The effect was reversed for K1 and K10 by adding all-trans retinoic acid (ATRA) but increased for K2 in the absence of PR. Furthermore, retinoid regulation of differentiation-specific keratins involves post-transcriptional mechanisms as we show KRT2 mRNA is stabilised whilst KRT1 and KRT10 mRNAs are destabilised in the presence of ATRA. Taken together, our results indicate that the presence of PR and SLP in cell culture media may significantly impact in vitro studies of keratinocyte differentiation.

Clinical correlation of opposing molecular signatures in head and neck squamous cell carcinoma.

BACKGROUND: The concept of head and neck cancers (HNSCC) having unique molecular signatures is well accepted but relating this to clinical presentation and disease behaviour is essential for patient benefit. Currently the clinical significance of HNSCC molecular subtypes is uncertain therefore personalisation of HNSCC treatment is not yet possible. METHODS: We performed meta-analysis on 8 microarray studies and identified six significantly up- (PLAU, FN1, CDCA5) and down-regulated (CRNN, CLEC3B and DUOX1) genes which were subsequently quantified by RT-qPCR in 100 HNSCC patient margin and core tumour samples. RESULTS: Retrospective correlation with sociodemographic and clinicopathological patient details identified two subgroups of opposing molecular signature (+q6 and -q6) that correlated to two recognised high-risk HNSCC populations in the UK. The +q6 group were older, male, and excessive alcohol users whilst the -q6 group were younger, female, paan-chewers and predominantly Bangladeshi. Additionally, all patients with tumour recurrence were in the latter subgroup. CONCLUSIONS: We provide the first evidence linking distinct molecular signatures in HNSCC with clinical presentations. Prospective trials are required to determine the correlation between these distinct genotypes and disease progression or treatment response. This is an important step towards the ultimate goal of improving outcomes by utilising personalised molecular-signature-guided treatments for HNSCC patients.

The monoclonal antibody EPR1614Y against the stem cell biomarker keratin K15 lacks specificity and reacts with other keratins.

Keratin 15 (K15), a type I keratin, which pairs with K5 in epidermis, has been used extensively as a biomarker for stem cells. Two commercial antibodies, LHK15, a mouse monoclonal and EPR1614Y, a rabbit monoclonal, have been widely employed to study K15 expression. Here we report differential reactivity of these antibodies on epithelial cells and tissue sections. Although the two antibodies specifically recognised K15 on western blot, they reacted differently on skin sections and cell lines. LHK15 reacted in patches, whereas EPR1614Y reacted homogenously with the basal keratinocytes in skin sections. In cultured cells, LHK15 did not react with K15 deficient NEB-1, KEB-11, MCF-7 and SW13 cells expressing only exogenous K8 and K18 but reacted when these cells were transduced with K15. On the other hand, EPR1614Y reacted with these cells even though they were devoid of K15. Taken together these results suggest that EPR1614Y recognises a conformational epitope on keratin filaments which can be reconstituted by other keratins as well as by K15. In conclusion, this report highlights that all commercially available antibodies may not be equally specific in identifying the K15 positive stem cell.

An altered keratinocyte phenotype in oral submucous fibrosis: correlation of keratin K17 expression with disease severity.

Oral submucous fibrosis (OSF) is characterized by abnormal collagen metabolism in the submucosal connective tissue. Its influence on the overlying epithelium is not known but about 14% of OSF cases undergo malignant transformation to squamous cell carcinoma indicating association with abnormality of the epithelium. Here, we have defined the keratin expression profile, by immunohistochemistry and quantitative image analysis, using a panel of 22 anti-keratin monoclonal antibodies on 28 OSF samples. We observed an increase of K1 and K10 in the suprabasal layers, induction of K6 in the basal layer and complete loss of K19 in the epithelium. Furthermore, there was increased K17 expression in the suprabasal layers, which correlated with disease severity. In a subset of the most severe OSF cases (14%), K17 expression was completely lost in the basal layer which might define them to be at most risk to undergo malignant transformation. There was no detectable expression of K8, K18, K7 and K9 and the expression of K4, K13, K14, K15 and K16 did not change in OSF. We propose that the altered keratin profiles could be useful as histological diagnostic markers and provide important insights into the pathogenesis of the disease and its predisposition to malignancy.

Changes in the expression of stem cell markers in oral lichen planus and hyperkeratotic lesions.

Despite the pivotal role of stem cells in homeostasis of oral epithelia the location of this cell population within the tissue is uncertain. How disease influences these cells in vivo also remains to be elucidated. In this study we have used six molecular markers to identify stem cells in normal and diseased buccal mucosa. Samples of normal oral mucosa (NOM), hyperkeratosis (OHK) and oral lichen planus (OLP) were immunostained for alpha6 and beta1 integrins, keratin 15 (K15), melanoma-associated chondroitin sulphate proteoglycan (MCSP), NG2 the rat homologue of human MCSP and notch 1. K15, NG2 and beta1 staining was continuous in the basal layer of NOM whilst alpha6 and MCSP were limited to basal cells at the tips of connective tissue papillae. K15 was downregulated in OLP whereas alpha6, beta1 and MCSP were upregulated in both OLP and OHK. NG2 remained unchanged and notch 1 was absent in all samples. Therefore, the stem cell phenotype in OLP and OHK maybe altered in response to pathological signaling. Classification of these changes is essential to understand the role of adult stem cells in the pathogenesis of oral diseases characterised by abnormal keratinocyte proliferation and differentiation.