Jang-Ho Son

Melatonin promotes osteoblast differentiation and mineralization of MC3T3-E1 cells under hypoxic conditions through activation of PKD/p38 pathways.

Osteoblastic differentiation and bone‐forming capacity are known to be suppressed under hypoxic conditions. Melatonin has been shown to influence cell differentiation. A number of in vitro and in vivo studies have suggested that melatonin also has an anabolic effect on bone, by promoting osteoblastic differentiation. However, the precise mechanisms and the signaling pathways involved in this process, particularly under hypoxic conditions, are unknown. This study investigated whether melatonin could promote osteoblastic differentiation and mineralization of preosteoblastic MC3T3‐E1 cells under hypoxic conditions. Additionally, we examined the molecular signaling pathways by which melatonin mediates this process. We found that melatonin is capable of promoting differentiation and mineralization of MC3T3‐E1 cells cultured under hypoxic conditions. Melatonin upregulated ALP activity and mRNA levels of Alp, Osx, Col1, and Ocn in a time‐ and concentration‐dependent manner. Alizarin red S staining showed that the mineralized matrix in hypoxic MC3T3‐E1 cells formed in a manner that was dependent on melatonin concentration. Moreover, melatonin stimulated phosphorylation of p38 Mapk and Prkd1 in these MC3T3‐E1 cells. We concluded that melatonin promotes osteoblastic differentiation of MC3T3‐E1 cells under hypoxic conditions via the p38 Mapk and Prkd1 signaling pathways.

Role of gingival manifestation in diagnosis of granulomatosis with polyangiitis (Wegener’s granulomatosis)

Purpose This report describes a case of granulomatosis with polyangiitis (GPA) in which the gingival manifestation was crucial in both making an early diagnosis and possibly in deciding the approach to treatment. Methods A 57-year-old sailor presented to the Department of Dentistry at Ulsan University Hospital complaining of gingival swelling since approximately 2 months. He had orofacial granulomatous lesions and the specific gingival manifestation of strawberry gingivitis. Results The diagnosis of GPA was made on the basis of clinical symptoms and signs, and confirmed by the presence of the anti-neutrophil cytoplasmic antibody and a positive biopsy. The patient was admitted to the hospital and subsequently placed on a disease-modifying therapy regimen that included methotrexate and prednisone. Conclusions Identification of the gingival manifestation of the disease permitted an early diagnosis and prompt therapy in a disease in which time is a crucial factor. Because of its rapid progression and potentially fatal outcome, an early diagnosis of GPA is important. Therefore, dentists should be aware of the oral signs and symptoms of such systemic diseases.

The involvement of histone methylation in osteoblastic differentiation of human periosteum-derived cells cultured in vitro under hypoxic conditions

Although oxygen concentrations affect the growth and function of mesenchymal stem cells (MSCs), the impact of hypoxia on osteoblastic differentiation is not understood. Likewise, the effect of hypoxia‐induced epigenetic changes on osteoblastic differentiation of MSCs is unknown. The aim of this study was to examine the in vitro hypoxic response of human periosteum‐derived cells (hPDCs). Hypoxia resulted in greater proliferation of hPDCs as compared with those cultured in normoxia. Further, hypoxic conditions yielded decreased expression of apoptosis‐ and senescence‐associated genes by hPDCs. Osteoblast phenotypes of hPDCS were suppressed by hypoxia, as suggested by alkaline phosphatase activity, alizarin red‐S‐positive mineralization, and mRNA expression of osteoblast‐related genes. Chromatin immunoprecipitation assays showed an increased presence of H3K27me3, trimethylation of lysine 27 on histone H3, on the promoter region of bone morphogenetic protein‐2. In addition, mRNA expression of histone lysine demethylase 6B (KDM6B) by hPDCs was significantly decreased in hypoxic conditions. Our results suggest that an increased level of H3K27me3 on the promoter region of bone morphogenetic protein‐2, in combination with downregulation of KDM6B activity, is involved in the suppression of osteogenic phenotypes of hPDCs cultured in hypoxic conditions. Although oxygen tension plays an important role in the viability and maintenance of MSCs in an undifferentiated state, the effect of hypoxia on osteoblastic differentiation of MSCs remains controversial. In addition, evidence regarding the importance of epigenetics in regulating MSCs has been limited. This study was to examine the role hypoxia on osteoblastic differentiation of hPDCs, and we examined whether histone methylation is involved in the observed effect of hypoxia on osteogenic differentiation of hPDCs.

Analysis of speech and tongue motion in normal and post-glossectomy speaker using cine MRI.

ABSTRACT Objective Since the tongue is the oral structure responsible for mastication, pronunciation, and swallowing functions, patients who undergo glossectomy can be affected in various aspects of these functions. The vowel /i/ uses the tongue shape, whereas /u/ uses tongue and lip shapes. The purpose of this study is to investigate the morphological changes of the tongue and the adaptation of pronunciation using cine MRI for speech of patients who undergo glossectomy. Material and Methods Twenty-three controls (11 males and 12 females) and 13 patients (eight males and five females) volunteered to participate in the experiment. The patients underwent glossectomy surgery for T1 or T2 lateral lingual tumors. The speech tasks “a souk” and “a geese” were spoken by all subjects providing data for the vowels /u/ and /i/. Cine MRI and speech acoustics were recorded and measured to compare the changes in the tongue with vowel acoustics after surgery. 2D measurements were made of the interlip distance, tongue-palate distance, tongue position (anterior-posterior and superior-inferior), tongue height on the left and right sides, and pharynx size. Vowel formants Fl, F2, and F3 were measured. Results The patients had significantly lower F2/Fl ratios (F=5.911, p=0.018), and lower F3/F1 ratios that approached significance. This was seen primarily in the /u/ data. Patients had flatter tongue shapes than controls with a greater effect seen in /u/ than /i/. Conclusion The patients showed complex adaptation motion in order to preserve the acoustic integrity of the vowels, and the tongue modified cavity size relationships to maintain the value of the formant frequencies.