Fluid Flow-Induced Mesenchymal Stem Cell Migration: Role of FAK and ROCK Mechanosensors

The study of mesenchymal stem cell (MSC) migration under mechanical stimulation conditions with investigation of the underlying molecular mechanism could lead to a better understanding and outcomes in stem cell-based regenerative medicine. MSCs having multipotent regenerative capability exist in niches in the bone marrow, muscle, vasculature, and in other tissues throughout the body, and their migration through tissues and vasculature for the repair of damaged tissue is a key process of cell and tissue homeostasis, remodeling, and regeneration. While cell migration in response to cytokines and other chemo-attractants is relatively well understood, little is revealed in regard to the effect of mechanical cues. In this study, we investigated the migration of C3H10T1/2 murine MSCs in response to fluid flow-induced shear stress in vitro. MSCs were subjected to steady flows with physiologically relevant shear stresses of 2, 15, and 25 dyne/cm 2 and compared with static control. Fluid shear induced cell migration following the flow direction, which effect was greater at higher shear stresses. To test the molecular mechanism, MSCs with stable knockdown of focal adhesion kinase (FAK) and RhoA kinase (ROCK), each constituting the key component of focal adhesion signaling and cytoskeletal tension signaling respectively, were fluid-sheared. FAK-silenced MSCs showed decreases in fluid shear-induced migration, for example, decreases in migration length, confinement ratio, and motility coefficient. Interestingly, in the presence of ROCK silencing, MSCs were more responsive to fluid shear, showing increases in such migration parameters. Our data may suggest a different role of focal adhesion and cytoskeletal tension in mechanical induction of MSC migration. iii Acknowledgements Thank you to Dr. Jung Yul Lim for the opportunity to conduct this research and for providing guidance and support. From you I have learned much about peer reviewed research and how to participate in the scientific community. Working in your lab has been the most enriching experience. my thesis committee. I appreciate the time and effort you have spent in reviewing this thesis and providing valuable feedback. To the student the education experience may at times seem to be a solitary endeavor but I recognize that this journey is not possible without enormous support and encouragement. I would like to thank my parents, family, and mentors for your investment in my life and education. Thank you to the educators who inspired me to love learning and who insisted I take the difficult classes. I am most grateful to the Susan Thompson Buffett …