Dr. Diala Abu-Hassan, DDS, PhD Central Nervous System Dr. Diala Abu-Hassan School of Medicine 1 Stem Cells & neurodegenerative diseases

Neurodegenerative Diseases  Awiderangeofacuteandchronicconditionsinwhich neuronsandglialcellsinthebrainandspinalcordare lost.  Acute :ischemicstrokeorspinalcordinjury  Chronic: Parkinsondisease(PD), amyotrophiclateralsclerosis (ALS),or Alzheimerdisease (AD). Dr. Diala Abu-Hassan2 Loss of one cell type or more For ex. May be due to trauma or a cut in the spinal cord

Neurodegenerative Diseases & Stem Cell Therapy  Clinicaltrialsusingstemcellshavealreadybeenperformedorinitiated neurodegenerativedisorder (e.g.,fortherare,fatal,autosomalrecessive Battendisease)  Nostemcell–basedtherapyhasyetbeenprovenbeneficialforany neurodegenerativecondition.  Despite this fact, unproven treatments for several neurodegenerative diseases are offered at “clinics” around the world without rationale and with poor scientific and clinical basis.  Ethical, regulatory,societal,andeconomicalissuesneedto beaddressed. 3 Dr. Diala Abu-Hassan This is heard often in the media (unethical) Doctor jumped to slide #7

Main considerations when we use stem cells to treat neurodegenerative diseases Dr. Diala Abu-Hassan  Whatisrequiredforthestemcell–basedapproachtobeclinicallycompetitive  Riskstothepatient that are acceptable, depending on disease severity. Animal modelsmaynotfullypredicttheirtoxicity,occurrenceofimmuneandother biologicresponses,andriskfortumorformationafterimplantationinpatients.  The variability between neurodegenerativediseases inthedegreeof disabilitythat optionsthatareavailable. theycauseandinthetherapeutic Parkinsons Disease- symptomatic treatment ALS- No efficient treatment 4 What is expected from this treatment Type of cells that I want to replace by stem cells Mainly dopaminergic neurons are affected

Main considerations when we use stem cells to treat neurodegenerative diseases Dr. Diala Abu-Hassan  The cell type to be regenerated and transplanted. PD- dopamine neurons ALS – motor neurons Stroke and Alzheimer's disease-several cell types  Thestemcell–basedapproachshould show substantialimprovementof functionaldeficits in animal models before their use in clinical application.  Todeterminethebiologicalmechanismunderlyingtheobservedeffectsof ananimalmodel. E.g. reconstruction ofastemcell–basedtreatmentin neuronal circuitry 5 Last step

Stem cell technology and cellular therapy classifications 6 Dr. Diala Abu-Hassan

Translating a stem cell-based treatment from the bench to bed 7 Dr. Diala Abu-Hassan Tissue culture Really expensive to perform Clinical trials are classified into 3 stages: stages 1,2,and 3. Each has its own regulations and permissions from the FDA Treatment might be beneficial now but no one knows what will happen in the long run

8 Common considerations when translating stem cell therapies to neurodegenerative disease patients Dr. Diala Abu-Hassan

Parkinson’s disease (PD) DegenerationofnigrostriatalDA neuronsis themainpathology Characteristic symptoms are rigidity,hypokinesia, tremor,andposturalinstability Tx: l-DOPA,DA agonists, enzyme inhibitors,anddeep brain stimulation No Tx for dementia iPSCs for modelling the genetically complex PD Dr. Diala Abu-Hassan 9 With some dementia

Stem cell–based therapies for PD Proof of principle: clinicaltrialswithintrastriataltransplantationofhumanembryonic mesencephalic tissue (richinpostmitoticDAneuroblasts). Dr. Diala Abu-Hassan 10

Stem cell–based therapies for PD ProsCons -The DA neurons thatform from the transplanted tissue reinnervate the denervated striatum and become functionally integrated, restoring striatal DA release and giving rise to clear symptomatic relief in some patients. -A small fraction of graft-derived DA neurons contain Lewy bodies (the hallmark of PD). - Availabilityof human embryonic mesencephalic tissue is limited. 11–16 years aftertransplantation, cell replacement remains a viable therapy. Variabilityof functional outcome after transplantation is high. The progression of pathology in graft-derived neurons is slow, and they are still functional after a decade. Poor standardization of the transplanted cell material contributes to the high variability Dr. Diala Abu-Hassan 11 Amount of improvement and quality of these transplanted cells)

Stem cell–based therapies for PD Dr. Diala Abu-Hassan 12 Other sources of DA neurons: EScells ClonedEScells NSCsandprogenitors ofembryonicventralmesencephalon AdultNSCsfromthesubventricularzone(SVZ) Bonemarrowstemcells Fibroblast-derivediPScells Humanstemcell–derivedDAneuron precursors/neuroblasts can surviveinanimalmodelsofPDand can be functional after maturation.

Stem cell–based therapies for PD Dr. Diala Abu-Hassan 13 Hurdles that prevent stem cell therapy for PD from bench to clinic: PD is amultisystemdisorder,if nondopaminergicsystemsare affected, they willnot improvebyintrastriatalDA grafts. Substantialre-innervation ofstriatum has not been demonstrated. Restoration ofDAreleaseinvivo has not been demonstrated. Markedimprovement (50-70%) in the deficitsand symptoms experiencedbyPD patients has not been demonstrated. Risk of tumor formation-even if minor, it is not acceptable. The need to inject cells at all sites of injury. Number of injections should be minimum for practical reasons

Alzheimer’s disease(AD) Memory impairment, cognitive decline, and dementia due to widespread and progressive pathological changes Neuronalandsynapticloss, neurofibrillarytangles,and deposits ofβ-amyloidprotein involvethebasal forebrain cholinergicsystem, amygdala, hippocampus,andcortical areas Dr. Diala Abu-Hassan

Stem cell–based therapies for AD Cholinergic neurons: acetylcholinesterase inhibitors,whichenhancecholinergic function,inducesome temporary improvement inADpatients Dr. Diala Abu-Hassan 2. Neurogenesis or maturation of hippocampal neurons as the formationofimmature hippocampal neurons was reported in AD. 3. Nerve growth factor (NGF) releasing stem cells. 4. Anti-β-amyloid antibodies or β-amyloid–degrading protease neprilysin. By using

Stem cell–based therapies for AD Dr. Diala Abu-Hassan 16 Hurdles that prevent stem cell therapy for AD from bench to clinic: Stemcellshavetobepre-differentiatedin vitrotomany differenttypesofneuroblasts forsubsequentimplantationin many brain areas. For a long-lastingsymptomaticbenefit,cholinergiccell replacementrequiresintacttargetcells (hostneuronsthatthe newcholinergicneuronscanacton) that are damagedinAD. Stemcell–basedcellreplacementstrategiesarevery farfrom clinicalapplicationinAD Bench to bed More diffused size of lesion, so harder 1 2 Because of 1 and 2

Stroke Neuronalplasticityandreorganizationofneuralcircuitriescontributeto spontaneousrecovery to varyingdegrees,butmost patients exhibitpersistent motor,sensory, orcognitiveimpairments Ischemicstroke, causedbyocclusion ofa cerebral artery,leads to focal deathofmultiple neuron types,as well as oligodendrocytes, astrocytes, andendothelial cells. Dr. Diala Abu-Hassan 17 fescenter.org 2 types of stroke depending on the cause:

Stem cell–based therapies for stroke 18 HumanES cell–derivedNSCs and MSCs, graftedinto rat stroke site, migrated towardthe lesionandimproveforelimbperformance. IV injectionofhuman NSCs induced improvementsafter hemorrhagic stroke in rats, probably through antiinflammatory actions Dr. Diala Abu-Hassan None of these moved to clinic

Stem cell–based therapies for stroke Dr. Diala Abu-Hassan 1919 NosubstantialclinicalimprovementsweredetectedafterIV injectionofautologousMSCsinpatientswithanischemic bythemiddlecerebralarterylesionintheregionssupplied (MCA). Severalclinicalstudiesusing intravenousorintraarterial (intodamagedterritory)infusionofautologousbone marrow–derivedstemcellsinstrokepatientsare ongoing. Aclinicaltrialinstrokepatientsinvolvingtransplantation ofclonal,conditionallyimmortalizedNSCsisolatedfrom humanfetal cortex.

Stem cell–based therapies for stroke Dr. Diala Abu-Hassan % of neuroblasts and neurons dieduringthefirsttwoweeksafterformation atstroke site inrats. A. Cell survival can be improved by: 1.Inflammation-modulatingagents 2.Caspaseinhibitors 3.Neurotrophicfactors B.Promotingthemigrationofthe newneuronstothedamagedarea by stromal cell–derivedfactor1α[SDF-1α],monocyte chemoattractantprotein–1, andmatrix metalloproteinase–9. C.Stimulation ofthedifferentiationofcortical neurons that form inlimited numbersafterstrokeby growth factordelivery. Inflammatory cytokines should be inhibited; IFM decreases cell survival Enhance the growth of neurons An enzyme involved in apoptosis Protease: digestion of proteins, so opens a path for migrating cells

Spinal cord injuries Dr. Diala Abu-Hassan 21 Pathologicalchanges after spinalcordinjuryare complex andinclude: 1.Interruptionofascendinganddescendingpathways 2.Lossofneuronsandglialcells 3.Inflammation 4.Scar formation 5.Demyelination medical.miragesearch.com Patientsexperience loss ofmovement,sensation,and autonomiccontrolbelowthelevel ofthe injuredspinal segment. Availabletreatmentsare ineffective. Different types of stem cells were tested and improved functional outcome in animal models through secretion of neurotrophic factors, remyelination of spared axons, or modulation of inflammation Lesion in the neck, so anything below it must be affected

Stem cell–based therapies for spinal cord injuries Formation of neurons, oligodendrocytes, & astrocytes. Formation of synapses and axons Remylenation : high-purity oligodendrocyte progenitorcells (OPCs)generated fromhuman ES cells in vitrocan differentiate into oligodendrocytes (clinical trial) Dr. Diala Abu-Hassan 22 By using Induce myelination

Stem cell–based therapies for spinal cord injuries Dr. Diala Abu-Hassan 23 Before moving to clinic: Determine how to control the proliferationoftransplanted stemcellsandtheir progeny Determine howto enhance thedifferentiationofthese cellstothespecific typesofneuronsthathavebeenlost Determine howtheresultingneuronscanbedirected toformatappropriate synapticcontacts

Stem cell–based therapies for spinal cord injuries Dr. Diala Abu-Hassan 24 Other stem cell types Umbilicalcordblood,bonemarrow–derivedHSCs,and MSCshave alreadybeenappliedinpatientswithspinalcord injury,withclaims ofpartialrecovery. Problems in these trials: 1.Theimplantedcellswereoftenpoorlycharacterized. 2.Thepreclinicalevidenceofefficacyforseveralof theseapproaches wasinsufficient. 3.Thetherapeuticbenefitwasreportedfrom open-labeltrialswhere patientshadbeensubjectedtophysiotherapy. 4.Themechanismsunderlyingobservedimprovements wereunclear.