Matrix stiffness regulates oxidative stress response of human dermal fibroblasts

• Main Author: Yao, Xuefeng
• Other Authors: Tan Lay Poh
• Format: Theses and Dissertations
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/87453; http://hdl.handle.net/10220/46707
• Institution: Nanyang Technological University

Reactive oxygen species (ROS) are widely involved in many physiological and pathological processes. It has been well known that decreased antioxidant ability resulted excessive ROS accumulation leads elderly people to have more risk in ageing related diseases. However, the underlying mechanism of why the antioxidant ability decreases with age remains unknown. Recent research progress shows that aged and diseased tissues have significantly altered mechanical microenvironment. Also, the regulatory role of mechanical microenvironment in numerous cellular processes such as cell adherent, cell morphology, cell migration, cell proliferation, cell differentiation and cell apoptosis has been well established. But, little has been known about the correlation between altered microenvironment and ROS dysregulation. As above, this dissertation aims to study the effect of extracellular matrix (ECM) stiffness on ROS regulation. In this study, polydimethylsiloxane (PDMS) substrates with different crosslinking ratio (1:10, 1:40 and 1:70, cross linker: base) were fabricated to mimic the microenvironment with different stiffness. Tissue culture plates (TCPs) and 750kPa PDMS substrates were used as stiff matrix, while 46kPa and 21kPa represented soft matrix. Human dermal fibroblasts (HDFs) were cultured on these substrates followed by additional exotic oxidative stress stimulation, and the cell behaviors were examined accordingly. Firstly, HDFs on stiff matrix were more susceptible to H2O2 induced ROS accumulation and apoptosis, while soft matrix significantly reduced H2O2 induced cellular damage. It is also suggested that the prevention is nuclear factor kappa B (NF-κB) involved and independent of the ROCK pathway. Then, it is demonstrated that the matrix stiffness might regulate cell oxidative stress tolerance via the YAP-Nox4/Nrf2 pathway. HDFs on stiff matrix exhibited high Nox4 expression, so that they were oxidative stress sensitive. Due to high expression of Nrf2, HDFs on soft matrix showed strong oxidative stress resistance. At last, matrix stiffness regulated oxidative stress was further confirmed by UV exposure. It is revealed that most HDFs accumulate excessive ROS and undergo senescence on stiff matrix, while it is slightly affected on soft matrix, upon UV irradiation. The results proved that the mechanical microenvironment has regulatory effect on cell oxidative stres s response, as well oxidative stress induced cell fate decision. It is also indicated that ECM stiffness increase is a possible cause of decreased antioxidant ability.