# Biomechanical Stimulation of Mesenchymal Stem Cells in 3D Peptide Nanofibers for Bone Differentiation

## TL;DR

This study shows how mechanical stretching in 3D environments can guide stem cells to become bone cells, using synthetic materials and modeling.

## Contribution

A new platform combining dynamic stretching and 3D peptide hydrogels to study and enhance bone differentiation of stem cells.

## Key findings

- Low-frequency, high-strain mechanical loading increased osteogenic marker expression by 2–3-fold.
- Dynamic stretching improved cytoskeletal alignment and actin stress fiber formation in 3D hydrogels.
- Mechanical stimulation activated RhoA/ROCK and YAP/TAZ pathways, promoting bone differentiation.

## Abstract

Mechanical stimulation critically regulates mesenchymal stem cell (MSC) differentiation, yet its effects in three-dimensional (3D) environments remain poorly defined. Here, we developed a custom dynamic stretcher integrating poly(dimethylsiloxane) (PDMS) chambers to apply cyclic strain to human MSCs encapsulated in Fmoc-diphenylalanine (Fmoc-FF) peptide hydrogels—a fully synthetic, tunable extracellular matrix mimic. Finite element modeling verified uniform strain transmission across the hydrogel. Dynamic stretching at 0.5 Hz and 10% strain induced pronounced cytoskeletal alignment, enhanced actin stress fiber formation (coherency index ≈ 0.85), and significantly increased proliferation compared to static or high-frequency (2.5 Hz, 1%) conditions (coherency index ≈ 0.6). Quantitative image analysis confirmed strain-dependent increases in coherency index and F-actin intensity, indicating enhanced mechanotransductive remodeling. Biochemical assays and qRT–PCR revealed 2–3-fold upregulation of osteogenic markers—RUNX2, ALP, COL1A1, OSX, BMP, ON, and IBSP—under optimal strain. These results demonstrate that low-frequency, high-strain mechanical loading in 3D peptide hydrogels activates RhoA/ROCK and YAP/TAZ pathways, driving osteogenic differentiation. The integrated experimental–computational approach provides a robust platform for studying mechanobiological regulation and advancing mechanically tunable biomaterials for bone tissue engineering.