Asymmetric Self-RenewalAsymmetric Self-RenewalBy Distributed Stem Cells:By Distributed Stem Cells:

Misunderstood in the Past, Important for the FutureMisunderstood in the Past, Important for the Future

James L. Sherley, M.D., Ph.D.James L. Sherley, M.D., Ph.D.DirectorDirector

The Adult Stem Cell Technology Center, LLCThe Adult Stem Cell Technology Center, LLCBoston, MA, USABoston, MA, USA

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Fetal, Neonatal, AdultFetal, Neonatal, AdultDevelopmentDevelopment

EarlyEarlyEmbryonicEmbryonicDevelopmentDevelopment

Fetal SCsFetal SCsGermline SCsGermline SCsPost-natal SCsPost-natal SCsSomatic SCsSomatic SCsTissue SCsTissue SCsAdult SCsAdult SCs

EpiblastsEpiblasts[embryonic SCs][embryonic SCs]EmbryonicEmbryonic precursorsprecursors

EmbryonicEmbryonic

Post-EmbryonicPost-Embryonic

Sources of Stem CellsSources of Stem Cells(SCs) During(SCs) During

Mammalian DevelopmentMammalian Development

Distributed Stem Cells?Distributed Stem Cells?(DSCs)(DSCs)

Fetal SCsFetal SCsGermline SCsGermline SCsPost-natal SCsPost-natal SCsSomatic SCsSomatic SCsTissue SCsTissue SCsAdult SCsAdult SCs

EmbryonicEmbryonic

Post-EmbryonicPost-Embryonic““DISTRIBUTED STEM CELLS”DISTRIBUTED STEM CELLS”DSCsDSCs

(Sherley, 2008,(Sherley, 2008,Breast DiseaseBreast Disease 2929, 37-46), 37-46)

For For DistributedDistributed Potency Potency

Asymmetric Self-RenewalAsymmetric Self-RenewalIn vivo and in vitroIn vivo and in vitro

Embryonic stem cellsEmbryonic stem cellsPrimordial germ cellsPrimordial germ cells

Induced pluripotent SCsInduced pluripotent SCsSymmetric Self-RenewalSymmetric Self-Renewal

In vitro In vitro

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The Pervasive Stem Cell Definition:The Pervasive Stem Cell Definition:

Self-renewaSelf-renewal or l or DifferentiationDifferentiation

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SymmetricSymmetricSelf-renewal Self-renewal

The Pervasive Stem Cell Definition:The Pervasive Stem Cell Definition:

Self-renewaSelf-renewal or l or DifferentiationDifferentiation

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SymmetricSymmetricSelf-renewal Self-renewal

An Inadequate Definition For Distributed Stem CellsAn Inadequate Definition For Distributed Stem Cells

A Gnomonic for Distributed Stem Cells:A Gnomonic for Distributed Stem Cells:

Self-renewaSelf-renewal AND l AND DifferentiationDifferentiation,,continuously and simultaneouslycontinuously and simultaneously

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““AsymmetricAsymmetricSelf-renewal” Self-renewal”

Tissue Cell TurnoverTissue Cell TurnoverThe mark of distributedThe mark of distributed

stem cells (DSCs):stem cells (DSCs):Asymmetric Self-RenewalAsymmetric Self-Renewal

Potten Potten et alet al., 2003., 2003

DeathDeath

TerminalTerminalArrestArrest

DifferentiationDifferentiation

SymmetricSymmetricKineticsKinetics

AsymmetricAsymmetricSelf-renewalSelf-renewalCell KineticsCell Kinetics

DSC (DSC (niche)niche)

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A CENTRAL QUESTION:A CENTRAL QUESTION:

What is the cell kinetics form ofWhat is the cell kinetics form ofasymmetric self-renewal?asymmetric self-renewal?

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Mathematical Identity, butMathematical Identity, but

Biological DistinctionsBiological Distinctions

pp1-p1-p

StochasticStochastic

vs.vs.

DeterminedDetermined

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Biological DistinctionsBiological Distinctions

StochasticStochastic1.1. Extinction probabilityExtinction probability2.2. Mutation accrualMutation accrual

DeterminedDetermined1.1. No DSC differentiationNo DSC differentiation2.2. Individual asymmetric divisionIndividual asymmetric division3.3. Mutation avoidance?Mutation avoidance?4.4. Unique cellular programs!Unique cellular programs!

pp1-p1-p vs.vs.

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≠≠

Developmental Asymmetric Divisions Are NotDevelopmental Asymmetric Divisions Are NotEquivalent to Asymmetric Self-Renewal DivisionsEquivalent to Asymmetric Self-Renewal Divisions

Asymmetric DivisionAsymmetric Division• Sisters unequalSisters unequal• Both sisters differBoth sisters differ from parentfrom parent• LimitedLimited

Asymmetric Self-RenewalAsymmetric Self-Renewal• Sisters unequalSisters unequal• One sister equalOne sister equal to parentto parent• Continuous over lifespanContinuous over lifespan

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Biological DistinctionsBiological Distinctions

StochasticStochastic1.1. Extinction probabilityExtinction probability2.2. Mutation accrualMutation accrual

DeterminedDetermined1.1. No DSC differentiationNo DSC differentiation2.2. Individual asymmetric divisionIndividual asymmetric division3.3. Mutation avoidance?Mutation avoidance?4.4. Unique cellular programs!Unique cellular programs!

pp1-p1-p vs.vs.

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Asymmetric Self-Renewal Associated (ASRA)Asymmetric Self-Renewal Associated (ASRA)Genes: Highly Specific Biomarkers for DSCsGenes: Highly Specific Biomarkers for DSCs

SYMSYM

ASYMASYM

[Noh [Noh et al.et al. 2011, 2011, PLoS ONEPLoS ONE]]

SYMSYM ASYMASYM

CyA

CyA

CX

CR

6C

XC

R6

DN

AD

NA

Pha

seP

hase

[Taghizadeh [Taghizadeh et alet al., 2010,., 2010, PLoS ONE PLoS ONE]] ASCTC

Stem CellStem CellTherapyTherapy

““Adult” Stem Cells (Adult” Stem Cells (DSCsDSCs))Embryonic Stem Cells (Embryonic Stem Cells (ESCsESCs))

Induced Pluripotent Stem Cells (Induced Pluripotent Stem Cells (iPSCsiPSCs))

Proposed Stem Cells for Tissue Replacement Proposed Stem Cells for Tissue Replacement

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StochasticStochastic

DeterministicDeterministic

(In Vitro)(In Vitro)Self-RenewalSelf-Renewal

OROR Differentiation Differentiation

Stemness PreservedStemness Preserved““AsymmetricAsymmetricSelf-Renewal”Self-Renewal”

Embryonic and iP Stem CellsEmbryonic and iP Stem Cells

Distributed Stem CellsDistributed Stem Cells

Mathematical Features of Cell Production with DifferentiationMathematical Features of Cell Production with Differentiation

pp1-p1-p

a

b

d

c

Self-RenewalSelf-Renewal

ANDAND Differentiation Differentiation

Loss of Loss of StemnessStemness

a

a

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Stem CellStem CellTherapyTherapy

““Adult” Stem Cells (Adult” Stem Cells (DSCsDSCs))Embryonic Stem Cells (Embryonic Stem Cells (ESCsESCs))

Induced Pluripotent Stem Cells (Induced Pluripotent Stem Cells (iPSCsiPSCs))

Proposed Stem Cells for Tissue Replacement Proposed Stem Cells for Tissue Replacement

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NormalNormalTissueTissue

Damaged or DiseasedDamaged or DiseasedTissueTissue

Tissue Therapy with ESCs and iPSCs?Tissue Therapy with ESCs and iPSCs?

REPAIR?REPAIR?

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NormalNormalTissueTissue

Damaged or DiseasedDamaged or DiseasedTissueTissue

Short-livedShort-livedRepair!!!!Repair!!!!

(Tumors!)(Tumors!)

Tissue Therapy with ESCs and iPSCsTissue Therapy with ESCs and iPSCs

hESCs and iPSCshESCs and iPSCs- ethical issues (hESCs)- ethical issues (hESCs)- epigenetic defects- epigenetic defects- genetic defects- genetic defects

PurificationPurification- ESCs!- ESCs!- iPSCs!- iPSCs!- other differentiated cells- other differentiated cells

““DevelopDevelopIn VitroIn Vitro”” Differentiated Cells (Immature)Differentiated Cells (Immature)

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NormalNormalTissueTissue

Damaged or DiseasedDamaged or DiseasedTissueTissue

DSC ExpansionDSC Expansionisis possible! possible!

• AutologousAutologous• AllogeneicAllogeneic• Informed ConsentInformed Consent

RenewingRenewingRepairedRepaired

TissueTissue

Tissue Therapy with Distributed Stem CellsTissue Therapy with Distributed Stem Cells

- purity not required- purity not required- expansion not always- expansion not always criticalcritical

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NormalNormalTissueTissue

Damaged or DiseasedDamaged or DiseasedTissueTissue

An DSC Bottleneck for Tissue TherapyAn DSC Bottleneck for Tissue Therapy

““DevelopDevelopIn VitroIn Vitro””

Isolate, stabilize, expandIsolate, stabilize, expand

Distributed Stem CellsDistributed Stem Cells

RepairedRepairedTissue?Tissue?

Tumor RiskTumor RiskRemainsRemains

[Sherley, J. L. 2004, [Sherley, J. L. 2004, J. Biomed. BiotechJ. Biomed. Biotech. 2, 71-72.]. 2, 71-72.]Differentiated Cells (Immature)Differentiated Cells (Immature)

hESCs and iPSCshESCs and iPSCs- ethical issues (hESCs)- ethical issues (hESCs)- epigenetic defects- epigenetic defects- genetic defects- genetic defects

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Distributed Stem Cell Distributed Stem Cell Asymmetric Self-RenewalAsymmetric Self-Renewal

Embryonic developmentEmbryonic development

hESCshESCs ??iPSCsiPSCs

Immature?Immature?

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Distributed Stem Cell Distributed Stem Cell Asymmetric Self-RenewalAsymmetric Self-Renewal

Embryonic developmentEmbryonic development

hESCshESCs ??iPSCsiPSCs

Xanthine (p53-KO mimic)Xanthine (p53-KO mimic)

Immature?Immature?

Pare & Sherley, 2011, Pare & Sherley, 2011, J. Biomed. Biotech.J. Biomed. Biotech.

New Patent: USPTO No. 8,759,098, June 24, 2014New Patent: USPTO No. 8,759,098, June 24, 2014

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DiseaseDiseaseResearchResearch