Why Not Expand Stem Cell Research That is Showing Real Results?

Date: 04/28/2004

Proponents of embryonic stem cells (ESCs) are demanding that the Bush Administration increase the number of ESC lines eligible for government support.

But the key factor in determining the allocation of precious research dollars should be: Which research is showing real progress in developing treatments and helping patients?

Embryonic stem cells have yet to treat one human patient, and their success in animal models has been very limited.

By contrast, clinical trials using adult stem cells are already underway and showing progress in treating patients; trials using animal models show progress as well. To cite just two examples:

Researchers at Massachusetts General Hospital have used adult cells from the spleen to regenerate insulin-producing cells and cure diabetes in mice.Essentially the spleen cells “retrain” the body’s immune system to stop attacking its own islet cells, and new cells then naturally regenerate from the spleen cells and the body’s own cells, eliminating the need for an islet cell transplant. The Boston Globe calls this “a surprising breakthrough that could soon be tested in local patients and pen a new chapter in diabetes research” (R. Mishra, “Juvenile diabetes cured in lab mice,” The Boston Globe, November 14, 2003, p. A2). Also see S. Kodama et al., “Islet Regeneration During the Reversal of Autoimmune Diabetes in NOD Mice,” 302 Science 1223 (2003).

The FDA has just approved the first clinical trial in the US of a treatment for heart disease using stem cells from adult bone marrow. Such trials have already taken place in Europe and Brazil where they showed success in treating damaged hearts. (see, e.g., www.genomenewsnetwork.org/articles/2004/04/16/stem_cell_trial.php

(Further examples of successful use of adult stem cells in human and animal trials are at www.stemcellresearch.org)

Efforts to develop therapies from ESCs face numerous hurdles, including:

• Difficulty in establishing and maintaining stable cell lines,
• Difficulty in obtaining pure cultures in the laboratory,
• Questions regarding functional differentiation into various cell types,
• Problems of immune rejection,
• Potential for tumor formation and tissue destruction when placed in animals,
• Genetic instability.

Even ESC proponents admit these problems:

• “Rarely have specific growth factors or culture conditions led to establishment of cultures containing a single cell type….[T]he possibility arises that transplantation of differentiated human ES cell derivatives into human recipients may result in the formation of ES cell-derived tumors.” J.S. Odorico et al., “Multilineage differentiation from human embryonic stem cell lines,” 19 Stem Cells 193-204 (2001).

• “Transplanted ES cells spontaneously differentiate into any of a variety of ectodermal, endodermal and mesodermal cell types–sometimes into a disorganized mass of neurons, cartilage and muscle; sometimes into teratomas containing an eye, hair or even teeth.” R. Lanza et al., “Human therapeutic cloning,” 5 Nature Medicine 975-977 (1999).

• “There are still many hurdles to clear before embryonic stem cells can be used therapeutically. For example, because undifferentiated embryonic stem cells can form tumors after transplantation in histocompatible animals, it is important to determine an appropriate state of differentiation before transplantation. Differentiation protocols for many cell types have yet to be established. Targeting the differentiated cells to the appropriate organ and the appropriate part of the organ is also a challenge.” E. Phimister and J. Drazen, “Two Fillips for Human Embryonic Stem Cells,” 350 New England Journal of Medicine 1351 (March 25, 2004).

• “Normally, if you take an embryonic stem cell, it will make all kinds of things, sort of willy-nilly,” says [Harvard ESC researcher Doug] Melton.” J. Mitchell, “Stem Cells 101,” PBS Scientific American Frontiers, May 28th, 2002, www.pbs.org/saf/1209/features/stemcell.htm).

Instead of throwing more federal dollars into embryonic stem cell research, the Administration should expand its support for adult stem cell research — research that is producing real results with real patients.