Yeh-Chuin Poh Department of Mechanical Science and Engineering 5 th May 2011 Mechanical Force Effects on Cellular Functions May 2011

Introduction 2 May 2011 What is “mechanotransduction”? The process and mechanisms by which living cells sense mechanical forces and convert them into biochemical signals. -S. Na et al, Science Signaling 2008

Introduction: Forces are Important in Living Cells 3 May 2011 Forces play a major role in biological functions like: Cell spreading Cell migration (wound healing) Cell contraction Cell division Regulates cell functions Gene expression Protein synthesis Cell proliferation Ingber, Nat. Rev. Mol. Cell. Biol., 2005

Cells Respond to External Mechanical Stimuli 4 May 2011 Wu, CC et al., PNAS, 2007 Katsumi, A et al., JCB, 2002 Kurpinski, K et al., PNAS, 2006

Cells Respond to External Mechanical Stimuli 5 May 2011 Hahn and Schwartz, Nat Rev Mol Cell Bio 2009 Discher et al, Science Rev 2009 Discher et al, Science 2005

Force Unfolding of Proteins and Opening of Ion Channels Within Cells 6 May 2011 C Johnson et al., Science, 2009  -spectrin undergoes force induced structure change exposing binding sites for ligands. Mechanosensitive ion channels Vogel & Sheetz, Nat Rev Mol Cell Biol, 2006

Stress Induced Src Activation is Rapid 7 May 2011 S Na et al., PNAS, 2008

Rac Signaling Pathway 8 May 2011 M Ouyang et al., PNAS, 2008 Plasma membrane PDGF PDGF R Src Rac Extracellular Cytoplasm

Stressed Induced Rac Signaling Pathway is Different from Soluble Factor 9 May 2011 Poh et al., PLoS ONE, 2009 Overlay s1.0 s5.0 s -Stress+Stress Brightfield +PP1 (10  M, 1 hr)

E-cadherin are mechanosensors 10 May 2011 Vinculin potentiates E- cadherin mechanosensing and is recruited to actin- anchored sites within adherens junctions in a myosin II–dependent manner Le Duc et al., JCB, 2010

Mechanical Effects on Stem Cells 11 May 2011 Maintain Pluripotency in ESCs mouse human LIF bFGF 2i mTOR Induce differentiation a.RA b.SaB-vitamin C c.Proprietary chemicals d.Endogenous factors e.Natural products iPS cell reprogamming with defined factors a.Yamanaka coktail b.Other defined factors Lutolf MP et al., Nat Biotechnol, 2005

Mechanical Effects on Stem Cells 12 May 2011 Force Discher, DE et al., Science, 2009 Force Pluripotency

Substrate Rigidity Dictates Mesenchymal Stem Cells Differentiation Lineage 13 May 2011 Engler et al, Cell 2006 NeurogenicMyogenicOsteogenic

Soft Substrate Promotes Self-Renewal of Embryonic Stem Cells 14 May 2011 F Chowdhury et al, PLoS ONE 2010

Cell Shape Affects Human Mesenchymal Stem Cell Differentiation Lineage 15 May 2011 Chen, CS et al., Dev. Cell, 2004

Topography Controls Adult Stem Cell Fate 16 May 2011 Chen, CS et al., Dev. Cell, 2004

Direct Mechanical Stress Induces Embryonic Stem Cell Differentiation 17 May 2011 Chowdhury et al, Nat Mat 2009

Stress Induced Spreading of Embryonic Stem Cell 18 May 2011 Chowdhury et al, Nat Mat 2009

Biomaterials in Stem Cell Differentiation 19 May 2011 Orthomimetics TM received CE Mark of approval for the repair or articular cartilage and bone. Currently undergoing clinical trial.

20 May 2011 Conclusion Cells respond to mechanical stimuli by altering cell shape, migration, contraction and division Cell signaling pathways induced by mechanical stress and soluble factors are different Mechanical environment (shape, substrate rigidity, forces, topography) affects stem cells differentiation lineage Directed differentiation of stem cells requires both chemical and mechanical cues Substrate rigidity may also promote embryonic stem cell self-renewal Stem cells have promising therapeutic advantages. We need better mechanistic understanding of developmental and homeostatic conditions (physiological, pathological)

21 Thank you for your attention! May 2011

22 May 2011 Y. Wang et al. Nature 2005 GC CFPSH2 substrate YFP Plasma membrane Membrane-targeted Src reporter 433 nm SH2 Src + ATP 476 nm 433 nm 527 nm

23 May 2011