Stem Cell-Based Self-Assembled Tissues Cultured on a Nano-Periodic-Structured Surface Patterned Using Femtosecond Laser Processing

The present study was conducted to determine the effects of a nano-periodic-structured surface on the morphological and mechanical properties of a stem-cell-based self-assembled tissue (scSAT) developed for biological tissue repair. Nano-periodic groove structures were patterned on a pure titanium surface using femtosecond laser processing, and the structure was replicated on polydimethylsiloxane (PDMS). The depth, periodic pitch, and surface roughness (Ra) of the PDMS grooves were 48 ± 21 nm, 522 ± 9 nm, and 17 ± 5 nm, respectively. Human synovial cells, including mesenchymal stem cells, were subjected to 4-time cell passage, and then cultured on the PDMS surface at a density of 4.0 × 10 5 cells/cm 2 in a growth medium with 0.2 mM ascorbic acid 2-phosphate to produce scSATs (nano-scSAT). For comparison, some of the cells subjected to 4-time cell passage were cultured on either a flat PDMS substrate with 6 ± 1 nm of surface roughness (Ra) (flat-scSAT) or a commercially available cell culture plate of polystyrene (normal-scSAT), at a cell density identical to that in the nano-scSAT group. At 28 days of cell culture, the scSATs were gently detached from the culture plates and subjected to morphological observation and mechanical testing. Microscopic observation revealed that the nano-scSATs exhibited a dense tissue of cells and an extracellular matrix with an anisotropic structure, while the flat- and normal-scSATs exhibited a sparse and isotropic structure. The tangent modulus and tensile strength were significantly higher in the nano-scSATs than in the flat- and normal-scSATs. These results suggest that a nano-periodic-structured surface improves the morphological and mechanical properties of scSATs.