cardiovascular tissue engineering devin nelson july 2010 department of bioengineering, university of...
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Cardiovascular Tissue Cardiovascular Tissue EngineeringEngineering
Devin NelsonDevin NelsonJuly 2010July 2010
Department of Bioengineering, University of PittsburghDepartment of Bioengineering, University of PittsburghMcGowan Institute for Regenerative MedicineMcGowan Institute for Regenerative Medicine
OverviewOverview
Tissue EngineeringBiomaterialsCellsTissue Engineered Heart ValvesTissue Engineered Blood VesselsTissue Engineered MyocardiumDiscussion
Tissue EngineeringTissue Engineering In recent years, the field of tissue engineering (TE) has
emerged as an alternative to conventional methods for tissue repair and regeneration
Health care costs in the U.S. for patients suffering from tissue loss and/or subsequent organ failure are $100,000,000,000’s of dollars a year
TE has grown to encompass many scientific disciplines Bioengineers Clinicians Pathologists Material Scientists Molecular Biologists Mechanical Engineers etc
SignalsScaffolds
Tissue Engineered Construct
CellsAutogeneicAllogeneic
XenogeneicPrimary
Stem
NaturalSynthetic
Growth FactorsCytokines
Mechanical StimulationDifferentiation Factors
From An Introduction to Biomaterials. Ch 24. Fig. 1. Ramaswami, P and Wagner, WR. 2005.
What do these have in common?What do these have in common?All BiomaterialsAll Biomaterials
BiomaterialsBiomaterials Synthetic biomaterials
Engineer can control the properties such as mechanical strength, biological activity, degradation rates etc
Natural biomaterials Built-in structure, environment and cues similar to native
body (extracellular matrix ECM, collagen, etc) Deliver drugs, cytokines, growth factors, and other
signals for cell differentiation, growth, and organization
Design criteria: proper mechanical and physical properties adequate degradation rate without the production of toxic
degradation products suitable cell adhesion integration into surrounding tissue without extensive
inflammatory response or support of infection proper mass transfer
CellsCells There has recently been much excitement
surrounding the use of stem cells for tissue repair and regeneration
In vitro differentiation of stem cells via humoral factors and direct in vivo utilization of these cells have been proposed as a method for tissue regeneration
The use of a biomaterial to guide stem cell commitment provides cells a scaffold on which to grow and permits cell differentiation in vivo while minimizing in vitro manipulation
The ideal cell source for various TE applications is still elusive
3-Dimensional Environment3-Dimensional Environment The context in which a cell is grown is critical to its The context in which a cell is grown is critical to its
development and subsequent functiondevelopment and subsequent function
Cells cultured Cells cultured ex vivoex vivo on TCPS are in a 2-D on TCPS are in a 2-D environment which is far-removed from the 3-D environment which is far-removed from the 3-D tissue from which the cells originated as well as the tissue from which the cells originated as well as the 3-D tissue into which the cells will be implanted 3-D tissue into which the cells will be implanted
Culture of cells in a 3-D vs. 2-D environment AND Culture of cells in a 3-D vs. 2-D environment AND WITH APPROPRIATE MECHANICAL STIMULATION WITH APPROPRIATE MECHANICAL STIMULATION has been shown to alter cell behavior, gene has been shown to alter cell behavior, gene expression, proliferation, and differentiationexpression, proliferation, and differentiation Especially for cardiovascular applicationsEspecially for cardiovascular applications
Tissue Engineered Heart Valves Tissue Engineered Heart Valves (TEHV)(TEHV)
An estimated 87,000 heart valve replacements were performed in 2000 in the United States alone
Approximately 275,000 procedures are performed worldwide each year
Heart valve disease occurs when one or more of the four heart valves cease to adequately perform their function, thereby failing to maintain unidirectional blood flow through the heart
Surgical procedures or total valve replacement are necessary
Adapted from http://z.about.com/d/p/440/e/f/19011.jpg
TEHV ReplacementsTEHV ReplacementsMechanical prostheses
Bioprostheses
Homografts
Each of these valve replacements has limitations for clinical use
Can you think of any limitations?
InfectionThromboembolismTissue deteriorationCannot remodel, repair, or grow
From http://www.rjmatthewsmd.com/Definitions/img/107figure.jpg
Requirements for a TEHVRequirements for a TEHV
BiocompatibleShould not elicit immune or inflammatory response
FunctionalAdequate mechanical and hemodynamic function,
mature ECM, durability to open and close > 31 million times a year
LivingGrowth and remodeling capabilities of the construct should mimic the native heart valve structure
What’s being done?What’s being done?
Cells Vascular cells Valvular cells Stem cells (MSCs)
Scaffolds• Synthetic (PLA, PGA)• Natural (collagen, HA, fibrin)• Decellularized biological matrices
Mechanical Stimulation• Pulsatile Flow Systems• Cyclic flexure bioreactors
From An Introduction to Biomaterials. Ch 24. Fig.3 Ramaswami, P and Wagner, WR. 2005.
R.T. Tranquillo Biomaterials 30 (2009) 4078–4084.
Tissue Engineered Blood Tissue Engineered Blood Vessels (TEBV)Vessels (TEBV)
From An Introduction to Biomaterials. Ch 24. Fig.4 Ramaswami, P and Wagner, WR. 2005.
Atherosclerosis, in the form of coronary artery disease results in over 515,000 coronary artery bypass graft procedures a year in the United States alone
Many patients do not have suitable vessels due to age, disease, or previous use
Synthetic coronary bypass vessels have not performed adequately to be employed to any significant degree
TEBV ReplacementsTEBV Replacements
Synthetic GraftsSynthetic GraftsWork well in large-Work well in large-
diameter replacements (6-diameter replacements (6-10 mm)10 mm)
Fail in small-diameter Fail in small-diameter replacements (3-5 mm)replacements (3-5 mm)
WHY???WHY???Intimal hyperplasiaIntimal hyperplasiaThrombosisThrombosis
Requirements for a TEBVRequirements for a TEBV
BiocompatibleBiocompatibleShould not elicit immune/inflammatory responseShould not elicit immune/inflammatory response
FunctionalFunctionalAdequate mechanical (burst pressure) and hemodynamic function, mature ECM, durability, nervous system response
LivingLivingGrowth and remodeling capabilities of the construct should
mimic the native blood vessel structure
LOOK FAMILIAR???LOOK FAMILIAR???
What’s being done?What’s being done?Cells Endothelial cells Smooth muscle cells Fibroblasts &
myofibroblasts Genetically modified cells Stem cells (MSCs & ESCs)
Scaffolds• Synthetic (PET, ePTFE, PGA, PLA, PU)
• Natural (collagen)
• Decellularized biological matrices
Mechanical Stimulation• Pulsatile Flow Systems
• Cyclic & longitudinal strain
Signalling Factors• Growth Factors (bFGF, PDGF, VEGF)
•Cytokines
Cell-Seeded CollagenCell-Seeded Collagen
Cells can remodel and reorganize in collagenCells can remodel and reorganize in collagen Collagen may be weak but is strengthened through Collagen may be weak but is strengthened through
various techniques (magnetic pre-alignment, glycation, various techniques (magnetic pre-alignment, glycation, mechanical training)mechanical training)
Mechanical TrainingMechanical Training
Seliktar et al. Ann Biomed Eng 2000
Self-Assembled SheetsSelf-Assembled Sheets
Good 3D architectureGood 3D architecture Good mechanical strengthGood mechanical strength Disadvantages: need cell Disadvantages: need cell
source, requires > 2 months in source, requires > 2 months in vitro to makevitro to make
Seeding and CultureSeeding and Culture
ElectrospinningElectrospinning
Stankus et al. Biomaterials 2007
Tissue Engineered MyocardiumTissue Engineered Myocardium
From www.aic.cuhk.edu.hk/web8/Hi%20res/Heart.jpg
Ischemic heart disease is one of the leading causes of morbidity and mortality in Western societies with 7,100,000 cases of myocardial infarction (MI) reported in 2002 in the United States alone
Within 6 years of MI, 22% of men and 46% of women develop CHF
MI and CHF will account for $29 billion of medical care costs this year in the US alone
Cardiac transplantation remains the best solution, but there is an inadequate supply of donor organs coupled with the need for life-long immunosuppression following transplantation
Requirements for a Myocardial PatchRequirements for a Myocardial Patch
Biological, Functional, and Living (same as TEHV and TEBV)
High metabolic demands High cell density Complex cell architecture High vascularity Mechanical and Electrical
anisotropy
VERY DIFFICULT!!!VERY DIFFICULT!!!
What’s being done?What’s being done?
Cells Cardiocytes Cardiac progenitor cells Skeletal muscle cells Smooth muscle cells Stem cells (MSCs &
ESCs)
Scaffolds• Synthetic (PET, ePTFE, PEUU)
• Natural (collagen, ECM proteins, alginate)
• Cell sheets
• Injectables
Mechanical Stimulation• Pulsatile Flow Systems• Rotational seeding• Cyclic mechanical strain
Signalling Factors• Growth Factors
•(Insulin-like, bFGF, PDGF, hGH)
• Cytokines
• Conditioned media
• Co-culture
Cardiac PatchCardiac Patch
Cell Sheet EngineeringCell Sheet Engineering
Artificial Muscle – Be CreativeArtificial Muscle – Be Creative
NATIVE
TISSUE ENGINEERED
Extracellular MatrixExtracellular Matrix
Injectable MaterialInjectable Material
In Conclusion…In Conclusion…
We have a lot of work to doWe have a lot of work to do
Taking these tissue engineered Taking these tissue engineered constructs from benchtop to bedsideconstructs from benchtop to bedside
Better understanding the human body Better understanding the human body and how to manipulate cellsand how to manipulate cells