Different cells have different talents

But - all came from one

How do cells

differentiate?

Some cell types continue to replace

Other cell types slow down or stop replacing

If an organ malfunctions, we might replace it, but….

Brain & spinal cord: no regrowth, no transplant

Defects in development when cell differentiation goes wrong

Cancer is cell differentiation gone wrong

How do cells

differentiate?

Original cell has a complete set of DNA directions

Every differentiated cell has all the DNA directions

…but they’re stuck.

All the genes are there, but only a few are switched on.

Control this, you control differentiation..but how?

Microarray technology detects switched-on genes

All the genes are there, but only a few are switched on.

Control this, you control differentiation!

Bone marrow the first known “stem cells” -they’re multipotent

Early embryos have pluripotent cells

Very earliest embryo cells are TOTIPOTENT

Nov 1998: Stem cellsGrown from Human embryos

John Gearhart, Hopkins

Scientists’ Benefit: replacement of diseased tissues

Public’s Concern: sacrifice of embryos

Adult stem cells produce neurons, heart cells,etc.

Nov 2000

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are needed to see this picture.

Q. Decision-makers:Can’t we use adult stem cells instead of embryos?

A. Most scientists say “we need both!”

Scientists repair damage from heart attack using adult bone marrow stem cells

Mar 2001

x

Bush approves limitedEmbryonic lines

Aug 2001:

Some of the promise of adult stem cellsNot panning out

2004

x

Exciting research gone elsewhere

2004

January 2005: All cell lines contaminated

Non-human Sialic acid Neu5Gc

Caveat: stem cell side effects

the case of the sensitive rats

Feb 2005

Science has a long way to go