Biomedical Engineering Reference
In-Depth Information
lost.tissue.structure.and.function..Traditional.tissue.engineering.methods.such.as.autolo-
gous.chondrocyte.transplantation.(ACT).may.involve.complex.procedures,.and.therefore.
the.proliferation.capabilities.of.stem.cells.render.them.a.potentially.ideal.cell.source.
22.1.2 Stem Cell Therapy
Stem.cells.exhibit.long-term.self-renewal.ability.and.respond.to.differentiation.cues.toward.
speciic.lineages..Stem.cells.are.being.explored.in.research.aimed.at.treatments.for.cancer,.
Parkinson's.disease,.Alzheimer's.disease,.loss.of.tissue,.and.many.more.conditions.
Two.principal.directions.for.stem.cell.therapies.include.isolated.stem.cell-based.ther-
apies.and.scaffold-based.cell.therapies..Isolated.stem.cell-based.therapies.utilize.direct.
stem.cell.injection.into.the.target.tissue/organ,.for.example,.blood.transfusion.and.bone.
marrow.transplant.for.lymphoma.treatment..These.approaches.have.been.successful.in.
the. treatment. of. those. suffering. from. blood-related. diseases.. However,. isolated. stem.
cell-based. therapies. may. be. less. effective. for. treatment. of. vascularized. tissues. and.
tissues. with. speciic. and. potentially. complex. structure. and. function.. To. help. tissue.
regenerate.successfully,.a.blood.supply.is.essential.for.providing.the.regenerating.tissue.
with.oxygen.and.nutrients,.particularly.with.vessels.spaced.in.the.range.of.100-200.μm.
(Muschler. et. al.. 2004).. One. method. to. enable. these. vascularized. tissues. to. regenerate.
has. been. to. employ. microluidic. technology. to. scaffold. development. to. form. an. engi-
neered.vascular.network.comprising.a.viable.blood.supply..In.addition.to.vasculature,.
another. important. factor. to. recapitulate. is. the. function. and. mechanical. structure. of.
the.targeted.organ.during.tissue.regeneration..Therefore,.much.work.has.been.done.on.
designing.complex.engraftment.of.scaffolds.to.allow.stem.cells.to.proliferate,.differenti-
ate,. and. eventually. to. function. fully. with. proper. stimulations. from. growth. hormone.
and.peptides.
Stem.cell.therapy.appears.to.be.a.promising.route.of.therapy.for.many.diseases..With.
advancing.knowledge.of.stem.cell.behavior.and.optimization.of.culture.conditions,.con-
struction.of.the.aforementioned.scaffolds.with.appropriate.features.and.functions.is.the.
next.critical.step.toward.translation.of.stem.cell.therapies.to.a.clinical.setting.
22.2 Fabrication Technologies in Synthetic Scaffolds
Scaffold.material.selection.and.fabrication.techniques.suited.toward.those.materials.have.
emerged.as.important.targets.for.research.in.the.ield.of.regenerative.medicine..In.order.to.
create.specialized.scaffolds.for.speciic.tissue.regeneration,.materials.must.provide.certain.
critical.functions:.(1).providing.temporary.structural.support.while.tissue.regenerates;.(2).
allowing.stem.cells.to.attach,.grow,.proliferate,.later.on.migrate,.differentiate.into.special-
ized.tissue.cell,.and.inally.regain.full.function;.and.(3).ensuring/enabling.nutrient.deliv-
ery.and.waste.removal.from.regenerating.site.(Muschler.et.al..2004)..These.three.functions.
are.critical.to.the.regenerating.process.and.require.the.scaffolding.material.to.have.some.
speciic.characteristics.
In. order. to. optimize. the. scaffold. functionalities,. important. requirements. of. the. scaf-
folds.must.be.considered:.biocompatibility,.biodegradability,.degradation.rate,.mechanical.
properties,.and.surface.properties.(Agrawal.and.Ray.2001,.Hutmacher.et.al..2001)..These.
topics.are.covered.in.the.following.section.
