Determinants of Dental Pulp Stem Cell Heterogeneity.

INTRODUCTION: The aim of this review is to provide a narrative review on the determinants of dental pulp stem cell (DPSC) heterogeneity that may affect the regenerative properties of these cells. METHODS: PubMed, Scopus, and MEDLINE (Ovid) literature searches were done on human dental pulp stem cell heterogeneity. The focus was on human dental pulp stem cells with a primary focus on DPSC heterogeneity. RESULTS: DPSCs display significant heterogeneity as illustrated by the various subpopulations reported, including differences in proliferation and differentiation capabilities and the impact of various intrinsic and extrinsic factors. CONCLUSIONS: The lack of consistent and reliable results in the clinical setting may be due to the heterogeneous nature of DPSC populations. Standardization in isolation techniques and criteria to characterize DPSCs should lead to less variability in results reported and improve comparison of findings between studies. Single-cell RNA sequencing holds promise in elucidating DPSC heterogeneity and may contribute to the establishment of standardized techniques.

Side Population: Its Use in the Study of Cellular Heterogeneity and as a Potential Enrichment Tool for Rare Cell Populations.

There is still much to learn about the cells used for cell- and gene-based therapies in the clinical setting. Stem cells are found in virtually all tissues in the human body. As a result, cells isolated from these tissues are a heterogeneous population consisting of various subpopulations including stem cells. Several strategies have been used to isolate and define the subpopulations that constitute these heterogeneous populations, one of which is the side population (SP) assay. SP cells are identified by their ability to efflux a fluorescent dye at a rate that is greater than the main cell population. This elevated rate of dye efflux has been attributed to the expression of members of the ATP-binding cassette (ABC) transporter protein family. SP cells have been identified in various tissues. In this review, we discuss the research to date on SP cells, focussing on SP cells identified in haematopoietic stem cells, adipose-derived stromal cells, and dental pulp.

Cancer Stem Cells in Head and Neck Carcinomas: Identification and Possible Therapeutic Implications.

The recurrence and/or lack of response of certain tumors to radio- and chemotherapy has been attributed to a small subpopulation of cells termed cancer stem cells (CSCs). CSCs have been identified in many tumors (including solid and hematological tumors). CSCs are characterized by their capacity for self-renewal, their ability to introduce heterogeneity within a tumor mass and its metastases, genomic instability, and their insensitivity to both radiation and chemotherapy. The latter highlights the clinical importance of studying this subpopulation since their resistance to traditional treatments may lead to metastatic disease and/or tumor relapse. Head and neck squamous cell carcinomas (HNSCCs) are the sixth most common malignancy worldwide with the highest incidence occurring in East Asia and eastern and southern Africa. Several cellular subpopulations believed to have CSC properties have been isolated from HNSCCs, but at present, identification and characterization of CSCs remains an experimental challenge with no established or standardized protocols in place to confirm their identity. In this review we discuss current approaches to the study of CSCs with a focus on HNSCCs, particularly in the context of what this might mean from a therapeutic perspective.

Immunohistochemical expression of CD56 in dog (Canis familiaris) odontogenesis.

AIM: To investigate the expression of CD56 in dog odontogenesis in order to elucidate the expression found in ameloblastomas. MATERIALS AND METHODS: Immunohistochemical analysis of CD56 expression of developing dog teeth in the bud, cap and bell stages including the remnants of the dental lamina. RESULTS: Weak CD56 expression was observed in the dental epithelium during the bud stage with intense staining of certain peripheral epithelial cells. Positive staining of epithelial cells was also observed in the cap stage with intense staining of the inner enamel epithelium at this stage. During the bell stage the staining was concentrated on the cervical loop areas. The dental papilla revealed positive staining throughout the cap and bell stages while the dental follicle stained intensely positive throughout all the phases examined. The dental lamina and Serres rests also stained positive for CD56. CONCLUSIONS: The expression of CD56 in dog odontogenic tissue varies according to the stage of tooth development. There is a positive correlation between the positive staining observed in ameloblastomas and their odontogenic cells of origin.