全歯再生のための歯胚様構築物の移植。ミニチュアブタにおけるin vivo研究

Tooth Germ-Like Construct Transplantation for Whole-Tooth Regeneration: An In Vivo Study in the Miniature Pig.

抄録

本研究の目的は、歯胚様構築物を用いた全歯再生の可能性を示すことである。性成熟したミニチュアブタから上顎切歯，犬歯，小臼歯，臼歯の歯髄を摘出した．歯髄組織はin vitroで培養・増殖させ，歯髄幹細胞（DPSC）を取得し，歯芽細胞および骨芽細胞へ分化させた．上皮細胞は歯肉上皮から分離した。上皮細胞、歯根膜細胞、骨芽細胞をそれぞれ生体活性足場の表層、上層、下層に播種した。下顎第一大臼歯および第二大臼歯の歯胚を両側から除去し、層状細胞/スキャフォールド構築物を豚の下顎歯槽窩に移植した。移植後13.5カ月で，8頭中7頭が歯冠，歯根，歯髄構造を有する2本の歯を発育させた．組織学的検査により，エナメル様組織，象牙質，セメント質，歯根膜，歯周組織が確認された．再生歯は，dentin matrix protein-1とosteopontinを発現していた．DPSCの調達に使用した元の歯に関係なく、すべてのブタに臼歯が再生された。歯胚を除去したブタや、空の足場を受け取ったブタには歯が生えなかった。また、歯根膜は形成されたものの、一部の動物ではアンキローシス（強直）が認められた。この研究により、歯胚様構造体を移植することで、高い成功率で完全な歯が生成されることが明らかになった。インプラントの位置は再生歯の形態に影響を与える可能性がある。

The purpose of this study was to demonstrate the feasibility of whole-tooth regeneration using a tooth germ-like construct. Dental pulp from upper incisors, canines, premolars, and molars were extracted from sexually mature miniature pigs. Pulp tissues were cultured and expanded in vitro to obtain dental pulp stem cells (DPSCs), and cells were differentiated into odontoblasts and osteoblasts. Epithelial cells were isolated from gingival epithelium. The epithelial cells, odontoblasts, and osteoblasts were seeded onto the surface, upper, and lower layers, respectively, of a bioactive scaffold. The lower first and second molar tooth germs were removed bilaterally and the layered cell/scaffold constructs were transplanted to the mandibular alveolar socket of a pig. At 13.5 months postimplantation, seven of eight pigs developed two teeth with crown, root, and pulp structures. Enamel-like tissues, dentin, cementum, odontoblasts, and periodontal tissues were found upon histological inspection. The regenerated tooth expressed dentin matrix protein-1 and osteopontin. All pigs had regenerated molar teeth regardless of the original tooth used to procure the DPSCs. Pigs that had tooth germs removed or who received empty scaffolds did not develop teeth. Although periodontal ligaments were generated, ankylosis was found in some animals. This study revealed that implantation of a tooth germ-like structure generated a complete tooth with a high success rate. The implant location may influence the morphology of the regenerated tooth.