stem cells differential gene expression and cell fate why manipulate stem cells?

I. Stem cellsII. Differential gene expression and cell fateIII. Why manipulate stem cells?IV. Potential sources of therapeutic cellsV. Concluding thoughts

pluripotent stem cell

pluripotent stem cell committed cell

pluripotent- having the potential to develop into any cell type of the body

http://departments.weber.edu/chfam/prenatal/blastocyst.html

I. Stem cellsII. Differential gene expression and cell fateIII. Why manipulate stem cells?IV. Potential sources of therapeutic cellsV. Concluding thoughts

Genes are made of DNA

DNA is within the nucleus of each of our cells.

This DNA is identical in each of the cells of our bodies…

…even though different cells have very different structures and functions

Q: How do cells with identical genetic compositions become so different from one another?

A: Different cells express different subsets of their genes.

Gene A Gene B Gene A Gene B

In neurons, gene A is expressed but not gene B:

In muscle cells, gene B is expressed but not gene A:

Gene A Gene B

(muscle cell specific transcription factors)

(promoter of gene B)

In muscle cells, gene B is expressed because muscle cells have transcription factors that bind to gene B’s promoter.

Gene A Gene B

In muscle cells, gene B is expressed because muscle cells have transcription factors that bind to gene B’s promoter.

I. Stem cellsII. Differential gene expression and cell fateIII. Why manipulate stem cells?IV. Potential sources of therapeutic cellsV. Progress on stem cell therapeutics

I. Stem cellsII. Differential gene expression and cell fateIII. Why manipulate stem cells?IV. Potential sources of therapeutic cells

A. Adult stem cellsB. Embryonic stem cells (IVF embryos)C. Induced pluripotent stem cellsD. Embryonic stem cells (SCNT-derived)E. Transdifferentiation

V. Concluding thoughts

Bone marrow contains Hematopoetic Stem Cells

irradiation

(injection with bone marrow)

Adult stem cell types that have been tested clinically

Hematopoetic stem cellsMesenchymal stem cellsNeural stem cellsAdipose stem cells

Lin et al., 2013

Lin, et al., 2013

Most stem cell clinical trials have used adult stem cells

Adult Stem Cell Therapies

pros

cons

• no ethical dilemmas• autologous (self) donations are possible• cells need not be manipulated or grown in culture• no risks of teratomas (tumors)

• few tissues are represented by adult stem cells• those tissues that DO have them have very few• if not autologous, MUST be tissue type matched• evidence of clinical efficacy limited to HSCs• cannot be amplified or maintained in culture

http://departments.weber.edu/chfam/prenatal/blastocyst.html

Deb and Sarda, 2008

Animal Models in which hESC-Derived Cells have been Effective

2009-2011 Geron Corporation hESC-derived oligodendrocyte progenitors for treatment of spinal cord injuries (Daley, 2012)

-in animal models, these cells car repair damaged neurons-the first hESC clinical study to overcome FDA restrictions-four patients enrolled-no publications yet; no reported negative effects, but

unclear if treatments were effective

Clinical Trials using hESCs

2009-present Advanced Cell Technology (ACT) hESC-derived retinal pigment epithelial cells are being used to treat macular degeneration (Schwartz,et al. 2012)

-started with 2 patients, both showed vision improvement and no signs of tumors after 4 months

-study is continuing with higher doses of cells and in more patients

Clinical Trials using hESCs, cont.

ESCs from IVF

pros

cons

• source tissue plentiful• cells divide infinitely in culture• easily programmable cells

• immune response problems• ethical controversy• tumor risks


A. Adult stem cellsB. Embryonic stem cells (IVF embryos)C. Induced pluripotent stem cells

1. issues with iPSCs2. progress with iPSCs

D. Embryonic stem cells (SCNT-derived)E. Transdifferentiation


Takahashi and Yamanaka 2006

• DNA inserted randomly could create problems with endogenous DNA.• DNA insertions are inherited by all progeny of manipulated cell.• The genes added could cause cells to be more prone to division.

New iPSC protocols do NOT require insertion of foreign DNA

• Exposure of differentiated cells to chemical treatments caused them to become pluripotent (Masuda et al., 2013).

• Protein transduction of somatic cells can produce iPS cells (Nemes et al., 2013).

• Mouse lymphocytes were induced to become pluripotent via acid treatment (Obokata et al., 2014).

Stadtfield & Hochedlinger 2010

With iPSCs, the pluripotency must be tested


A. Adult stem cellsB. Embryonic stem cells (IVF embryos)C. Induced pluripotent stem cells

1. issues with iPSCs2. progress with iPSCs

D. Embryonic stem cells (SCNT-derived)E. Transdifferentiation


Many cell types have been derived from human iPS cells

• hepatocytes (Takebe et al., 2014)• neurons (Prilutsky et al, 2014)• folliculogenic stem cells (Yang et al., 2014)• cardiomyocytes (Seki et al., 2014)• pancreatic beta cells (Thatava et al, 2011)

First iPSC clinical trial to begin this year

• lab of Dr. Masayo Takahashi at Riken in Kobe, Japan

• 6 patients with macular degeneration in trial

• iPSCs will be reprogrammed in culture to become retinal pigment epithelium

• once 50,000 cells per patient are produced, these will be introduced back into the retinas

Grskovic, et al. 2011

Successful “disease in a dish” models

• Familial dysautonomia, a genetic disease of autonomic nervous system

• Rett Syndrome, a disease within the autism spectrum

• HGPS (progeria), premature aging

• Parkinson’s, degradation of midbrain dopaminergic neurons leading to loss of motor activity

Grskovic, et al. 2011

iSPCs

pros

cons

• patient-derived pluripotent cells• once established, cells divide infinitely in culture• easily programmable cells• less ethical controversy than ESCs• produce excellent tools for studying disease

• cells require a lot of manipulation to become iSPC • evidence of immunogenicity of iPSCs (Fu, 2013)• low rate of induced pluripotency (~.2%)• tumor risks

Freeman, 2012

ESCs from SCNT

pros

cons

• cells divide infinitely• easily programmable cells• genetically identical to patient• great for disease modeling

• ethical controversy• will require oocyte donors• not tested much with human cells

Transdifferentiation

Graf, 2011

Graf, 2011

ESCs iPSCs

embryos

high

high

good

good

somatic cells

very high

some?

good

good

derivation

cancer risk

immunogenicity

growth in culture

ability to program

ESCs are currently considered the “gold standard” for pluripotency.

Current research is investigating whether iPSCs are truly equivalent to ESCs.

Many scientists developing iPSCs still must use ESCs for comparison in their experiments.

macular degenerationParkinson’sType II DiabetesAltzheimer’sheart diseasespinal cord injuriesburnsHuntington’s

Conditions that might be alleviated using stem-cell derived transplantations (a partial list)

cancer risk from cultured cells

immune response from cultured cells

creating cultured cells to have all the functions of those cells produced by the body

the necessity of producing a LOT of the target cells in culture

creating cultured cells that integrate with host tissues

Challenges to cell culture-derived transplantations

useful as a way to test drugs without experimenting on patients

a means to generate therapies specific to specific patients

can be used also to study diseased cells and figure out what is wrong with them

iPSCs are outstanding tools for disease modeling

stem cells differential gene expression and cell fate why manipulate stem cells?

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