Differential expression of stem cell-like proteins in normal, hyperplastic and dysplastic oral epithelium

Objective The identification of stem cells (SC) remains challenging. In the human oral mucosal epithelium, these cells are believed to be in the basal layer (stem cell niche), but their exact location is unclear. The aim of this study was to examine the dysplastic oral epithelium for these SC-like proteins in order to assess their diagnostic value as biomarkers complementing the histological grading of dysplasia. Material and Methods Thirty oral epithelial dysplasia (OED), 25 oral lichen planus (OLP), 10 oral hyperkeratosis and 5 normal oral epithelium (OE) were immunohistochemically examined for four SC markers [integrin β1, neuron-glial-2 (NG2), notch 1 (N1) and keratin 15 (K15)]. Results Three of four SC markers were heterogeneously detected in all samples. K15 overexpression in the lower two-thirds of severe OED suggests an expanded SC niche. Integrin β1 distribution pattern was not measurably different between OEDs and control. NG2 was almost negative to absent in all samples examined. N1 expression was weak and highly variable in normal and dysplastic epithelium, making it an unreliable epithelial stem cell marker. Conclusions Present findings suggest that these markers were unable to identify individual epithelial stem cells. Instead, subpopulations of cells, most probably stem cells and transit amplifying cells with stem cell-like properties were identified in the dysplastic oral epithelium. The characteristic expressions of K15 might be of diagnostic value for oral dysplasia and should be investigated further. .

Immunohistochemical expression of p63, epidermal growth factor receptor (EGFR) and notch-1 in radicular cysts, dentigerous cysts and keratocystic odontogenic tumors

The aim of this study was to assess the immunohistochemical expression of p63 protein, epidermal growth factor receptor (EGFR) and Notch-1 in the epithelial lining of radicular cysts (RC), dentigerous cysts (DC) and keratocystic odontogenic tumors (KOT). For this study, 35 RC, 22 DC and 17 KOT were used. The clinical and epidemiological data were collected from the patient charts filed in the Oral Pathology Laboratory, University of Ribeirão Preto, Brazil. Immunohistochemical reactions against the p63, EGFR and Notch-1 were performed in 3-µm-thick histological sections. The slides were evaluated according to the following criteria: negative: <5% of positive cells, low expression: 5-50% of positive cells, and high expression: >50% of positive cells. Moreover, the intensity of EGFR and Notch-1 expressions was also evaluated. Fisher's exact test and Spearman's correlation coefficients were used for statistical analysis, considering a significance level of 5%. Almost all cases demonstrated p63, EGFR and Notch-1 expressions. The p63 expression was significantly higher in KOT (p<0.001). Positive correlation between these immunomarkers was observed. These findings suggest the participation of p63, EGFR and Notch-1 in the development, maintenance and integrity of cystic odontogenic epithelial lining, favoring lesion persistence. The high expression of p63 in KOT suggests that it may be related to their more aggressive biological behavior and marked tendency to recurrence.

O objetivo deste estudo foi avaliar a expressão imunoistoquímica da proteína p63, receptor do fator de crescimento epidérmico (EGFR) e Notch-1 no revestimento epitelial de cistos radiculares (CR), cistos dentígeros (CD) e tumores odontogênicos queratocísticos (TOQ). Para este estudo, 35 CR, 22 CD e 17 TOQ foram utilizados. Os dados clínicos e epidemiológicos foram coletados das fichas dos pacientes arquivadas no Laboratório de Patologia Oral, Universidade de Ribeirão Preto, Brasil. Reações imunoistoquímicas contra p63, EGFR e Notch-1 foram realizadas em cortes histológicos de 3 µm. As lâminas foram avaliadas de acordo com os seguintes critérios: negativo <5% das células positivas, baixa expressão - 5%-50% das células positivas e alta expressão >50% das células positivas. Além disso, a intensidade de expressão de EGFR e Notch-1 foi também avaliada. Teste exato de Fisher e coeficiente de correlação de Spearman foram usados para análise estatística, considerando um nível de significância de 5%. Quase todos os casos demonstraram expressão de p63, EGFR e Notch-1. A expressão de p63 foi significativamente maior nos TOQ (p<0.001). Correlação positiva entre os imunomarcadores foi observada. Esses achados sugerem a participação de p63, EGFR e Notch-1 no desenvolvimento, manutenção e integridade do revestimento epitelial cístico, favorecendo a persistência das lesões. A alta expressão de p63 no TOQ sugere que ela pode estar relacionada ao comportamento biológico mais agressivo e marcada tendência a recorrência.