EphrinB2 Stabilizes Vascularlike Structures Generated by Endothelial Cells and Stem Cells from Apical Papilla.

INTRODUCTION: This study aimed to investigate the roles of ephrinB2 in stabilizing vascularlike structures generated by stem cells from apical papilla (SCAPs) and human umbilical vein endothelial cells (HUVECs). METHODS: HUVECs were seeded alone or with SCAPs concurrently or 12 hours later. Angiogenesis and ephrinB2 phosphorylation were assayed at different time points. Additionally, ephrinB2 expression in SCAPs and HUVECs was silenced with small interfering RNA, and vascularlike structure formation within coculture was assessed; 1 × 10(5) HUVECs were seeded in transwell inserts, and 6 × 10(5) SCAPs were plated in lower wells with or without ephrinB2-Fc. Migratory cells were stained and counted. Delayed addition of ephrinB2-Fc to the coculture of HUVECs and SCAPs was performed to evaluate the role of ephrinB2 on the stabilization of vascularlike structures. RESULTS: Concurrent coculture of SCAPs and HUVECs yielded significantly longer tubule lengths at 4, 8, and 12 hours (P < .05). Delayed addition of SCAPs to coculture with HUVECs resulted in vascularlike structures persisting longer than the HUVEC monoculture. Western blot confirmed that ephrinB2 phosphorylation was initiated at 0.5 hours of coculture and peaked at 1 hour. Silencing ephrinB2 expression in SCAPs and HUVECs resulted in the absence of vascularlike structures. Enhanced migration of HUVECs by SCAPs could be inhibited by ephrinB2-Fc. When ephrinB2-Fc was added at 3 hours of coculture, the vascularlike structures were stabilized for more than 12 hours as compared with 9 hours in the control group. CONCLUSIONS: EphrinB2 plays an important role in the stabilization of vascularlike structures generated by HUVECs and SCAPs.

Long-term follow-ups of revascularized immature necrotic teeth: three case reports.

Revascularization of immature necrotic teeth is a reliable treatment alternative to conventional apexogenesis or apexification. In case 1, a 12-year-old boy had his necrotic, immature mandibular left second premolar treated with a revascularization technique. At a24-month follow-up, periapical radiolucency had disappeared and thickening of the root wall was observed. In cases 2 and 3, a10-year-old boy had his necrotic, immature, bilateral mandibular second premolars treated with the same modality. At 48-month(in case 2) and 42-month (in case 3) follow-ups, loss of periapical radiolucencies and increases in the root wall thickness were also observed.

Differentiation potential of dental papilla, dental pulp, and apical papilla progenitor cells.

INTRODUCTION: Regenerative endodontic procedures use the differentiation potential of embryonic and adult pulp progenitor cell populations to reconstitute dental structures. METHODS: An in-depth search of the literature was accomplished to review biologic knowledge from basic research on tooth morphogenesis and differentiation, root development, dentin-pulp regeneration, pulp revascularization and apexification, experimental and clinical studies on the dentinogenic differentiation potential of progenitor cells in the embryonic dental papilla, dental pulp, and associated mesenchymal tissues of the developing root. RESULTS: Odontogenic potential is determined during early tooth morphogenesis in the odontogenic mesenchyme. Progenitor cells from the odontogenic mesenchyme give rise to primary dentin-forming cells (odontoblasts) in the presence of stage-specific enamel epithelium and/or basement membrane and tertiary dentin-forming cells (odontoblast-like cells) in experimental conditions. The specificity of odontogenic mesenchymal cells to form tertiary dentin might be related to the repertoire of signaling pathways operated by the temporospatial pattern of epithelial-mesenchymal interactions during tooth formation. Dental papilla cells isolated from tooth germs before the onset of odontoblast differentiation have not shown any competence to become odontoblasts in the absence of enamel epithelium. On the other hand, the specificity of progenitor cells in the mesenchymal cell populations of the developing root apex remains to be determined. CONCLUSIONS: It seems evident that the dental pulp might be only used as a source of progenitor cells with dentinogenic competence for the regeneration of the dentin-pulp complex. The nature of dental or apical papilla progenitor cells in terms of their specificity for dentin regeneration has to be first characterized.

Modifications of interdental papilla microcirculation: a possible cause of periodontal disease in Hashimoto's thyroiditis?

BACKGROUND: Hypothyroidism is defined by a decrease in thyroid hormone production and thyroid gland function. The aim of the present research has been to evaluate the morphologic interdental papilla microcirculation of patients suffering from Hashimoto thyroiditis (HT) and to evaluate a possible correlation with the associated periodontal disease. METHODS: Fifteen healthy subjects and 15 patients suffering from HT were examined. The patients who showed conditions known to compromise microcirculation, such as diabetes, hypertension and pharmacological treatments, were not included in the group of healthy patients. All patients were non-smokers. Gingival capillaroscopy was used to investigate the characteristics of microcirculation. Visibility, course, tortuosity, the average caliber of the capillary loops and the number of visible capillary loops per square millimeter were evaluated for each patient. RESULTS: An interdental papilla vascular modification results in HT. In patients suffering from HT, it was possible to observe a reduced caliber of capillaries, as well as a greater number and tortuosity of capillary loops. CONCLUSIONS: This study shows that capillary alterations in patients suffering from HT occur in gingival microcirculation.

Association between vascular endothelial growth factor (VEGF) expression and tumor angiogenesis in ameloblastomas.

BACKGROUND: Expression of vascular endothelial growth factor (VEGF), a major angiogenic factor, and microvessel density (MVD), assessed by the use of anti-CD34 antibody, were immunohistochemically examined in benign and malignant ameloblastomas, as well as tooth germs, to clarify the possible role of angiogenesis in epithelial odontogenic tumors. METHODS: Specimens of 5 tooth germs, 35 benign ameloblastomas and 5 malignant ameloblastomas were examined by immunohistochemistry using anti-VEGF and CD34 monoclonal antibodies. RESULTS: Immunoreactivity for VEGF was detected in both normal and neoplastic odontogenic epithelial cells, and weakly in microvessels near odontogenic epithelial cells, suggesting that this angiogenic factor acts on endothelial cells via a paracrine mechanism in odontogenic tissues. Both benign and malignant ameloblastomas showed elevated VEGF expression as compared to tooth germs. VEGF expression was low in keratinizing cells in acanthomatous ameloblastomas and granular cells in granular cell ameloblastomas, and acanthomatous ameloblastomas showed the lowest VEGF reactivity among the subtypes of ameloblastomas. MVD in both benign and malignant ameloblastomas was higher than that in tooth germs, indicating increased demands for blood in the neoplastic tissues. CD34-positive microvessels in follicular ameloblastomas were numerous and small, whereas those in plexiform ameloblastomas were scattered and dilated. MVD tended to depend on VEGF expression levels in both benign and malignant ameloblastomas. CONCLUSIONS: VEGF was considered to be an important mediator of angiogenesis in these epithelial odontogenic tumors, and up-regulation of VEGF might be associated with neoplastic or malignant changes of odontogenic epithelial cells.

Immunohistochemical and biochemical analysis of laminin in neonatal rat first molars.

Rabbit polyclonal antibody against mouse EHS laminin was used to investigate the distribution and composition of laminin in the rat first molar tooth germ. Immunohistochemical analysis showed that laminin is expressed in the inner and outer epithelia of the enamel organ and in small blood vessels in the dental papilla and strellate reticulum. Immunoblots revealed that tooth germ laminin differs from EHS laminin. Tooth germ laminin contains beta chains, while the alpha 1 chain is substituted by a 300-kDa chain. Two-dimensional electrophoresis analysis of tooth germ extract showed that beta chains appeared as four spots with approximate pI values of 6.6, 7.5, 7.8 and 8.5. These results indicate that more than-one type of laminin isoform is present in the first molar tooth germ. Additionally, we have shown that despite the early degradation of tooth germ basement membrane, the laminin molecule is still intact at the time of birth.

Microcirculation of human fetal tooth buds: a SEM study of corrosion casts.

The microcirculation of tooth buds at the bell stage obtained from 5-month-old human fetuses was studied using corrosion casting and scanning electron microscopy. Each tooth bud has two independent vascular networks: one of the enamel organ and one of the dental papilla. Both systems are supplied by vertical branches of the inferior alveolar artery. The vascular bed of the enamel organ consists of capillaries relatively uniform in shape, forming a moderately dense network with irregular meshes. In contrast, the vasculature of dental papilla is extremely dense and its vessels show a sinusoidal character and signs of a vivid angiogenesis. The cast surfaces of capillaries in both vascular systems show the presence of tiny blebs probably representing extravasations of the casting medium through endothelial fenestrations.

Presence of multinucleate cells in the papillary layer of the Macaca fuscata enamel organ.

The enamel organ of Macaca fuscata from post-secretory transition to the early maturation stage of was investigated by means of light and electron microscopy. Unusual, large multinucleated cells were observed in the papillary layer. These cells contained organelles characteristic of the maturation stage ameloblast and often extended to the enamel surface, suggesting a possible origin from the ameloblast layer.

A scanning electron microscope study of vascular development in the dental papilla of prenatal rat molars.

Prenatal development of the vascular supply to the dental papilla was studied in the maxillary first molar teeth of rats from 18.5 to 22.0 days gestation, using the vascular casting/scanning electron microscope method. Five pulp horns developed in order, central, distal, mesial, disto-lingual and mesio-lingual with the development of the dental papilla. The first vessels that invaded each pulp horn were slightly depressed and formed an irregular network. The newly developed blood vessels were found to grow by sprouting and loop formation. After the invasion, blood vessels at the top of the horn became wider and then diminished in size to form a dense vascular network. The growth of the blood vessels in the latter stages is thought to take place mainly at the tops of the horns, and it is suggested that narrower capillaries arise from wide vessels. A dense and flattened vascular network consisting of thin blood vessels was formed when mesenchymal cells were beginning to differentiate into odontoblasts. The increase in density is thought to correlate with the differentiation of odontoblasts.