Differentiation and regenerative capacities of human odontoma-derived mesenchymal cells

Ameloblastic Fibro-Odontoma: At the Crossroad Between "Developing Odontoma" and True Odontogenic Tumour

Ameloblastic fibro-odontoma (AFO) is a controversial, rare benign mixed odontogenic tumour that was re-defined as "developing odontoma" in the 2017 WHO classification arguing that once dental hard tissues form, it is programmed to transform into odontoma. However, AFO still remains unclear in terms of its nature. We aimed to analyze a large series of AFOs and compare it to a large series of odontomas (ODs) in an attempt to set cut-off diagnostic parameters between these entities and discuss latest updates on AFO histopathologic, clinical and molecular features. A total of 23 well-documented AFOs were analyzed versus 310 ODs focusing on the age of the patients and size of the lesions. For AFO, mean age was 9.4 ± 3.9 years (range 3-16 years) and mean size (greatest diameter) was 2.9 ± 1.5 cm (range 0.8-5.5 cm). For OD-mean age was 26.5 ± 15.6 years (range 3-81 years), mean size 1.9 ± 0.9 cm (range 1-5 cm). Receiver operating curve (ROC) showed that a cut-off age of 13.5 years and below [area under the curve (AUC) 0.902, 95%CI 0.859-0.945; p < 001; sensitivity 80%, specificity 87%] and a cut-off size of 2.1 cm and above are likely to be associated with AFO (AUC 0.7, 95%CI 0.574-0.827; p = 0.001; sensitivity 57%, specificity 77%). Thus, the combination of age and lesion size may be used to distinguish between lesions of a true neoplastic nature (i.e., AFO) and hamartomatous formation (i.e., OD). Further molecular and genetic specifications are needed to provide a better understanding on the pathogenesis of AFO in support of our suggestion and aid in an accurate classification of AFO.

Hypoxia enhances basal autophagy of epithelial-derived ameloblastoma cells

Ameloblastoma is a locally aggressive odontogenic tumor. Etiopathogenesis and locally aggressive growth properties of ameloblastoma can be attributed to a hypoxic microenvironment conducive to tumor cell survival. Epithelial-derived follicular ameloblastoma cells (EP-AMCs) display enhanced basal autophagy, but the interplay of hypoxia and autophagy in EP-AMCs survival and ameloblastoma recurrence is unclear. We evaluated differential expression of autophagic markers in primary and recurrent ameloblastomas and hypothesized that hypoxia-induced autophagy supports EP-AMC survival. Primary and recurrent ameloblastomas were comparatively assessed for expression levels of pan-cytokeratin, Vimentin, and autophagic markers SQSTM1/p62, LC3, and pS6. EP-AMCs compared with human odontoma-derived cells (HODCs) were subjected to severe hypoxia to determine the interplay of hypoxia and autophagic process in posthypoxia survival. Pan-cytokeratin and SQSTM1/p62 were expressed by both primary and recurrent ameloblastoma epithelial cells while the ameloblastoma connective tissues displayed weak reactivity to vimentin. Under hypoxia, EP-AMC expression levels of hypoxia-inducible factor (HIF)-1α, p62, and LC3 were increased while pS6 was decreased posthypoxia. The combined decrease in pS6 and enhanced LC3 in EP-AMCs under hypoxia indicate that EP-AMCs re-establish basal autophagy under hypoxia. Taken together, these suggest a possible role of LC3-associated phagocytosis (LAP) in ameloblastoma cell survival.

Biocompatibility between Silicon or Silicon Carbide surface and Neural Stem Cells

Silicon has been widely used as a material for microelectronic for more than 60 years, attracting considerable scientific interest as a promising tool for the manufacture of implantable medical devices in the context of neurodegenerative diseases. However, the use of such material involves responsibilities due to its toxicity, and researchers are pushing towards the generation of new classes of composite semiconductors, including the Silicon Carbide (3C-SiC). In the present work, we tested the biocompatibility of Silicon and 3C-SiC using an in vitro model of human neuronal stem cells derived from dental pulp (DP-NSCs) and mouse Olfactory Ensheathing Cells (OECs), a particular glial cell type showing stem cell characteristics. Specifically, we investigated the effects of 3C-SiC on neural cell morphology, viability and mitochondrial membrane potential. Data showed that both DP-NSCs and OECs, cultured on 3C-SiC, did not undergo consistent oxidative stress events and did not exhibit morphological modifications or adverse reactions in mitochondrial membrane potential. Our findings highlight the possibility to use Neural Stem Cells plated on 3C-SiC substrate as clinical tool for lesioned neural areas, paving the way for future perspectives in novel cell therapies for neuro-degenerated patients.

Ectodermal and ectomesenchymal marker expression in primary cell lines of complex and compound odontomas: a pilot study

BACKGROUND

Odontomas are odontogenic tumors with hamartoma features that are classified as compound or complex. Our objective was to characterize the proliferation of ectodermal and ectomesenchymal profile markers of primary cell cultures of complex and compound odontomas.

METHODS

Four samples of compound odontomas (OdCm) and three of complex odontomas (OdCx) were obtained from patients attending the Oral Pathology and Medicine Clinic of the Graduate Dental School, National Autonomous University of Mexico for primary culture generation. MTT, immunocytochemistry and RT-PCR assays of CD34, Sox2, Amel, Ambn, p21, EDAR, Msx1, Msx2, Pax9, RUNX2, BSP, OPN, Barx1 and GAPDH (control) were performed. Additionally, six paraffin-embedded odontomas were obtained for immunocytochemistry and RT-PCR validation assays. The mean and standard deviation were determined, and ANOVA and Kruskall-Wallis tests were performed.

RESULTS

Cultured compound odontoma exhibited higher proliferation, and an ectomesenchymal immunocytochemistry profile with predominant expression of Amel, BSP, Pax9, EDAR, Barx and Msx2; in complex cultured odontoma Sox2, CD34, RUNX2 and OPN predominated. Our statistical analysis showed a significant difference in PCR analysis (P<0.05) for OPN and CD34. Paraffin-embedded odontomas showed similar pattern with difference for NGFR and Sox2 for immunohistochemistry and EDAR, BARX1 and PAX9 for RT-PCR assays.

CONCLUSIONS

The results suggested heterogeneous behavior for both odontoma cell lines, because in compound odontomas predominant biomarkers are related to the enamel knot, late-stage odontogenesis and ectomesenchymal interactions; and in complex odontoma the significant expression of CD34 and OPN could be responsible for the difference behavior and mineralized amorphous structure.

Enhanced basal autophagy supports ameloblastoma-derived cell survival and reactivation

OBJECTIVES

Ameloblastoma is an aggressive odontogenic jaw neoplasm. Its unlimited growth confers high potential for malignant transformation and recurrence. It is unclear why ameloblastoma is highly recurrent despite surgical resection with a wide margin of normal tissue. While canonical autophagy can be used to degrade and eliminate damaged cellular components, it is also a protective mechanism that provides energy and vital metabolites for cell survival. We used ameloblastoma-derived cells to test the hypothesis that autophagic processes play a role in survival and reactivation of ameloblastoma.

METHODS

Primary epithelial (EP-AMCs) and mesenchymal (MS-AMCs) ameloblastoma-derived cells were established from tissue samples of solid multicystic ameloblastoma. Clonogenic capacity and basal autophagic capacity were assessed in ameloblastoma-derived cells relative to human odontoma-derived cells (HODCs) and maxilla-mesenchymal stem cells (MX-MSCs). Ability of ameloblastoma-derived cells to survive and form new ameloblastoma was assessed in mouse tumor xenografts.

RESULTS

EP-AMCs were highly clonogenic (p < 0.0001) and demonstrated enhanced basal levels of autophagic proteins microtubule-associated protein 1-light chain 3 (LC3) (p < 0.01), p62 (Sequestosome 1, SQSTM1) (p < 0.01), and the LC3-adapter, melanoregulin (MREG) (p < 0.05) relative to controls. EP-AMCs xenografts regenerated solid ameloblastoma-like tumor with histological features of columnar ameloblast-like cells, loose stellate reticulum-like cells and regions of cystic degeneration characteristic of follicular variant of solid multicystic ameloblastoma. The xenografts also displayed stromal epithelial invaginations strongly reactive to LC3 and p62 suggestive of epithelial-mesenchymal transition and neoplastic odontogenic epithelium.

CONCLUSIONS

EP-AMCs exhibit altered autophagic processes that can support survival and recurrence of post-surgical ameloblastoma cells.

Long-term culture of human odontoma-derived cells with a Rho kinase inhibitor

Because of cellular senescence/apoptosis, no effective culture systems are available to maintain replication of cells from odontogenic tumors especially for odontoma, and, thus, the ability to isolate human odontoma-derived cells (hODCs) for functional studies is needed. The current study was undertaken to develop an approach to isolate hODCs and fully characterize the cells in vitro. The hODCs were cultured successfully with a Rho-associated protein kinase inhibitor (Y-27632) for an extended period with stabilized lengths of the telomeres to sustain a similar phenotype/property as the primary tumoral cells. While the hODCs showed stable long-term expansion with expression of major dental epithelial markers including dentin sialophosphoprotein (DSPP) even in the three-dimensional microenvironment, they lack the specific markers for the characteristics of stem cells. Moreover, cells from dental pulp showed significant up-regulation of DSPP when co-cultured with the hODCs, while control fibroblasts with the hODCs did not. Taken together, we propose that the hODCs can be isolated and expanded over the long term with Y-27632 to investigate not only the development of the hODCs but also other types of benign human tumors.

Miracle cells for natural dentistry - A review

Stem cells are undifferentiated cells that can differentiate into specialized cells. Recently, enormous growth has been seen in the recognition of stem cell-based therapies, which have the potential to ameliorate the life of patients with conditions that span from Parkinson's disease to cardiac ischemia to bone or tooth loss. This research has produced new but unexplored possibilities in the regeneration of different organs and tissues. Presently, research is focused on the proficiency of stem cells and their utilization in dentistry, which is gaining interest. The tooth is nature's "esteem" for these precious stem cells and there are a number of these cells in permanent and primary teeth, as well as in the wisdom teeth. Dental stem cells are easy, convenient, and affordable to collect. They hold promise for a range of very potential therapeutic applications, such as in the treatment of cancer, spinal cord injury, brain damage, myocardial infarction, hearing loss, diabetes, wound healing, baldness, etc. Since these cells were used to regenerate damaged tissue in medical therapy successfully, it is possible that the dentist in future might use stem cell to regenerate lost or damaged dental and periodontal structures. This paper reviews the current concepts, characteristics of stem cells in regeneration, and its subsequent uses in dentistry.

Different Tissue-Derived Stem Cells: A Comparison of Neural Differentiation Capability

BACKGROUND

Stem cells are capable of self-renewal and differentiation into a wide range of cell types with multiple clinical and therapeutic applications. Stem cells are providing hope for many diseases that currently lack effective therapeutic methods, including strokes, Huntington's disease, Alzheimer's and Parkinson's disease. However, the paucity of suitable cell types for cell replacement therapy in patients suffering from neurological disorders has hampered the development of this promising therapeutic approach.

AIM

The innovative aspect of this study has been to evaluate the neural differentiation capability of different tissue-derived stem cells coming from different tissue sources such as bone marrow, umbilical cord blood, human endometrium and amniotic fluid, cultured under the same supplemented media neuro-transcription factor conditions, testing the expression of neural markers such as GFAP, Nestin and Neurofilaments using the immunofluorescence staining assay and some typical clusters of differentiation such as CD34, CD90, CD105 and CD133 by using the cytofluorimetric test assay.

RESULTS

Amniotic fluid derived stem cells showed a more primitive phenotype compared to the differentiating potential demonstrated by the other stem cell sources, representing a realistic possibility in the field of regenerative cell therapy suitable for neurodegenerative diseases.

Comparative study of LHX8 expression between odontoma and dental tissue-derived stem cells

BACKGROUND

LHX8 (LIM-homeobox gene 8) is known as an important regulating factor in tooth morphogenesis. Odontoma is a mixed odontogenic tumor where epithelium and mesenchyme differentiated together, resulting in anomalous tooth structures. In this study, gene and protein expressions of LHX8 were analyzed in human odontoma-derived mesenchymal cells (HODC) compared to adult dental mesenchymal stem cells (aDSC), as well as morphological and histological characteristics of odontoma were analyzed.

METHODS

aDSCs were isolated from normal teeth, and HODCs were isolated from surgically removed odontoma mass. Morphological and histological evaluations were performed to compare between compound odontomas and normal premolars. RT-PCR and real-time PCR were performed to identify LHX8 mRNA expression in the HODCs and aDSCs. LHX8 protein expression levels were observed by immunoblotting and immunofluorescent staining.

RESULTS

The compound odontoma was composed of multiple tooth-like structures, which contained disorganized but recognizable enamel matrix, dentin, pulp, and cementum. LHX8 mRNA and LHX8 protein expressions were all higher in HODCs compared to those in aDSCs examined by RT-PCR, immunoblot, and immunofluorescent staining. Especially, real-time PCR showed 2.77-fold higher LHX8 expression in HODCs than in normal periodontal ligament stem cells (PDLSCs), while alveolar bone marrow stem cells (ABMSCs) expressed 0.12-fold LHX8 than PDLSCs.

CONCLUSIONS

Based on these observations, LHX8 might play an important role in odontoma formation. This is the first report regarding the comparison of LHX8 expression between HODC and normal aDSCs and its overexpression in human samples. The specific mechanism of LHX8 in odontoma morphogenesis awaits further study.

beta-Catenin initiates tooth neogenesis in adult rodent incisors

beta-Catenin signaling is required for embryonic tooth morphogenesis and promotes continuous tooth development when activated in embryos. To determine whether activation of this pathway in the adult oral cavity could promote tooth development, we induced mutation of epithelial beta-catenin to a stabilized form in adult mice. This caused increased proliferation of the incisor tooth cervical loop, outpouching of incisor epithelium, abnormal morphology of the epithelial-mesenchymal junction, and enhanced expression of genes associated with embryonic tooth development. Ectopic dental-like structures were formed from the incisor region following implantation into immunodeficient mice. Thus, forced activation of beta-catenin signaling can initiate an embryonic-like program of tooth development in adult rodent incisor teeth.