Cyclic tensile loading regulates human mesenchymal stem cell differentiation into neuron-like phenotype

Area of Science:

• Biomedical Engineering
• Stem Cell Biology
• Neuroscience

Background:

• Mechanical loading is established for directing mesenchymal stem cell (MSC) differentiation into mesodermal lineages.
• Inducing MSC transdifferentiation into neural lineages via mechanical cues remains unexplored.

Purpose of the Study:

• To investigate the potential of uniaxial cyclic tensile loading for inducing neuronal differentiation in human MSCs (hMSCs).
• To explore the effects of varying strain amplitudes and frequencies on hMSC morphology, gene expression, and signaling pathways.

Main Methods:

• hMSCs were cultured on modified biodegradable poly(ε-caprolactone) (PCL) scaffolds.
• Cells were subjected to uniaxial cyclic tensile loading at different amplitudes (0.5%, 2%, 3.5%) and frequencies (0.5, 1, 1.5 Hz) for 8 hours.
• Analysis included cell morphology, neurogenic gene and protein expression (Nestin, Tuj1), microfilament organization, and Rho GTPase activity.

Main Results:

• Cyclic stretching induced distinct microfilament organization in hMSCs.
• Optimal neuronal differentiation was observed at 0.5% strain amplitude and 0.5 Hz frequency, evidenced by filopodia outgrowth and neurogenic gene upregulation.
• hMSCs expressed Nestin and Tuj1, indicating commitment to early neuronal progenitors.
• Rac1, but not RhoA, was activated under these specific loading conditions, and Rac1 inhibition blocked the differentiation effect.

Conclusions:

• Low-amplitude, low-frequency cyclic tensile loading can trigger neuron-like differentiation in hMSCs.
• This differentiation occurs via the regulation of Rho GTPase activity, specifically Rac1 activation.
• Mechanical stimulation offers a promising, medium-free approach for neural differentiation of MSCs.