Stem Cells inStem Cells inRegenerative MedicineRegenerative Medicine

Todd C. McDevitt, Ph.D.June 21, 2006

The Era of Regenerative Medicine

Tissue Engineering(1980s 2005)

Regenerative Medicine(2005+)

(So whats changed?)

Scaffolds +

Biomolecules +

Cells

Tissues

Make the tissue Repair the tissue

Stem Cells +

Materials (?) +

Biomolecules (?)

Tissues

Objective:

Stem Cells & Tissue Engineering

Somatic cell tissue engineering:

- committed cell types- tissue assembled upon a

biodegradable scaffold

Stem cell tissue engineering:

- uncommitted cell types- direct differentiation by

environmental cues Stock & Vacanti, Annu Rev Med 2001.

Hope or Hype?

http://stemcells.nih.gov/info/media/DSC_1185.jpg

Cancer diagnosis & treatment

Stem Cell History

1998 Human ES & embryonic germ cell lines derived2001 Federal approval of human ES cell research

1961 Stem cells first discovered in the blood

1981 Mouse embryonic stem (ES) cell lines derived

1964 Embryonic carcinoma (EC) cell lines derived

1995 Rhesus monkey ES cell lines derived

2004 Cloned human ES cells produced

1968 First bone marrow transplantation performed

1984 Human EC cell lines derived

1968 First human egg fertilized in vitro

Definition of a Stem Cell

Zandstra & Nagy, Annu Rev Biomed Eng 2001.

Criteria

1) Self-renewal- Proliferative- Clonogenic potential

2) Differentiate into mature (somatic) cell types

- Often times, multi-lineage potential

Potency of Stem Cells

Totipotent all cell/tissue types Pluripotent embryonic & adult cells Multipotent multiple cell types

Modified from:LaGasse et al., Immunity 2001.

Potential

Stem Cell PotencyEmbryonic Bone marrow Satellite cell

Pluripotent Multipotent Unipotent

Potency affects applications & ease of manipulation

Types of Stem Cells

Embryonic (Pluripotent)- Stem cells (inner cell mass) ES- Germ cells (embryonic gonad) EG- Carcinoma (testes) EC

Isolation of Pluripotent Stem Cells

Donovan & Gearhart, Nature 2001.

ES EG EC

Derivation of ES Cells

Adapted from: Gepstein, Circ Res 2002.

(Morula)

(Blastocyst)

Somatic Cell Nuclear Transfer

Advanced Cell Technology

Therapeutic cloning

Lanza et al., Nature Biotech 1999.

Reproductive cloning

Cloning & Stem Cell Research

A minority of stem cell research involves cloning.

ES Cell Culture & DifferentiationUndifferentiatedUndifferentiated

10x

SuspensionSuspension

Embryoid bodies (EBs)

Outgrowths

ES Cell Differentiation

http://www.geron.com/showpage.asp?code=prodst

Types of Stem Cells

Fetal (Multipotent)- Umbilical cord, placenta, amniotic fluid

Embryonic (Pluripotent)- Stem cells (inner cell mass) ES- Germ cells (embryonic gonad) EG- Carcinoma (P19s) EC

Fetal Stem Cells

- Umbilical cord

- Placenta

- Amniotic fluid

http://webmd.lycos.com/content/asset/adam_imagepage_9980

Types of Stem Cells

Adult (Multi/Unipotent)- Bone marrow (hematopoietic & mesenchymal)- Tissue: neural, skin, skeletal muscle (satellite

cells), fat, endothelial progenitors (EPCs)

Fetal (Multipotent)- Umbilical cord, placenta, amniotic fluid

Embryonic (Pluripotent)- Stem cells (inner cell mass) ES- Germ cells (embryonic gonad) EG- Carcinoma (P19s) EC

Tissue-Derived Adult Stem CellsSome examples:

Bone marrow

Skin

Neural- central & peripheral

nervous system

Endothelial progenitors- circulating

Adipose tissue

Satellite cells (skeletal muscle)

Even more:

Dental pulp

Cardiac

Pancreas

Liver

Intestine

Adult vs. Embryonic Stem Cells

- Pluripotent (+)- Highly proliferative (+)

- Multipotent- Limited proliferativecapacity

Embryonic Adult

- Non-autologous- Ethical concerns- Tumorigenic

- Autologous (+)- Less controverserial (+)- Non-tumorigenic (+)

Assaying Stem Cell Potential

1) In vitro differentiation- Culture dish

2) Teratoma formation- Grafted into animal

3) Chimera formation- Injected into blastocyst

Smith, Annu Rev Cell Dev Biol 2001.

Developmentalpotential assays

Bone Marrow Cell Fate

Blau, Brazelton & Weiman, Cell 2001.

Male

Female

(-gal, GFP)

Bone Marrow Cell Potential

Blau, Brazelton & Weiman, Cell 2001.

Dystrophin

mdx mouseFAH-/- mouse

Gussoni et al.,Nature 1999.

Jackson et al.,J Clin Inv 2001.

Cardiomyocyte

Lagasse et al.,Nat Med 2000.

FAH+ hepatocytes

Brazelton et al.,Science 2000.

Y chromosome

NeuN

GFP

Stem Cell Differentiation Models

Frisn, Neuron 2002.

Misinterpretation ?

Frisn, Neuron 2002.

Questions to be Resolved

- What stem cell(s) are useful for which therapies?Differentiation potential

- What controls stem cell differentiation?Signals requiredDelivery/presentation methods

- How to obtain or derive stem cells?Cell/tissue sourceGenetic manipulation

Stem Cell Translation

Cell biologists

Clinicians

Engineers

Adapted from: Gepstein, Circ Res 2002 & http://stemcells.nih.gov/info/media/DSC_1187.jpg

Derivation

Regenerative MedicineStem Cell Biology

Identification

DifferentiationTissue

morphogenesis

Cellular therapies

Propagation

-- Quantitative approachQuantitative approach-- Environmental controlEnvironmental control