Guest Lecture by Dr. Andrew Holle on “Tight squeeze: Engineering confinement for mechanobiology research”

Abstract: 

Self-induced cellular confinement has been shown to play a role in a wide variety of biological processes, including cancer invasion and metastasis, immune cell navigation, and mechanosensitive gene expression and localization. However, the ability of adult stem cells to enter tight confinements has been less studied, despite the fact that stem cells are capable of finely tuned mechano-transduction, must migrate from their home niche to their regenerative niche, and have been shown to integrate past stimuli in a form of ‘mechanical memory’. Here, we characterize the interstitial spaces in cleared tissue, providing a physiological basis for the design of biomimetic microchannel devices. Next, we show that adipose-derived stem cells (ASCs) and bone marrow stem cells (hMSCs) are capable of entering and permeating PDMS-based microchannels as narrow as 3 µm. Patterns of microchannel permeation as a function of width are similar to those found in cancer cells, despite the fact that these stem cells are more well-spread and exhibit higher cell diameters. Both narrow and wide confinements were shown to induce an upregulation of the osteogenic differentiation marker CBFA1. Interestingly, narrow confinements led to enhanced CBFA1 nuclear localization compared to wide channels, suggesting that the level of confinement imposed upon a stem cell via its extracellular environment ultimately plays a role in differentiation. In conjunction with these changes in fate, stem cells exposed to confinement also showed significant changes in epigenetic state as measured by H3K9Ac localization. Future work will ultimately discern if the migratory journey a stem cell undergoes during development and regeneration, and the confinement it experiences along the way, drive tissue-specific stem cell differentiation

About the Speaker:

Dr. Andrew Holle is currently an Assistant Professor at the Department of Biomedical Engineering, National University of Singapore (NUS) and the Principal Investigator at the Mechanobiology Institute, NUS. He received Ph.D. at the University of California, San Diego, where he worked in Prof. Adam Engler’s Stem Cell Biology and Bioengineering group. He identified the mechanosensitive role of the focal adhesion protein vinculin in substrate stiffness-induced stem cell differentiation. Looking to explore the commonalities between stem cells and cancer mechanobiology, he then joined Prof. Joachim Spatz’s Cellular Biophysics group at the Max Planck Institute for Medical Research (Stuttgart, Germany). He used photolithography and microfluidics to build microchannel assays better to characterize cancer cell invasion and migration in confinement. His current work at the Mechanobiology Institute and in the NUS Biomedical Engineering department is focused on the role of confinement in mechanobiology, with an emphasis on novel strategies for controlling stem cell differentiation.