Stem Cells and Neurological Disorders Induced Pluripotent Stem Cells (iPSCs) Pluripotent cells make all types of cells Multipotent cells make some types

Stem Cells and Neurological Disorders

Induced Pluripotent Stem Cells (iPSCs)

Pluripotent cells make all types of cellsMultipotent cells make some types of cellsunipotent cells make just one type of cells

-Embryonic cells are the most potent but have ethical &rejection problems

-The best days to take the embryo cells are from 4-5 days


Induced Pluripotent Stem Cells (iPSCs): (By a Japanese scientist and took the Nobel prize after 5 years of the discovery)

= Retro-differentiation = Re-programming

Producing stem cells from differentiated cells !!!

Pluripotent embryonic like stem cells are produced

Reversal of normal process

Does Not require human embryos

No donor…..No rejection

Less expensive

No Ethical issues

Induced means that not naturally exist and we make it

Pluripotent=acts like embryonic cell

In this procedure we format the cell and make it forget its function and back it to its native home which is the embryonic cells

Main Key Genes:

- iPSCs are derived from adult somatic cells by inducing expression

of certain Stemness genes: (usually by viral vectors: risk !!!)

- eg: Master transcriptional regulators:

Oct-4

Sox2

Nonog

- other genes: c-Myc (oncogene: cancer risk !!!!)


These master transcription factor can activate any type of genes but they are inactivated in differentiated cells so we put an external master transcription gene by a viral vector and this master key can activate all genes so the cell becomes a pluripotent cells and the scientists even can make more earlier cells (Totipotent) !!

So from this induced stem cell now we can make any type of cells we want

In each cells there are many genes but there are just a fraction of them are active depending on the type of the cell,so the heart and liver cells have the same genes but in each of them some genes have been activated and the rest are sleepy

Pluripotency:

Believed to be identical to embryonic stem (ES) cells in many respects:

- expression of certain stemness genes

- chromatin methylation patterns

- doubling time

- embryoid body formation

- teratoma formation

- viable chimera formation

- potency and differentiability


(1) Isolate and culture donor cells.

(2) Transfect stemness genes into cells by viral vectors. Red cells express those genes

(3) Harvest and culture the cells according to ES cell culture, on feeder cells (light gray)

(4) A subset of the transfected cells become iPS cells and generate ES-like colonies

Generation of induced pluripotent stem (iPS) cells


http://en.wikipedia.org/wiki/File:Induction_of_iPS_cells.svg

http://upload.wikimedia.org/wikipedia/commons/0/09/Induction_of_iPS_cells.svg

Neurogenesis of iPS Pluripotent Neuronal Stem Cells derived from Adult Leukocytes


Potential target disorders for Stem Cell Therapy:

• Leukemia• Heart damage • Anemia • Cornea damage • Retinal damage• Parkinson’s • Alzhimer’s• Diabetes • Spinal Cord Injury • Kidney Failure • Skin grafts

leukemia



Heart damage

Injecting a stem cells to the damaged myocardium and will return to its work


Diabetes


Tissue Engineering &

Regenerative Medicine

Bone Repair


Skin graft grown from stem cells



Cornea


trachea from stem cellsIn the Trachea and the ear we need a scaffold to

put the stem cells in and then cells will take the shape of the scaffold


A grown ear seeded with cartilage cellsThe scaffold is from a biodegradable matter so when the ear cells finish

replication and take their final form we remove the scaffold

Stem Cells

&

Neurological Disorders


This is one of the most important aspects of regenerative medicine because the neurons are postmitotic and cannot

regenerate themselves rather than other tissues


Which Stem Cell:

1. Neural stem cells

2. Other Adult SC (HSCs & MSCs)(Plastisity)

3. Cord Blood SC

3. Embryonic SC(Ethical problem)

4. iPSCs

Delivery Strategy:

1. Injection into brain2. Into Blood stream (Homing + immobilization by cytokines)

Graft type:

3. Stem cells + Biomaterial (a scaffold that will dissolve)4. Stem Cells + Gene therapy (I play with the genes of the stem cells so

a certain chemical will be released more to treat the problem)

All have been shown to generate neural tissue

(Adult SCs are the mostlyused in clinical trials)

Homing means that the cells know where to go

HSC : Hematopoietic stem cellsMSC : Mesencymal stem cells


Comparison:

Stem Cell (Disadvantage)

Embryonic Pluirpotent Ethics

Fetal Pluripotent Ethics

Cord Blood Potent RejectionAvailable

Adult Neural / Autologus Self low Numbers Same tissue Isolation

Adult (HSCs, MSCs,…) Easy isolation rejection (if allo.)

Easy culture Plasticity ?!!

iPCs Pluripotent vector safetySelf

From the same person

Ongoing clinical Trials in US and the world 2012

Sanberg et al.February 2012

Different strategies for stem cell delivery to repair degenerated tissue


http://www.discoverymedicine.com/Antonio-Orlacchio/files/2010/06/discovery_medicine_orlacchio_no49_figure_1.jpg


Neural stem cells:

- Generate new neural cells throughout the lifetime

- Can migrate and replace dying neurons

- Give rise to all types of neurons, astrocytes and oligodendrocytes, …

- Capable of only Minor repairs

- Their activity is up-regulated following injury

- Found in: - Sub-ventricular zone of lateral ventricles (Most neurogenic area)

- Dentate gyrus of Hippocampus (2nd)

fewer in:- Cerebellum - Spinal Cord




Therapeutic Applications:

Main target disorders:

- Parkinson’s: localized degeneration (in substantia nigra) easier cell therapy

- Huntington’s: clear etiology, single gene disorders (Gene/Cell Therapy)

- Alzheimer : damage is less defined, widespread neuro-degeneration

- Spinal Cord injuries: very promising prospects

- Other: - Multiple Sclerosis (Siatskas and Bernard, 2009)

- Ischemia / stroke- Epilepsy (Naegele et al., 2010) - Amyotrophic Lateral Sclerosis (ALS) (Wolfson et al., 2009).


Parkinson’s:

- Main Strategy:

- Replacing degenerated neurons with dopamine-producing cells

- Site:- Substantia nigra: area were most degeneration occurs in PD

- Source of SCs:

- Pieces of fetal midbrain tissue (Mendez et al., 2005)

- Autologous adult neural stem/progenitor cells (Michel et al., 2009)

- Embryonic SCs (Friling et al. 2009)


Huntington’s:

- Good Model: well characterized single gene disorder

- Main Strategy:

Blocking neuronal cell death & replacing lost neurons in striatum

- Source of SCs:

- SCs of fetal striatal primordium into striatum of HD patients (Bachoud-Lévi et al., 2006)

- Autologous adult neural stem/progenitor cells (Yu and Silva, 2008; Visnyei et al., 2006).


Alzheimer’s:

- Neuro-genesis in hippocampus deteriorates in AD patients

Example approaches: (Lunn et al., 2011)

1. Implanting Neural Stem Cells:

- Replace lost neurons

- Delay degeneration by producing Brain-Derived Neurotrophic Factor (BDNF)

2. Nerve growth factor (NGF) production:

- Genetically engineered patient fibroblasts that produce NGF …!!!

- Integration of NGF fibroblasts into a major cholinergic center of the basal forebrain provided some benefit to AD patients


Spinal cord injuries: (Salewski et al., 2010; Hu et al., 2010, Mathai et al 2008).

Stem cells can:

1. Replace neurons that died from injury

2. Generate supporting cells to re-form the myelin sheath & stimulate re- growth of damaged nerves

3. Protect cells at injury site from further damage, by releasing protective factors

Stem cells under trials:

- Embryonic SCs - Umbilical cord SCs - Adult neural SCs - Mesenchymal / bone marrow SCs - induced pluripotent Scs


Christopher Reeve

1952 - 2004


Paralyzed Patients Walking Again

http://www.youtube.com/watch?v=KGUAyKQKmmY

http://www.youtube.com/watch?v=-kygF2leZCE

http://www.youtube.com/watch?v=ZgI4tm8Tr5M


Conclusion:

- Very promising clinical trial results in the last few years

- More research needed to optimize diff. SC replacement protocols:- Cell type- Route- No. of cells- Single or multiple cell doses

- Choice between ESCs / ASCs / iPSCs: yet to be resolved

- Ethics (ESCs and Fetal tissue): Each Country has to decide

THANK YOU


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Stem Cells and Neurological Disorders Induced Pluripotent Stem Cells (iPSCs) Pluripotent cells make all types of cells Multipotent cells make some types