In vivo dynamic analysis of BMP-2-induced ectopic bone formation

Bone morphogenetic protein (BMP)-2 plays a central role in bone-tissue engineering because of its potent bone-induction ability. However, the process of BMP-induced bone formation in vivo remains poorly elucidated. Here, we aimed to establish a method for intravital imaging of the entire process of BMP-2-induced ectopic bone formation. Using multicolor intravital imaging in transgenic mice, we visualized the spatiotemporal process of bone induction, including appearance and motility of osteoblasts and osteoclasts, angiogenesis, collagen-fiber formation, and bone-mineral deposition. Furthermore, we investigated how PTH1-34 affects BMP-2-induced bone formation, which revealed that PTH1-34 administration accelerated differentiation and increased the motility of osteoblasts, whereas it decreased morphological changes in osteoclasts. This is the first report on visualization of the entire process of BMP-2-induced bone formation using intravital imaging techniques, which, we believe, will contribute to our understanding of ectopic bone formation and provide new parameters for evaluating bone-forming activity.Hashimoto K., Kaito T., Furuya M., et al. In vivo dynamic analysis of BMP-2-induced ectopic bone formation. Scientific Reports 10, 4751 (2020); https://doi.org/10.1038/s41598-020-61825-2

高齢者の咀嚼・嚥下機能評価 : 文献レビューから考える高齢者の健康長寿

Dysphagia is a mechanical or functional difficulty in one or more phases of the swallowing process from food ingestion in the oral cavity to a bolus passing through the esophagus. Recent studies have shown that the cause of dysphagia is in the oral phase of swallowing; Therefore there is increasing importance in evaluations of the relationship between oral function and swallowing. Oral functions of oral organs, tongue, jaw, teeth, and cheek, have been studied from the viewpoint of prosthetic dentistry for rehabilitation of the oral structure and function. However, such studies focused on mastication rather than swallowing. In this report, we review recent literature on (1) senescence changes in swallowing of the elderly, (2) dysphagia and oral function, (3) oral prosthesis and swallowing; especially our past studies on the relationship between complete dentures and swallowing in the elderly. In the near future, with the rapid increase of an aged Japanese population, prosthetic dentistry will need more information to be available with respect to oral prostheses for oral feeding functions that include not only mastication but also swallowing data. Furthermore, prosthetic dentistry should research relevancies among oral prostheses, reconstruction of the oral feeding function, and preservation of deconditioning. From this some indications might be found for how to prevent disuse syndrome and aspiration pneumonia. This will be one of the responsibilities of prosthetic dentistry in its contribution to oral rehabilitation for health and long life of the elderly

全部床義歯装着が舌骨の位置と咽頭の幅径に与える影響

高齢者の摂食・嚥下機能を考える上では,加齢変化による摂食・嚥下機能の予備力低下を考慮する必要がある.特に,加齢による中咽頭拡大という器質的な変化は,咽頭残留の増加などの機能的変化の一因となると考えられている.一方,高齢者の口腔には,上下顎に全部床義歯が装着されていることが多く,義歯の装着と撤去は下顎位を偏位させて,中咽頭の形態に影響を及ぼすと推察されるが,その詳細は明らかになっていない.そこで本研究では,全部床義歯の装着状況が中咽頭の三次元的形態に与える影響を明らかにすることを目的とした.対象は,全部床義歯装着者17名(平均年齢72.9±9.2歳)とした.上下顎全部床義歯装着(上下顎あり),上顎全部床義歯装着(上顎のみ),上下顎全部床義歯非装着(上下顎なし)の3条件において,CBCTによる撮影を行い,三次元解析を用いて1)下顎の位置(FMA),2)舌骨の位置,3)中咽頭の幅径を測定し,各条件間で比較検討を行った.FMAは,上下顎ありに比べて,他の2条件では有意に減少した.舌骨の位置は,上下顎なしでは,上下顎ありに比べ有意に上方また前方に移動した.中咽頭の前後径は,喉頭蓋谷最深点の高さにおいて,上下顎なしでは,他の2条件に比べ有意に増加した.左右径は,上下顎なしでは,上下顎ありに比べ舌背と舌根の境界の高さ,および喉頭蓋谷最深点での高さにおいて有意に増加した.全部床義歯の撤去は,下顎を前上方に回転させ,舌骨を前上方に牽引する.その結果,舌根部が前方移動し,中咽頭の下部が前後左右方向に拡大したものと考えられた.義歯の撤去は,加齢によって生じた中咽頭の拡大という予備力低下のさらなる増悪に通じ,嚥下の際により大きな筋の収縮を必要とさせると考えられた.摂食・嚥下障害を有する高齢者は義歯が必要にも関わらず装着していないことも多く,本研究の結果より,義歯装着の新たな重要性が示された.In rehabilitation for dysphagia in the elderly, it is necessary to take into account both age-related changes and reduced reserve capacity for swallowing. Especially, since it was thought that the oropharyngeal expansion as morphological age-related change causes functional changes such as pharyngeal residue. Wearing complete dentures is common in elderly people, and although wearing and removing dentures is thought to affect the morphology of the oropharynx, the details of this effect remain unclear. The present study aimed to elucidate the relationship between wearing dentures and changes in the hyoid bone position and pharyngeal diameter. The subjects were 17 elderly people fitted with complete dentures who underwent cone-beam computed tomography imaging while wearing maxillary and mandibular dentures (MM), maxillary denture only (OM), and with neither maxillary nor mandibular dentures (ED). Computed tomography images were subjected to analysis of mandibular position (FMA), hyoid bone position, and antero-posterior and left-right oropharyngeal diameters. FMA decreased significantly in the order MM, OM, ED. In the ED condition, the hyoid bone shifted significantly in the antero-superior direction as compared with the MM and OM conditions. Antero-posterior and left-right oropharyngeal diameters in the ED condition were significantly larger than those in the MM condition at the height of the base of the epiglottis. Removal of complete dentures causes an antero-superior shift of the mandible, resulting in an anterior and superior shift of the hyoid bone and the expansion of the inferior part of the oropharynx. These findings suggest that removal of dentures exacerbate reduced reserve capacity for swallowing by age-related changes in the elderly

Comparison of three representative subjective evaluations of chewing function

In 2018, oral hypofunction was registered officially as a disease in Japan. It is important to detect oral hypofunction symptoms early in patients, before frank oral dysfunction symptoms occur. Subjective evaluations of chewing function, which help to identify foods that cannot be chewed, might be useful in diagnosing oral hypofunction. Previous evaluations used to identify patients with oral hypofunction used varying standards, making it impossible to compare and integrate them without first developing a unified screening method. This study aimed to compare and integrate known evaluation methods that are useful for diagnosing oral hypofunction. A total of 76 elderly participants （aged ＞65 years） were enrolled after providing consent to participate in this study. The established subjective evaluation methods of chewing function investigated for this study included the Yamamoto denture performance judgment table, the Sato table for evaluation of chewing function in complete denture wearers, and the Hirai evaluation method for the masticatory function in complete denture wearers. As the Yamamoto method lacks scoring, the total number of circles was used as the score. A time study was performed on the time taken for the description, entry, and analysis of these tables. There was a strong correlation between the Sato and Hirai methods （r＝0.71） and between the Sato and Yamamoto （r＝0.68） and Hirai and Yamamoto （r＝0.60） methods. During the time study, the description time was the shortest with the Yamamoto method, and the entry and analysis times were the shortest with the Sato method. The total time was significantly shorter with the Sato method than with the Yamamoto method. Three evaluation methods showed correlation, but the examination times varied. In future studies, we plan to clarify the selection criteria, including the relevance of objective evaluation and usability

Oral hypofunction in the older population : Position paper of the Japanese Society of Gerodontology in 2016

Background: There is growing international interest in identifying the effects of ageing on oral health and on appropriate strategies for managing oral disorders. The Japanese Society of Gerodontology (JSG), as the official representative of researchers and clinicians interested in geriatric dentistry in Japan, makes several recommendations on the concept of “oral hypofunction.” Aims: This study proposes diagnostic criteria and management strategies to reduce the risk of oral hypofunction among older people. Conceptual Framework: We define oral hypofunction as a presentation of 7 oral signs or symptoms: oral uncleanness; oral dryness; decline in occlusal force; decline in motor function of tongue and lips; decline in tongue pressure; decline in chewing function; and decline in swallowing function. The criteria of each symptom were determined based on the data of previous studies, and oral hypofunction was diagnosed if the criteria for 3 or more signs or symptoms were met. Conclusions: We recommend that more evidence should be gathered from clinical studies and trials to clarify our diagnostic criteria and management strategies

ビデオ内視鏡を用いた咀嚼の食塊形成機能評価

歯科補綴学の分野で従来行われてきた咀嚼機能評価の多くは,咀嚼後の試料を口腔外に取り出して評価するため,咀嚼・嚥下という一連の運動としての評価は困難であった.本研究では,摂食・嚥下障害の分野で咽頭期嚥下の評価に用いられる嚥下内視鏡検査を応用し,咀嚼・嚥下の一連の運動中に,ビデオ内視鏡を用いて食塊を直接観察し,咀嚼機能を食塊形成の点から評価することを試みた.対象は健常有歯顎者10名とした.被験食品は白色と緑色の2色米飯および2色ういろうとし,咀嚼回数を10,15,20,30回と規定して摂食させた.経鼻的に挿入したビデオ内視鏡にて,摂食中の中咽頭内の食塊を静止画にて観察し,その際,食塊の粉砕程度を粉砕度,まとまり程度を集合度,緑色と白色の混合程度を混和度とし,0,1,2の3段階の定性的評価を行った.また,1回の嚥下ごとに飲み込みやすさに関する主観的評価を視覚的アナログ尺度(Visual analogue scale:VAS)を用いて行った.米飯およびういろう摂食時において,集合度には咀嚼回数との相関は認めず,常に高い値を示した.粉砕度と混和度については,咀嚼回数の増加に伴って,高い値を示し,有意な高い正の相関が認められた(p<0.01).また,嚥下の容易さについてのVAS値と,咀嚼回数,粉砕度,混和度との間に有意な正の相関が認められた(p<0.05).以上より,これまで咽頭期の嚥下機能評価に限定されていたビデオ内視鏡が咀嚼機能評価にも十分に適用可能であることが明らかになった.また,咀嚼を十分行うことにより,形成される食塊の粉砕度や混和度が調節され,円滑な嚥下の遂行につながることが示された.In the field of prosthodontics, many methods for evaluating the masticatory function were carried out by ejection of the food bolus from the mouth. Yet, these methods could not evaluate mastication and swallowing function comprehensively. The purpose of present study is to evaluate masticatory functions during a series of masticatory and swallowing movements by using videoendoscopy (VE). Subjects are ten healthy dentulous adults without dysphagia. The test foods used were two-colored (green and white) molded rice and uirou. The test foods were consumed under the restriction on the number of mastication (10, 15, 20, and 30). The food bolus in the oropharynx was evaluated qualitatively by using VE in terms of the degree of grindability, cohesiveness, and mixing. In addition, the degree of easiness of swallowing was measured with visual analogue scale (VAS). In both rice and uirou, degree of cohesiveness showed a constant high value under all conditions. The significant correlation coefficients were observed between the number of mastication, the degree of grindability, and mixing. In addition, the significant correlation coefficients were observed between the value of VAS, degree of grindability, mixing, and the number of mastication. The present study demonstrates that VE can be applicable for evaluating the masticatory function, although the aim of VE has so far been limited to the evaluation of swallowing in the pharyngeal stage. And also, although these results suggest that adequate mastication induces smooth swallowing, it could be adjusted to the degree of grindability and mixing of food bolus by mastication

SLPI is a critical mediator that controls PTH-induced bone formation

Osteoclastic bone resorption and osteoblastic bone formation/replenishment are closely coupled in bone metabolism. Anabolic parathyroid hormone (PTH), which is commonly used for treating osteoporosis, shifts the balance from osteoclastic to osteoblastic, although it is unclear how these cells are coordinately regulated by PTH. Here, we identify a serine protease inhibitor, secretory leukocyte protease inhibitor (SLPI), as a critical mediator that is involved in the PTH-mediated shift to the osteoblastic phase. Slpi is highly upregulated in osteoblasts by PTH, while genetic ablation of Slpi severely impairs PTH-induced bone formation. Slpi induction in osteoblasts enhances its differentiation, and increases osteoblast–osteoclast contact, thereby suppressing osteoclastic function. Intravital bone imaging reveals that the PTH-mediated association between osteoblasts and osteoclasts is disrupted in the absence of SLPI. Collectively, these results demonstrate that SLPI regulates the communication between osteoblasts and osteoclasts to promote PTH-induced bone anabolism.Morimoto A., Kikuta J., Nishikawa K., et al. SLPI is a critical mediator that controls PTH-induced bone formation. Nature Communications 12, 2136 (2021); https://doi.org/10.1038/s41467-021-22402-x

Osteoblast-derived vesicles induce a switch from bone-formation to bone-resorption in vivo

Bone metabolism is regulated by the cooperative activity between bone-forming osteoblasts and bone-resorbing osteoclasts. However, the mechanisms mediating the switch between the osteoblastic and osteoclastic phases have not been fully elucidated. Here, we identify a specific subset of mature osteoblast-derived extracellular vesicles that inhibit bone formation and enhance osteoclastogenesis. Intravital imaging reveals that mature osteoblasts secrete and capture extracellular vesicles, referred to as small osteoblast vesicles (SOVs). Co-culture experiments demonstrate that SOVs suppress osteoblast differentiation and enhance the expression of receptor activator of NF-κB ligand, thereby inducing osteoclast differentiation. We also elucidate that the SOV-enriched microRNA miR-143 inhibits Runt-related transcription factor 2, a master regulator of osteoblastogenesis, by targeting the mRNA expression of its dimerization partner, core-binding factor β. In summary, we identify SOVs as a mode of cell-to-cell communication, controlling the dynamic transition from bone-forming to bone-resorbing phases in vivo.Uenaka M., Yamashita E., Kikuta J., et al. Osteoblast-derived vesicles induce a switch from bone-formation to bone-resorption in vivo. Nature Communications 13, 1066 (2022); https://doi.org/10.1038/s41467-022-28673-2

Direct cell–cell contact between mature osteoblasts and osteoclasts dynamically controls their functions in vivo

Bone homeostasis is regulated by communication between bone-forming mature osteoblasts (mOBs) and bone-resorptive mature osteoclasts (mOCs). However, the spatial–temporal relationship and mode of interaction in vivo remain elusive. Here we show, by using an intravital imaging technique, that mOB and mOC functions are regulated via direct cell–cell contact between these cell types. The mOBs and mOCs mainly occupy discrete territories in the steady state, although direct cell–cell contact is detected in spatiotemporally limited areas. In addition, a pH-sensing fluorescence probe reveals that mOCs secrete protons for bone resorption when they are not in contact with mOBs, whereas mOCs contacting mOBs are non-resorptive, suggesting that mOBs can inhibit bone resorption by direct contact. Intermittent administration of parathyroid hormone causes bone anabolic effects, which lead to a mixed distribution of mOBs and mOCs, and increase cell–cell contact. This study reveals spatiotemporal intercellular interactions between mOBs and mOCs affecting bone homeostasis in vivo