Takeshi Mitsuyasu

Immunohistochemical evaluation of PCNA and Ki-67 in ameloblastoma

Thirty-two ameloblastoma tissues were immunohistochemically studied using monoclonal anti-proliferating cell nuclear antigen (PCNA) and anti-Ki-67 antibodies. Positive cells were evaluated and analyzed in relation to the WHO classification, cytological pattern of the outer layer cell, clinical appearance, tumor location, radiographic appearance and patients age. In regard to the cytological pattern of the outer layer cells, the basal cell type had significantly higher PCNA and Ki-67 (P<0.05) labeling indices than the cuboidal cell type. The solid type had significantly higher PCNA and Ki-67 (P<0.05) labeling indices than the cystic and the mixed type. The labeling index of the younger patient was found to be the lowest, the middle age was in the middle and the older patient was the highest. These results indicated that the proliferating activities of ameloblastomas are quite variable, and the evaluations of Ki-67 and PCNA seem to be good indicators to assess the proliferating activity of each type of ameloblastomas.

Two relatively distinct patterns of ameloblastoma: an anti‐apoptotic proliferating site in the outer layer (periphery) and a pro‐apoptotic differentiating site in the inner layer (centre)

Two relatively distinct patterns of ameloblastoma: an anti‐apoptotic proliferating site in the outer layer (periphery) and a pro‐apoptotic differentiating site in the inner layer (centre)

Epithelial stem cells in teeth

Abstract Many tissues and organs maintain a process known as homeostasis, in which cells are replenished as they die as a result of apoptosis or injury. The continuously growing mouse incisors are an excellent model for studying the molecular mechanisms of cell homeostasis, renewal, and repair. We elucidated these mechanisms in mouse incisors by detecting adult stem cells and analyzing the stem cell lineage by bromodeoxyuridine (BrdU) labeling analysis. The stem cells divide slowly, giving rise to a daughter cell that remains in the cervical loop and a second daughter cell that enters the zone of rapidly dividing inner enamel epithelial cells (transit-amplifying cell population). During subsequent rounds of cell division, the latter cells move toward the incisal end and differentiate into ameloblasts that form the enamel matrix. Recent evidence from gene knockout mice suggests that fibroblast growth factor (Fgf10) plays an important role in the formation and maintenance of stem cells in the development of mouse incisors. The role of dental stem cells in odontogenic tumors is discussed.

Telomerase activity in oral and maxillofacial tumors

Telomerase activity was measured in biopsy specimens as well as surgically resected tissues of 39 oral squamous cell carcinomas (SCCs), 22 oral leukoplakias, 13 normal oral mucosas, 12 malignant salivary gland tumors, 10 benign salivary tumors and five normal salivary gland tissues adjacent to tumors using a polymerase chain reaction (PCR)-based telomerase assay. Telomerase activity was detectable in 38.5% (5/13) of normal oral mucosa samples, 54.5% (12/22) of leukoplakia samples, 82.1% (32/39) of oral SCC samples, 83.3% (10/12) of malignant salivary gland tumor samples and 0% (0/10, 0/5) of benign salivary gland tumor and normal salivary gland samples. High-level enzyme activities were seen in 20% (3/15) of mild dysplasia specimens, 50% (2/4) of moderate-severe dysplasia specimens, 48.7% (19/39) of oral SCC tissue specimens, and no high activity was seen in the normal mucosa and hyperkeratosis specimens (P for trend, <0.001). We also analyzed the proliferative activity of dysplastic leukoplakia, oral SCC, and salivary gland tumor specimens using Ki-67 immunohistochemistry. The Ki-67 labeling indices (LI) were significantly higher in dysplastic leukoplakia and oral SCC with high telomerase activity than in dysplastic leukoplakias and oral SCC with low and negative telomerase activity (P<0.01 and P<0.05). These results indicate that telomerase activity has some correlation with the progression of multistep oral carcinogenesis with the cellular proliferation, and also indicate that telomerase may be a specific marker used to distinguish malignant salivary gland tumors from their benign counterparts.

Fibroblast growth factors 7 and 10 are involved in ameloblastoma proliferation via the mitogen-activated protein kinase pathway.

Ameloblastoma is an epithelial benign tumor of the odontogenic apparatus and its growth mechanisms are not well understood. Fibroblast growth factor (FGF) 3, FGF7 and FGF10, which are expressed by the neural crest-derived ectomesenchymal cells, induce the proliferation of odontogenic epithelial cells during tooth development. Therefore, we examined the expression and function of these FGFs in ameloblastoma. We examined 32 cases of ameloblastoma as well as AM-1 cells (an ameloblastoma cell line) and studied the expression of FGF3, FGF7, FGF10 and their specific receptors, namely, FGF receptor (FGFR) 1 and FGFR2. Proliferation, mitogen-activated protein kinase (MAPK) signaling and PI3K signaling were examined in AM-1 cells after the addition of FGF7, FGF10 and these neutralizing antibodies. The expression of FGF7, FGF10, FGFR1 and FGFR2 was detected in ameloblastoma cells and AM-1 cells, while that of FGF3 was not. FGF7 and FGF10 stimulated AM-1 cell proliferation and phosphorylation of p44/42 MAPK. However, Akt was not phosphorylated. Blocking the p44/42 MAPK pathway by using a specific mitogen-activated protein/extracellular signal-regulated kinase (MEK) inhibitor (U0126) completely neutralized the effects of FGF7 and FGF10 on AM-1 cell proliferation. However, Anti FGF7 and FGF10 neutralizing antibodies did not decrease cell proliferation and MAPK phosphorylation of AM-1 cells. These results suggested that FGF7 and FGF10 are involved in the proliferation of ameloblastoma cells through the MAPK pathway.

Anti-apoptotic role of the sonic hedgehog signaling pathway in the proliferation of ameloblastoma

Sonic hedgehog (SHH) signaling pathway is crucial to growth and patterning during organogenesis. Aberrant activation of the SHH signaling pathway can result in tumor formation. We examined the expression of SHH signaling molecules and investigated the involvement of the SHH pathway in the proliferation of ameloblastoma, the most common benign tumor of the jaws. We used immunohistochemistry on ameloblastoma specimens and immunocytochemistry and reverse transcription-PCR on the ameloblastoma cell line AM-1. We also used the inhibitors of SHH signaling, SHH neutralizing antibody and cyclopamine, to assess the effects of SHH on the proliferation of AM-1 cells. We detected expression of SHH, patched, GLI1, GLI2 and GLI3 in the ameloblastoma specimens and AM-1 cells. The proliferation of these cells was significantly inhibited in the presence of SHH neutralizing antibody or cyclopamine; this was confirmed by BrdU incorporation assays. Furthermore, in the presence of SHH neutralizing antibody, nuclear translocation of GLI1 and GLI2 was abolished, apoptosis was induced, BCL-2 expression decreased and BAX expression increased. Our results suggest that the SHH signaling pathway is constitutively active in ameloblastoma and plays an anti-apoptotic role in the proliferation of ameloblastoma cells through autocrine loop stimulation.

An Anti-apoptotic Role of NF-κB in TNFα-induced Apoptosis in an Ameloblastoma Cell Line

Abstract Nuclear factor-κB (NF-κB) is involved in the promotion of cell survival in a variety of cell types. The present study focused on the role of NF-κB in TNFα-induced apoptosis in an ameloblastoma. Immunohistochemical staining revealed p65 NF-κB protein to be expressed in ameloblastoma tissues. Furthermore, immunoblotting and immunocytochemistry analyses showed that the stimulation of TNFα in an ameloblastoma cell line (AM-1) induced p65 NF-κB translocation from the cytoplasm to the nucleus, indicating NF-κB activation. These findings were confirmed by an NF-κB luciferase reporter assay, which detected enhanced NF-κB transcription activity of AM-1 cells by TNFα stimulation. Moreover, pretreatment with SN50, a nuclear translocation inhibitor, prior to TNFα stimulation, effectively inhibited TNFα-induced NF-κB activation in AM-1 cells. In order to reveal the role of NF-κB activation during TNFα-induced apoptosis in AM-1 cells, an apoptosis assay was performed, and showed that the potential of TNFα in inducing apoptosis in AM-1 cells was significantly elevated by inhibiting the NF-κB activation. These results suggest that NF-κB plays an anti-apoptotic role in TNFα-induced apoptosis in AM-1 cells.

Upward advancement of the nasolabial components at unilateral cleft lip repair prevents postoperative long lip

Objective To prevent the occurrence of postoperative long lip, longitudinal postoperative changes in nasolabial forms of patients with unilateral cleft lip who underwent primary lip repair with or without upward advancement of the nasolabial components were compared. Patients Forty-three subjects (24 unilateral cleft lip and palate [UCLP] and 19 unilateral cleft lip solely, and cleft lip and alveolus [UCL/UCLA]) who underwent primary lip repair with upward advancement of the nasolabial components (NA group) and 30 subjects (16 UCLP and 14 UCL/UCLA) without upward advancement (LA group) were enrolled. Outcome Measures Postoperative photos taken at 1 and 6 months and at 1, 2, and 3 years were used for measuring the heights of the nasal alar base (NBH), the columellar base (CBH), Cupids peak (CPH), and the upper lip (ULH). The ratios of these measurements between the affected and unaffected sides were calculated in both groups. Results In the LA group, the 3-year postoperative all-items ratios of UCLP were significantly larger than those at 1 month postoperatively, demonstrating drooping of the nasolabial tissues in the affected side (all P < .01). Furthermore, the 3-year postoperative CPH and ULH ratio of UCL/UCLA was significantly larger than that at 1 month postoperatively, demonstrating the long lip (P < .01). In the NA group, the NBH, CBH, and CPH ratios of both UCLP and UCL/UCLA did not show significant differences between 1 month and 3 years postoperatively. Conclusion Upward advancement of the nasolabial components prevents postoperative long lip.

Surface vacuolar ATPase in ameloblastoma contributes to tumor invasion of the jaw bone

Ameloblastoma is the most common benign odontogenic tumor in Japan. It is believed that it expands in the jaw bone through peritumoral activation of osteoclasts by receptor activator of nuclear factor kappa-B ligand (RANKL) released from the ameloblastoma, as in bone metastases of cancer cells. However, the clinical features of ameloblastoma, including its growth rate and patterns of invasion, are quite different from those of bone metastasis of cancer cells, suggesting that different underlying mechanisms are involved. Therefore, in the present study, we examined the possible mechanisms underlying the invasive expansion of ameloblastoma in the jaw bone. Expression levels of RANKL assessed by western blotting were markedly lower in ameloblastoma (AM-1) cells than in highly metastatic oral squamous cell carcinoma (HSC-3) cells. Experiments coculturing mouse macrophages (RAW264.7) with AM-1 demonstrated low osteoclastogenic activity, as assessed by tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cell formation, probably because of low release of RANKL, whereas cocultures of RAW264.7 with HSC-3 cells exhibited very high osteoclastogenic activity. Thus, RANKL release from AM-1 appeared to be too low to generate osteoclasts. However, AM-1 cultured directly on calcium phosphate-coated plates formed resorption pits, and this was inhibited by application of bafilomycin A1. Furthermore, vacuolar-type H+-ATPase (V-ATPase) and H+/Cl- exchange transporter 7 (CLC-7) were detected on the surface of AM-1 cells by plasma membrane biotinylation and immunofluorescence analysis. Immunohistochemical analysis of clinical samples of ameloblastoma also showed plasma membrane-localized V-ATPase and CLC-7 in the epithelium of plexiform, follicular and basal cell types. The demineralization activity of AM-1 was only 1.7% of osteoclasts demineralization activity, and the growth rate was 20% of human normal skin keratinocytes and HSC-3 cells. These results suggest that the slow expansion of several typical types of ameloblastomas in jaw bone is attributable to its slow growth and low demineralization ability.

Perceptual and videofluoroscopic analyses of relation between backed articulation and velopharyngeal closure following cleft palate repair

Abstract Purpose Perceptual and videofluoroscopic (VF) analyses were performed to analyze velopharyngeal (VP) closure motions and tongue backing movement in subjects with postalveolar, palatal, and velar backed articulation (BA). Materials and methods For perceptual analysis, the timing of the appearance of BA and the VP closure level of 22 children with BA following palatal repair were compared to those of 17 subjects with normal articulation, 17 subjects with lateral articulation, and 11 subjects with glottal stop. For VF analysis, 16 subjects with BA and two healthy adult males as references were enrolled. On VF images, the proportions of the time required to complete VP closure and the duration of articulation (VPC/DA) were recorded and then analyzed based on the various degrees of tongue backing movement. Results The appearance of BA was recognized just after the acquisition of VP closure, and it was later than that of glottal stop and earlier than lateral articulation. On VF images, VP closure was achieved before tongue movement in healthy individuals, but after tongue movement in BA subjects. VPC/DA on articulation of both /ta/ and /sa/ were significantly smaller for healthy individuals than for BA subjects ( P P Conclusions BA may result from precedent tongue backing movement before the completion of VP closure, as a process that may assist the VP closure motion for articulation.