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Mesenchymal Stem Cells from Dental Tissues
Published in Vincenzo Guarino, Marco Antonio Alvarez-Pérez, Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Febe Carolina Vázquez Vázquez, Jael Adrián Vergara-Lope Núñez, Juan José Montesinos, Patricia González-Alva
In their study, Seo et al. (Seo et al. 2004) demonstrated that PDLSCs were similar to other MSCs regarding their expression of STRO-1/CD146, and suggested that PDLSCs might also be derived from a population of perivascular cells. Moreover, later works showed that PDLSCs’ differentiation could be promoted by Hertwig’s epithelial root sheath cells in vitro (Sonoyama et al. 2007). Besides, the lineages of differentiation for PDLSCs are cementoblast-like cells, adipocytes and fibroblasts that secrete collagen type I (Sedgley and Botero 2012).
Odontogenic Epithelium and its Residues
Published in Roger M. Browne, Investigative Pathology of the Odontogenic Cysts, 2019
During the later stages of crown formation, the development of the root begins. In the area of the cervical loop, the inner and outer enamel epithelium are continuous and with proliferation and downward growth of this bilaminar structure (Hertwig’s epithelial root sheath), the root is mapped out. This epithelial root sheath promotes the differentiation of root odontoblasts as well as being important in cementum formation. The inner epithelial layer of the root sheath is separated from the pulpal mesenchyme by a basement membrane that stains more strongly for fibronectin than the basement membrane on its enamel epithelial layer.62 Laminin and type IV collagen, however, appear to be more evenly distributed. Pulpal mesenchymal cells align themselves perpendicular to the inner basement membrane prior to differentiation into odontoblasts. A close relationship between the fibronectin and mesenchymal cell alignments along the inner basement membrane has been suggested.62,63 Thus, root and crown odontoblast differentiation appear to be similar processes although it has been reported64 that conversion of pre-dentin to dentin is faster in the root than crown analog of the mouse incisor. The inner cells of the epithelial root sheath do not differentiate into ameloblasts and after pre-dentin secretion, the basement membrane becomes discontinuous and these cells lose their cuboidal shape becoming progressively more flattened. The cells are thought to have a short secretory phase prior to fragmentation of the sheath65,70 giving rise to a matrix, which is thought to contribute to the intermediate cementum observed between dental cementum and Tomes’ granular layer in the tooth root. Similarities between intermediate cementum and the innermost, aprismatic layer of enamel have been reported,68,70 and it has been shown that the initial cementum exhibits immunoreactivity to enamel proteins,71,72 although this has not been confirmed.73 After tooth sheath fragmentation, the thin layer of matrix derived from it may be responsible for inducing cells of the dental follicle to differentiate into cementoblasts. Interestingly, cementum-like matrix has been observed on the enamel surface of teeth taken from 9-day-old mice in which the ameloblasts had been removed and the teeth re-inserted crown downwards into their bony crypts followed by transplantation in the subcutaneous tissue of hosts.74 The epithelial root sheath fragments persist in close proximity to the root surface as cell clusters in the periodontal ligament where they are known as the epithelial rests of Malassez.75
The dental manifestations and orthodontic implications of hypoparathyroidism in childhood
Published in Journal of Orthodontics, 2018
Amy Arora Gallacher, M. N. Pemberton, D. T. Waring
Previous case reports have reported a number of dental anomalies in patients with both hypoparathyroidism and pseudohypoparathyroidism occurring in childhood including hypodontia, microdontia, shortened and round roots, enamel hypoplasia, malformed root, enlarged pulp chambers, pulp calcifications and delayed tooth eruption (Greenburg et al. 1969; Nally 1970; Weltman et al. 2010; Kamarthi et al. 2013; Sirangarajan et al. 2014). It appears that these dental anomalies occur as a result of the low serum calcium that occurs as a result of the reduced PTH coinciding with dental development (Bronsky et al. 1958). Disturbances in mineralisation, alterations in the formation of the Hertwig epithelial root sheath, lack of differentiation of odontoblasts and disturbed resorptive processes (Jensen et al. 1981) have been proposed as mechanisms for these anomalies.
Dental stem cells for tooth regeneration: how far have we come and where next?
Published in Expert Opinion on Biological Therapy, 2023
At the beginning of tooth development in the first (mandibular) arch of an embryo the tooth germ consists of two tissues: the dental mesoderm, which originates from neural crest cells, and the dental ectoderm, which is part of the surface ectoderm [3,4]. These two types of cells are the origin of the tooth germ and make up the entire tooth [5]. However, during development these two dental cell types become three tissues, one derived from the ectoderm – enamel organ – and two from the mesoderm – dental papilla and dental follicle (dental sac) [6,7]. While the enamel organ is the source of ameloblasts and is heavily involved in tooth crown morphology, some dental epithelial cells become Hertwig’s epithelial root sheath cells involved in tooth root development [8]. The dental mesodermal tissues deliver stem cells for the development of the tooth root and the dental pulp/dentin complex [9]. Interestingly, both dental mesodermal tissues can be harvested from impacted wisdom teeth and their stem cells isolated and used for different applications [10]. In contrast, the enamel organ and most dental ectodermal cells are lost beforehand. Only epithelial rests of Malassez can be obtained for example from impacted wisdom teeth, but a significant number of dental ectodermal progenitor cells cannot be isolated from this source [11,12]. Moreover, these cells are not the genuine progenitors for ameloblasts and it remains nuclear whether they can be used as ectodermal tooth germ cells in whole tooth regeneration approaches, which is the most advanced goal in regenerative dentistry. This article first summarizes the state of the art in tooth engineering.
Dental stem cells in tooth regeneration and repair in the future
Published in Expert Opinion on Biological Therapy, 2018
Christian Morsczeck, Torsten E. Reichert
For the initiation of the tooth root development the Hertwig’s epithelial root sheath is formed as an extension of the enamel organ. This thin cell-sheath separates a second dental mesenchymal tooth-germ tissue from the dental mesenchymal pulp/dentin complex. This tooth germ tissue is known as the dental sac or the dent follicle and surrounds the tooth germ. The dental follicle is crucial both for tooth eruption and for the development of the tooth root [79,80]. It contains dental mesenchymal progenitor cells for the periodontium, which consists of the alveolar bone, the PDL, and the cementum. Moreover, this tissue contains also epithelial cells, which are derived from the epithelial cells of the Hertwig’s epithelial root sheath, which disappears during tooth root development [79]. The dental follicle is similar to the dental apical pad-like tissue and can be isolated from impacted human wisdom teeth. It contains multipotent ectomesenchymal stem cells that are known as dental follicle precursor cells, dental follicle stem cells, or dental follicle cells (DFCs). Human DFCs were initially isolated as plastic-adherent and clonogenic cells [81]. They have a DPSC-like morphology and also express typical markers of progenitor/stem cells such as NESTIN, NOTCH-1, CD44, CD105, and STRO-1 [81,82]. DFCs can be cultivated under serum-free cell culture conditions for an extended period of time and then behave like neural progenitor cells [83]. DFCs are multipotent stem cells, and especially the genuine precursor cells of periodontal tissue cells [81–85]. Even under in vitro condition, DFCs formed a robust connective tissue-like structure with many mineralized clusters after long-term cultures in osteogenic differentiation medium. Interestingly, this periodontium-like tissue occasionally had blood-vessel-like structures [81]. We suppose that DFCs should be considered for the treatment of periodontitis and/or for the reconstruction of a tooth attachment apparatus [86,87]. Tian and colleagues, for example, showed that rat DFCs formed a tooth root when seeded on scaffolds of a treated dentin matrix (TDM) and transplanted into alveolar fossa microenvironment [88]. Interestingly, this particular environment is necessary for the production of a tooth root, since DFCs do not form a tooth root after transplantation in skull and omental pockets [88]. Unfortunately, autologous TDM is rare as scaffolds and the use of xenogenic scaffolds, for example, porcine TDM, in combination with allogeneic DFCs is problematic, since this combination induces bone resorption [89]. DFCs are also considered for bone regeneration, because they support bone regeneration in critical size defect models of the calvaria of immunocompromised rats [86]. Here, compared to untreated animals, stem cells improved the process of bone regeneration. Therefore, DFCs as the genuine progenitors of alveolar osteoblasts are an attractive source for bone tissue engineering. We expect DFCs to be taken into account for dental stem cell-based therapies in the future.