Novel ITGB6 variants cause hypoplastic-hypomineralized amelogenesis imperfecta and taurodontism: characterization of tooth phenotype and review of literature.

OBJECTIVES: To characterize phenotype and genotype of amelogenesis imperfecta (AI) in a Thai patient, and review of literature. MATERIALS AND METHODS: Variants were identified using trio-exome and Sanger sequencing. The ITGB6 protein level in patient's gingival cells was measured. The patient's deciduous first molar was investigated for surface roughness, mineral density, microhardness, mineral composition, and ultrastructure. RESULTS: The patient exhibited hypoplastic-hypomineralized AI, taurodontism, and periodontal inflammation. Exome sequencing identified the novel compound heterozygous ITGB6 mutation, a nonsense c.625 G > T, p.(Gly209*) inherited from mother and a splicing c.1661-3 C > G from father, indicating AI type IH. The ITGB6 level in patient cells was significantly reduced, compared with controls. Analyses of a patient's tooth showed a significant increase in roughness while mineral density of enamel and microhardness of enamel and dentin were significantly reduced. In dentin, carbon was significantly decreased while calcium, phosphorus, and oxygen levels were significantly increased. Severely collapsed enamel rods and a gap in dentinoenamel junction were observed. Of six affected families and eight ITGB6 variants that have been reported, our patient was the only one with taurodontism. CONCLUSION: We report the hypoplasia/hypomineralization/taurodontism AI patient with disturbed tooth characteristics associated with the novel ITGB6 variants and reduced ITGB6 expression, expanding genotype, phenotype, and understanding of autosomal recessive AI.

Utilization of rapid antigen tests for screening SARS-CoV-2 prior to dental treatment.

Potential aerosols containing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral particles can be generated during dental treatment. Hence, patient triage is essential to prevent the spread of SARS-CoV-2 in dental clinical settings. The present study described the use of rapid antigen tests for SARS-CoV-2 screening prior to dental treatment in an academic dental clinical setting in Thailand during the pandemic. The opinions of dental personnel toward the use of rapid antigen test screening prior to dental treatment were also assessed. From August 25 to October 3, 2021, dental patients who were expected to receive aerosols generating dental procedures were requested to screen for SARS-CoV-2 using a rapid antigen test before their treatment. A total of 7,618 cases completed the screening process. The average was 212 cases per day. Only five patients (0.07%) were positive for SARS-CoV-2 in the rapid antigen screening tests. All positive cases exhibited mild symptoms. For the questionnaire study, experienced dental personnel frequently and consistently agreed with the use of the rapid antigen test for SARS-CoV-2 screening, which made them feel safer during their patient treatment. However, implementing rapid antigen tests for SARS-CoV-2 may increase the total time spent on a dental appointment. In conclusion, a rapid antigen test could detect the infected individual prior to dental treatment. However, the specificity of rapid antigen tests for SARS-CoV-2 must be taken into account for consideration as a screening process before dental treatment. The enhanced infection control protocols in dental treatment must be consistently implemented.

Reduced ELANE and SLPI expression compromises dental pulp cell activity.

BACKGROUND: Patients with ELANE variants and severe congenital neutropenia (SCN) commonly develop oral complications. Whether they are caused only by low neutrophil count or the combination of neutropenia and aberrant dental cells is unknown. METHODS: Genetic variant was identified with exome sequencing. Dental pulp cells isolated from the SCN patient with an ELANE mutation were investigated for gene expression, enzyme activity, proliferation, colony formation, wound healing, apoptosis, ROS, attachment, spreading and response to lipopolysaccharide. RESULTS: ELANE cells had diminished expression of ELANE and SLPI and reduced neutrophil elastase activity. Moreover, ELANE cells exhibited impaired proliferation, colony forming, migration, attachment and spreading; and significantly increased ROS formation and apoptosis, corresponding with increased Cyclin D1 and MMP2 levels. The intrinsic levels of TGF-ß1 and TNF-α were significantly increased; however, IL-6, IL-8 and NF-kB1 were significantly decreased in ELANE cells compared with those in controls. After exposure to lipopolysaccharide, ELANE cells grew larger, progressed to more advanced cell spreading stages and showed significantly increased SLPI, TNF-α and NF-kB1 and tremendously increased IL-6 and IL-8 expression, compared with controls. CONCLUSION: This study, for the first time, suggests that in addition to neutropenia, the aberrant levels and functions of ELANE, SLPI and their downstream molecules in pulp cells play an important role in oral complications in SCN patients. In addition, pulp cells with diminished neutrophil elastase and SLPI are highly responsive to inflammation.

Phenotypic features of dentinogenesis imperfecta associated with osteogenesis imperfecta and COL1A2 mutations.

OBJECTIVE: Dentinogenesis imperfecta (DI) requires dental treatment. This study investigated the characteristics of DI teeth associated with osteogenesis imperfecta (OI) and COL1A2 mutations. STUDY DESIGN: Whole exome and Sanger sequencing were performed. Three primary teeth (called "OIDI teeth") obtained from 3 unrelated COL1A2 patients were investigated and compared with 9 control teeth from age-matched healthy individuals using colorimetry, micro-computed tomography, Knoop microhardness, energy dispersive X-ray spectroscopy, scanning electron microscopy, and histology. RESULTS: All patients were identified with heterozygous glycine substitutions in COL1A2. The COL1A2 mutations, c.1531G>T and c.2027G>T, were de novo, whereas c.3106G>C was inherited. OIDI1, 2, and 3 teeth had a substantial decrease in dentin microhardness and lightness. OIDI2 enamel microhardness was significantly reduced, whereas OIDI1 and 3 had enamel microhardness comparable to that of control individuals. The OIDI1 pulp cavity was large; OIDI2 was narrow; and OIDI3 was obliterated. OIDI1 and 3 had significantly higher carbon levels than those in control individuals. Numerous ectopic calcified masses, sparse and obstructed dentinal tubules, dentin holes, and collagen disorientation were observed. CONCLUSIONS: OIDI teeth had reduced lightness and variable pulp morphology. Weak dentin, mineral disproportion, and abnormal ultrastructure could contribute to the brittleness of OIDI teeth and adhesive restoration failure. Here, we expand the phenotypic spectrum of COL1A2 mutations and raise awareness among dentists seeing patients with OI.

Tooth ultrastructure of a novel COL1A2 mutation expanding its genotypic and phenotypic spectra.

OBJECTIVES: To investigate tooth ultrastructure and mutation of two patients in a family affected with osteogenesis imperfecta (OI) type IV and dentinogenesis imperfecta (DGI). METHODS: Mutations were detected by whole exome and Sanger sequencing. The permanent second molar obtained from the proband (DGI1) and the primary first molar from his affected son (DGI2) were studied for their color, roughness, mineral density, hardness, elastic modulus, mineral content, and ultrastructure, compared to the controls. RESULTS: Two novel missense COL1A2 variants, c.752C > T (p.Ser251Phe) and c.758G > T (p.Gly253Val), were identified in both patients. The c.758G > T was predicted to be the causative mutation. Pulp cavities of DGI1 (permanent teeth) were obliterated while those of DGI2 (primary teeth) were wide. The patients' teeth had darker and redder colors; reduced dentin hardness; decreased, disorganized, and scattered dentinal tubules and collagen fibers; and irregular dentinoenamel junction (DEJ), compared to controls. Lacunae-like structures were present in DGI2. CONCLUSIONS: We reported the novel causative mutation, c.758G > T (p.Gly253Val), in COL1A2 for OI type IV and DGI. The DGI dentin demonstrated inferior mechanical property and ultrastructure, suggesting severe disturbances of dentin formation. These could contribute to fragility and prone to infection of DGI teeth. This study expands phenotypic and genotypic spectra of COL1A2 mutations.

NOTCH2 participates in Jagged1-induced osteogenic differentiation in human periodontal ligament cells.

Jagged1 activates Notch signaling and subsequently promotes osteogenic differentiation in human periodontal ligament cells (hPDLs). The present study investigated the participation of the Notch receptor, NOTCH2, in the Jagged1-induced osteogenic differentiation in hPDLs. NOTCH2 and NOTCH4 mRNA expression levels increased during hPDL osteogenic differentiation. However, the endogenous NOTCH2 expression levels were markedly higher compared with NOTCH4. NOTCH2 expression knockdown using shRNA in hPDLs did not dramatically alter their proliferation or osteogenic differentiation compared with the shRNA control. After seeding on Jagged1-immobilized surfaces and maintaining the hPDLs in osteogenic medium, HES1 and HEY1 mRNA levels were markedly reduced in the shNOTCH2-transduced cells compared with the shControl group. Further, shNOTCH2-transduced cells exhibited less alkaline phosphatase enzymatic activity and in vitro mineralization than the shControl cells when exposed to Jagged1. MSX2 and COL1A1 mRNA expression after Jagged1 activation were reduced in shNOTCH2-transduced cells. Endogenous Notch signaling inhibition using a γ-secretase inhibitor (DAPT) attenuated mineralization in hPDLs. DAPT treatment significantly promoted TWIST1, but decreased ALP, mRNA expression, compared with the control. In conclusion, Notch signaling is involved in hPDL osteogenic differentiation. Moreover, NOTCH2 participates in the mechanism by which Jagged1 induced osteogenic differentiation in hPDLs.

Interaction Between Dendritic Cells and Candida krusei ß-Glucan Partially Depends on Dectin-1 and It Promotes High IL-10 Production by T Cells.

Host-Candida interaction has been broadly studied during Candida albicans infection, with a progressive shift in focus toward non-albicans Candida species. C. krusei is an emerging multidrug resistant pathogen causing rising morbidity and mortality worldwide. Therefore, understanding the interplay between the host immune system and C. krusei is critically important. Candia cell wall ß-glucans play significant roles in the induction of host protective immune responses. However, it remains unclear how C. krusei ß-glucan impacts dendritic cell (DC) responses. In this study, we investigated DC maturation and function in response to ß-glucans isolated from the cell walls of C. albicans, C. tropicalis, and C. krusei. These three distinct Candida ß-glucans had differential effects on expression of the DC marker, CD11c, and on DC maturation. Furthermore, bone-marrow derived DCs (BMDCs) showed enhanced cytokine responses characterized by substantial interleukin (IL)-10 production following C. krusei ß-glucan stimulation. BMDCs stimulated with C. krusei ß-glucan augmented IL-10 production by T cells in tandem with increased IL-10 production by BMDCs. Inhibition of dectin-1 ligation demonstrated that the interactions between dectin-1 on DCs and cell wall ß-glucans varied depending on the Candida species. The effects of C. krusei ß-glucan were partially dependent on dectin-1, and this dependence, in part, led to distinct DC responses. Our study provides new insights into immune regulation by C. krusei cell wall components. These data may be of use in the development of new clinical approaches for treatment of patients with C. krusei infection.

Compromised alveolar bone cells in a patient with dentinogenesis imperfecta caused by DSPP mutation.

OBJECTIVES: Dentin sialophosphoprotein (DSPP) plays an important role in the mineralization of both dentin and bones. The Dspp null mice developed periodontal diseases. Patients with DSPP mutations have dentinogenesis imperfecta (DGI), but very little is known about their bone characteristics. This study aims to characterize alveolar bone cells of a DGI patient with DSPP mutation. MATERIALS AND METHODS: Pathogenic variants were identified by whole exome and sanger sequencing. Cells isolated from the alveolar bones of a DSPP patient were investigated for their characteristics including cell morphology, attachment, spreading, proliferation, colony formation, mineralization, and osteogenic differentiation. RESULTS: We identified a Thai family with three members affected with autosomal dominant DGI harboring a heterozygous pathogenic missense mutation, c.50C > T, p.P17L, in exon 2 of the DSPP gene. The patients' phenotypes presented deteriorated opalescent teeth with periapical lesions, thickening of lamina dura, furcation involvement, alveolar bone loss, and bone exostoses. The alveolar bone cells isolated from DSPP patient exhibited compromised proliferation and colony formation. Scanning electron microscope revealed altered cellular morphology and spreading. The DSPP cells showed deviated mRNA levels of OCN, ALP, and COL1 but maintained in vitro mineralization ability compared to the control. CONCLUSIONS: We demonstrate that the DSPP p.P17L mutant alveolar bone cells had compromised cell spreading, proliferation, colony formation, and osteogenic induction, suggesting abnormal bone characteristics in the patient with DGI caused by DSPP mutation. CLINICAL RELEVANCE: DSPP mutation can induce the behavior alterations of alveolar bone cells.