Substrate loss modulus promotes the differentiation of SHSY-5Y neuroblastoma cells

Moduli of the extracellular matrix influence multiple cellular functions such as proliferation, migration, senescence, and differentiation. However, the in vitro studies predominantly consider the Young's (or elastic) modulus of the substrate, and the independent role of its loss (or viscous) modulus, is often not acknowledged. In this work, the effect of loss modulus on neuronal differentiation was investigated using human neuroblastoma (SHSY-5Y) cells. Two polyacrylamide gels with low (similar to 45 Pa) and high (similar to 300 Pa) loss modulus were prepared while maintaining a constant storage modulus similar to 1 kPa. The cells cultured on high loss modulus substrate (HLMS) exhibited a significant increase in the neurite length (morphological differentiation parameter) and the acetylated tubulin levels (early-stage positive biochemical differentiation marker) as compared to low loss modulus substrate (LLMS) and glass at both 24 and 96 h in the growth medium. Therefore, the results indicate that the high loss modulus can be a potential independent mechanical property that influences neuronal differentiation as both the substrates featured similar storage modulus. Further, the combined effects of loss modulus and retinoic acid-induced chemical stimulation on neuronal differentiation were investigated. This combination enhanced the neuronal differentiation on all the substrates. However, HLMS displayed maximum neuronal differentiation both morphologically and biochemically. This study elucidates the crucial role of loss modulus of the substrate on neuronal differentiation and highlights the significance of combining mechanical and chemical cues in cellular differentiation processes.