Nanostructured Ti surfaces and retinoic acid/dexamethasone present a spatial framework for the maturation and amelogenesis of LS-8 cells

Nan Jiang,1–3 Lu Chen,1–3 Qianli Ma,4,5 Jianping Ruan1–3 1Department of Preventive Dentistry, College of Stomatology, Xi’an JiaoTong University, Xi’an, People’s Republic of China; 2Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, College of Stomatology, Xi’an JiaoTong University, Xi’an, People’s Republic of China; 3Clinical Research Center of Shaanxi Province for Dental and Maxillofacial Diseases, College of Stomatology, Xi’an JiaoTong University, Xi’an, People’s Republic of China; 4Department of Immunology, School of Basic Medicine, Fourth Military Medical University, Xi’an, People’s Republic of China; 5Department of Prosthodontics, College of Stomatology, Xi’an JiaoTong University, Xi’an, People’s Republic of China Purpose: To investigate the amelogenesis-inductive effects of surface structures at the nanoscale. For this purpose, variable nanostructured titanium dioxide (TiO2) surfaces were used as a framework to regulate the amelogenic behaviors of ameloblasts with the administration of retinoic acid (RA)/dexamethasone (DEX). Materials and methods: TiO2 nanotubular (NT) surfaces were fabricated via anodization. Mouse ameloblast-like LS-8 cells were seeded and cultured on NT surfaces in the presence or absence of RA/DEX for 48 h. The amelogenic behaviors and extracellular matrix (ECM) mineralization of LS-8 cells on nanostructured Ti surfaces were characterized using field emission scanning electron microscope, laser scanning confocal microscope, quantitative polymerase chain reaction, MTT assay, and flow cytometry. Results: TiO2 NT surfaces (tube size ~30 and ~80 nm) were constructed via anodization at 5 or 20 V and denoted as NT5 and NT20, respectively. LS-8 cells exhibited significantly increased spread and proliferation, and lower rates of apoptosis and necrosis on NT surfaces. The amelogenic gene expression and ECM mineralization differed significantly on the NT20 and the NT5 and polished Ti sample surfaces in standard medium. The amelogenic behaviors of LS-8 cells were further changed by RA/DEX pretreatment, which directly drove maturation of LS-8 cells. Conclusion: Controlling the amelogenic behaviors of ameloblast-like LS-8 cells by manipulating the nanostructure of biomaterials surfaces represents an effective tool for the establishment of a systemic framework for supporting enamel regeneration. The administration of RA/DEX is an effective approach for driving the amelogenesis and maturation of ameloblasts. Keywords: TiO2 nanotube, LS-8, surface nanostructure, amelogenesis, retinoic acid