Biomedical Engineering Reference
In-Depth Information
leakage.or.provide.a.homogeneous.surface.to.obtain.intact.endothelial.cell.sheets,.or.act.as.
a.supporting.outer.surface.in.cardiovascular.scaffolds.(Hong.et.al.,.2009;.Soletti.et.al.,.2010)..
Conversely,.iber.spacing.and.density.may.also.be.adjusted.and.loosened.to.promote.cell.
iniltration.in.the.myocardial.patches.
Anisotropy. in. the. architecture. of. the. constructs. plays. an. important. role. in. achieving.
compliance. and. functionality. in. cardiovascular. tissue. engineering.. Parallel. submicron.
ibers.may.be.produced.to.have.circumferential.orientations.similar.to.those.of.the.cells.
and.ibrils.of.the.medial.layer.of.the.native.artery.(Xu.et.al.,.2004)..It.was.demonstrated.that.
anisotropic.poly(ester.urethane)urea.scaffolds.exhibit.mechanical.properties.closely.resem-
bling. those. of. the. native. pulmonary. heart. valve. lealets. (Courtney. et. al.,. 2006).. Cardiac.
muscle.contracts.like.a.syncytium.owing.to.the.multicellular.assembly.of.myoibers.ori-
ented.parallel.to.each.other,.connected.end.to.end.via.intercalated.discs.in.the.longitudinal.
direction.and.connected.side.to.side.in.the.transverse.direction..It.is.this.cellular.arrange-
ment.that.integrates.individual.contraction.into.a.synchronous.pumping.action,.whereas.
myoiber.disarrays.are.known.to.cause.arrhythmia..It.was.shown.by.Black.et.al..(2009).that.
cardiomyocyte.alignment.augments.the.twitch.force..Prior.to.emergence.of.techniques.to.
produce.aligned.nano/microibrous.scaffolds,.anisotropy.had.been.introduced.to.the.car-
diomyocytes.on.the.polymer.scaffolds.in.three.different.ways:.(1).by.micropatterning.(e.g.,.
using.biodegradable,.elastomeric.polyurethane.ilms.patterned.by.microcontact.printing.
of. laminin. (McDevitt. et. al.,. 2003)),. (2). by. cyclic. stretching. (e.g.,. stretching. of. cardiomyo-
cyte-seeded.scaffolds.(Akhyari.et.al.,.2002;.Zimmermann.et.al.,.2002,.2004;.Zimmermann.
and.Eschenhagen,.2003;.Fedak.et.al.,.2003)),.and.(3).by.applying.electrical.signals.designed.
to.mimic.those.in.the.native.heart.to.the.tissue.engineered.constructs.(e.g.,.rat.cardiomyo-
ctes. resuspended. in. Matrigel. were. seeded. onto. collagen. sponges. (Radisic. et. al.,. 2004))..
Electrospinning,.on.the.other.hand,.offers.a.much.simpler.way.to.achieve.the.anisotropy.
and. allows. greater. control. over. composition,. mechanical. properties,. and. structure. of. a.
graft,.thus.making.it.easier.to.match.the.properties.of.the.scaffold.and.the.native.tissue..
It.was.shown.by.Zong.et.al..(2005).that.cardiomyocytes.can.align.parallel.to.micron-size.
ibers..Their.electrospun.mats.with.oriented.ibers.of.PLLA.and.PLGA.were.used.to.assess.
the.inluence.of.scaffolds.on.primary.cardiomyocyte.attachment,.structure,.and.function..
The. primary. cardiomyocytes. showed. a. preference. for. relatively. hydrophobic. surfaces.
(PLLA),.where.they.aligned.along.the.direction.of.ibers.and.developed.mature.contractile.
machinery.(sarcomers)..The.only.drawback.of.these.aligned.iber.scaffolds.was.the.inabil-
ity.of.the.cardiomyocytes.to.penetrate.into.the.scaffold.due.to.the.inadequate.space.among.
the.ibers..A.very.similar.phenomenon.was.reported.by.Evans.et.al..(2003),.who.observed.
that. rat. embryonic. cardiac. myocytes. were. unable. to. penetrate. the. 3D. aligned. collagen.
iber.scaffold.with.a.pore.size.of.1-10.microns.on.the.outer.surface.of.a.tubular.scaffold..
Aligned.iber.scaffolds.with.a.iber.density.suitable.for.cell.penetration.were.produced.by.
our.group.by.using.a.frame.collector.to.obtain.aligned.ibers.(Kenar.et.al.,.2010)..At.least.
eight.or.nine.Wharton's.jelly.(WJ).MSC.layers.could.be.obtained.in.a.single.mat.of.average.
thickness.of.12.±.3.μm..Both.cytoskeletal.and.nuclear.alignments.of.the.cells.were.observed.
(Figure 10.3)..A.wrapping.method.was.used.to.obtain.a.thicker.homogeneous.construct,.
which. maintained. its. original. anisotropic. property.. Another. technique,. microintegra-
tion,.was.developed.by.Stankus.et.al..(2006),.where.simultaneous.electrospraying.of.cells.
and.electrospinning.of.poly(ester.urethane)urea.(PEUU).was.utilized.in.order.to.fabricate.
thicker.constructs.with.more.uniform.cell.incorporation.for.use.in.cardiovascular.tissue.
engineering.applications..Smooth.muscle.cell-microintegrated.PEUU.was.strong,.lexible,.
and.anisotropic,.and.Trypan.blue.staining.revealed.no.signiicant.decrease.in.cell.viability.
as.a.result.of.the.fabrication.process.
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