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Shaw WJ, Tarasevich BJ, Buchko GW, Arachchige RMJ, Burton SD. Controls of nature: Secondary, tertiary, and quaternary structure of the enamel protein amelogenin in solution and on hydroxyapatite. J Struct Biol 2020; 212:107630. [PMID: 32979496 PMCID: PMC7744360 DOI: 10.1016/j.jsb.2020.107630] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 09/12/2020] [Accepted: 09/17/2020] [Indexed: 10/23/2022]
Abstract
Amelogenin, a protein critical to enamel formation, is presented as a model for understanding how the structure of biomineralization proteins orchestrate biomineral formation. Amelogenin is the predominant biomineralization protein in the early stages of enamel formation and contributes to the controlled formation of hydroxyapatite (HAP) enamel crystals. The resulting enamel mineral is one of the hardest tissues in the human body and one of the hardest biominerals in nature. Structural studies have been hindered by the lack of techniques to evaluate surface adsorbed proteins and by amelogenin's disposition to self-assemble. Recent advancements in solution and solid state nuclear magnetic resonance (NMR) spectroscopy, atomic force microscopy (AFM), and recombinant isotope labeling strategies are now enabling detailed structural studies. These recent studies, coupled with insights from techniques such as CD and IR spectroscopy and computational methodologies, are contributing to important advancements in our structural understanding of amelogenesis. In this review we focus on recent advances in solution and solid state NMR spectroscopy and in situ AFM that reveal new insights into the secondary, tertiary, and quaternary structure of amelogenin by itself and in contact with HAP. These studies have increased our understanding of the interface between amelogenin and HAP and how amelogenin controls enamel formation.
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Affiliation(s)
- Wendy J Shaw
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - Barbara J Tarasevich
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Garry W Buchko
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA; School of Molecular Bioscience, Washington State University, Pullman, WA 99164, USA
| | - Rajith M J Arachchige
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Sarah D Burton
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
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2
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Malyshev IY, Runova GS, Poduraev YV, Mironov VA. [Natural amelogenesis and rationale for enamel regeneration by means of robotic bioprinting of tissues in situ]. STOMATOLOGII︠A︡ 2018; 97:58-64. [PMID: 29795109 DOI: 10.17116/stomat201897258-64] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- I Yu Malyshev
- Moscow State University of Medicine and Dentistry named after A.I. Evdokimov, Moscow, Russia, 127473
| | - G S Runova
- Moscow State University of Medicine and Dentistry named after A.I. Evdokimov, Moscow, Russia, 127473
| | - Yu V Poduraev
- Moscow State Technological University STANKIN, Moscow, Russia, 127055
| | - V A Mironov
- Biotechnology Research Laboratory '3D Bioprinting Solutions', Moscow, Russia, 115409
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Guo Y, Guo W, Chen J, Tian Y, Chen G, Tian W, Bai D. Comparative study on differentiation of cervical-loop cells and Hertwig's epithelial root sheath cells under the induction of dental follicle cells in rat. Sci Rep 2018; 8:6546. [PMID: 29695816 PMCID: PMC5916884 DOI: 10.1038/s41598-018-24973-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 04/12/2018] [Indexed: 02/05/2023] Open
Abstract
Cervical loop cells (CLC) and Hertwig's epithelial root sheath (HERS) cells are believed to play critical roles in distinct developmental patterns between rodent incisors and molars, respectively. However, the differences in differentiation between CLC and HERS cells, and their response to inductions from dental follicle cells, remain largely unknown. In present study, CLC and HERS cells, as well as incisor dental follicle (IF) cells and molar dental follicle (MF) cells were isolated from post-natal 7-day rats. IF and MF cell derived conditioned medium (CM) was obtained for induction of CLC and HERS cells. In vitro experiments, we found that, under the induction of dental follicle cell derived CM, CLC cells maintained the epithelial polygonal-shapes and formed massive minerals, while part of HERS cells underwent shape transformation and generated granular minerals. CLC cells expressed higher enamel-forming and mineralization related genes, while HERS cells showed opposite expression patterns of BMP2, BMP4, AMBN and AMGN. In vivo, CLC cells generated enamel-like tissues while HERS cells formed cementum-periodontal ligament-like structures. Taken together, CLC and HERS cells present distinct differentiation patterns under the inductions from dental follicle cells.
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Affiliation(s)
- Yongwen Guo
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China
| | - Weihua Guo
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,Department of Pediatric Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, P.R. China
| | - Jie Chen
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China
| | - Ye Tian
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China
| | - Guoqing Chen
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China
| | - Weidong Tian
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China. .,National Engineering Laboratory for Oral Regenerative Medicine, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China. .,Department of Oral and Maxillofacial Surgery, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.
| | - Ding Bai
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China. .,Department of Orthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, 610041, P.R. China.
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4
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Silva BLL, Medeiros DL, Soares AP, Line SRP, Pinto MDGF, Soares TDJ, do Espírito Santo AR. Type 1 diabetes mellitus effects on dental enamel formation revealed by microscopy and microanalysis. J Oral Pathol Med 2017; 47:306-313. [PMID: 29243281 DOI: 10.1111/jop.12669] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/07/2017] [Indexed: 11/30/2022]
Abstract
BACKGROUND Type 1 diabetes mellitus (T1DM) largely affects children, occurring therefore at the same period of deciduous and permanent teeth development. The aim of this work was to investigate birefringence and morphology of the secretory stage enamel organic extracellular matrix (EOECM), and structural and mechanical features of mature enamel from T1DM rats. METHODS Adult Wistar rats were maintained alive for a period of 56 days after the induction of experimental T1DM with a single dose of streptozotocin (60 mg/kg). After proper euthanasia of the animals, fixed upper incisors were accurately processed, and secretory stage EOECM and mature enamel were analyzed by transmitted polarizing and bright field light microscopies (TPLM and BFLM), energy-dispersive x-ray (EDX) analysis, scanning electron microscopy (SEM), and microhardness testing. RESULTS Bright field light microscopies and transmitted polarizing light microscopies showed slight morphological changes in the secretory stage EOECM from diabetic rats, which also did not exhibit statistically significant alterations in birefringence brightness when compared to control animals (P > .05). EDX analysis showed that T1DM induced statistically significant little increases in the amount of calcium and phosphorus in outer mature enamel (P < .01) with preservation of calcium/phosphorus ratio in that structure (P > .05). T1DM also caused important ultrastructural alterations in mature enamel as revealed by SEM and induced a statistically significant reduction of about 13.67% in its microhardness at 80 μm from dentin-enamel junction (P < .01). CONCLUSIONS This study shows that T1DM may disturb enamel development, leading to alterations in mature enamel ultrastructure and in its mechanical features.
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Affiliation(s)
- Bruna Larissa Lago Silva
- Multidisciplinary Institute of Health, Federal University of Bahia-UFBA, Vitória da Conquista, Brazil
| | | | - Ana Prates Soares
- Multidisciplinary Institute of Health, Federal University of Bahia-UFBA, Vitória da Conquista, Brazil
| | | | | | - Telma de Jesus Soares
- Multidisciplinary Institute of Health, Federal University of Bahia-UFBA, Vitória da Conquista, Brazil
| | - Alexandre Ribeiro do Espírito Santo
- Laboratory of Orofacial Biology, Department of Biomorphology, Institute of Health Sciences, Federal University of Bahia-UFBA, Salvador, Brazil
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Soares AP, do Espírito Santo RF, Line SRP, Pinto MDGF, Santos PDM, Toralles MBP, do Espírito Santo AR. Effects of Pamidronate on Dental Enamel Formation Assessed by Light Microscopy, Energy-Dispersive X-Ray Analysis, Scanning Electron Microscopy, and Microhardness Testing. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2016; 22:640-648. [PMID: 27212049 DOI: 10.1017/s1431927616000726] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The aim of the present work was to investigate birefringence and morphology of the secretory-stage enamel organic extracellular matrix (EOECM), and structural and mechanical properties of mature enamel of upper incisors from adult rats that had been treated with pamidronate disodium (0.5 mg/kg/week for 56 days), using transmitted polarizing and bright-field light microscopies (TPLM and BFLM), energy-dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM) and microhardness testing. BFLM showed no morphological changes of the EOECM in pamidronate and control groups, but TPLM revealed a statistically significant reduction in optical retardation values of birefringence brightness of pamidronate-treated rats when compared with control animals (p0.05). The present study indicates that pamidronate can affect birefringence of the secretory-stage EOECM, which does not seem to be associated with significant changes in morphological and/or mechanical properties of mature enamel.
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Affiliation(s)
- Ana P Soares
- 1Multidisciplinary Institute of Health,Federal University of Bahia-UFBA,Rua Rio de Contas,58,Quadra 17,Lote 58,Candeias,Vitória da Conquista,BACEP 45.029-094,Brasil
| | - Renan F do Espírito Santo
- 2Faculty of Pharmacy,Federal University of Bahia-UFBA,Rua Barão de Jeremoabo,S/N,Campus Universitário de Ondina,Ondina,Salvador,BA CEP 40.170-115,Brasil
| | - Sérgio R P Line
- 3Piracicaba Dental School,University of Campinas-UNICAMP,Av. Limeira,901,Areião,Piracicaba,SP CEP 13.414-903,Brasil
| | - Maria das G F Pinto
- 4School of Veterinary Medicine and Zootechny,Federal University of Bahia-UFBA,Av. Ademar de Barros,500,Ondina,Salvador,BA CEP 40.170-110,Brasil
| | - Pablo de M Santos
- 5Professor Edgard Santos University Hospital,Federal University of Bahia-UFBA,Rua Augusto Viana,S/N,Canela,Salvador,BA CEP 40.110-060,Brasil
| | - Maria Betania P Toralles
- 6Institute of Health Sciences,Federal University of Bahia-UFBA,Av. Reitor Miguel Calmon,S/N,Vale do Canela,Salvador,BA CEP 40.110-902,Brasil
| | - Alexandre R do Espírito Santo
- 6Institute of Health Sciences,Federal University of Bahia-UFBA,Av. Reitor Miguel Calmon,S/N,Vale do Canela,Salvador,BA CEP 40.110-902,Brasil
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Neves EG, Ramos-Perez FMDM, Freitas DQ, Bóscolo FN, Almeida SM. Radioprotective effect of sodium selenite on developing teeth. Braz Dent J 2015; 24:375-9. [PMID: 24173260 DOI: 10.1590/0103-6440201302193] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 05/17/2013] [Indexed: 06/22/2024] Open
Abstract
Radioprotective agents like selenium are used to reduce the damage caused by radiation in healthy tissues. The aim of this study was to evaluate the effect of sodium selenite on the development of the molars of offspring of rats irradiated during odontogenesis. Twenty pregnant rats were randomly divided into 4 groups: control, irradiated, selenium and selenium/irradiated. The selenium and selenium/irradiated groups received 0.3 mg/kg of sodium selenite at 18 days of pregnancy. The rats of the irradiated and selenium/irradiated groups received a single dose of 4 Gy of X rays on the abdominal region at the 19th day of pregnancy. The offspring was sacrificed at 3 and 4 days after birth for evaluation of the birefringence of the enamel organic matrix, and at 30 days for evaluation of the intercuspal dimensions of the molars. The selenium/irradiated group was similar to the irradiated group with respect to the thickness and irregularity of the enamel organic matrix region in the evaluated birefringence, as the intercuspal dimensions of the molars. In conclusion, sodium selenite had no radioprotective action on the development of the molars of offspring of rats irradiated during odontogenesis and had a toxic effect in the initial time.
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Affiliation(s)
- Ellen Gaby Neves
- Department of Oral Diagnosis, Oral Radiology Area, Piracicaba School of Dentistry, UNICAMP - University of Campinas, PiracicabaSP, Brazil
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Abstract
Enamel is unique. It is the only epithelial-derived mineralized tissue in mammals and has a distinct micro- and nanostructure with nanofibrous apatite crystals as building blocks. It is synthesized by a highly specialized cell, the ameloblast, which secretes matrix proteins with little homology to any other known amino acid sequence, but which is composed of a primary structure that makes it competent to self-assemble and control apatite crystal growth at the nanometer scale. The end-product of ameloblast activity is a marvel of structural engineering: a material optimized to provide the tooth with maximum biting force, withstanding millions of cycles of loads without catastrophic failure, while also protecting the dental pulp from bacterial attack. This review attempts to bring into context the mechanical behavior of enamel with the developmental process of amelogenesis and structural development, since they are linked to tissue function, and the importance of controlling calcium phosphate mineralization at the nanometer scale. The origins of apatite nanofibers, the development of a stiffness gradient, and the biological processes responsible for the synthesis of a hard and fracture-resistant dental tissue are discussed with reference to the evolution of enamel from a fibrous composite to a complex, tough, and damage-tolerant coating on dentin.
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Affiliation(s)
- S Habelitz
- Preventive and Restorative Dental Sciences, University of California, San Francisco, CA, USA
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de Moraes Ramos-Perez FM, do Espírito Santo AR, da Cruz Perez DE, Novaes PD, Bóscolo FN, Line SRP, de Almeida SM. Ionizing radiation effects on the secretory-stage ameloblasts and enamel organic extracellular matrix. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2014; 53:589-598. [PMID: 24699801 DOI: 10.1007/s00411-014-0539-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 03/23/2014] [Indexed: 06/03/2023]
Abstract
This study assessed the effects of high doses of ionizing radiation on eruption rate, odontogenic region morphology, secretory-stage ameloblasts, and enamel organic extracellular matrix (EOECM) of rat maxillary incisors. For the study, 30 male rats were divided into three experimental groups: control (non-irradiated), irradiated by 15 Gy, and irradiated by 25 Gy. Irradiated groups received a single dose of 15 or 25 Gy of X-rays in the head and neck region. The maxillary incisor eruption rate was measured. Sections of 5-µm thickness of the maxillary incisor odontogenic regions were evaluated using bright field light microscopy. Ultrathin sections of secretory ameloblasts and their EOECM were analyzed by transmission electron microscopy (TEM). Irradiated groups showed significantly diminished eruption rate values at the 4th and at the 6th day after irradiation. Reduced optical retardation values were observed in the irradiated groups. The odontogenic region of maxillary incisors from irradiated rats exhibited altered and poorly organized preameloblasts. TEM showed degeneration areas in the secretory-stage EOECM and several autophagosomes in the secretory ameloblasts from irradiated animals. In conclusion, high radiation doses delay eruption and induce disturbances in secretory ameloblasts and EOECM of rat maxillary incisors. These findings may be associated with structural defects of mature enamel.
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Affiliation(s)
- Flávia Maria de Moraes Ramos-Perez
- Área de Radiologia Odontológica, Departamento de Clinica e Odontologia Preventiva, Universidade Federal de Pernambuco, Avenida Prof. Moraes Rego, 1235, Cidade Universitária, CEP 50670-901, Recife, PE, Brazil,
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Mofatto LS, Frozoni MRS, do Espírito Santo AR, Guimarães GN, de Souza AP, de Campos Vidal B, Line SRP. Fluoride effect on the secretory-stage enamel organic extracellular matrix of mice. Connect Tissue Res 2011; 52:212-7. [PMID: 21117895 DOI: 10.3109/03008207.2010.511731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The formation of an ordered enamel organic extracellular matrix (EOECM) seems to be a crucial step for the proper formation of the enamel mineral phase. The ordered supramolecular structure of the EOECM in the secretory stage can be analyzed using polarizing microscopy, as it is strongly birefringent. Excessive fluoride (F) ingestion during tooth development can cause enamel fluorosis, leading to increased porosity in mature enamel. We analyzed the effects of F on the birefringence of the EOECM in the A/J, CBA, and DBA/2 strains of mice given 0, 11.25, and 45 ppm of fluoride in drinking water. In the CBA and DBA/2 strains, the 11.25 and 45 ppmF groups presented a significant decrease in optical retardation (OR) when compared with the respective 0 (CBA 11.25 ppmF p = 0.0056 and 45 ppmF p < 0.0001; DBA/2 11.25 and 45 ppmF p < 0.05). ORs in A/J 0 ppmF were significantly higher than in 45 (p < 0.0001). The enamel of the A/J strain was more severely affected by fluoride than it was in the other strains of mice and exhibited the lowest levels of fluoride in plasma, whereas its normal secretory enamel presented a significantly higher protein absorbance than it did in CBA and DBA mice (p = 0.0099 and p = 0.0025, respectively). The results showed that experimental fluorosis can alter the supramolecular organization of EOECM in the secretory stage of amelogenesis and that the susceptibility to dental fluorosis seems to be influenced by the inherent characteristics of the developing enamel.
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Affiliation(s)
- Luciana Souto Mofatto
- Department of Morphology, Piracicaba Dental School, University of Campinas-UNICAMP, Piracicaba, SP, Brazil
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Gomes JR, Omar NF, dos Santos Neves J, Narvaes EAO, Novaes PD. Immunolocalization and activity of the MMP-9 and MMP-2 in odontogenic region of the rat incisor tooth after post shortening procedure. J Mol Histol 2011; 42:153-9. [PMID: 21308405 DOI: 10.1007/s10735-011-9318-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Accepted: 01/26/2011] [Indexed: 11/28/2022]
Abstract
MMP-9 and MMP-2 are metalloproteinases which degrade the denatured collagen fibers. However, there is no report about roles of these MMPs in the odontogenic region of the adult rat incisor tooth under different eruption conditions. Male Wistar rats were divided in a normofunctional group (NF) in which their lower teeth remained in a normal eruption. In a hypofunctional group (HP) rats underwent shortening of their lower left incisor tooth every 2 days during 12 days. The eruption rate as well as the expression and activities of MMP-9 and MMP-2 were evaluated using imunohistochemistry and zymography. Although the shortening increased the eruption rate, no changes in the MMP-9 and MMP-2 were observed. We conclude that in adult rats, in opposite to development of tooth, the MMP-9 and MMP-2 present in the odontogenic region does not seem to play a direct role in the remodeling matrix, even after post-shortening procedures which to lead an acceleration of the eruption process in the incisor.
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Affiliation(s)
- Jose Rosa Gomes
- Departamento de Biologia Estrutural Molecular e Genética, UEPG, Avenue Carlos Cavalcanti, 4748, Ponta Grossa, PR, 84030-900, Brazil.
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Increase of MT1-MMP, TIMP-2 and Ki-67 proteins in the odontogenic region of the rat incisor post-shortening procedure. J Mol Histol 2010; 41:333-41. [DOI: 10.1007/s10735-010-9295-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2010] [Accepted: 09/07/2010] [Indexed: 10/19/2022]
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do Espírito Santo AR, Frozoni MRS, Ramos-Perez FMM, Novaes PD, Line SRP. Birefringence of the secretory-stage enamel organic extracellular matrix from rats submitted to successive injections of bisphosphonates. Connect Tissue Res 2010; 51:208-15. [PMID: 20109069 DOI: 10.3109/03008200903280115] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The aim of the present study was to assess birefringence of the secretory-stage enamel organic extracellular matrix (ECM) and mechanical properties of mature enamel from rats treated with bisphosphonates. Longitudinal sections were obtained from upper incisors of rats that had been submitted to injections of bisodic etidronate (8 mg/Kg/day), sodium alendronate (30 microg/Kg/day), or sodium chloride as control (8 mg/Kg/day) for 42 days. Sections were immersed in 80% glycerin for 30 min and optical retardation of birefringence brightness in the secretory-stage enamel organic ECM was determined in nanometers. Etidronate-treated rats exhibited extensive morphological changes in the secretory-stage enamel organic ECM inclusive nonbirefringent conspicuous incremental lines, but presented optical retardation values similar to those showed by control rats (p > 0.05). Birefringence of secretory enamel organic ECM from etidronate rats presented an irregular aspect. Alendronate-treated rats did not show morphological alterations in the secretory-stage enamel organic ECM, however, they presented significant reduction in optical retardation of birefringence brightness when compared with control and etidronate rats (p < 0.01). Alendronate and etidronate groups exhibited reductions of approximately 6-10% in mature enamel cross-sectional microhardness when compared with control group (p < 0.01). Scanning electron microscopy analysis showed extensive alterations in mature enamel only from etidronate group with absence of enamel rods. The present work shows that bisphosphonates can affect the birefringence of the secretory-stage enamel organic ECM. The results presented here suggest that alterations in the supramolecular organization of the secretory-stage enamel organic ECM are a plausible mechanism by which environmental factors may cause enamel defects.
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do Espirito Santo AR, Marques MR, Line SRP. A study in situ of the effect of metallo- and serine proteinase inhibitors on the birefringence of the secretory stage enamel organic extracellular matrix. Biotech Histochem 2010; 86:108-14. [PMID: 20109097 DOI: 10.3109/10520290903472407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dental enamel formation occurs extracellularly and establishment of an ordered enamel organic extracellular matrix (ECM) seems to be crucial for proper construction of the enamel mineral phase. Polarizing microscopy shows that the ordered supramolecular structure of the secretory stage enamel organic ECM exhibits strong birefringence. We reported earlier that this birefringence is lost in unfixed specimens, probably due to extensive proteolytic cleavage of enamel proteins. Therefore, we investigated the association between enamel proteinase activities by analyzing the effects of metallo- and serine proteinase inhibitors in situ on the birefringence of the secretory stage enamel organic ECM. Male rats were used in the present study. After sacrifice, distal 10 mm fragments of upper incisors were removed and immersed for 15 h under continuous shaking at 37°C in one of the following solutions: 1) 10 mM Tris, pH 8.0; 150 mM NaCl (negative control, n = 8); 2) 2% paraformaldehyde and 0.5% glutaraldehyde in 0.2 M phosphate-buffered saline (PBS), pH 7.2 (positive control, n = 5); 3) 10 mM Tris, pH 8.0; 150 mM NaCl; 2 mM 1,10-phenanthroline (n = 9); 4) 10 mM Tris, pH 8.0; 150 mM NaCl; 2 mM phenylmethyl-sulfonyl fluoride (PMSF) (n = 8); 5) 10 mM Tris, pH 8.0; 150 mM NaCl; 2 mM 1,10-phenanthroline; 2 mM PMSF (n = 9). Samples then were immersed in fixative solution for 24 h and processed to obtain 5 μm thick longitudinal sections of the secretory stage enamel organic ECM. The sections were immersed in 80% glycerin for 30 min and analyzed by transmitted polarizing light microscopy. 1,10-Phenanthroline (inhibitor of metalloproteinases) and 1,10-phenanthroline + PMSF (inhibitor of serine proteinases) clearly prevented a decrease in the optical retardation of birefringence brightness from the tissue. PMSF alone promoted a slight preservation of the birefringence exhibited by the secretory stage enamel organic ECM. Rapid loss of birefringence in secretory stage enamel organic ECM that is not fixed immediately is caused by enamel proteinases and the activity of metalloproteinases seems to lead to preliminary degradation of the enamel organic ECM, which in turn facilitates subsequent serine proteinase activity.
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Affiliation(s)
- A R do Espirito Santo
- Department of Morphology, Piracicaba Dental School, University of Campinas - UNICAMP, Piracicaba, São Paulo, Brazil
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