Bevacizumab or fibronectin gene editing inhibits the osteoclastogenic effects of fibroblasts derived from human radicular cysts.

Fibronectin (FN) is a main component of extracellular matrix (ECM) in most adult tissues. Under pathological conditions, particularly inflammation, wound healing and tumors, an alternatively spliced exon extra domain A (EDA) is included in the FN protein (EDA+FN), which facilitates cellular proliferation, motility, and aggressiveness in different lesions. In this study we investigated the effects of EDA+FN on bone destruction in human radicular cysts and explored the possibility of editing FN gene or blocking the related paracrine signaling pathway to inhibit the osteoclastogenesis. The specimens of radicular cysts were obtained from 20 patients. We showed that the vessel density was positively associated with both the lesion size (R = 0.49, P = 0.001) and EDA+FN staining (R = 0.26, P = 0.022) in the specimens. We isolated fibroblasts from surgical specimens, and used the CRISPR/Cas system to knockout the EDA exon, or used IST-9 antibody and bevacizumab to block EDA+FN and VEGF, respectively. Compared to control fibroblasts, the fibroblasts from radicular cysts exhibited significantly more Trap+MNCs, the relative expression level of VEGF was positively associated with both the ratio of EDA+FN/total FN (R = 0.271, P = 0.019) and with the number of Trap+MNCs (R = 0.331, P = 0.008). The knockout of the EDA exon significantly decreased VEGF expression in the fibroblasts derived from radicular cysts, leading to significantly decreased osteoclastogenesis; similar results were observed using bevacizumab to block VEGF, but block of EDA+FN with IST-9 antibody had no effect. Furthermore, the inhibitory effects of gene editing on Trap+MNC development were restored by exogenous VEGF. These results suggest that EDA+FN facilitates osteoclastogenesis in the fibrous capsule of radicular cysts, through a mechanism mediated by VEGF via an autocrine effect on the fibroblasts. Bevacizumab inhibits osteoclastogenesis in radicular cysts as effectively as the exclusion of the EDA exon by gene editing.

Transforming growth factor beta-1 expression in macrophages of human chronic periapical diseases.

The objective of this study was to observe the distribution of macrophages (MPs) expressing transforming growth factor beta-1 (TGF-ß1) in tissue samples from patients with different human chronic periapical diseases. In this study, samples were collected from 75 volunteers, who were divided into three groups according to classified standards, namely, healthy control (N = 25), periapical granuloma (N = 25), and periapical cyst (N = 25). The samples were fixed in 10% buffered formalin for more than 48 h, dehydrated, embedded, and stained with hematoxylin and eosin for histopathology. Double immunofluorescence was conducted to analyze the expression of TGF-ß-CD14 double-positive MPs in periapical tissues. The number of double-positive cells (cells/mm2) were significantly higher in the chronic periapical disease tissues (P < 0.01) compared to that in the control tissue; in addition, the density of TGF-ß1-CD14 double positive cells was significantly higher in the periapical cyst group than in the periapical granuloma group (P < 0.01). The number of TGF-ß1 expressing macrophages varied with human chronic periapical diseases. The TGF-ß1-CD14 double-positive cells might play an important role in the pathology of human chronic periapical diseases.

BRAFV600E mutation in the diagnosis of unicystic ameloblastoma.

BACKGROUND: Unicystic ameloblastoma, an odontogenic neoplasm, presents clinical and radiographic similarities with dentigerous and radicular cysts, non-neoplastic lesions. It is not always possible to reach a final diagnosis with the incisional biopsy, leading to inappropriate treatment. The BRAFV600E activating mutation has been reported in a high proportion of ameloblastomas. The purpose of the study was to assess the utility of the detection of the BRAFV600E mutation in the differential diagnosis of unicystic ameloblastoma with dentigerous and radicular cysts. METHODS: Twenty-six archival samples were included, comprising eight unicystic ameloblastomas (UAs), nine dentigerous and nine radicular cysts. The mutation was assessed in all samples by anti-BRAFV600E (clone VE1) immunohistochemistry (IHC) and by TaqMan mutation detection qPCR assay. Sanger sequencing was further carried out when samples showed conflicting results in the IHC and qPCR. RESULTS: Although all UAs (8/8) showed positive uniform BRAFV600E staining along the epithelial lining length, the mutation was not confirmed by qPCR and Sanger sequencing in three samples. Positive staining for the BRAFV600E protein was observed in one dentigerous cyst, but it was not confirmed by the molecular methods. Furthermore, 2/9 dentigerous cysts and 2/9 radicular cysts showed non-specific immunostaining of the epithelium or plasma cells. None of the dentigerous or radicular cysts cases presented the BRAFV600E mutation in the qPCR assay. CONCLUSIONS: The BRAFV600E antibody (clone VE1) IHC may show non-specific staining, but molecular assays may be useful for the diagnosis of unicystic ameloblastoma, in conjunction with clinical, radiological and histopathological features.

Gene-expression analysis of matrix metalloproteinases 1 and 2 and their tissue inhibitors in chronic periapical inflammatory lesions.

BACKGROUND: Periapical inflammatory lesions have been investigated previously, but understanding of pathogenesis of these lesions (granulomas and radicular cysts) at the molecular level is still questionable. Matrix metalloproteinases (MMPs) are enzymes involved in the development of periapical pathology, specifically inflammation and tissue destruction. To elucidate pathogenesis of periapical granulomas and radicular cysts, we undertook a detailed analysis of gene expression of MMP-1, MMP-2 and their tissue inhibitors, TIMP-1 and TIMP-2. METHODS: A total of 149 samples were analyzed using real-time PCR (59 radicular cysts, 50 periapical granulomas and 40 healthy gingiva samples as controls) for expression of MMP-1, MMP-2, TIMP-1 and TIMP-2 genes. The determination of best reference gene for expression analysis of periapical lesions was done using a panel of 12 genes. RESULTS: We have shown that ß-actin and GAPDH are not the most stable reference controls for gene expression analysis of inflammatory periapical tissues and healthy gingiva. The most suitable reference gene was determined to be SDHA (a succinate dehydrogenase complex, subunit A, flavoprotein [Fp]). We found that granulomas (n = 50) and radicular cysts (n = 59) exhibited significantly higher expression of all four examined genes, MMP-1, MMP-2, TIMP-1, and TIMP-2, when compared to healthy gingiva (n = 40; P < 0.05). CONCLUSION: This study has confirmed that the expression of MMP-1, MMP-2, TIMP-1, and TIMP-2 genes is important for the pathogenesis of periapical inflammatory lesions. Since the abovementioned markers were not differentially expressed in periapical granulomas and radicular cysts, the challenge of finding the genetic differences between the two lesions still remains.

Inflammation-associated long non-coding RNA signature in radicular cyst tissues.

Radicular cysts are characterized by significant levels of changes in inflammatory biomarkers. Among them, interleukins and growth factors have been reported to be deregulated in radicular cyst tissues. Moreover, long non-coding RNAs are recently discovered non-coding RNA molecules that regulate various intracellular stimuli to keep homeostasis in balance. A growing body of evidence suggests that lncRNAs are significantly involved in the regulation of inflammation by targeting various inflammatory biomarkers. Accordingly, the present study was aimed to investigate the gene expression levels of inflammation-related lncRNAs in radicular cysts and show their possible roles in the development of radicular cysts. For the study, a total of 25 patients with a radiologically and pathologically confirmed radicular cyst were enrolled. For the determination of non-coding RNA expression levels, real-time qPCR was used. As a result of the current study, expression levels of PACER and THRIL were found to be significantly elevated in radicular cyst tissues compared to control tissue samples. However, MALAT1, ANRIL, and NEAT1 expression levels were not significantly altered in radicular cyst tissues compared to control tissue samples. In conclusion, long non-coding RNAs, PACER and THRIL, seem to have significant pathophysiological roles by acquiring molecular changes during inflammation and might be involved in the development and formation of radicular cysts.

Alterations of FHIT and P53 genes in keratocystic odontogenic tumor, dentigerous and radicular cyst.

BACKGROUND: The purpose of this study was to determine fragile histidine triad (FHIT) and p53 protein expression, and to analyze FHIT and p53 gene status in keratocystic odontogenic tumor (KOT), dentigerous cysts (DC) and radicular cysts (RC). METHODS: The methods used were immunohistochemistry and molecular genetic methods including loss of heterozygosity (LOH) and gene sequencing. RESULTS: FHIT protein expression was different among groups. Aberrant expression was the highest in KOT, then in RC and DC. p53 protein expression was different among groups. LOH in paraffin-embedded specimens was detected in 22.6% and 12.9% for FHIT and p53 respectively. Mutation of p53 gene at codon 237 was observed in only two specimens (one KOT and one DC). Of the six frozen specimens, three exhibited FHIT gene LOH (two RC and one KOT). KOT showed loss of exons 6-7 at FHIT locus and mutation at codon 237 at p53 locus, but this could be a chance result. CONCLUSION: Aberrations of FHIT and p53 genes/proteins could be considered markers responsible for the development of odontogenic lesions.

DNA Methylation of MMP9 Is Associated with High Levels of MMP-9 Messenger RNA in Periapical Inflammatory Lesions.

INTRODUCTION: Matrix metalloproteinases (MMPs) are the major class of enzymes responsible for degradation of extracellular matrix components and participate in the pathogenesis of periapical inflammatory lesions. MMP expression may be regulated by DNA methylation. The purpose of the present investigation was to analyze the expression of MMP2 and MMP9 in periapical granulomas and radicular cysts and to test the hypothesis that, in these lesions, their transcription may be modulated by DNA methylation. METHODS: Methylation-specific polymerase chain reaction was used to evaluate the DNA methylation pattern of the MMP2 gene in 13 fresh periapical granuloma samples and 10 fresh radicular cyst samples. Restriction enzyme digestion was used to assess methylation of the MMP9 gene in 12 fresh periapical granuloma samples and 10 fresh radicular cyst samples. MMP2 and MMP9 messenger RNA transcript levels were measured by quantitative real-time polymerase chain reaction. RESULTS: All periapical lesions and healthy mucosa samples showed partial methylation of the MMP2 gene; however, periapical granulomas showed higher MMP2 mRNA expression levels than healthy mucosa (P = .014). A higher unmethylated profile of the MMP9 gene was found in periapical granulomas and radicular cysts compared with healthy mucosa. In addition, higher MMP9 mRNA expression was observed in the periapical lesions compared with healthy tissues. CONCLUSIONS: The present study suggests that the unmethylated status of the MMP9 gene in periapical lesions may explain the observed up-regulation of messenger RNA transcription in these lesions.

Bioinformatics, interaction network analysis, and neural networks to characterize gene expression of radicular cyst and periapical granuloma.

INTRODUCTION: Bioinformatics has emerged as an important tool to analyze the large amount of data generated by research in different diseases. In this study, gene expression for radicular cysts (RCs) and periapical granulomas (PGs) was characterized based on a leader gene approach. METHODS: A validated bioinformatics algorithm was applied to identify leader genes for RCs and PGs. Genes related to RCs and PGs were first identified in PubMed, GenBank, GeneAtlas, and GeneCards databases. The Web-available STRING software (The European Molecular Biology Laboratory [EMBL], Heidelberg, Baden-Württemberg, Germany) was used in order to build the interaction map among the identified genes by a significance score named weighted number of links. Based on the weighted number of links, genes were clustered using k-means. The genes in the highest cluster were considered leader genes. Multilayer perceptron neural network analysis was used as a complementary supplement for gene classification. RESULTS: For RCs, the suggested leader genes were TP53 and EP300, whereas PGs were associated with IL2RG, CCL2, CCL4, CCL5, CCR1, CCR3, and CCR5 genes. CONCLUSIONS: Our data revealed different gene expression for RCs and PGs, suggesting that not only the inflammatory nature but also other biological processes might differentiate RCs and PGs.

P53 protein expression in odontogenic cysts.

p53 protein seems to be related to the suppression of cell proliferation. p53-positive tissues seem to have a higher proliferative activity than p53-negative ones. Odontogenic keratocyst (OKC) has a different behavior from other types of cysts because it is more aggressive, with a tendency to recurrence. Twenty-two dentigerous cysts, 24 radicular cysts, and 20 OKCs were used in the present study. Two dentigerous cysts (9.1%), 2 radicular cysts (8.3%), and 9 OKCs (45%) expressed the p53 protein. The differences between the three groups were statistically significant (p = 0.003). In 10 cases of OKCs epithelial dysplasia was found. One of the 10 OKCs without dysplasia and 8 of the 10 OKCs with dysplasia were p53-positive: the difference between the two groups was statistically significant (p = 0.007). The overexpression of p53 protein was not on the other hand correlated with the occurrence of multiple, bilateral, and recurrent OKCs. Moreover the distribution of p53-positive cells was parabasal in contrast with other types of cysts. These qualitative and quantitative differences in proliferative activity in OKCs seem to point to an alteration in cell cycle control.

Methylation pattern of IFNG in periapical granulomas and radicular cysts.

INTRODUCTION: Interferon-γ plays an important role in the pathogenesis of periapical lesions, and the methylation of IFNG has been associated with transcriptional inactivation. The purpose of the present study was to investigate IFNG promoter methylation in association with gene transcription and protein levels in periapical granulomas and radicular cysts. METHODS: Methylation-specific polymerase chain reaction was used to assess the DNA methylation pattern of the IFNG gene in 16 periapical granulomas and 13 radicular cyst samples. The transcription levels of IFNG mRNA were verified by quantitative real-time polymerase chain reaction, and protein expression was evaluated by immunohistochemistry. RESULTS: All the periapical lesion samples exhibited partial or total methylation of the IFNG gene. In addition, an increased methylation profile was found in radicular cysts compared with periapical granulomas. Increased IFNG mRNA expression was observed in the partially methylated periapical lesion samples relative to the samples that were completely methylated. CONCLUSIONS: The present study provides the first evidence of the possible impact of IFNG methylation on IFNG transcription in periapical lesions.

Comparative immunohistochemical expression of RANK, RANKL and OPG in radicular and dentigerous cysts.

OBJECTIVE: Receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) and osteoprotegerin (OPG) are members of the superfamily of ligands and receptors of tumour necrosis factor family involved in bone metabolism. The formation, differentiation and activity of osteoclasts are regulated by these proteins. To clarify the roles of osteoclast regulatory factors in cystic expansion of odontogenic cysts, expression of these proteins were analysed in radicular and dentigerous cysts. DESIGN: The immunohistochemistry expression of these biomarkers were evaluated and measured in lining epithelium and fibrous capsule of the radicular (n=20) and dentigerous cysts (n=20). RESULTS: A similar expression in lining epithelium was observed in the lesions. The fibrous capsule of dentigerous cyst showed a higher content of RANK-positive and RANKL-positive cells than fibrous capsule of radicular cyst. In the lining epithelium the RANKL/OPG ratio showed higher numbers of OPG-positive than RANKL-positive cells, whereas fibrous capsule of the cysts had a tendency to present a similar expression (OPG=RANKL). CONCLUSION: Ours findings indicate the presence of RANK, RANKL and OPG in cysts. Moreover, increased expression of OPG compared to RANKL in the lining epithelium could contribute to the differential bone resorption activity in theses lesions.

The cytobiological differences between two odontogenic cyst-lining keratinocytes.

PURPOSE: Odontogenic cysts are classified into a developmental group, including follicular cysts (FC) and keratocysts, and an inflammatory group including radicular cysts (RC). In clinical cases, we frequently encounter RC and FC. The purpose of this study was to investigate the cytobiological differences between two odontogenic cyst-lining keratinocytes using a cytobiological approach from the aspect of metabolic function and the degree of maturation of the epithelium. MATERIALS AND METHODS: Samples of odontogenic cyst-lining keratinocytes and oral keratinocytes collected at surgery, and of cultured oral keratinocytes, were analyzed (1) by immunohistochemical staining of granulocyte macrophage colony stimulating factor (GM-CSF), human beta defensin-2 (HBD-2) and chemokine receptor 6 (CCR6) expressing cell (Langerhans cell, helper T cell and suppressor T cell) antibodies, (2) by reverse transcription-polymerase chain reaction (RT-PCR) to determine the expression of GM-CSF and HBD-2 mRNA and (3) by gas chromatography to evaluate the composition of fatty acids (16:0, 18:2, 20:4) in the cell membranes of the keratinocytes. RESULTS: 1. Immunohistochemical staining indicated that HBD-2 and GM-CSF expression were higher in RC than in FC. 2. The same results were obtained from the RT-PCR analysis. 3. The % composition of palmitic acid (16:0) was significantly higher in the RC-lining keratinocytes (38.62±5.86%) and in the FC-lining keratinocytes (30.37±1.38%) than in the normal gingiva (23.00±1.40%). The % composition of essential fatty acids (18:2+20:4) was significantly higher in the FC-lining keratinocytes (26.20±3.55%) than in the RC-lining keratinocytes (20.50±8.17%). CONCLUSION: The present study demonstrated definite cytobiological evidence of the differences between RC and FC.

Cell synthesis, proliferation and apoptosis in human dental periapical lesions analysed by in situ hybridisation and immunohistochemistry.

OBJECTIVE: The role of structural and host defensive cells in periapical lesions has been assessed previously by morphometric and immunohistochemical studies. The aim of this study was to investigate the function of peri- apical cells by employing molecular techniques to estimate the cell synthetic activity, proliferation and apoptosis in these lesions. We specifically sought answers to the following questions. Which cells of the periapical lesions are quiescent or actively synthesising proteins? Do immune cells proliferate in this region in the same way as epithelial cells proliferate? Furthermore do cells in peri- apical lesions undergo apoptosis, and if so which cells exhibit this programmed cell death? MATERIALS: Twenty-five periapical tissue samples (15 granulomas and 10 radicular cysts) were assessed. Poly-adenosine (poly (A)) RNA and ribosomal RNA (rRNA) bearing cells in formalin-fixed/paraffin-embedded peri- apical tissues were analysed by in situ hybridization (ISH) using digoxigenin-labelled oligo d (T) and 28S rRNA probes respectively in order to estimate cell synthetic activity. Furthermore, S-phase proliferating and cycling cells were examined by ISH using a histone probe and Ki-67 immunostaining so as to assess cellular proliferation. Mononuclear cells were further differentiated by immunohistochemistry (IHC) as T cells, B cells and macrophages. Apoptotic cells were determined by in situ end-labelling methodology for detecting fragmented DNA. RESULTS: Poly (A) RNA (mostly messenger RNA) and 28S rRNA-expressing cells were detected in all samples. Plasma cells exhibited strongest staining for the two probes, with slight to moderate staining found in the epithelium, fibroblasts, macrophages, endothelial cells and lymphocytes, whereas almost all polymorphonuclear leucocytes (PMN) were negative for these probes. A few histone mRNA-expressing cells were detected in basal and suprabasal epithelial cells and mononuclear cells in 15/25 cases but their reactivity was weak. Ki-67 positive cells were found in all samples and their numbers were generally higher than histone mRNA positive cells. Apo- ptotic cells were detected in 23/25 cases and the majority of apoptotic cells were PMN which were engulfed by large cytophagocytic macrophages. CONCLUSION: This study indicates that in dental periapical lesions, apoptosis occurs predominantly in PMN. It is evident that most cells apart from PMN are exhibiting synthetic activity but only epithelial cells undergo proliferation which implies that immune cells must proliferate at distant lymph nodes and travel to the periapical lesion rather than proliferating within the lesion. These results suggest considerable advantages in estimating gene expression within cells in addition to the immunohistochemical detection of cells to determine cell activity at inflamed sites. Clearly, functional cell synthetic activity, resolution and clearance systems operate in peri- apical cystic and granuloma lesions.

Quantification of PCNA+ cells within odontogenic jaw cyst epithelium.

The aim of this study was to investigate the reactivity of the epithelial linings of the three major types of odontogenic cyst with a monoclonal antibody to proliferating cell nuclear antigen (PCNA; clone PC10). PCNA expression was studied in odontogenic cysts (n = 31) and normal oral epithelium (n = 10) using a biotin-streptavidin method on routinely processed paraffin sections. PCNA+ cells were counted manually and related to the length of basement membrane (mm) and the epithelial area (mm2) as determined by TV image analysis. The epithelial linings of odontogenic keratocysts (OKC; n = 11) contained the highest number of PCNA+ cells, most of which were located in the suprabasal layers. The mean value of PCNA+ cells in OKC linings (94.4 +/- 22.7 cells/mm) was similar to that of oral epithelia (80.8 +/- 20.6 cells/mm), but both were significantly higher than that of dentigerous (n = 10, 5.1 +/- 3.0 cells/mm) and radicular (n = 10, 11.0 +/- 4.1 cells/mm) cyst linings (P < 0.005). The epithelial distribution of PCNA+ cells differed between groups with the basal/suprabasal PCNA+ cell ratio in OKC linings (0.05 +/- 0.02) being significantly lower than that of normal oral epithelium (0.5 +/- 0.14), dentigerous (1.6 +/- 1.23) and radicular (1.9 +/- 1.09) cyst linings respectively (P < 0.005). These results demonstrate differences in PCNA expression between the epithelial linings of the major odontogenic cyst types, indicating differences in proliferative and differentiation processes within these lesions.

Localization of mRNA for inflammatory cytokines in radicular cyst tissue by in situ hybridization, and induction of inflammatory cytokines by human gingival fibroblasts in response to radicular cyst contents.

The expression of mRNA encoding the inflammatory cytokines interleukin-1alpha (IL-1alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor alpha(TNF-alpha) have been examined in radicular cysts by in situ hybridization. Furthermore, the biological activity of the contents of radicular cysts (RCC) has been assayed by adding extracts of RCC to cultured human gingival fibroblasts (HGFs) and analyzing the culture medium for the release of inflammatory cytokines. In the epithelial layer, keratinocytes expressed all cytokine mRNAs examined at various levels. Basal layer cells expressed mRNA for each cytokine. In the subepithelial granulation tissue of the cysts, fibroblasts and macrophages expressed mRNA for IL-6, IL-8, IL-1beta and TNF-alpha mRNA at varying levels; especially clear expression of TNF-alpha and IL-1beta mRNA was detected on macrophages. The infiltrating lymphoid cells, largely composed of T cells and plasma cells, expressed these cytokine mRNAs, especially those encoding IL-6 and IL-8, at various levels. In vitro analysis indicated dose-dependent release of both IL-6 and IL-8 by HGFs in response to RCC. After heating to 100 degrees C for 10 min, RCC almost completely failed to stimulate IL-6 release from HGFs. Furthermore, anti-IL-1beta antibody (neutralization test) did not prevent the stimulation of IL-6 release by RCC. Significant amounts of IL-6 and IL-8 were detected in RCC in two cases, and a trace amount of IL-1beta was detected in one case. This study demonstrated the wide expression of mRNA encoding inflammatory cytokines in radicular cyst tissues, and RCC itself was capable of stimulating IL-6 and IL-8 production from HGFs.

p53 expression in odontogenic keratocyst epithelium.

The expression of p53 protein was studied in odontogenic keratocysts (OKC, 11 solitary, 5 recurrent and 6 NBCCS cysts), radicular (RC, n = 5) and dentigerous (DC, n = 5) cysts, using a panel of antibodies to p53 (clone BP53-12, clone 1801 and polyclonal CM1) and a sensitive biotin-streptavidin method on paraffin embedded sections. Of the three antibodies tested, clone BP53-12 gave the most intense and consistent nuclear staining pattern. Clone 1801 and polyclonal CM1 stained only 38% and 71% OKC linings, respectively, but not RC and DC linings. However, BP53-12+ cells were detected in the epithelial linings of all cyst types. Quantification of BP53-12+ cells was performed by manual counting and by relating cell number to unit length of basement membrane as determined by TV image analysis. BP53-12+ cell counts in solitary OKC linings (25.5 +/- 11.0 cells/mmBM) were significantly greater than those in DC (9.3 +/- 4.9 cells/mmBM, P < 0.01) and RC (6.7 +/- 2.6 cells/mmBM, P < 0.01) linings. The epithelial distribution of positive cells in OKC was predominantly suprabasal, which also varied from that of DC and RC linings (P < 0.005). There were no detectable differences in BP53-12 reactivity between the different subtypes of OKC (i.e., solitary, recurrent and NBCCS-associated OKC; P > 0.1). When data for the NBCCS-related OKC group were excluded, there was a significant correlation (r = 0.55, P < 0.01) between p53 and Ki67 labelling. To detect the presence of p53 gene mutations, genomic DNA, extracted from paraffin sections of OKC (4 solitary, 2 recurrent and 4 NBCCS cysts), RC (n = 3) and normal oral mucosa (n = 1), was subjected to a combination of polymerase chain reaction and single-stranded conformation polymorphism (PCR-SSCP) analysis for exons 5-10 of the p53 gene. Exon 4 was not analysed because of compromised DNA quality. No abnormality in banding patterns was found and all samples gave results similar to DNA from known, sequenced, normal p53 gene controls. Absence of p53 mutations within exons 5-9 was confirmed by the direct sequencing of 2 fresh frozen OKC samples (1 solitary and 1 NBCCS cyst). These results suggest that overexpression of p53 protein in OKC epithelium, detected by immunocytochemistry, is not reflected by alteration of the p53 gene and presumably reflects overproduction and/or stabilisation of normal p53 protein.

PTCH gene altered in dentigerous cysts.

Motivated by the evidence that odontogenic keratocysts are associated with genetic alterations, we examined the possibility that development of other odontogenic cysts can be attributed to gene malfunctioning, in particular to the PTCH gene. Cyst epithelium was examined for polymorphism on chromosome 9q22.3, the region that contains the PTCH gene. Loss of heterozygosity (LOH) for the D9S287 marker and/or D9S180 marker was observed in about 50% of dentigerous cysts, whereas radicular cysts gave no indication of lesions in the PTCH region. As a more direct argument for PTCH involvement in cystic growth, we report evidence of PTCH expression in dentigerous cyst lining, which indicates malfunctioning of the relevant signaling pathway. While we found no reason to believe that PTCH should be associated with radicular cysts, other genes may be implicated in their development. We performed immunohistochemical comparisons of keratocysts, dentigerous and radicular cysts for the nonmetastatic marker Nm23. A graded response placed radicular cysts in between the other two types, suggesting a similar neoplastic character for their epithelial proliferation.

Features of odontogenesis and expression of cytokeratins and tenascin-C in three cases of extraosseous and intraosseous calcifying odontogenic cyst.

To characterize further the nature of calcifying odontogenic cyst (COC), we studied histologically and immunohistochemically an extraosseous and two intraosseous lesions. The extraosseous COC was in continuity with the stratified squamous epithelium of the alveolar mucosa. Immunostaining with monoclonal antibodies showed reactivity of both low- and high-molecular-weight cytokeratins, the degree of coexpression decreasing with the increasing morphological diversity of the cyst/tumour epithelium. Staining for the matrix glycoprotein tenascin-C was seen not only in the connective tissue, where its distribution patterns corresponded to the stage of hard tissue formation, but also in epithelial elements. The staining patterns were analogous to those described during normal tooth formation. Both the morphological characteristics and expression patterns of the various cytokeratin types and tenascin-C implied that COC represents a pathological counterpart of normal odontogenesis. In the case of the extraosseous COC, the correspondence could be traced back to early stages of tooth development.