# The effects of nanopillar and nanopit arrays on the morphology and osteogenic differentiation of adipose-derived stem cells

## TL;DR

This study compares how nanopillar and nanopit structures affect the shape and bone-forming ability of fat-derived stem cells.

## Contribution

The study reveals that nanopit arrays enhance cell spreading and early bone development more effectively than nanopillar arrays.

## Key findings

- Nanopit arrays increase cell area and promote early osteogenic differentiation more than nanopillar arrays.
- Nanopit arrays lead to greater focal adhesion formation and maturation compared to nanopillar arrays.
- RUNX2 expression, an early osteogenic marker, is increased on nanopit arrays due to continuous adhesive paths.

## Abstract

Nanotopographic control of cell behavior offers great potential in designing biomimetic scaffolds for cell therapy. However, the behavior of cells on different nanotopographies is not fully understood. In this study, we investigated the effect of nanostructures on human adipose-derived stem cells (ASCs) by directly comparing nanopillar and nanopit arrays. Morphological changes, cell viability and early osteogenic differentiation of ASCs have been analyzed on the nanostructures. Nanopit arrays were found to increase cell areas and promote early osteogenic differentiation more than nanopillar arrays. Analysis of focal adhesion (FA) formation indicated a larger increase in total area as well as the number of FAs during cell spreading on nanopit arrays. The maturation of FA is related to cellular traction forces, which are known to stimulate osteogenic induction through the RhoA-ROCK pathway. We conclude that ASCs can spread more on the nanopit array than on the nanopillar array due to the presence of continuous adhesive paths on the nanopit array, which is associated with increased expression of RUNX2 as an early osteogenic marker. Our results suggest that a connected path in nanopit arrays plays a critical role in controlling stem cell behavior compared to nanopillar arrays. A comparative understanding of nanostructures can provide a guideline for designing an artificial substrate for osteogenesis and tissue engineering.