Abstract
Introduction
Vascular endothelial cells respond to a variety of biophysical cues such as shear stress and substrate stiffness. In peripheral vasculature, extracellular matrix (ECM) stiffening alters barrier function, leading to increased vascular permeability in atherosclerosis and pulmonary edema. The effect of ECM stiffness on blood-brain barrier (BBB) endothelial cells, however, has not been explored. To investigate this topic, we incorporated hydrogel substrates into an in vitro model of the human BBB.
Methods
Induced pluripotent stem cells were differentiated to brain microvascular endothelial-like (BMEC-like) cells and cultured on hydrogel substrates of varying stiffness. Cellular changes were measured by imaging, functional assays such as transendothelial electrical resistance (TEER) and p-glycoprotein efflux activity, and bulk transcriptome readouts.
Results
The magnitude and longevity of TEER in iPSC-derived BMEC-like cells is enhanced on compliant substrates. Quantitative imaging shows that BMEC-like cells form fewer intracellular actin stress fibers on substrates of intermediate stiffness (20 kPa relative to 1 and 150 kPa). Chemical induction of actin polymerization leads to a rapid decline in TEER, agreeing with imaging readouts. P-glycoprotein activity is unaffected by substrate stiffness. Modest differences in RNA expression corresponding to specific signaling pathways were observed as a function of substrate stiffness.
Conclusions
iPSC-derived BMEC-like cells exhibit differences in passive but not active barrier function in response to substrate stiffness. These findings may provide insight into BBB dysfunction during neurodegeneration, as well as aid in the optimization of more complex three-dimensional neurovascular models utilizing compliant hydrogels.
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Acknowledgments
Funding for this work was provided by a Ben Barres Early Career Acceleration Award from the Chan Zuckerberg Initiative (Grant 2018-191850 to ESL), the BrightFocus Foundation (Grant A20170945 to ESL), National Institutes of Health grants R21 NS106510 (to ESL), R01 NS110665 (to ESL), R61 NS112445 (to ESL), and K01 EB030039 (to KPO), and National Science Foundation grant 1846860 (to ESL). BJO was supported by the Vanderbilt Interdisciplinary Training Program in Alzheimer’s Disease (T32 AG058524). Support for RNA sequencing was provided by the Vanderbilt VANTAGE core facility, which is supported in part by a Clinical and Translational Science Award (5UL1 RR024975), the Vanderbilt Ingram Cancer Center (P30 CA68485), the Vanderbilt Vision Center (P30 EY08126), a CTSA award from the National Center for Advancing Translational Sciences (UL1 TR002243), and the National Center for Research Resources (G20 RR030956). CTSA award UL1 TR002243 also provided pilot funding for this project. The authors would like to thank Dr. Jean-Philippe Cartailler for helpful discussions on RNA sequencing experiments, Dr. Cynthia Reinhart-King and Wenjun Wang for helpful discussions and training on polyacrylamide hydrogel synthesis, and Dr. Anthony Hmelo and John Thornton for guidance with AFM measurements.
Data Accessibility
RNA sequencing data have been uploaded to ArrayExpress under the accession number E-MTAB-10336.
Conflict of interest
Allison Bosworth, Hyosung Kim, Kristin O’Grady, Isabella Richter, Lynn Lee, Brian O’Grady, and Ethan Lippmann declare no conflicts of interest.
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Bosworth, A.M., Kim, H., O’Grady, K.P. et al. Influence of Substrate Stiffness on Barrier Function in an iPSC-Derived In Vitro Blood-Brain Barrier Model. Cel. Mol. Bioeng. 15, 31–42 (2022). https://doi.org/10.1007/s12195-021-00706-8
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DOI: https://doi.org/10.1007/s12195-021-00706-8