Research Seminar: Chiao Hwei Lee

Title: Cell shape dominates over physiological substrate stiffness by limiting nuclear localisation of the fibrogenesis gatekeeper, YAP/TAZ

Presented by: Chiao Hwei Lee, Department of Biomedical Engineering, University of Melbourne, Australia

Chiaohwei pursued her bachelor's degree at the University of California Davis in Pharmaceutical Chemistry, where she identified the feasibility of using near-infrared spectroscopy (NIR) to detect olive oil quality under the supervision of Associate Prof. Selina Wang. In 2020, she obtained her master's degree at Loughborough University, where she investigated the stability of collagen hydrogen bonds in osteoarthritis using computational methods with Pooja Goddard and Paul Roach. She is currently pursuing her Ph.D. at the University of Melbourne under the supervision of Prof. Peter Lee and Prof. Alastair Stewart, where she investigates the influence of cell shape and substrate stiffness on fibrogenic lung markers.

Micropatterning allows for fine-tuned microenvironmental control over factors such as spatial constraints and orientation in both three-dimensional and two-dimensional platforms. The feasibility of controlling both cell orientation, shape and substrate stiffness becomes crucial in modelling diseases that are highly governed by tissue stiffness, such as Idiopathic pulmonary fibrosis (IPF). IPF is a disease known to be accompanied by the augmentation of matrix stiffness caused by aberrant deposition and the remodelling of extracellular matrix. The stiffening of the lungs enhances Transforming Growth Factor-β (TGF-β) positive feedback loops by activating latent TGF-β, resulting in irreversible pulmonary damage.¹

Polyacrylamide gels with strictly controlled shapes printed on substrate of tuneable stiffness enables multidimensional disease modelling in cell culture. Current work explores the relationship between cell shape, substrate stiffness and TGF- β treatment with the use of novel micropatterning methods on polyacrylamide gels. Collagen micropatterns of 500 mm2 were created by using UV-C range light (189nm) on glass and polyacrylamide substrates. MRC-5 human embryonic lung fibroblast cell line was seeded on the substrate to create single cell arrays. Immunofluorescence staining revealed the effects of microenvironmental factors, such as cell aspect ratios (AR) and substrate stiffness on the location and abundance of Yes-associated protein/transcriptional coactivator with a PDZ-binding domain (YAP/TAZ). Under stiff glass condition, substrate stiffness dominates the effects of cell shape, showing distinct YAP/TAZ translocation to nucleus. In contrast to the extremes of substrate stiffness, TGF-β appeared to induce YAP/TAZ nuclear localization at 5 kPa only in elongated (AR=5) cells. Conversely, rounded cells (AR=1) displayed an attenuation of TGF-β YAP/TAZ nuclear localisation, suggesting a potential effect of cell shape on TGF-β and YAP/TAZ pathway. Our results show that a tipping point between the effects of cell shape and substrate stiffness exists, such that mechanotransduction mechanism has the potential to slow the progression of IPF by shifting fibroblastic-like cells towards anti-fibrogenic phenotype.

1. Barratt, S. L., Creamer, A., Hayton, C. & Chaudhuri, N. Idiopathic Pulmonary Fibrosis (IPF): An Overview. J. Clin. Med. 7, 201 (2018).