scholarly journals Tooth Removal in the Leopard Gecko and the de novo Formation of Replacement Teeth

2021 ◽  
Vol 12 ◽  
Author(s):  
Kirstin S. Brink ◽  
Joaquín Ignacio Henríquez ◽  
Theresa M. Grieco ◽  
Jesus Rodolfo Martin del Campo ◽  
Katherine Fu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
De Novo ◽  
Microscopic Analysis ◽  
Tooth Replacement ◽  
Epithelial Stem Cells ◽  
Dental Lamina ◽  
Eublepharis Macularius ◽  
Post Surgery ◽  
Leopard Gecko

Many reptiles are able to continuously replace their teeth through life, an ability attributed to the existence of epithelial stem cells. Tooth replacement occurs in a spatially and temporally regulated manner, suggesting the involvement of diffusible factors, potentially over long distances. Here, we locally disrupted tooth replacement in the leopard gecko (Eublepharis macularius) and followed the recovery of the dentition. We looked at the effects on local patterning and functionally tested whether putative epithelial stem cells can give rise to multiple cell types in the enamel organs of new teeth. Second generation teeth with enamel and dentine were removed from adult geckos. The dental lamina was either left intact or disrupted in order to interfere with local patterning cues. The dentition began to reform by 1 month and was nearly recovered by 2–3 months as shown in μCT scans and eruption of teeth labeled with fluorescent markers. Microscopic analysis showed that the dental lamina was fully healed by 1 month. The deepest parts of the dental lamina retained odontogenic identity as shown by PITX2 staining. A pulse-chase was carried out to label cells that were stimulated to enter the cell cycle and then would carry BrdU forward into subsequent tooth generations. Initially we labeled 70–78% of PCNA cells with BrdU. After a 1-month chase, the percentage of BrdU + PCNA labeled cells in the dental lamina had dropped to 10%, consistent with the dilution of the label. There was also a population of single, BrdU-labeled cells present up to 2 months post surgery. These BrdU-labeled cells were almost entirely located in the dental lamina and were the likely progenitor/stem cells because they had not entered the cell cycle. In contrast fragmented BrdU was seen in the PCNA-positive, proliferating enamel organs. Homeostasis and recovery of the gecko dentition was therefore mediated by a stable population of epithelial stem cells in the dental lamina.

scholarly journals Terminal differentiation of ectodermal epithelial stem cells of Hydra can occur in G2 without requiring mitosis or S phase.

1990 ◽  
Vol 110 (4) ◽  
pp. 939-945 ◽  
Author(s):  
S Dübel ◽  
H C Schaller
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Epithelial Cells ◽  
Terminal Differentiation ◽  
S Phase ◽  
Epithelial Stem Cells ◽  
Proliferating Cells ◽  
Specific Differentiation ◽  
G2 Phase

Using bromodeoxyuridine incorporation to label cells in S phase we found that ectodermal epithelial cells of Hydra can start and complete their terminal differentiation in the G2 phase of the cell cycle. Most of the cells traversed their last S phase before the signal for differentiation, namely excision of head or foot, was given. The S phase inhibitor aphidicolin accordingly did not inhibit head or foot specific differentiation. The results show that differentiation to either head- or foot-specific ectodermal epithelial cells can start and is completed within the same G2 phase. This is therefore the first description of a complete differentiation from a population of proliferating cells to terminally differentiated, cell cycle-arrested cells without the necessity of passing through an S phase or mitosis.

Chemotherapy-Induced Senescence Reprograms Lymphoma and Leukemia Cells into Latent Cancer Stem Cells That Are Susceptible to Conceptually Novel Treatments

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 4788-4788 ◽  
Author(s):  
Clemens A. Schmitt ◽  
Maja Milanovic ◽  
Henry Daebritz ◽  
Zhen Zhao ◽  
Andreas Trumpp
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Stem Cell ◽  
B Cell ◽  
De Novo ◽  
Leukemia Cells ◽  
Matched Pair ◽  
Stem Cell Markers ◽  
B Cell Lymphomas ◽  
Acute Leukemias

Abstract Cellular senescence is a stress-responsive cell-cycle arrest program that terminates further expansion of (pre-)malignant cells. Senescence imposes a tumor-suppressive barrier in lymphomagenesis, and acts as an effector program in response to chemotherapy in various hematological malignancies. Interestingly, many key signaling components of the senescence machinery also operate as critical regulators of stem cell functions (collectively termed ‘stemness’), among them the p53 axis and control of lysine 9 trimethylation at histone H3 (H3K9). We investigated here in vitro and in vivo whether chemotherapy-induced senescence may change stem cell-related functionalities in aggressive B-cell lymphomas and acute leukemias of murine and human origin. Gene expression and functional analyses comparing senescent vs. non-senescent Eµ-myc transgenic B-cell lymphomas unveiled massive upregulation of an adult tissue stem cell signature, activated Wnt signaling, and de novo expression of distinct stem cell markers in senescence. Utilizing Suv39h1- (an H3K9-targeting methyltransferase) and p53-based genetically switchable ‘matched pair’ on/off models of senescence to mimic spontaneous escape (‘previously senescent’, PS), we found PS cells to re-enter the cell-cycle with strongly enhanced and Wnt-dependent clonogenic growth when compared to their equally chemotherapy-exposed but never senescent (NS) counterparts.In vivo, these PS lymphoma cells presented with a much higher tumor initiation potential, which was neutralized upon pharmacological or genetic Wnt inhibition. Strikingly, temporary enforcement of senescence in a p53-regulatable leukemia model reprogrammed non-stem bulk PS leukemia cells into leukemia-initiating stem cells, whose de novo self-renewing potential was also Wnt-dependent. In contrast, equally chemotherapy-exposed NS bulk cells (i.e. p53 always ‘off’) did not acquire stemness potential. Our data, further supported by consistent findings in various human cancer cell lines and primary patient-derived lymphoma and leukemia samples, characterize senescence as a fundamentally reprogrammed cellular condition, and uncover senescence-associated stemness as an unexpected, cell-autonomous feature that exerts its detrimental potential upon escape from the cell-cycle block. These findings raise concerns about the long-term benefit of senescence-inducing cancer therapies, and provide new mechanistic insights into the plasticity of the “cancer stem cell” condition. In turn, we present synthetic lethal targeting of senescence-associated stemness as a conceptually novel, outcome-improving treatment strategy in lymphoma, leukemia and possibly other cancer entities as well. Disclosures No relevant conflicts of interest to declare.

Continuous tooth replacement: the possible involvement of epithelial stem cells

BioEssays ◽  
2004 ◽  
Vol 26 (6) ◽  
pp. 665-671 ◽  
Author(s):  
Ann Huysseune ◽  
Irma Thesleff
Keyword(s):  
Stem Cells ◽  
Tooth Replacement ◽  
Epithelial Stem Cells

Phosphorylation of Smad2/3 at the specific linker threonine residue indicates slow-cycling esophageal stem-like cells before re-entry to the cell cycle

2016 ◽  
Vol 29 (2) ◽  
pp. 1-8 ◽  
Author(s):  
Y. Takahashi ◽  
T. Fukui ◽  
M. Kishimoto ◽  
R. Suzuki ◽  
T. Mitsuyama ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Epithelial Cells ◽  
Light Microscope ◽  
Basal Layer ◽  
Immunofluorescent Staining ◽  
Epithelial Stem Cells ◽  
Significant Expression ◽  
Slow Cycling ◽  
Regeneration Phase

Summary The stem cell compartment in the esophageal epithelium is possibly located in the basal layer. We have identified significant expression of Smad2/3, phosphorylated at specific linker threonine residues (pSmad2/3L-Thr), in the epithelial cells of murine stomach and intestine, and have suggested that these cells are epithelial stem cells. In this study, we explore whether pSmad2/3L-Thr could serve as a biomarker for esophageal stem cells. We examined esophageal tissues from normal C57BL/6 mice and those with esophagitis. Double immunofluorescent staining of pSmad2/3L-Thr with Ki67, CDK4, p63, or CK14 was performed. After immunofluorescent staining, we stained the same sections with hematoxylin-eosin and observed these cells under a light microscope. We used the 5-bromo-2-deoxyuridine (BrdU) labeling assay to examine label retention of pSmad2/3L-Thr immunostaining-positive cells. We collected specimens 5, 10, 15 and 20 days after repeated BrdU administrations and observed double immunofluorescent staining of pSmad2/3L-Thr with BrdU. In the esophagus, pSmad2/3L-Thr immunostaining-positive cells were detected in the basal layer. These cells were detected between Ki67 immunostaining-positive cells, but they were not co-localized with Ki67. pSmad2/3L-Thr immunostaining-positive cells showed co-localization with CDK4, p63, and CK14. Under a light microscope, pSmad2/3L-Thr immunostaining-positive cells indicated undifferentiated morphological features. Until 20 days follow-up period, pSmad2/3L-Thr immunostaining-positive cells were co-localized with BrdU. pSmad2/3L-Thr immunostaining-positive cells significantly increased in the regeneration phase of esophagitis mucosae, as compared with control mice (esophagitis vs. control: 6.889 ± 0.676/cm vs. 4.293 ± 0.659/cm; P < 0.001). We have identified significant expression of pSmad2/3L-Thr in the specific epithelial cells of murine esophagi. We suggest that these cells are slow-cycling epithelial stem-like cells before re-entry to the cell cycle.

scholarly journals Identification of putative dental epithelial stem cells in a lizard with life-long tooth replacement

Development ◽  
2010 ◽  
Vol 137 (21) ◽  
pp. 3545-3549 ◽  
Author(s):  
G. R. Handrigan ◽  
K. J. Leung ◽  
J. M. Richman
Keyword(s):  
Stem Cells ◽  
Tooth Replacement ◽  
Epithelial Stem Cells

scholarly journals Shark tooth regeneration reveals common stem cell characters in both human rested lamina and ameloblastoma

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Gareth J. Fraser ◽  
Samar S. Hamed ◽  
Kyle J. Martin ◽  
Keith D. Hunter
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Stem Cell Markers ◽  
Human Tissues ◽  
Tooth Replacement ◽  
Dental Stem Cells ◽  
Proliferating Cells ◽  
Dental Lamina ◽  
Dental Stem Cell ◽  
Mammalian System

Abstract The human dentition is a typical diphyodont mammalian system with tooth replacement of most positions. However, after dental replacement and sequential molar development, the dental lamina undergoes apoptosis and fragments, leaving scattered epithelial units (dental lamina rests; DLRs). DLRs in adult humans are considered inactive epithelia, thought to possess limited capacity for further regeneration. However, we show that these tissues contain a small proportion of proliferating cells (assessed by both Ki67 and PCNA) but also express a number of common dental stem cell markers (Sox2, Bmi1, β-catenin and PH3) similar to that observed in many vertebrates that actively, and continuously regenerate their dentition. We compared these human tissues with the dental lamina of sharks that regenerate their dentition throughout life, providing evidence that human tissues have the capacity for further and undocumented regeneration. We also assessed cases of human ameloblastoma to characterise further the proliferative signature of dental lamina rests. Ameloblastomas are assumed to derive from aberrant lamina rests that undergo changes, which are not well understood, to form a benign tumour. We suggest that dental lamina rests can offer a potential source of important dental stem cells for future dental regenerative therapy. The combined developmental genetic data from the shark dental lamina and ameloblastoma may lead to the development of novel methods to utilise these rested populations of adult lamina stem cells for controlled tooth replacement in humans.

Abstract 395: Transient Inactivation of Retinoblastoma Induces De-Novo Cardiomyogenesis From Human Myocardial Progenitors but Not Pre-Existing Cardiomyocyte Replication

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Konstantinos E Hatzistergos ◽  
Julien Sage ◽  
Jamie F Conklin ◽  
Michael Bellio ◽  
Krystalenia Valasaki ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
De Novo ◽  
Embryonic Stem ◽  
Fold Increase ◽  
Embryoid Bodies ◽  
Cardiac Cell ◽  
Cardiac Progenitors ◽  
Proliferation And Differentiation

Introduction: Activation of cardiac cell cycle re-entry is considered the primary therapeutic strategy for cardiomyocyte (CM) regeneration. However, the role of cardiac cell-cycle control in cardiomyogenesis remains elusive. Here, we combined RNA interference and stem cell modeling to investigate the role of Retinoblastoma (RB) in human cardiomyogenesis. Hypothesis: RB regulates proliferation and differentiation of cardiac progenitors (CPCs) but not CM replication. Methods: H9 human embryonic stem cells (hESCs) stably expressing tetracycline (tet)-inducible shRNAs against RB (hESCshRB) or hemagglutinin-tagged RB (hESCHA-RB) were tet-induced at selected time-points during or after CM differentiation. Results: Analysis of ser-608 illustrated stage-specific differences in the degree of RB inactivation during normal hESCs-cardiogenesis. Transient shRB knockdown in hESCshRB-derived embryoid bodies (EBs) during the CPC-stage (EB-days 5-8), significantly upregulated GATA4, ISL1, CTNNI, and cKit transcription (p<0.05), while increasing the yield of beating EBs by 2.4-fold (n=6/group, p<0.0001 vs. vehicle). Gene-expression arrays of 22 RB-related genes, illustrated that shRB-knockdown upregulated CCND1, CCND2, CCND3, and CDK4, CDK6 (p<0.05), followed by a 3.6-fold increase in E2F3 (p<0.05) expression. Moreover, expression of p107 and p130, p27, p57, ARF and CDKN3 were also significantly increased (p<0.05), whereas TP53 and MDM2 remained unchanged. Ectopic HA-RB in CPCs did not significantly affect cardiogenesis (n=18). Conversely, shRB knockdown in EB-day 60-derived CMs (n=15) did not stimulate cell cycle re-entry, as assessed by analysis of EdU incorporation and Aurora-B kinase (AurB). Remarkably, co-culture of hESCHA-RB-derived CMs with adult cardiac (CSCs) and/or mesenchymal (MSCs) stem cells (n=15/group), increased cell-cycle re-entry ~2.8-fold, assessed by ser-10 Histone H3 (p=0.0002) and AurB (p<0.0001). Conclusions: These findings suggest that RB regulates proliferation and differentiation of human CPCs in a cell-autonomous manner, via a CCND-CDK4/6-E2F3 mechanism. Conversely, CM replication may be enhanced via cell-cell interactions with MSCs and/or CSCs, but not cell-autonomously via RB inactivation.

scholarly journals Autism-associated CHD8 keeps proliferation of human neural progenitors in check by lengthening the G1 phase of the cell cycle

2021 ◽  
Author(s):  
Emma Coakley-Youngs ◽  
Susan Shorter ◽  
Medhavi Ranatunga ◽  
Simon Richardson ◽  
Giulia Getti ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Cell Cycle Progression ◽  
De Novo ◽  
Cell Model ◽  
Embryonic Stem ◽  
Mapk Signaling ◽  
Developmental Trajectory ◽  
G1 Phase ◽  
Loss Of Function

AbstractCHD8 (Chromodomain Helicase DNA Binding Protein 8) is a chromatin remodeler that preferentially regulates expression of genes implicated in early development of the cerebral cortex. De novo mutations (DNMs) in CHD8 are strongly associated with a specific subtype of autism characterized by enlarged foreheads and distinct cranial features. The vast majority of these DNMs are heterozygous loss-of-function mutations with high penetrance for autism. How CHD8 haploinsufficiency alters the normal developmental trajectory of the human cortex is poorly understood and debated. Previous studies in the mammalian developing cortex have shown progressive lengthening of the G1 phase of the cell cycle as neural stem cells transition from proliferative to neurogenic divisions. G1 length has been proposed to operate as a molecular clock that controls timing of this crucial developmental switch. To determine the influence of CHD8 on cell cycle timing, we disrupted one allele of CHD8 in human embryonic stem cells (hESCs), differentiated these cells into neural precursor cells (NPCs), and imaged cell cycle progression of individual CHD8+/− NPCs — in parallel with their isogenic CHD8+/+ counterparts — during several rounds of cell division. We found a specific and marked decrease in G1 duration in CHD8+/− NPCs, resulting in an overall shortening of the cell cycle. Consistent with faster progression of CHD8+/− NPCs through G1 and the G1/S checkpoint, we observed increased expression of E cyclins and elevated phosphorylation of Erk in these mutant cells — two central signalling pathways involved in S phase entry. Together, our findings show dysregulated proliferation of NPCs in a human stem cell model of CHD8 haploinsufficiency and predict enlargement of the neural progenitor pool in CHD8+/− developing brains, a phenotype that may explain macrocephaly in individuals with CHD8 DNMs. Furthermore, our work provides further evidence for a link between autism and cancer and identifies MAPK signaling as a potential therapeutic target for the treatment of this autism subtype.

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