Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR, USA.
Post-Graduation Program in Dentistry, Federal University of Ceará, Fortaleza, Ceará, Brazil.
Lab Chip. 2020 Jan 21;20(2):405-413. doi: 10.1039/c9lc00915a. Epub 2019 Dec 19.
The tooth has a unique configuration with respect to biomaterials that are used for its treatment. Cells inside of the dental pulp interface indirectly with biomaterials via a calcified permeable membrane, formed by the dentin matrix and several thousands of dentinal tubules (∼2 μm in diameter). Although the cytotoxic response of the dental pulp to biomaterials has been extensively studied, there is a shortage of in vitro model systems that mimic the dentin-pulp interface and enable an improved understanding of the morphologic, metabolic and functional influence of biomaterials on live dental pulp cells. To address this shortage, here we developed an organ-on-a-chip model system which integrates cells cultured directly on a dentin wall within a microfluidic device that replicates some of the architecture and dynamics of the dentin-pulp interface. The tooth-on-a-chip is made out of molded polydimethylsiloxane (PDMS) with a design consisting of two chambers separated by a dentin fragment. To characterize pulp cell responses to dental materials on-chip, stem cells from the apical papilla (SCAPs) were cultured in odontogenic medium and seeded onto the dentin surface, and observed using live-cell microscopy. Next, to evaluate the tooth-on-a-chip as a platform for materials testing, standard dental materials used clinically (2-hydroxyethylmethacrylate - HEMA, phosphoric acid - PA, and Adper-Scotchbond - SB) were tested for cytotoxicity, cell morphology, and metabolic activity on-chip, and compared against standardized off-chip controls. All dental materials had cytotoxic effects in both on-chip and off-chip systems in the following order: HEMA > SB > PA (p < 0.05), and cells presented consistently higher metabolic activity on-chip than off-chip (p < 0.05). Furthermore, the tooth-on-a-chip enabled real-time tracking of gelatinolytic activity in a model hybrid layer (HL) formed in the microdevice, which suggests that dental pulp cells may contribute to the proteolytic activity in the HL more than endogenous proteases. In conclusion, the tooth-on-a-chip is a novel platform that replicates near-physiologic conditions of the pulp-dentin interface and enables live-cell imaging to study dental pulp cell response to biomaterials.
牙齿在用于治疗的生物材料方面具有独特的结构。牙髓内的细胞通过由牙本质基质和数千个牙本质小管（直径约为 2μm）形成的钙化可渗透膜，间接与生物材料相互作用。尽管牙髓对生物材料的细胞毒性反应已得到广泛研究，但缺乏模拟牙本质-牙髓界面的体外模型系统，无法深入了解生物材料对活牙髓细胞的形态、代谢和功能影响。为了解决这一不足，我们开发了一种器官芯片模型系统，该系统将直接在微流控装置中的牙本质壁上培养细胞，该装置复制了牙本质-牙髓界面的一些结构和动力学。该牙齿芯片由模压聚二甲基硅氧烷（PDMS）制成，设计由两个腔室组成，中间由牙本质碎片隔开。为了研究牙髓细胞对牙本质材料的反应，我们在牙源性培养基中培养根尖乳头干细胞（SCAPs），并将其接种到牙本质表面，然后使用活细胞显微镜进行观察。接下来，为了评估牙齿芯片作为材料测试平台的性能，我们测试了临床上使用的标准牙科材料（2-羟乙基甲基丙烯酸酯-HEMA、磷酸-PA 和 Adper-Scotchbond-SB）的细胞毒性、细胞形态和代谢活性，同时与标准的离片对照进行了比较。所有牙科材料在离片和离片系统中均具有细胞毒性作用，顺序为：HEMA>SB>PA（p<0.05），并且细胞在离片系统中的代谢活性始终高于离片系统（p<0.05）。此外，牙齿芯片能够实时跟踪微装置中形成的混合层（HL）中的明胶酶活性，这表明牙髓细胞可能比内源性蛋白酶对 HL 中的蛋白水解活性有更大的贡献。总之，牙齿芯片是一种新颖的平台，可复制牙髓-牙本质界面的近生理条件，并能够进行活细胞成像，以研究牙髓细胞对生物材料的反应。
