Lect 13-14 Tissue Engineering_print

8/11/2019 Lect 13-14 Tissue Engineering_print

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MSE 598/494 Bio-inspired Materials and BiomaterialsMSE 598/494 Bio-inspired Materials and Biomaterials

Instructor: Ximin He

TA: Xiying Chen Email: [email protected]

2014-04-08

Lecture 13-14. Tissue Engineering

Organs, Cell Seeding and TE scaffolds

Artificial lung

Organs

Artificial heart


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Tissues

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blood vessel regeneration

Bone repair Bone healing Tooth Bone/Enamel reconstruction

cardiac tissues engineering

Cell Seeding & Scaffold

cartilage formation Porous alginate scaffold

artificial skin growth


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Tissue engineering

Themes: Generating functional organs (or organ components) outside of the body,

e.g. on the laboratory bench-top, which could be subsequently implanted

and/or substituted for damaged or defective organs.

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Constructing functional tissues fortesting of drug candidates and

examination of biological processes andphenomena in environments which

best mimic actual physiological andcellular conditions

Fundamental requirement of

organ/tissue created in an artificial environment To morphologically resemble its native counterpart

To perform similar biological functions

Tissue engineering

Definition:The structural and functional reconstitution of tissues inwhich the cells, biomaterials, and biological signals are combined andfully mimic their physiological settings.

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Challenges: Engineered tissuesneed to

be physiologically compatible, i.e.integrate well and satisfactorilyperform their functions afterimplantation into the body.

respond and transform externalstimuli in the same way as nativetissues for example lengthening

and thickening of a muscle tissuefollowing extended physical exercises


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What you will learn in the next 90 minutes?

Tissue Engineering:

Organ Tissue Cell

Lecture 13. Artificial Organs

Artificial Kidney

Artificial lung, heart (option for Lit Rev Presentation)

Lecture 14. Cell Seeding and TE Scaffold

Porous (polysaccharides, hydrogel, printing, carbonmicrostructures)

Responsive & Dynamic (4-D scaffold)

Tissue engineering and drug design (option for Lit RevPresentation)

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2014-04-08

Lecture 13. Tissue Engineering

Artificial Organs


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Organs from bench

yet huge challengesComplex structure with huge number of

cells

Organs from others

find donorsimmunosuppressant drugs to prevent

rejection

Organs grown from patients own cells

incapable of regeneration slow

Creating body parts for damaged or defective organs

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Artificial Organs

Strategies:

partial organ regeneration regeneration of organ constituents, ultimately embedding them as

substitutes for damaged or defective counterparts within the native organ.

to use a hierarchical approach in which core elements of the organ are

synthetically constructed, while more peripheral parts are produced inmore conventional manners.

Challenges of incorporation of synthetic, foreign assemblies in the

human body:

the embedded component has to adhere to specific requirements in termsof functionality, long-term stability, and robustness.

more crucial and often problematic is the issue of host rejection of the

foreign object

Current Research: the relatively simple and already available as products(commercial production of human skin for burn therapy) OR growing heart,kidney, liver and similarly complex organs


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Levels of Creating Artificial Organs

Varies Challenges

1. Type of tissue being recreated in the laboratory

2. Properties of the scaffold materials used, esp. stability in thephysiological environment and biocompatibility

3. Ultimately the viability and integrationof the produced tissuesin their target locations in the body

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Recreation of entire organsOrgan

Constructing artificial tissues in lab

Subsequently implanting them in thebody

Tissue

growth and proliferation of healthyand functional cells outside of bodyCell




2014-04-08

Lecture 13. Tissue Engineering

Cell Seeding & TE Scaffold


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Example - CardiacTissues

Requirement for impact and benefits for Heart diseases or thoseexperiencing myocardial infarction or heart failure:

distinct mechanical, electrical, and metabolic properties of heart tissue which

are ultimately responsible for efficient systolic and diastolic performance

Ideal artificially-created cardiac tissue: mimic the functional andmorphological characteristics of a native heart muscle:

capable of efficient contraction and expansion,

respond to electrophysiological signals,

exhibit long-term mechanical stability,

develop an effective vascular (i.e. blood vessel) network after implantation

not be rejected by the body

Three components of TE research

growth and proliferation of healthy and functional cells

proper design of scaffolds upon which the cells will assemble

achievement of effective biological signalingwithin the artificiallycreated tissue

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Challenges in cell seeding and growth in engineered tissues:

Limited availability of desired cells which often had to be carefully matched to

the individual in whom the tissue will be grafted in order to minimize tissue

rejection (stem cell technology)

The risk of adversely affecting cell properties during cell growth in engineered

tissues


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Tissue regeneration through seeding cells in blood vessels

Discovery against conventional knowledge: stem cellsembedded and grown within laboratory-engineered

blood vessels gradually disappeared after implanting thevessels around the heart

Seeded cells can recruit host immune cells to the

engineered tissue for subsequent rapid formation of newblood vessels

Employ standard cell lines Trigger the immunesystem to induce vascularization within the artificial

tissue Enable growth of the endogenous cells

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1wk 6 wk 10 wk

Roh, J.D. et al., PNAS 2010 107, 46694674.

TE scaffolds

Focus of TE:

Facilitating appropriate scaffold

configurationsin order to recreate the

actual organization and

environments of the tissues within

the body

Controlling the microscopic andmacroscopic architecture of the

scaffold

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TE scaffold materials

A critical precondition for effective tissue growth is the need for thescaffold material to be both

biocompatibleand biodegradable

Identify new materials to exhibit specific physical properties andarchitectures allowing their use in TE designs

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Biological tissue Artificial tissuePorous tissue scaffoldings for tissue

regeneration for cardiac repair

copoly(ether-esters)-polyamides blend hydrogel

(synthetic hydrogel)

Biological tissue scaffold revealed a porous

structure with an apparent interconnectivity

Collagen

hydrogel

(Natural

hydrogel)

10 m 6 m

Bone scaffold

Collagen hydrogel-ceramic composite

(natural-synthetic blend)

1 cm

1) PorousTE Scaffolds

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1) PorousTE Scaffolds

Synthetically Controlled Structures and Surface Chemistry

host cells in their pore structure.

large internal surface areas for cell attachment, proliferation, and physicalsupport for the tissue formed

efficient transport of molecules to and from cells (vital metabolic pathways,

signaling, and cell-cell communication)

Chung, H.J. and Park, T.G., Surface engineered and drug releasing pre-fabricated scaffolds for tissue

engineering,Adv. Drug Deliv. Rev.2007 59, 249262.21

1) PorousTE Scaffolds - materials

Materials:

poly lactide glycolic acid (PLGA)

polysaccharides

chitosan

cellulose

alginate

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Porous alginate scaffold

Advantages of Porous Scaffold:

Interconnecting networks of pores for effective migration growth and attachment of cells transport of nutrients and cell secretions

Mechanical stability and inert framework materials unreactive withcells, while biodegradable through digestion by proteolytic enzymes


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i) Hydrogels

Functions:

1. Serving as scaffold:

mimics the physiological (hydrous) conditions in the human body

biological macromolecules, particularly proteins

allow exploiting the protein gel framework to act both as the scaffolding,

means to generate biological signals to the attached cells

2. Three-dimensional models for cell migration and proliferation

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Endothelial biomaterials

Vascular endothelial growth factor(VEGF), within the porousframework of hydrogels designed

to facilitate spatial guidance of cellgrowth, particularly endothelial cells(ECs) lining blood vessel walls

VEGF-mimic peptide fibers forblood vessel regeneration

the VEGF-mimic peptide assembles

into nanofibers; showing the porousgel structure formed by the peptide

fibers


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ii) Rapid prototyping (RP)

solid free form (SFF) fabrication and aided by advances in three-dimensional printing are capable of producing complex rigid

structures directly from computer models

Especially for bone

25 Fedorovich, N.E. Organ printing:the future of bone regeneration,Trends Biotech. 2011 29, 601606.

accomplish cell deposition and seeding

concurrent with template fabrication

iii) Artificial skin

Inclusion of the natural proteincollagen in a polysaccharidepolymer scaffold is essential for

promoting cell attachment andproliferation within thescaffold.

Only with collagen, skinfibroblast cells succeed to forma continuous graft

physical organization of the

collagen fiber network,

to putative biological cuesprovided by this protein

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polymer scaffold:

poly-DL-lactic-co-glycolic acid (PLGA) mesh

Cell proliferation:

only PLGA

PLGA+collagen

30 mins 5 days


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iv) Wood

remarkable resemblance of the microchannel structure in Rattanwood tohuman bone

withstanding heavy loads, microscopic stretching, and shape flexibility

Unique hierarchical microstructural architecture of wood confers anattractive combination of high strength,stiffness and toughness at relativelylow material density.

Sprio, S. et al., Biomimesis and biomorphic transformations: New concepts applied to bone

regeneration, J. Biotech. 2011 156, 347355.

v) Carbon nanostructures

Alignment of cells on an electrically-stimulated carbon nanotubescaffold. Effects of a carbon nanotube scaffold and electricalstimulation (duration: 14 days) upon the morphology of seededmesenchymal stem cells (MSCs).

Pronouncedelongation and cellalignment were clearly

linked to applicationof electrical

stimulation throughthe carbon nanotube

cell-growth scaffold

Mooney, E. et al., The electrical stimulation of carbon nanotubes

to provide a cardiomimetic cue to MSCs, Biomaterials 2012 33, 61326139.


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vi) Endothelial biomaterials

Synthetic vascular graftsgradually coated withendothelial cells (ECs)

Vascularization (bloodvessel formation) ofendothelial scaffolds

Modular tissue engineering:

Small scaffolds pre-seeded withECs can be implanted directly at

the target site, or delivered in alarger container.

The ECs form an interconnected

network, ultimately producing aviable EC layer enabling blood

transport.

Mooney, E. et al., The electrical stimulation of carbon nanotubes to provide a cardiomimetic cue to MSCs,

Trends Biotech. 2012 26, 61326139.

at the implanted site

at the implanted sitePre-implantation

Pre-implantation

Diffuse Dense cytoskeleton

Apoptosis Proliferation

Stiffness

Size

Howcellsbehaveinmechanically dynamicenvironment?

Cell Mechanobiology, Mechanotransduction,Cytoskeletaldynamics

Cell culture materials Petri dish Natural ECM Artificial ECM

2D semi-3D3D (3D+ time) 4D?

Static Dynamic

Chris Chan et al, Nature 2011

Anseth et al, Science, 2009

React to cellular mechanical and chemical signals Spatio-temporally tunable

strain

Gel: homogeneous@nanocellular response to gel structure

& mechanics:

heterogeneous@micro

Mechanics spatio-temporally

Assaying Stem Cell Mechanobiology on Microfabricated

Elastomeric Substrates with Geometrically Modulated Rigidity

2) Responsive DynamicTE scaffolds

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Dynamicscaffolds to study cell biology in four dimensions

Spread & move dividecell: Round

Bond open Pore size increasesgel : Bond close

1. Interaction 2. In-situ monitor

3. Color mapping 4. Damage sensing

New Features: tunable in space and time

by 1) external or 2) cell-induced stimuli

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Concept:

Using responsive gel with active crosslinkers

Cellularly /Enzymatic degradable peptide linker

Isomerizable linker (reversible)

Steps:

1. Creating responsiveness to mechano, along with

other signals, such light and pH, with color change

2. Chemical cues

Advantages:

Initiate chem reaction with mechanical force:

Provide precise spatial and temporal control over

1) Bond formation; 2) Degradation

3) Pendant ligand tethering and releasing

Cell ECM

dictate/

regulate

direct

remold

respond

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Hydrogels with Enzymatic Cleavage of Networks

ECM-mimicking hydrogels composed of PEG-based hydrogelcrosslinked by the oligopeptides which are cleavable by thematrix metalloproteinases (MMPs).


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Summary

Tissue Engineering:

Organ Tissue Cell

Lecture 13. Artificial Organs

Artificial Kidney

Artificial lung, heart (option for Lit Rev Presentation)

Lecture 14. Cell Seeding and TE Scaffold

Porous (polysaccharides, hydrogel, printing, carbonmicrostructures)

Responsive & Dynamic (4-D scaffold)

Tissue engineering and drug design (option for Lit RevPresentation)

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Reading Resources

Prof. David Mooney (hydrogel based scaffold)

Prof. Kit Parker (cardiac cell based jellyfish)

4-D cell culturing scaffold

Ear on mice


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Homework of Lecture 13-14

1. Please state the general requirements for creating tissueengineering scaffold, using an example of successful scaffoldmaterials.

Due by 04/17/2014

Hand in hard copy of homework at the TA, Xiying Chen, at thebeginning of the 04/17 class

Please contact [email protected] for questions.

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Lect 13-14 Tissue Engineering_print

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