1
|
Hubbard MJ, Mangum JE, Perez VA, Williams R. A Breakthrough in Understanding the Pathogenesis of Molar Hypomineralisation: The Mineralisation-Poisoning Model. Front Physiol 2022; 12:802833. [PMID: 34992550 PMCID: PMC8724775 DOI: 10.3389/fphys.2021.802833] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 11/26/2021] [Indexed: 11/13/2022] Open
Abstract
Popularly known as "chalky teeth", molar hypomineralisation (MH) affects over 1-in-5 children worldwide, triggering massive amounts of suffering from toothache and rapid decay. MH stems from childhood illness and so offers a medical-prevention avenue for improving oral and paediatric health. With a cross-sector translational research and education network (The D3 Group; thed3group.org) now highlighting this global health opportunity, aetiological understanding is urgently needed to enable better awareness, management and eventual prevention of MH. Causation and pathogenesis of "chalky enamel spots" (i.e., demarcated opacities, the defining pathology of MH) remain unclear despite 100 years of investigation. However, recent biochemical studies provided a pathomechanistic breakthrough by explaining several hallmarks of chalky opacities for the first time. This article outlines these findings in context of previous understanding and provides a working model for future investigations. The proposed pathomechanism, termed "mineralisation poisoning", involves localised exposure of immature enamel to serum albumin. Albumin binds to enamel-mineral crystals and blocks their growth, leading to chalky opacities with distinct borders. Being centred on extracellular fluid rather than enamel-forming cells as held by dogma, this localising pathomechanism invokes a new type of connection with childhood illness. These advances open a novel direction for research into pathogenesis and causation of MH, and offer prospects for better clinical management. Future research will require wide-ranging inputs that ideally should be coordinated through a worldwide translational network. We hope this breakthrough will ultimately lead to medical prevention of MH, prompting global health benefits including major reductions in childhood tooth decay.
Collapse
Affiliation(s)
- Michael J Hubbard
- Faculty of Medicine Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, VIC, Australia.,Department of Pharmacology & Therapeutics, The University of Melbourne, Parkville, VIC, Australia.,Melbourne Dental School, The University of Melbourne, Parkville, VIC, Australia
| | - Jonathan E Mangum
- Department of Pharmacology & Therapeutics, The University of Melbourne, Parkville, VIC, Australia
| | - Vidal A Perez
- Department of Pharmacology & Therapeutics, The University of Melbourne, Parkville, VIC, Australia.,Department of Pediatric Stomatology, Faculty of Health Sciences, University of Talca, Talca, Chile
| | - Rebecca Williams
- Department of Pharmacology & Therapeutics, The University of Melbourne, Parkville, VIC, Australia.,Melbourne Dental School, The University of Melbourne, Parkville, VIC, Australia
| |
Collapse
|
2
|
Perez VA, Mangum JE, Hubbard MJ. Pathogenesis of Molar Hypomineralisation: Aged Albumin Demarcates Chalky Regions of Hypomineralised Enamel. Front Physiol 2020; 11:579015. [PMID: 33101060 PMCID: PMC7556231 DOI: 10.3389/fphys.2020.579015] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 09/04/2020] [Indexed: 11/13/2022] Open
Abstract
Molar hypomineralisation (MH) is becoming globally recognised as a significant public health problem linked to childhood tooth decay. However, with causation and pathogenesis unclear after 100 years of investigation, better pathological understanding is needed if MH is to become preventable. Our studies have implicated serum albumin in an extracellular pathomechanism for chalky enamel, opposing longheld dogma about systemic injury to enamel-forming cells. Hypothesising that chalky enamel arises through developmental exposure to serum albumin, this study used biochemical approaches to characterise demarcated opacities from 6-year molars. Addressing contradictory literature, normal enamel was found to completely lack albumin subject to removal of surface contamination. Querying surface permeability, intact opacities were found to lack salivary amylase, indicating that “enamel albumin” had become entrapped before tooth eruption. Thirdly, comparative profiling of chalky and hard-white enamel supported a dose-response relationship between albumin and clinical hardness of opacities. Moreover, albumin abundance delineated chalky enamel from white transitional enamel at opacity borders. Finally, addressing the corollary that enamel albumin had been entrapped for several years, clear signs of molecular ageing (oxidative aggregation and fragmentation) were identified. By establishing aged albumin as a biomarker for chalky enamel, these findings hold methodological, clinical, and aetiological significance. Foremost, direct inhibition of enamel-crystal growth by albumin (here termed “mineralisation poisoning”) at last provides a cogent explanation for the clinical presentation of demarcated opacities. Together, these findings justify pursuit of an extracellular paradigm for the pathogenesis of MH and offer exciting new prospects for alleviating childhood tooth decay through medical prevention of MH.
Collapse
Affiliation(s)
- Vidal A Perez
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, VIC, Australia.,Department of Pediatric Stomatology, Faculty of Health Sciences, University of Talca, Talca, Chile
| | - Jonathan E Mangum
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, VIC, Australia
| | - Michael J Hubbard
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, VIC, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, VIC, Australia.,Faculty of Medicine Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, Australia.,Melbourne Dental School, The University of Melbourne, Parkville, VIC, Australia
| |
Collapse
|
3
|
Lelis IMP, Molina GF, Souza C, Perez WB, Laure HJ, Rosa JC, Gerlach RF. Peptide Characterization of Mature Fluorotic and Control Human Enamel. Braz Dent J 2017; 27:66-71. [PMID: 27007349 DOI: 10.1590/0103-6440201600424] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 01/25/2016] [Indexed: 11/22/2022] Open
Abstract
Exposure to high fluoride levels during amelogenesis causes enamel fluorosis. This study aimed to determine and compare the amino acid sequences in the enamel of fluorotic and control teeth. This investigation included enamel samples obtained from erupted and non-erupted third molars with either TF grade 4-6 (n=7) fluorosis or no sign of fluorosis (controls, n=7). The samples were kept frozen at -20 °C until protein extraction. Samples were etched and processed with a cocktail of proteinase inhibitors and immediately analyzed. Matrix Assisted Laser Desorption/Ionization-Time-Of-Flight/Time-of-Flight Mass Spectrometry (MALDI-TOF/TOF) followed by MASCOT search aided the peptides analysis. The more abundant peptides bore the N-terminal amelogenin sequences WYQSIRPPYP (which is specific for the X-encoded amelogenin) and MPLPPHPGHPGYINF (which does not show sexual dimorphism) were not different in control or fluorotic enamel. There was no missing proteolytic cleavage in the fluorotic samples, which suggested that the increased amount of protein described in fluorotic enamel did not stem from the decreased ability of proteinases to cleave the proteins in humans. This study showed how to successfully obtain peptide from superficial enamel. A relatively low number of teeth was sufficient to provide good data on the actual peptides found in mature enamel.
Collapse
Affiliation(s)
- Isabel Maria Porto Lelis
- Department of Morphology, Dental School of Piracicaba, Universidade Estadual de Campinas, Piracicaba, SP, Brazil
| | - Gabriela F Molina
- Departament of Morphology, Physiology and Basic Patology, Dental School of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | | | - Walter B Perez
- Department of Stomatology, Health Sciences Center, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | - Helen J Laure
- Departament of Cellular and Molecular Biology and Bio-Agents Pathogens, Medical School of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - José C Rosa
- Departament of Cellular and Molecular Biology and Bio-Agents Pathogens, Medical School of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Raquel F Gerlach
- Departament of Morphology, Physiology and Basic Patology, Dental School of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| |
Collapse
|
4
|
Hubbard MJ, McHugh NJ, Mangum JE. Exclusion of all three calbindins from a calcium-ferry role in rat enamel cells. Eur J Oral Sci 2012; 119 Suppl 1:112-9. [PMID: 22243236 DOI: 10.1111/j.1600-0722.2011.00890.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
It is widely accepted that healthy enamel formation depends on a steady supply of calcium, yet only fragmentary understanding exists about the mechanisms underlying transepithelial calcium transport. Several lines of evidence indicate that calcium principally follows a transcellular route, which classically is thought to be facilitated by cytosolic calcium-binding proteins termed calbindins. In enamel cells, however, this 'calcium-ferry' dogma appears to fail as we previously found that the major calbindin in murine enamel cells (calbindin-28 kDa) was down-regulated during the peak period of calcium transport and enamel was formed normally in mice lacking calbindin-28 kDa. It remains to be clarified whether the two other known calbindins could function as calcium ferries instead. This study used biochemical and proteomic approaches to obtain definitive identification and quantification of the 30-kDa calbindin (calretinin) and calbindin-9 kDa (S100-G) in enamel epithelium from rat. By establishing that both of these calbindins contribute insufficient calcium capacities in molars and incisors, our results render the calcium-ferry dogma untenable. Of significance to enamel defects and dental bioengineering, these findings support other evidence for an alternative organelle-based mode of calcium transport (calcium transcytosis) and also implicate S100-G/calbindin-9 kDa, but not calretinin, in a calcium-signaling role during enamel maturation.
Collapse
Affiliation(s)
- Michael J Hubbard
- Department of Biochemistry, University of Otago, Dunedin, New Zealand.
| | | | | |
Collapse
|