Cell Rests Of Malassez Research Articles

Organoids from human tooth showing epithelial stemness phenotype and differentiation potential

Insight into human tooth epithelial stem cells and their biology is sparse. Tissue-derived organoid models typically replicate the tissue’s epithelial stem cell compartment. Here, we developed a first-in-time epithelial organoid model starting from human tooth. Dental follicle (DF) tissue, isolated from unerupted wisdom teeth, efficiently generated epithelial organoids that were long-term expandable. The organoids displayed a tooth epithelial stemness phenotype similar to the DF’s epithelial cell rests of Malassez (ERM), a compartment containing dental epithelial stem cells. Single-cell transcriptomics reinforced this organoid-ERM congruence, and uncovered novel, mouse-mirroring stem cell features. Exposure of the organoids to epidermal growth factor induced transient proliferation and eventual epithelial-mesenchymal transition, highly mimicking events taking place in the ERM in vivo. Moreover, the ERM stemness organoids were able to unfold an ameloblast differentiation process, further enhanced by transforming growth factor-β (TGFβ) and abrogated by TGFβ receptor inhibition, thereby reproducing TGFβ's known key position in amelogenesis. Interestingly, by creating a mesenchymal-epithelial composite organoid (assembloid) model, we demonstrated that the presence of dental mesenchymal cells (i.e. pulp stem cells) triggered ameloblast differentiation in the epithelial stem cells, thus replicating the known importance of mesenchyme-epithelium interaction in tooth development and amelogenesis. Also here, differentiation was abrogated by TGFβ receptor inhibition. Together, we developed novel organoid models empowering the exploration of human tooth epithelial stem cell biology and function as well as their interplay with dental mesenchyme, all at present only poorly defined in humans. Moreover, the new models may pave the way to future tooth-regenerative perspectives.

Analysis of the cells isolated from epithelial cell rests of Malassez through single-cell limiting dilution

The epithelial cell rests of Malassez (ERM) are essential in preventing ankylosis between the alveolar bone and the tooth (dentoalveolar ankylosis). Despite extensive research, the mechanism by which ERM cells suppress ankylosis remains uncertain; perhaps its varied population is to reason. Therefore, in this study, eighteen unique clones of ERM (CRUDE) were isolated using the single-cell limiting dilution and designated as ERM 1–18. qRT-PCR, ELISA, and western blot analyses revealed that ERM-2 and -3 had the highest and lowest amelogenin expression, respectively. Mineralization of human periodontal ligament fibroblasts (HPDLF) was reduced in vitro co-culture with CRUDE ERM, ERM-2, and -3 cells, but recovered when an anti-amelogenin antibody was introduced. Transplanted rat molars grown in ERM-2 cell supernatants produced substantially less bone than those cultured in other cell supernatants; inhibition was rescued when an anti-amelogenin antibody was added to the supernatants. Anti-Osterix antibody staining was used to confirm the development of new bones. In addition, next-generation sequencing (NGS) data were analysed to discover genes related to the distinct roles of CRUDE ERM, ERM-2, and ERM-3. According to this study, amelogenin produced by ERM cells helps to prevent dentoalveolar ankylosis and maintain periodontal ligament (PDL) space, depending on their clonal diversity.

Direct reprogramming of epithelial cell rests of malassez into mesenchymal-like cells by epigenetic agents

The DNA demethylating agent, 5-Azacytidine (5Aza), and histone deacetylase inhibitor, valproic acid (Vpa), can improve the reprogramming efficiencies of pluripotent cells. This study aimed to examine the roles of 5Aza and Vpa in the dedifferentiation of epithelial cell rests of Malassez (ERM) into stem-like cells. Additionally, the ability of stem-like cells to differentiate into mesenchymal cells was evaluated. ERM was cultured in embryonic stem cell medium (ESCM) with 1 µM of 5Aza, or 2 mM of Vpa, or a combination of 5Aza and Vpa. The cells stimulated with both 5Aza and Vpa were named as progenitor-dedifferentiated into stem-like cells (Pro-DSLCs). The Pro-DSLCs cultured in ESCM alone for another week were named as DSLCs. The stem cell markers were significantly higher in the DSLCs than the controls (no additions). The mRNA and protein levels of the endothelial, mesenchymal stem, and osteogenic cell markers were significantly higher in the Pro-DSLCs and DSLCs than the controls. The combination of a demethylating agent and a deacetylated inhibitor induced the dedifferentiation of ERM into DSLCs. The Pro-DSLCs derived from ERM can be directly reprogrammed into mesenchymal-like cells without dedifferentiation into stem-like cells. Isolated ERM treated with epigenetic agents may be used for periodontal regeneration.

Management of a nonvital discolored tooth associated with radicular cyst: A multidisciplinary approach

The radicular cyst arises from proliferated epithelial cell rests of malassez when they get stimulated by an inflammatory process originating from pulpal necrosis of a nonvital tooth. The associated tooth is usually asymptomatic and may result in swelling of the soft tissues and mobility of the teeth involved. The typical radiographic description of the lesion is a round or oval, well-circumscribed radiolucency involving the apex of the tooth. Radicular cysts can be managed either surgically or nonsurgically. The nonvital, discolored anterior tooth associated with the lesion is a common esthetic concern for patients. It can effect their self-confidence and employability. Discolored nonvital teeth are frequently compromised due to root canal treatment, previous trauma, or caries. Invasive treatment options like crowns or veneers further weaken the tooth structure. This case report presents the successful surgical management of a radicular cyst associated with a nonvital discolored anterior tooth. This will also include the technicalities involved in the inside/outside nonvital bleaching technique.

A Review of the Epithelial Cell Rests of Malassez on the Bicentennial of Their Description

The epithelial cell rests of Malassez (ERM) were first described in 1817, yet their significance has remained an enigma for more than 200 years. Given their embryological origins and persistence in adult periodontal tissue, recent research has investigated whether the ERM could be useful as stem cells to regenerate tissues lost as a consequence of periodontitis. The objective of this review is to describe results of studies that have vigorously investigated the functional capabilities of ERM, particularly with regard to periodontal ligament homeostasis and prevention of dentoalveolar ankylosis. The significance of the ERM relative to evolution of the dental attachment apparatus will be examined. The current status of use of ERM as stem cells for dental tissue engineering and in other applications will be reviewed.

Biology of teeth and implants: Host factors - pathology, regeneration, and the role of stem cells.

In chronic periodontitis and peri-implantitis, cells of the innate and adaptive immune systems are involved directly in the lesions within the tissues of the patient. Absence of a periodontal ligament around implants does not prevent a biologic process similar to that of periodontitis from affecting osseointegration. Our first focus is on factors in the biology of individuals that are responsible for the susceptibility of such individuals to chronic periodontitis and to peri-implantitis. Genetic factors are of significant importance in susceptibility to these diseases. Genetic factors of the host affect the composition of the oral microbiome in the same manner that they influence other microbiomes, such as those of the intestines and of the lungs. Our second focus is on the central role of stem cells in tissue regeneration, in the functioning of innate and adaptive immune systems, and in metabolism of bone. Epithelial cell rests of Malassez (ERM) are stem cells of epithelial origin that maintain the periodontal ligament as well as the cementum and alveolar bone associated with the ligament. The tissue niche within which ERM are found extends into the supracrestal areas of collagen fiber-containing tissues of the gingivae above the bony alveolar crest. Maintenance and regeneration of all periodontal tissues involves the activity of a variety of stem cells. The success of dental implants indicates that important groups of stem cells in the periodontium are active to enable that biologic success. Successful replantation of avulsed teeth and auto-transplantation of teeth is comparable to placing dental implants, and so must also involve periodontal stem cells. Biology of teeth and biology of implants represents the biology of the various stem cells that inhabit specialized niches within the periodontal tissues. Diverse biologic processes must function together successfully to maintain periodontal health. Osseointegration of dental implants does not involve formation of cementum or collagen fibers inserted into cementum - indicating that some stem cells are not active around dental implants or their niches are not available. Investigation of these similarities and differences between teeth and implants will help to develop a better understanding of the biology and physiologic functioning of the periodontium.

Comparison of components of odontogenic cyst fl uids: A review

The cystic lesions that affect the oral and maxillofacial region are predominantly odontogenic in origin. The odontogenic cell rests entangled within tissue of the jaws such as cell rests of Malassez, cell rests of serre, and enamel organ leads to its formation. The factors leading to the enlargement of these jaw cysts are increased the permeability of cyst wall, increased the protein content of the cyst fluid, and when the intracystic fluid pressure on the jaw bone is increased. This review is an attempt to analyze and compare the components of cystic fluids such as albumin, prealbumin, globulin, and total protein content among various odontogenic cysts.

Residual radicular cyst in primary molar extraction socket: An unusual clinical entity

Radicular cyst is a most common type of odontogenic cyst that develops mostly as sequel of untreated dental caries. It is classified as inflammatory type originated mostly from cell rests of Malassez. Radicular cyst arising from deciduous teeth is rare, accounting for just 0.3% to 5% of the total number. Residual kind of radicular cyst in deciduous teeth are still very sparse in literature. Most of the residual cysts are asymptomatic and are found only on routine radiographic examination. We are presenting an interesting and rare case of symptomatic residual radicular cyst of left primary first molar extraction socket with secondary infection in a 5-year-old child. Our aim is to emphasize on investigations, recognition, and treatment of such inflammatory residual radicular lesions associated with deciduous teeth, which has been an unreported clinical entity.

Non-Syndromic Multiple Keratocystic Odontogenic Tumor: A Rare Case Report and Review of Literature

Keratocystic Odontogenic tumor (KCOT) has been the topic of various researchers and is distinctive for its potentially aggressive behavior and tendency for multiplicity. It is anodontogenic tumorthat exhibits a hyper keratinized epithelial lining. The lesion originates from the cell-rests of the dental lamina rather than from the reduced enamel epithelium or the cell rests of Malassez. It constitutes for 3.11% of all odontogenic cysts. It often occurs as a solitary lesion at the angle of mandible and multiple lesions may occur in association with systemic changes. Here is a rare case report ofmultiple KCOTsassociated with an ovarian cyst in 30 years old female.

Apexification with Calcium Hydroxide: 27 Months Follow Up of a Case

Dental trauma is common in young patients with immature teeth. When necrosis of pulp follows in such a tooth, apexification of the root is the most recognized and accepted treatment of choice. Calcium hydroxide paste is the most popular material used to induce the apical hard tissue barrier which may be composed of different tissues. Hertwig’s epithelial root sheath and (or) its remnants, the cell rests of Malassez may contribute to the apical closure. In the presented case, careful multidisciplinary treatment approach helped to regain esthetic and function. After 27 months the tooth showed every sign of success. DOI: http://dx.doi.org/10.3329/medtoday.v25i1.16071 Medicine Today 2013 Vol.25(1): 42-45

The characteristics of epithelial cell rests of Malassez during tooth eruption of development mice

It has been demonstrated that Hertwig's epithelial root sheath (HERS) has an important role in root development, closely related to development of cementum epithelial rests of Malassez (ERM) as the residuum after HERS fragment, and is the exclusive epithelial structure in the mature periodontal ligament. Some studies reported that ERM may play a role in maintaining a stable environment of periodontal, and likely to be involved in regeneration of periodontal tissue, especially of cementum. However, the function of the ERM is not well understood. In this study, we observed the morphology and biological characteristics of ERM of the maxillary 1st molar with surrounding periodontal tissues of BALB/c mice during the period of tooth cusp erupted out of the gingiva to occlusion stability. Immunohistochemistry revealed ERM predominately located at the cervical and root furcation regions of the periodontal ligament. The number of ERM cells at the cervical and root furcation regions of the post-built occlusion stage decreased compared to pre-built occlusion stage and occlusion building stage. Transmission electron microscopy analysis showed that epithelial cell nuclei with typical features of apoptosis were observed at the post-built occlusion stage, and consistent with positive bodies labeled by TUNEL(terminal deoxy-transferase (TdT)-mediated dUTP-biotin nick end labeling), while proliferating cell nuclear antigen positive bodies mainly located at occlusion built stage. It suggests that ERM may regulate in alveolar bone remodeling in association with the periodontal ligament during tooth erupting to occlusion stability and may play important roles potentially in regeneration and homeostasis of the periodontal tissues.

Dental follicle cells and cementoblasts induce apoptosis of ameloblast‐lineage and Hertwig’s epithelial root sheath/epithelial rests of Malassez cells through the Fas–Fas ligand pathway

Hertwig's epithelial root sheath (HERS), epithelial rests of Malassez (ERM) cells, and reduced ameloblasts undergo apoptosis during tooth development. This study examined the effects of dental follicle cells and cementoblasts on the apoptosis of ameloblast-lineage and HERS/ERM cells derived from the enamel organ. We also elucidated the induction pathways and identified the apoptotic pathway involved in this process. Here, we showed terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling (TUNEL)-positive HERS cells and reduced ameloblasts near dental follicle cells during tooth development. Co-culturing ameloblast-lineage cell line (ALC) ameloblasts and HERS/ERM cells with either dental follicle cells or OCCM-30 cementoblasts markedly enhanced the apoptosis of ameloblasts and HERS/ERM cells compared with cells cultured alone. However, dental follicle cells and cementoblasts did not modulate the apoptotic responses of co-cultured non-odontogenic MCF10A or KB cells. When ameloblasts + HERS and cementoblasts + dental follicle cells were co-cultured, the expression of Fas ligand (FasL) increased in cementoblasts + dental follicle cells, while the expression of Fas increased in ameloblasts + HERS. Interestingly, recombinant FasL induced ameloblast apoptosis while the cementoblast-induced ameloblast apoptosis was suppressed by the Fas/FasL antagonist Kp7-6. These results suggest that during tooth development, dental follicle cells and cementoblasts induce apoptosis of ameloblast-lineage and HERS/ERM cells through the Fas-FasL pathway, but do not induce the apoptosis of non-odontogenic epithelial cells.

Capturing the Regenerative Potential of Periodontal Ligament Fibroblasts

The cell population within the periodontal ligament (PDL) tissue is remarkably heterogeneous1. Fibroblasts, a mixed population of cells, are the main cellular component of the PDL and the cell type most often studied for periodontal regeneration. Osteoblasts and osteoclasts are found on the bone side, while fibroblasts, macrophages, undifferentiated adult/mesenchymal stem cells, neural elements, and endothelial cells are found throughout the PDL. Epithelial rests of Malassez cells and cementoblasts are focused near the root surface. PDL tissue also includes loose connective tissue between dense fiber bundles that contain branches of the periodontal blood vessels and nerves2. The complexity of the PDL tissue, with its various cell types and cell progenitor components, explains the challenges involved in therapies to restore tissue following periodontal disease. Cementoblasts, osteoblasts, and endothelial cells must migrate, differentiate, and coordinately interact with a variety of soluble mediators to regenerate the periodontium3. Stem cells located in the PDL tissue are key contributors to this process4. Stem cells in the PDL are important not only for formation and maintenance of the tissue but also for repair, remodeling, and regeneration of adjacent alveolar bone and cementum5. Our laboratory has shown that progenitor cells isolated from PDL tissue by selection with cell surface markers STRO-1+ and CD146+ are capable of differentiating into chondrogenic, osteogenic, and adipogenic phenotypes under appropriate culture conditions

Odontogenic tumours-an enigma to surgeon

Odontogenic tumours are one of the common lesions occurring in the oral cavity. They are derived from various remnants of dental forming tissues such as cell rests of Malassez, cell rests of Serre’s or may arise from odontogenic cysts. It represents major health hazard causing morbidity and mortality. An understanding of biologic behaviour of various odontogenic tumours is of fundamental importance to the overall treatment of patients. These tumours have varying histopathological and clinical presentations and based on these, some are aggressive and some are non aggressive.

The inflammatory paradental cyst: a critical review of 342 cases from a literature survey, including 17 new cases from the author's files.

A total of 325 cases of inflammatory paradental cysts (IPCs) and 17 own cases were reviewed. Although known since 1930, the IPC is still unrecognized by many clinicians. The IPCs show a relative frequency of 0.9-4.7%. The majority of cysts occur distally or distobuccally to vital, permanent mandibular molars with a history of pericoronitis (IPC/3rd mandibular molar alone accounts for 64.9%). Radiologically, the cyst appears as a well-defined, semilunar unilocular radiolucency. Cases of inflammatory paradental cysts and related lesions were retrieved from a worldwide literature survey. In addition, 17 new cases from the files of the authors have been added. The mean ages for patients with IPC/1st, 2nd and 3rd mandibular molars are 8.7, 17.4 and 27.6 years, respectively. The male:female ratio was 1 : 0.9 for IPC/1st and 2nd mandibular molars, and 1 : 0.4 for 3rd mandibular molar. Reduced enamel epithelium, cell rests of Malassez and remnants of the dental lamina stimulated by inflammation are thought to play a role in the pathogenesis of IPC. Histological features are indistinguishable from those of the inflammatory, periapical (radicular) cyst.

Ciliated epithelium-lined radicular cysts.

This report describes 3 cases of ciliated epithelium-lined radicular cysts among 256 apical periodontitis lesions and also illustrates the occurrence of an Actinomyces-infected periapical cyst. Serial and step serial sections of 256 plastic-embedded root apices with attached apical periodontitis lesions that were prepared for a previous investigation were reviewed for the presence of ciliated epithelium-lined radicular cysts. The lesions that were found to have such epithelial lining were examined in a transmission electron microscope to elaborate the fine structure of the ciliated cells. A total of 3 ciliated columnar epithelium-lined cysts was found among the 256 apical periodontitis lesions examined. Two of the lesions also contained stratified squamous epithelium. All 3 lesions affected maxillary premolars. One of the lesions was a true cyst, and the other 2 were periapical pocket cysts. The lumen of 1 of the latter revealed the presence of typical "ray-fungus" actinomycotic colonies. Although the stratified squamous component of the epithelia that lined the radicular cysts reported here may be derived from the cell rests of Malassez, the ciliated epithelial cells may be of sinus origin. Microbial agents from diseased root canals can advance into radicular cysts, particularly in pocket cysts, with the possible threat of such infection in upper posterior teeth spreading into the maxillary sinus.

Reactive pocket epithelium in untreated chronic periodontal disease: possible derivation from developmental remnants of the enamel organ and root sheath.

The pathological lining epithelium of destructive periodontitis was studied by analysis of the expression of intermediate filament proteins in biopsies of untreated advanced periodontitis. The cytokeratin (CK) pair 8/18 characteristic of simple epithelia was expressed consistently in a distribution pattern confined to the reactive pocket epithelium. The pattern of CK8/18 expression was complex with two broad presentations evident. In two-thirds of the advanced disease biopsies, the entire pathological lining epithelium was strongly reactive for both CK8 and CK18. In the remainder, the more superficial lining epithelium was mixed with foci of reactive and unreactive cells, with the deeper epithelium uniformly reactive. Only occasional highly localised reactivity for the simple keratins (CK8/18) was found in the lining epithelia of biopsies from minimally inflamed periodontal tissues. The pathological lining epithelium of advanced periodontitis was further characterised by the co-expression in basal layers of CK14, and of CK13 but not CK4, which are characteristic of suprabasal layers of stratified squamous epithelia. Cytokeratin 17, a marker of high turnover and migrating epithelial cells was extremely variable with no clear association between expression pattern and location of the epithelium ordisease status. There was no reactivity for CK10/11 typical of cornifying cells nor of vimentin, the characteristic intermediate filament of mesenchymal cells. The intermediate filament protein profile of the reactive lining epithelium was indistinguishable from the reactive epithelium present in three of five biopsies of periapical granulomas containing hyperplastic epithelium from activation of the developmental remnants of Hertwig's sheath, known as the cell rests of Malassez. The data reported are compatible with a contribution by remnants of developmental epithelium, including the reduced enamel epithelium and the cell rests of Malassez, to the reactive lining epithelium of the subgingival pocket in the pathogenesis of chronic periodontitis.

Discrimination of parakeratinised odontogenic keratocysts from other odontogenic and non‐odontogenic cyst types by expression of a 38kd cell‐surface glycoprotein

We have identified strong expression of a 38-kD cell surface glycoprotein (gp38), a marker of basal cell carcinomas (BCCs), in basal and suprabasal epithelial cell membranes of parakeratinised odontogenic keratocysts. In contrast, orthokeratinised cysts and most other odontogenic cyst types, ameloblastomas, normal stratified oral epithelium, cell rests of Malassez and glands of Serres, all proved negative. To our knowledge this is the first histochemical marker to distinguish between these major cyst types. It has obvious uses in the diagnosis of inflamed keratocysts and the separation of ameloblastomas from BCCs and may find a role in studies of the developmental biology of other odontogenic structures.

Expression of fibronectin and integrins in cultured periodontal ligament epithelial cells.

The process of attachment of epithelial cells obtained from the porcine periodontal ligament (cell rests of Malassez) to different extracellular matrix proteins and their expression of fibronectin and integrin receptors were studied by means of immunocytochemistry, in situ hybridization, and time-lapse cinemicrography techniques. The cell lines of periodontal ligament epithelial cells (PLE cells) attached to and spread rapidly on fibronectin, vitronectin, and type I collagen. One of the cell lines also attached to laminin, while the other cell line showed poor attachment to both laminin and Matrigel, a basement membrane material. By use of the in situ hybridization technique, some PLE cells were found to express the fibronectin gene strongly. Immunocytochemical staining localized fibronectin in extracellular fibrils and intracellular granules. Fibronectin was also found in the tracks left behind by the cells migrating on the substratum. Arg-gly-asp-ser peptide inhibited the attachment of the PLE cells to fibronectin, laminin, type I collagen, and vitronectin by 47%, 43%, 83%, and 94%, respectively, suggesting that the cell-matrix interactions were partly mediated by receptors related to the integrin family. Antibodies against the beta 1-integrin subunit stained the cell bodies and the plasma membrane projections of spreading cells. After 24 h or longer in culture, beta 1-integrins were localized to the regions of cell-cell contact. Cinemicrography of the arg-gly-asp-ser-peptide-treated cells demonstrated that the spreading and migration of isolated cells were prevented by the peptide. The peptide did not appear to dissociate the cell-cell contacts or interfere with migration of spread-cell colonies.(ABSTRACT TRUNCATED AT 250 WORDS)

Proliferating Oral Epithelial Cells in Culture are Capable of Both Extracellular and Intracellular Degradation of Interstitial Collagen

The potential of epithelial cells to degrade interstitial collagen was studied by culturing human masticatory mucosa on decalcified dentin matrix. Morphological changes were observed in the underlying collagen substratum and in the connective tissue of the explant. Degradation of the substratum was initiated two days after the first contact with epithelial cells exhibiting basal cell markers. Electron microscopic studies confirmed extensive collagen degradation in the vicinity of these cells. No collagen degradation was observed underneath the connective tissue portion of the explant. Experiments in which the explant was partially separated from the underlying substratum by a filter further showed that connective tissue was apparently not involved in the collagen degradation by the epithelial cells. Lysis of connective tissue of the explant was observed in association with epithelial cells that showed a disrupted basal lamina and release of vesicular material from the exposed cell membrane. Collagen fibers were visible inside some epithelial cells suggesting intracellular collagenolysis. Primary cultures of human gingival epithelial cells and porcine periodontal ligament epithelial cells (epithelial cell rests of Malassez) that expressed similar basal cell cytokeratins as the active cells of the mucosal explants secreted collagenase, gelatinase and TIMP to the culture medium. They also contained acid collagenolytic proteinases. When cultured on a porous polycarbonate membrane the epithelial cells secreted collagenolytic enzymes from the pores at cell membrane sites lacking basal lamina. These results provide evidence that proliferating basal epithelial cells have a strong capacity for collagen degradation. It seems that the absence of basement membrane is the signal for these cells to secrete matrix degrading enzymes.