Stem Cells

Podcast

Why this episode?

Flurry of recent news on stem cells, courtesy of a new potential approach to stem cell therapy

Thought it might help to provide a bit of background, help sort out some of the pile of jargon that is part of the territory of stem cell research.

Mainstream media has an unfortunate tendency to focus on drama, controversies

Stem cells are primal, unspecialized cells which can both self-renew (make more stem cells by cell division) as well as differentiate (divide and with each cell division evolve more and more into different types of cells). This allows stem cells to act as a repair system for the body, replenishing other cells as long as the organism is alive.

The study of stem cells began in the 1960s with research by Canadian scientists Ernest A. McCulloch and James E. Till

Stem cells characterized in two ways -- potency (what cell / tissue types it can develop into), source (where derived from)

Potency -- describes specificity of the cell, what cell / tissue types it can develop into

Totipotent stem cells

Pluripotent stem cells

Multipotent stem cells

Unipotent stem cells

Where a stem cell falls in terms of potency is a function of where it's extracted from the series of cell divisions that form an embryo.

Source -- embryonic vs. adult (somatic)

Embryonic

Adult / Somatic (Greek σωμα sōma = body)

Ethical issues of stem cell use

Most ethical conflicts come from research on / use of embrionic stem cells

Other ethical conflicts arise over the use of therapeutic cloning.

Why should we care? What treatments can they be used for?

Medical researchers believe stem cell research has the potential to change the face of human disease by being used to repair specific tissues or to grow organs. Yet as government reports point out, "significant technical hurdles remain that will only be overcome through years of intensive research."

Types of treatment (as a function of donor & patient) -- more jargon

For over 30 years, bone marrow (adult) stem cells have been used to treat cancer patients with conditions such as leukemia and lymphoma.

Brain cancer

Spinal cord injury

Heart damage

Low blood supply

Baldness

Missing teeth

Blindness

Challenges of stem cell therapy

It is important to make sure the embryonic stem cells are fully differentiated into the desired cell type (i.e. tissue) before they are transplanted into the patient, as undifferentiated embryonic stem cells may develop into a tumor after transplantation.

Scientists are trying to develop techniques to prevent rejection of implanted cells by the patient (i.e. host-versus-graft response).

The online edition of Nature Medicine published a study on January 23, 2005 which stated that the human embryonic stem cells available for federally funded research are contaminated with nonhuman molecules from the culture medium used to grow the cells, for example, mouse cells and other animal cells.

New news

A number of groups have been able to essentially "re-program" mouse skin cells into embryonic stem cells

Effort pioneered by a team at Kyoto University in Japan, led by Shinya Yamanaka.

In 2006, Yamanaka announced his first results -- using mouse fibroblasts, a common cell type harvested from skin. Four genes were transferred into the cells, which triggered other genes, which led to the cells behaving like pluripotent stem cells. But the announcement was met with skepticism, since these cells (which Yamanaka called induced pluripotent stem cells, or iPS cells) had some characteristics of embryonic cells, but lacked others.

But recently, Yamanaka announced a second generation of research -- and now his iPS cells pass all the tests for embryonic cells. More importantly, groups in Cambridge, Massachusetts and at UCLA used the same technique and got very similar results. After the whole fiasco over Hwang Woo-Suk's fraudulent stem cell announcements, this independent confirmation helped a lot of folks.

Advantages of this approach:

No ethical issues from cloning

No ethical issues from embryonic stem cells

Perfect match with donor

Uses basic cells (not egg cells), can be accomplished using simple lab techniques

Work to go

Have to make it work in humans

Concern it could cause cancer -- one of the genes "seems to contribute to cancer" in 20% of mice

Might have to turn off the introduced genes at some later point in the process to avoid causing a tumor

Wrapup

Stem cell research has great potential for future medical therapies

A number of potential medical & ethical potholes on the road