Autoimmune amelogenesis imperfecta in patients with APS-1 and coeliac disease.

Ameloblasts are specialized epithelial cells in the jaw that have an indispensable role in tooth enamel formation-amelogenesis1. Amelogenesis depends on multiple ameloblast-derived proteins that function as a scaffold for hydroxyapatite crystals. The loss of function of ameloblast-derived proteins results in a group of rare congenital disorders called amelogenesis imperfecta2. Defects in enamel formation are also found in patients with autoimmune polyglandular syndrome type-1 (APS-1), caused by AIRE deficiency3,4, and in patients diagnosed with coeliac disease5-7. However, the underlying mechanisms remain unclear. Here we show that the vast majority of patients with APS-1 and coeliac disease develop autoantibodies (mostly of the IgA isotype) against ameloblast-specific proteins, the expression of which is induced by AIRE in the thymus. This in turn results in a breakdown of central tolerance, and subsequent generation of corresponding autoantibodies that interfere with enamel formation. However, in coeliac disease, the generation of such autoantibodies seems to be driven by a breakdown of peripheral tolerance to intestinal antigens that are also expressed in enamel tissue. Both conditions are examples of a previously unidentified type of IgA-dependent autoimmune disorder that we collectively name autoimmune amelogenesis imperfecta.

The innate host response in caries and periodontitis.

INTRODUCTION: Innate immunity rapidly defends the host against infectious insults. These reactions are of limited specificity and exhaust without providing long-term protection. Functional fluids and effector molecules contribute to the defence against infectious agents, drive the immune response, and direct the cellular players. AIM: To review the literature and present a summary of current knowledge about the function of tissues, cellular players and soluble mediators of innate immunity relevant to caries and periodontitis. METHODS: Historical and recent literature was critically reviewed based on publications in peer-reviewed scientific journals. RESULTS: The innate immune response is vital to resistance against caries and periodontitis and rapidly attempts to protect against infectious agents in the dental hard and soft tissues. Soluble mediators include specialized proteins and lipids. They function to signal to immune and inflammatory cells, provide antimicrobial resistance, and also induce mechanisms for potential repair of damaged tissues. CONCLUSIONS: Far less investigated than adaptive immunity, innate immune responses are an emerging scientific and therapeutic frontier. Soluble mediators of the innate response provide a network of signals to organize the near immediate molecular and cellular response to infection, including direct and immediate antimicrobial activity. Further studies in human disease and animal models are generally needed.

Immunohistochemical and Western blot analyses of collar enamel in the jaw teeth of gars, Lepisosteus oculatus, an actinopterygian fish.

Although most fish have no enamel layer in their teeth, those belonging to Lepisosteus (gars), an extant actinopterygian fish genus, do and so can be used to study amelogenesis. In order to examine the collar enamel matrix in gar teeth, we subjected gar teeth to light and electron microscopic immunohistochemical examinations using an antibody against bovine amelogenin (27 kDa) and antiserum against porcine amelogenin (25 kDa), as well as region-specific antibodies and antiserum against the C-terminus and middle region, and N-terminus of porcine amelogenin, respectively. The enamel matrix exhibited intense immunoreactivity to the anti-bovine amelogenin antibody and the anti-porcine amelogenin antiserum in addition to the C-terminal and middle region-specific antibodies, but not to the N-terminal-specific antiserum. These results suggest that the collar enamel matrix of gar teeth contains amelogenin-like proteins and that these proteins possess domains that closely resemble the C-terminal and middle regions of porcine amelogenin. Western blot analyses of the tooth germs of Lepisosteus were also performed. As a result, protein bands with molecular weights of 78 kDa and 65 kDa were clearly stained by the anti-bovine amelogenin antibody as well as the antiserum against porcine amelogenin and the middle-region-specific antibody. It is likely that the amelogenin-like proteins present in Lepisosteus do not correspond to the amelogenins found in mammals, although they do possess domains that are shared with mammalian amelogenins.

A histological processing technique that preserves the integrity of calcified tissues (bone, enamel), yolky amphibian embryos, and growth factor antigens in skeletal tissue.

We have devised a processing technique to embed calcified tissues, such as bone and tooth enamel, in paraffin, to preserve the delicate antigenic sites of molecules such as growth factors. The same technique, omitting the decalcification step, allows delicate tissues, such as axolotl embryos (Ambystoma mexicanum) containing large yolk masses, to be easily handled during tissue processing and to be serially sectioned. Specimens were all fixed in periodate-lysine-paraformaldehyde (PLP) fixative at 5 degrees C. Bone and teeth were decalcified in an EDTA-G solution at -4 degrees C. Maintaining a temperature of 5 degrees C, the decalcified samples were then washed (with PBS, pH 7.2, under vacuum) to remove glycerol. Both the decalcified tissues and the yolky embryos were dehydrated through an ascending series of isopropanol and embedded in low melting-point paraffin under vacuum. Acidic fibroblast growth factor (aFGF) was located in cells of the expanded cambial layer in the early fracture calluses of male CD-1 mice, demonstrating retention of antigenic sites. The results reported here have not previously been obtained with existing processing and embedding techniques.

An antisera for the fluorescent labeling of mouse amelogenesis.

Embryonic mammalian enamel extracellular matrix is immunogenic. Antisera has been produced in New Zealand white rabbits using 5-day-old (post-natal) C57B1/6J mandibular and maxillary incisor and molar tooth organs as immunogens. The expression of secretory amelogenesis in mouse molar tooth organs was studied from the "cap stage" (circa 17-day fetus) to the fifth day of postnatal odontogenesis using indirect immunofluorescent microscopy. The specificity of the antisera for enamel matrix secretion was unequivocal. Secretory amelogenesis was observed in molar tooth organs as early as day-2 postnatal age. These reagents and methods provide a significant strategy in studies of epithelial-mesenchymal interactions during tooth development.

Anti-peptide antibodies reactive with epitopic domains of porcine amelogenins at the C-terminus.

This was an immunological investigation of the processing of porcine amelogenins in situ. Rabbit and rat anti-peptide sera reacted specifically with the hydrophilic segment of the intact amelogenins at the C-terminus. The immunogens used were the synthetic peptides: (a) C13 composed of PATDKTKREEVDC and (b) C25 composed of MQSLLPDLPLEAWPATDKTKREEVD. These peptides correspond to the C-terminal 12- and 25-residue segments of porcine amelogenin, respectively. Cystine was introduced at the C-terminus of C12 for KLH-binding (C13). Western blot analysis disclosed that: (i) both rabbit and rat anti-C13 sera reacted selectively with the 25-kDa porcine amelogenin and three other minor components (27, 22 and 18 kDa); (ii) anti-C25 peptide sera, additionally, reacted with the 23-kDa amelogenins (a degradation derivative of the 25-kDa protein, lacking the 12-residue segment at the C-terminus) and as trace components, 20-, 16- and 14-kDa moieties. Importantly, all the proteins reactive with the anti-C13 serum were concentrated in the outer secretory enamel adjacent to the ameloblasts, decreasing significantly in the underlying inner secretory enamel. Immunohistochemical studies applying the anti-peptide sera to the developing tooth germs of a minipig also confirmed the localization of reactivity in the outer secretory region. Neither anti-peptide serum reacted with porcine non-amelogenins, serum proteins nor dentine matrix proteins at the dilutions tested. however, it was found that both the anti-C13 and C25 sera reacted with human keratin.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification and characterization of a squamate reptilian amelogenin gene: Iguana iguana.

As the principal components of the developing tooth enamel matrix, amelogenins play a significant role in tooth enamel formation and organization. In order to elucidate the structure and function of amelogenins in the evolution of enamel, we have selected the Iguana iguana as a squamate model organism. Here we report the first complete squamate amelogenin sequence available as of yet and document unique features of Iguana amelogenins and enamel. Transmission electron microscopy documented randomly oriented Iguana enamel crystals during the elongation phase compared with organized enamel crystal patterns at comparable stages in mammals. Sequencing of PCR amplified products revealed a full-length I. iguana amelogenin cDNA containing 877 nucleotides with a 564 nucleotide coding sequence encoding 187 amino acids. The homologies of the newly discovered I. iguana amelogenin amino acid sequence with the published mouse, caiman (Palaeosuchus), and snake (Elaphe) amelogenin were 41.3%, 53.5%, and 55.5%, respectively. On Western blots one major protein with a molecular weight of 24 kDa, and two minor proteins with molecular weights of 28 and 13.5 kDa, respectively, were detected based on the cross-reactivity of antisera against recombinant Rana pipiens amelogenin proteins. Sequence analysis revealed a moderate sequence homology between mammalian and reptilian amelogenin genes. A significant alteration was the deletion of the hydrophilic GSP sequence from exon 3 in the mouse sequence resulting in a conversion to a hydrophobic region in Iguana. Together, these findings identified a novel amelogenin cDNA sequence in the squamate reptilian I. iguana and functional implications for the evolution of amelogenins and enamel in squamates.

In vitro attachment of streptococci to the tooth surface.

The ability of Streptococcus strains to adhere to the tooth surface in vitro was investigated. Polished enamel slabs, with and without acquired pellicles, were incubated with buffer suspensions of oral streptococci, and attached bacteria were counted under a microscope using incident light. Low numbers of bacteria adhered to uncoated enamel; the presence of an acquired pellicle significantly enhanced the attachment of all strains tested. The adherence of Streptococcus sanguis was significantly greater than that of Streptococcus salivarius, and both of these strains adhered in greater numbers than did Streptococcus mutans. When bacteria were suspended in whole saliva, the adherence of S. salivarius and S. mutans was inhibited, whereas the adherence of S. sanguis was enhanced in some experiments and inhibited in others. The adherence of S. sanguis and S. salivarius was consistently inhibited by parotid fluid; this inhibitory effect persisted after thorough washing and resonication of the bacterial cells. Incubation in oral fluids was associated with the attachment of bacterial clumps to the pellicle, and parallel investigation revealed agglutination of S. sanguis and S. salivarius by whole saliva and, in particular, parotid fluid. The results are discussed in terms of surface microecology, and are related to the development of dental plaque.

IgE in postsecretory ameloblasts suggesting a hypersensitivity reaction at tooth eruption.

The clinical symptoms associated with the eruption of primary teeth resemble a mild hypersensitivity reaction. Light microscopic examination showed that IgE accumulated in postsecretory ameloblasts. The formation of IgE was elicited by enamel matrix proteins, which are chemotactic for mast cells.

Tooth enamel dust as an asthma stimulus. A case report.

A case report of a first-year dental student with asthma, who experienced exacerbation of symptoms and a severe asthmatic crisis in the course of her preclinical dental training, is presented. Dust generated as a result of preparing natural teeth triggered the bronchoconstrictive response. Her subsequent medical and preventive measures are cited. This case identifies, for the first time, enamel dust as an asthma stimulus, thus serving as a precaution to prospective dental students and personnel afflicted with the disease and emphasizing the importance of effective face masks in dental laboratories during dust-generating procedures.

Immunoblotting demonstration of antibodies to the organic matrix of developing bovine enamel.

Antiserum was raised against an acetic acid extract of partly mineralized bovine enamel. By use of immunoblotting it was shown that rabbit antibodies react with both high and low molecular weight proteins. Most but not all of the enamel proteins isolated by different extraction solutions were antigenic identical. The blotting time was found to be important when immunoblotting of enamel proteins is carried out.

A histochemical study on lectin binding in the immature enamel and secretory ameloblasts of rat incisors.

Four lectin-fluorescent marker conjugates (Con A-F, MPA-F, PNA-F, WGA-R) were used for visualizing their binding sites on tissue sections by fluorescent microscopy. The immature enamel, Tomes' processes and distal cytoplasm of ameloblasts were stained with MPA-F and WGA-R on paraformaldehyde-fixed and paraffin-embedded tissue sections. The MPA- and WGA-binding glycoconjugates seemed to be main components of the organic enamel matrix because of the intense fluorescence from the tissue sections. The central portion of distal cytoplasm of ameloblasts was stained with PNA-F but the immature enamel and Tomes' processes were not. This suggests the PNA-binding glycoconjugates to be intermediates during the process of modifying their oligosaccharide chains or to be elements of Golgi area. Tomes' processes, the distal cytoplasm and periphery of nuclei of ameloblasts were stained with Con A-F. The Con A-binding glycoconjugates except those localizing on Tomes' processes may also be intermediates and/or intracellular elements like the PNA-binding glycoconjugates. Cells of stratum intermedium were stained with Con A-F, MPA-F and WGA-R. Cells of stellate reticulum and outer enamel epithelium were stained with Con A-F and WGA-R. It was indicated that enamel proteins, major organic components of immature enamel, are highly possible candidates for the MPA- and WGA-binding glycoconjugates.

Production of a monoclonal antibody against human amelogenin.

The extracellular organic matrix of developing human enamel is composed of two major classes of proteins, the hydrophobic amelogenins and the acidic enamelins. In order to identify, purify, and characterize the amelogenins from this complex mixture of proteins, and to study their ultrastructural localization and their pathways of synthesis, secretion, and degradation, specific and sensitive probes are needed. In the present paper the production of a monoclonal antibody against human amelogenin employing an intrasplenic primary immunization protocol is described. The monoclonal antibody produced is IgM and recognizes major human amelogenin protein bands in Western immunoblot assays. It also recognizes amelogenin protein bands from other species, specifically bovine and porcine. Indirect immunohistochemical studies showed the monoclonal antibody to react specifically with the extracellular matrix of human developing enamel. It did not react with the underlying dentin layer.

Immunohistochemical detection of an enamel protein-related epitope in rat bone at an early stage of osteogenesis.

Monoclonal antibody MI315 was produced against hamster tooth germ homogenate by in vitro immunization. It was found that MI315 reacted with enamel matrix, ameloblasts, and bone matrix at an early stage of osteogenesis. Decalcified tissues of rat femurs and mandibles were examined with MI315 using indirect immunofluorescence. In endochondral ossification of femurs, immunoreactivity was found in bone extracellular matrix (ECM) deposited on the surface of the cartilage core of primary spongiosa, but not in the cartilage core itself. In intramembranous ossification of 0-day-old rat mandibles, intense immunofluorescence was detected in bone ECM and a few young osteocytes, but not in osteoblasts. Immunoreactivity in bone ECM of 2-day-old rats decreased and almost disappeared from bone ECM of 4-day-old rats. Although in nondecalcified sections of 0-day-old rats, negligible immunofluorescence was detected in bone ECM which showed positive staining in decalcified tissues, the immunostaining appeared after decalcification using ethylenediaminetetraacetic acid (EDTA). These results indicate that a substance(s), which had a common epitope with an enamel-derived protein(s), existed in immature bone ECM of both endochondral and intramembranous ossification, and that it might be masked by bone mineral. Monoclonal antibody MI315 is a useful tool to investigate the time- and position-specific changes in osteogenesis and amelogenesis.

Transient accumulation of proteins at interrod and rod enamel growth sites.

Conceptually, there should be a brief interval in time when newly secreted proteins "pile up" at secretory sites just outside the membrane of ameloblasts. Indeed, previous cytochemical studies have suggested that glycosylated and/or sulfated glycoproteins accumulate at enamel growth sites. Colloidal gold lectin cytochemistry and immunocytochemistry with antibodies to enamel proteins and phosphoserine, combined with cycloheximide and brefeldin A to inhibit protein synthesis and secretion, were applied to characterize the distribution of newly formed proteins at enamel interrod and rod growth sites. Although enamel growth sites show a "rarefied" appearance, the results indicate that one or more subclasses of enamel proteins accumulate near the cell surface at sites where elongation of enamel crystallites contributes to thickening of the enamel layer. These proteins are glycosylated and/or phosphorylated and, at least in the case of the glycosylated ones, are rapidly processed after they are released extracellularly. In contrast, immunolabeling for amelogenins is generally weaker near the cell surface and more intense at a short distance away from the site where crystallites elongate. The data suggest that the enamel proteins accumulating at growth sites likely belong to the non-amelogenin category and play a transient role in promoting the lengthening of crystallites. It is concluded that areas near the ameloblast membrane where certain enamel proteins accumulate in fact constitute the equivalent of a mineralization front.

Inhibition by yeast killer toxin-like antibodies of oral Streptococci adhesion to tooth surfaces in an ex vivo model.

BACKGROUND: Monoclonal (KTmAb) and recombinant (KTscFv) anti-idiotypic antibodies, representing the internal image of a yeast killer toxin, proved to be microbicidal in vitro against important eukaryotic and prokaryotic pathogens such as Candida albicans, Pneumocystis carinii, Mycobacterium tuberculosis, Staphylococcus aureus, S. haemolyticus, Enterococcus faecalis, E. faecium, and Streptococcus pneumoniae, including multidrug-resistant strains. KTmAb and KTscFv exerted a strong therapeutic effect in well-established animal models of candidiasis and pneumocystosis. Streptococcus mutans is the most important etiologic agent of dental caries that might result from the metabolic end products of dental plaque. Effective strategies to reduce the disease potential of dental plaque have considered the possibility of using antibiotics or antibodies against oral streptococci in general and S. mutans in particular. In this study, the activity of KTmAb and KTscFv against S. mutans and the inhibition and reduction by KTmAb of dental colonization by S. mutans and other oral streptococci in an ex vivo model of human teeth were investigated. MATERIALS AND METHODS: KTscFv and KTmAb were used in a conventional colony forming unit (CFU) assay against a serotype C strain of S. mutans, and other oral streptococci (S. intermedius, S. mitis, S. oralis, S. salivarius). An ex vivo model of human teeth submerged in saliva was used to establish KTmAb potential of inhibiting or reducing the adhesion to dental surfaces by S. mutans and other oral streptococci. RESULTS: KTmAb and KTscFv kill in vitro S. mutans and other oral streptococci. KTmAb inhibit colonization of dental surfaces by S. mutans and oral streptococci in the ex vivo model. CONCLUSIONS: Killer antibodies with antibiotic activity or their engineered derivatives may have a potential in the prevention of dental caries in vivo.

An extracellular matrix protein of dentine, enamel, and bone shares common antigenic determinants with keratins.

EDTA-soluble proteins extracted from rabbit dentine were injected into mice and antibodies were prepared by the hybridoma technique. A monoclonal antibody, MC9B5, was found to react with a 68 kd protein, a major component of the EDTA-soluble proteins present in rabbit and rat dentine. Weston immunoblotting demonstrated that the antigen was also present in rat enamel and bone. By indirect immunofluorescence, MC9B5 was found to specifically stain epithelial filamentous cytoskeletal structures. Double staining experiments using MC9B5 and antikeratin antibodies showed extensive co-localization on the epithelial cell cytoskeleton. Furthermore, the 68 kd extracellular matrix protein was recognized in dentine, enamel, and bone extracts by antikeratin antibodies as shown by immunoblotting. These data support a structural relationship between a mineralized tissue extracellular protein and keratins.

Tuft protein: its relationship with the keratins and the developing enamel matrix.

The relationship among tuft protein derived from mature human molars, human skin keratins, and the developing enamel matrix of the rat incisor was investigated using polyclonal antibodies in immunocytochemical and Western blotting techniques. Antibodies to tuft protein and keratin cross-reacted with proteins in the Mr range 50-70 K from demineralized developing enamel, enamel organ, human skin, and tuft extract. An immunocytochemical technique was used to locate the site of cross-reactivity in situ within secretory ameloblasts, enamel, and keratinized epithelium at the ultrastructural level. Antibodies to keratin cross-reacted with cytoplasmic tonofilaments and those inserted into desmosomes. Antibodies to tuft protein, however, did not cross-react with cytoskeletal components but produced labeling of the golgi and secretory vesicles. Labeling with this antibody was also observed within the stratum granulosum of the rat foot pad. It is concluded that tuft protein contains secretory products of the ameloblast that may represent a less specialized product of other epithelial tissues, perhaps related to the keratins.