再生医療は、21世紀の新しい医療システムとして期待されている。未来の歯科治療の大きな目標は、喪失した歯を再生により取り戻す「歯の再生治療」である。私たちは、三次元的な細胞操作技術である「器官原基法」を開発し、再生歯胚の同所性移植により、歯根膜や神経機能など完全な機能を有する歯の再生を可能とした。未来の歯科治療として完全な機能回復をさせる歯の再生としては、再生歯胚を移植するのみならず、現在の骨結合型インプラント治療に歯根膜を付与することによってう蝕になることがない機能強化型の歯の再生が考えられる。私たちは、次世代インプラント治療として、歯周組織を有して歯の生理機能を発現するバイオハイブリッドインプラントを開発した。さらにインプラント体の開発を進めると共に、大型動物を用いて非臨床有効性の検討を進めている。本稿では、未来の歯科治療としての歯科再生医療の実現に向けた研究の戦略とその進展を紹介する。

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組織工学や再生医療分野における目覚ましい研究の発展により、人体のさまざまな疾患や機能不全となった組織に対して、体外で培養した細胞を用いた細胞治療の可能性が広く提唱されている。歯科領域においても、種々の口腔組織の再生や、歯周病、歯髄炎、粘膜疾患、唾液腺疾患など、あらゆる疾患に対して、細胞を用いた新規治療の開発研究が日々行われている。私共は歯周病の進行によって失われた歯周組織の再生を研究目的として、細胞移植による歯周組織再生の可能性について検討してきた。その中で、簡便かつ確実に細胞を移植する方法として細胞シート技術の歯周組織再生における有用性を見出した。さらに、本技術を用いてチタンインプラント表面への歯周組織再生についても検証した。本総説では、細胞シート技術とそれを用いた歯周組織を有するインプラント作製の可能性について概説する。

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Herein we focused on NANOZR, which has high fracture toughness and elasticity, to create a new implant material by applying surface structure control via concentrated alkali treatment. We investigated the initial adhesion of bone marrow cells and the ability of this material to induce hard tissue differentiation. Two experimental samples were used: NANOZR treated with a concentrated alkali at room temperature and titanium treated with an alkali solution. A commercially available NANOZR plate with a mechanically polished surface was used as a control. Analysis was performed using scanning electron microscopy (SEM) and scanning probe microscopy (SPM), as well as X-ray photoelectron spectroscopy (XPS) for surface analysis. In addition, the contact angle of distilled water on the surface of each group was measured, and the initial adhesion of bovine serum albumin was investigated. After bone marrow mesenchymal cells were collected from the bilateral femurs of 7-week-old male Sprague-Dawley rats, a primary culture was established, and the third generation was used for the experiment. We also measured alkaline phosphatase activity at 14 and 21 days after culturing, the amount of osteocalcin produced, and the amount of calcium precipitated after 21 and 28 days. In addition, the expression of gene markers related to differentiation induction was examined from the mRNA obtained after reverse transcription from the cells 3 days after culture. Observation using SEM and SPM showed that a nanometer-level network structure was formed on the alkali-treated titanium, but there was no change in the NANOZR. In XPS observations, it was found that a deep oxide film layer was formed on the alkali-treated titanium and alkali-treated NANOZR. The expression of various differentiation-inducing markers and gene markers was higher in the experimental group than in the control group at all measurement times, and there was no difference in the values between the alkali-treated titanium and the alkali-treated NANOZR. Based on the above results, it is suggested that nano-level surface modification may be useful for improving the differentiation-inducing ability of bone marrow cells in alkali-treated NANOZR, similar to the case of titanium.

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Diet restriction and fasting could promote tissue regeneration and enhance the immune system by increasing the number of stem cells in the body. Thus, temporary restriction of nutrients at a cellular level may affect its proliferation or differentiation capacity. The present study aimed to investigate and evaluate the effect of glucose reduction and recovering (GRR) regimens on mouse bone marrow cells (BMCs). BMCs were extracted from femurs of 17-week-old male CB57L/6 mice and were grown in a 24-well plate. Then, the cells were divided into 3 groups: intermittent GRR (IGRR), prolonged GRR (PGRR), and control (C), each with (+) or without (–) osteogenic supplements. After 2 weeks of GRR regimens, cell proliferation was measured, osteogenic differentiation was evaluated by an alkaline phosphatase (ALP) activity assay and mineralized nodule staining, and mRNA expression reflecting osteoblast differentiation was evaluated by reverse-transcription quantitative polymerase chain reaction. Cell proliferation significantly increased in IGRR+/- and PGRR+/- cells than in C+/- cells. There was a significant increase in ALP-positive cells and mineralized nodule formation as well as in the gene expression of alkaline phosphatase (ALP), Bone Morphogenetic Protein-2 (BMP-2), Osterix (OSX), and Osteocalcin (OCN) in PGRR+ cells. However, IGRR+/- and PGRR- cells did not show a significant difference in those genes when compared to C+/-. Both IGRR and PGRR enhanced cell proliferation. Moreover, PGRR+ promoted osteoblast differentiation of BMCs in vitro, whereas IGRR+ did not show any positive effects on osteogenic differentiation of BMCs. Conclusively, GRR, especially PGRR, enhanced osteoblast proliferation and upregulated gene expression of ALP, BMP-2, OSX, and OCN.

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