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Emulating the early phases of human tooth development in vitro.

ABSTRACT: Functional in vitro models emulating the physiological processes of human organ formation are invaluable for future research and the development of regenerative therapies. Here, a developmentally inspired approach is pursued to reproduce fundamental steps of human tooth organogenesis in vitro using human dental pulp cells. Similar to the in vivo situation of tooth initiating mesenchymal condensation, a 3D self-organizing culture was pursued resulting in an organoid of the size of a human tooth germ with odontogenic marker expression. Furthermore, the model is capable of epithelial invagination into the condensed mesenchyme, mimicking the reciprocal tissue interactions of human tooth development. Comprehensive transcriptome analysis revealed activation of well-studied as well as rather less investigated signaling pathways implicated in human tooth organogenesis, such as the Notch signaling. Early condensation in vitro revealed a shift to the TGFß signal transduction pathway and a decreased RhoA small GTPase activity, connected to the remodeling of the cytoskeleton and actin-mediated mechanotransduction. Therefore, this in vitro model of tooth development provides a valuable model to study basic human developmental mechanisms.

SUBMITTER: Rosowski J

PROVIDER: S-EPMC6505527 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Emulating the early phases of human tooth development in vitro.

Rosowski Jennifer J Bräunig Julia J Amler Anna-Klara AK Strietzel Frank P FP Lauster Roland R Rosowski Mark M

Scientific reports 20190507 1

Functional in vitro models emulating the physiological processes of human organ formation are invaluable for future research and the development of regenerative therapies. Here, a developmentally inspired approach is pursued to reproduce fundamental steps of human tooth organogenesis in vitro using human dental pulp cells. Similar to the in vivo situation of tooth initiating mesenchymal condensation, a 3D self-organizing culture was pursued resulting in an organoid of the size of a human tooth g ...[more]

PMID: 31065008

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Project description:PurposeWhile in the past, most clinical trial applications (CTAs) following non-integrated (standard) protocols were used to investigate one primary objective concerning a (new) drug, nowadays, the use of integrated protocols investigating multiple objectives within the same CTA becomes more and more popular. The aims of the present study were to investigate the usage and the impact of integrated protocols on regulatory activities and to find the motivation for their increasing use.MethodsTwo thousand nine hundred sixty-nine phase I and I/II CTAs submitted to the German Federal Institute for Drugs and Medical Devices (BfArM) during the time period from August 1, 2004, until August 31, 2014, were analysed with regard to protocol and sponsor status, duration until initial authorisation and the number of substantial amendments and their respective approval times. Additionally, applicants who submitted integrated protocols to BfArM were interviewed with respect to their opinion on integrated protocols in an online survey.ResultsThe percentage of integrated protocols has constantly increased by approximately 10% within the last 10 years from 17.9% in 2004 to 28.2% in 2014. It could be shown that authorisation procedures with single integrated protocols take significantly longer until initial authorisation (58 vs. 53 days) requires more substantial amendments (1.9 vs. 1.2 amendments per CTA) and the approval of the entirety of amendments takes longer to process as compared to standard protocols (22 vs. 14 days). Nevertheless, applicants prefer the use of integrated protocols due to higher time and cost economy for the entire phase I development process.ConclusionAlthough clinical trials (CTs) following integrated protocols are partly more time-consuming and costly, still, time and/or money may be saved during drug development due to the fact that overall, fewer CTs are needed than with standard protocols. Hence, the main reason for the increasing use of integrated protocols is improved time and cost efficiencies when conducting CTs.

Project description:Human CLCN7 encodes voltage-gated chloride channel 7 (ClC-7); mutations of CLCN7 lead to osteopetrosis which is characterized by increased bone mass and impaired osteoclast function. In our previous clinical practice, we noticed that osteopetrosis patients with CLCN7 mutations had some special deformities in craniofacial morphology and tooth dysplasia. It is unclear whether these phenotypes are the typical features of CLCN7 involved osteopetrosis and whether ClC-7 could regulate the development of craniofacial bone and tooth in some signaling pathways. Methods: First, we collected 80 osteopetrosis cases from the literature and compared their craniofacial and dental phenotypes. Second, four osteopetrosis pedigrees with CLCN7 mutations were recruited from our clinic for gene testing and clinical analysis of their craniofacial and dental phenotypes. Third, we used a zebrafish model with clcn7 morpholino treatment to detect the effects of ClC-7 deficiency on the development of craniofacial and dental phenotypes. General observation, whole mount alcian blue and alizarin red staining, whole mount in situ hybridization, scanning electron microscope observation, lysoSensor staining, Q-PCR and western blotting were performed to observe the in vivo characteristics of craniofacial bone and tooth changes. Fourth, mouse marrow stromal cells were further primarily cultured to detect ClC-7 related mRNA and protein changes using siRNA, Q-PCR and western blotting. Results: Over 84% of osteopetrosis patients in the literature had some typical craniofacial and tooth phenotypes, including macrocephaly, frontal bossing, and changes in shape and proportions of facial skeleton, and these unique features are more severe and frequent in autosomal recessive osteopetrosis than in autosomal dominant osteopetrosis patients. Our four pedigrees with CLCN7 mutations confirmed the aforementioned clinical features. clcn7 knockdown in zebrafish reproduced the craniofacial cartilage defects and various dental malformations combined the decreased levels of col10a1, sp7, dlx2b, eve1, and cx43. Loss of clcn7 function resulted in lysosomal storage in the brain and jaw as well as downregulated cathepsin K (CTSK). The craniofacial phenotype severity also presented a dose-dependent relationship with the levels of ClC-7 and CTSK. ClC-7/CTSK further altered the balance of TGF-β/BMP signaling pathway, causing elevated TGF-β-like Smad2 signals and reduced BMP-like Smad1/5/8 signals in clcn7 morphants. SB431542 inhibitor of TGF-β pathway partially rescued the aforementioned craniofacial bone and tooth defects of clcn7 morphants. The ClC-7 involved CTSK/BMP and SMAD changes were also confirmed in mouse bone marrow stromal cells. Conclusion: These findings highlighted the vital role of clcn7 in zebrafish craniofacial bone and tooth development and mineralization, revealing novel insights for the causation of osteopetrosis with CLCN7 mutations. The mechanism chain of ClC-7/CTSK/ TGF-β/BMP/SMAD might explain the typical craniofacial bone and tooth changes in osteopetrosis as well as pycnodysostosis patients.

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Emulating the early phases of human tooth development in vitro.

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Emulating the early phases of human tooth development in vitro.

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