An oriented hydroxyapatite film with arrayed plate-like particles enhance chondrogenic differentiation of ATDC5 cells

Osteochondral defects of articular cartilage cannot regenerate spontaneously. For its surgical treatment, advancements in cartilage tissue engineering have particularly focused on subchondral bone lesions that tend to delay healing. Therefore, it is important to understand interactions between subchondral bone and chondrocytes. This study aimed to investigate the behavior of chondrogenic ATDC5 cells on oriented hydroxyapatite (HAp) films that mimic bone surfaces. HAp nanoparticles prepared herein were needle like and plate like. HAp films were formed through self-organization of the nanoparticles and had 2D structures regularly arrayed with the particles. Both films prominently comprised a-plane orientation surfaces but differed in the degree of hydrophilicity because of the patterns of particle self-assembly. ATDC5 cells cultured on the HAp film with plate-like particles could adhered in a shorter period but could not spread. The adhesive force of cells was weaker with the hydrophilic surface than with other surfaces, as determined using a trypsin-based cell detachment assay. In addition, ATDC5 cells displayed enhanced proliferation and chondrogenic differentiation. Our results suggest that the oriented HAp film formed using plate-like particles provided chondrogenic cells with a desired scaffold as that of subchondral bone to increase cell proliferation and differentiation.