Regulation of Periodontal Ligament Cell Behavior by Cyclic Mechanical Loading and Substrate Nanotexture

Abstract

Periodontal ligament (PDL) cells play an important role in regulating osseous remodeling and ligament formation. Mechanical loading and the specific cellular environment are involved in these processes, regulating cell behavior. However, most in vitro experimental setups investigate mechanical loading or substrate texture separately and thus do not fully represent the PDL microenvironment. Therefore, the authors investigated the influence of combined mechano-topographical stimuli on PDL cell morphology, proliferation, and osteogenic and ligament differentiation. Human PDL cells were subjected to nanometric substrate patterning and cyclic tensile stress for 2 days. Cell morphology was assessed by fluorescent staining. Further, DNA content and messenger RNA expression of osteogenic (Runx2, OCN) and ligament-related (scleraxis transcription factor (SCXA), ELN) genes were determined. PDL cells adapted to the topography of nanometric groove patterns, aligning parallel with the texture. When subjected to mechanical stress, cells lost their initial orientation to the nanopattern. When subjected to dual stimuli, total DNA amounts were increased at 3 days of culture. Moreover, a significant synergistic effect on upregulation of Runx2 was observed in the combined group. For ligament-related markers, SCXA and elastin expression increased with mechanical loading and decreased on nanopatterned surfaces. These results suggest that mechanical stimulation is crucial in regulating periodontal cell behavior, through modulation of osteogenic and ligament gene activity, while extracellular matrix-resembling structures induce different responses from PDL cells in morphology and gene expression.