CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 1
Cellular Response to Mechanical Force
Sharon L. Dunn, PT, PhD, OCS
Associate Professor, LSUHSC
A Clinician’s Approach to Basic Science
• Application of practice to science
• Quest for relevance
• So much to do…….
– so little time
Genome Mapping and PT
• Genetic Profiling – Susceptibility to disease
– Specificity of management
• Genetic Engineering – Gene therapy
– Regenerative medicine
• Influence of our interventions on genetic regulation – “Mechanotransduction”
www.cottonexpressions.com
Mechanotransduction: “Our” Basic Science?
Transduction Transcription & Translation
Mechanoreceptors we know Joint Receptors and Muscle Spindle
Mechanoreceptors we know Hair Cells – Inner Ear
Oghalai lab - Stanford
Gellespie & Muller Cell, 2009
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 2
Cellular Receptors for Mechanical Loads
Zollner, et al, J Mechanical Behavior of Biomedical Materials, 2013
Cellular Receptors for Mechanical Loads:
Focal Adhesion Complex
http://www.answers.com/topic/mechanotransduction
Dr. Hislop’s Dream Wolff’s Law
German anatomist and surgeon Julius Wolff (1836–1902)
“Every change in the function of a bone is followed by certain definite changes in its internal architecture and its external conformation.”
Physical Stress Theory Tissue Adaptation to Physical Stress Cellular Mechanisms
Basic Review of Cell Biology
Cell Structure
• Membrane
• Receptors
• Cytoskeleton
• Organelles
Cell Function
• Signaling
• Transduction
• Transcription
• Translation
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 3
Cell Structure: Membrane
• Lipid bilayer
• Integral proteins
• Lipid rafts
Cell Structure: Receptors
Zollner, et al, J Mechanical Behavior of Biomedical Materials, 2013
Cell Structure: Cytoskeleton Cell structure and motility
http://thebuildingblockofbiology.wordpress.com/
Cell Structure: Cytoskeleton
Extracellular Matrix More than just “Ground Substance”
Brizzi, et al, 2012
Tensegrity
Dalby, Medical Engineering and Physics, 2005
Ingber, MD, PhD Harvard
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 4
Cell Structure: Organelles
http://people.eku.edu/
Cell Function: Signaling
Nature Rev: Mol Cell Biol
Molecular Biology 101
• Transduction: A signal is received and converted into an intracellular message.
• Transcription: The message is
transported to the nucleus for DNA (genetic) response - coding mRNA.
• Translation: mRNA transported
to cytosol for ribosomal decoding - 3 nucleotides (codon) of mRNA encode for an amino acid, which links up with others to form a protein.
http://sph.bu.edu/
Cell Function: Transduction
Wederell et al, Sem Cell Dev Biol, 2006 Secko, http://www.scq.ubc.ca/
DNA – Packaged in Chromosomes Unwound for Transcription
http://sph.bu.edu/
Cell Function: Transcription
http://hyperphysics.phy-astr.gsu.edu/ http://www.brooklyn.cuny.edu/
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 5
Cell Function: Translation
http://www.funnelbrain.com/
Cell Function: Protein Folding and Transport
Kaufman, R.J. et al. Nature Rev. Mol. Cell Biol.2002
Cellular Responses to Injury: Phases of Healing
• Inflammation
• Repair/proliferation
• Remodeling/maturation
Trauma
Rolling Leukocyte
Alon & Feigelson, Cur Opin Cell Biol 2012
Inflammatory Cascade
Nature, 420, Dec. 2002
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 6
Mast Cells
• Resident in tissue, first responders
• Release – Histamine “rubor”
– Cytokines
– Chemokines
– Proteases
– Tryptases – vasodilation – Nathan C, Nature, 420, Dec.
2002.
– Diegelmann R et al, Front in Biosc, 9, Jan. 2004.
www.pathology.duke.edu
Neutrophils
• Activated by TNF from Mast cells (or bacteria)
• Release – More cytokines
– Elastase (frees own integrins to bind ECM)
– Proteases (MMPs)
– Oxidants (activate MMPs)
• Phagocytose bacteria “puss” – Nathan C, Nature, 420, Dec. 2002.
– Diegelmann R et al, Front in Biosc, 9, Jan. 2004.
Monocytes/Macrophages
• Activated by cytokines
• Release – TGF-ß
– PDGF
– ROI
• Phagocytose debris, damaged ECM, bacteria-filled neutrophils, etc
• Marker of phase transition from inflammatory to proliferative
– Diegelmann R et al, Front in Biosc, 9, Jan. 2004.
www.zoology.ubc.ca
Lymphocytes
• Recruited by sustained activation of mast cells and neutrophils
• Require antigen-receptor engagement for activation
• B-lymphcytes release antibodies
• T-lymphocytes target and kill bacterial or viral cells
www.uni-mainz.de
ww
w.b
ioen
g.au
ckla
nd
.ac.
nz
Repair: Fibroblasts
• Maintain and restore structural integrity of connective tissue
• Some acquire smooth muscle features – myofibroblasts, for wound contraction
• Important for matrix production during repair
www.molbiolcell.org
Remodeling
Moore et al, Dev Cell Rev, 2010
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 7
Remodeling
Moore et al, Dev Cell Rev, 2010
Daley W P et al. J Cell Sci 2008;121:255-264
©2008 by The Company of Biologists Ltd
ECM-mediated Effects on Matrix Remodeling
Remodeling
Moore et al, Dev Cell Rev, 2010
Tissue Specific Cells: Mechanotransduction and
Genetic Response to Loading
• Bone
• Ligament
• Tendon
• Cartilage
Bone Osteocyte Transduction
Santos et al, Osteoporos Int (2009) 20:1027–1031
Burger, E. H., Klein-Nulend, J, FASEB J. 13 (Suppl.), S101–S112 (1999)
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 8
Ligament Ligament Response to Load
Woo et al J Orthop Res, 1987
Tendon Tendon Response to Loading Design
Exercise Group Non-exercise Group
4 weeks
biologic testing
6 weeks mechanical testing
Right hind limb - experimental Left hind limb - negative control
Novel Method of Immobilization Exercise Protocol
• Rats placed under anesthesia
• Splint removed for exercise
• Passive ROM of hip, knee and ankle joints initiated 3 days p.o.
• 12 cycles per minute, 5 minutes, 3 times a week
• Splint replaced
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 9
Tendon Response to Load
Uninvolved Limb
Exercised Limb
Splinted, Unexercised Limb
Fibroblast Transduction
Zollner, et al, J Mechanical Behavior of Biomedical Materials, 2013
Fibroblast Transduction
A mouse embryonic fibroblast plated on collagen, stained for actin (green), paxillin (magenta) and p130CAS (cyan) and captured on a spinning disk microscope. This image, highlighting stress fibers and cell-matrix adhesions, was captured by Alvin Guo of the Sawada lab
A mouse embryonic fibroblast stained for the actin cytoskeleton (red) and nucleus (blue) and captured on a spinning disk microscope. This image of stress fibers was captured by Alvin Guo of the Sawada lab
Fibroblast Transduction/Transcription
Chiquet, Matrix Biol, 2003
Fibroblast Response to Strain Articular Cartilage
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 10
Cartilage Matrix Cartilage Response to Loading
• Unloaded left hind limb
• Proteoglycan stained with Alcian blue
Behrens et al, J Orthop Res, 1989
Chondrocyte Transduction
Wong & Carter, Bone, 2003
Chondrocyte Transduction Primary Cilia
Seeger-Nukpezah & Golemis, 2012
Primary Cilia: The Mechano-sensor?
Seeger-Nukpezah & Golemis, 2012
Call to Action: Khan’s call out
CPTA Annual Conference September 20, 2013
Sharon L. Dunn, PT, PhD, OCS 11
Call to Action: PASS Call to Action: Research Collaboration
Ambrosio & Russell, JRRD, 2010
Gene Chip Technology Call to Action: Think Biologically!