Scientists at StemCells California, Inc. Report the First Identification of Purified Blood Stem Cells as a Source of Mature Liver Cells

SUNNYVALE, Calif. -- (BW HealthWire) -- April 19, 2000 --

Liver Function Restored in Mutant Mice Injected
With Bone Marrow Cells

Scientists from StemCells California, Inc., a wholly owned subsidiary of CytoTherapeutics, Inc (Nasdaq: CTII), reported at the annual meeting of the Society for Experimental Biology in San Diego that that they have managed to produce mature liver cells from rigorously purified blood stem cells in mice. The work was reported by Eric Lagasse, Ph.D., principal author of the study and Director of Liver Stem Cell Research at StemCells.

"There have been two parts to our study so far," explained Dr. Lagasse. "In the first set of experiments, our collaborator Markus Grompe, M.D., of the Oregon Health Sciences University injected a group of mice undergoing liver failure with unfractionated bone marrow cells (that is, samples of bone marrow that had not been purified or selected for certain types of cells). Dr. Grompe found that this led to the restoration of liver functions, as measured by liver enzyme levels and survival, in some of these animals (4 of 9 transplanted mice).

"In a second series of experiments, we demonstrated that transplantation of as few as 50 purified, bone marrow-derived adult hematopoietic stem cells -- the so-called blood stem cells -- can produce mature hepatocytes (liver cells). Moreover, when we fractionated the bone marrow into subsets, in each case only the blood stem cell-containing subsets were able to give rise to hepatocyte colonies following transplantation. These results suggests that the hematopoietic stem cells are the only cells in the bone marrow responsible for the restoration of liver functions observed," Dr. Lagasse added. "To our knowledge, this is the first time that restoration of liver function has been demonstrated after treatment with blood stem cells."

The research collaboration leading to these results also included Milton Finegold from the Baylor College of Medicine and Irving L. Weissman from Stanford University.

Potential future applications

Discussing the potential significance of the research, Dr. Lagasse said, "The discovery that blood stem cells can give rise to mature liver cells (hepatocytes) is a breakthrough that could open the way to use blood stem cells to replace or repair diseased or damaged tissue in a patient with hepatic disorders. The ability of blood stem cells from adult individuals to give rise to hepatocytes is important for several reasons. First, it could provide a relatively easy source of stem cells for liver cell therapy. Second, it creates the possibility that the problems of tissue rejection that plague transplant recipients can be overcome by using the same cells to give rise to both the blood system and the liver system. Third, it opens the way to better understanding the properties of the blood stem cells and how they might be manipulated to treat a variety of diseases. Finally, if it turns out that resident blood stem cells from the bone marrow can form a variety of cell types, they may be more multipotent than initially thought."

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Statements in this press release other than statements of historical facts constitute forward looking statements regarding, among other things, the future business operations of CytoTherapeutics, Inc., or of StemCells California, Inc., its wholly-owned subsidiary (collectively, "the Company"). The Company's actual results may vary materially from those contemplated in the forward looking statements due to risks and uncertainties to which the Company is subject, including uncertainties regarding the protection and acquisition of intellectual property rights; the Company's ability to obtain the significant additional capital resources needed to conduct the time-consuming research, preclinical development and clinical trials that are necessary for regulatory approvals and to establish production and marketing capabilities, if such approvals are obtained; the fact that the Company's stem cell technology is at the pre-clinical stage and has not yet led to the development of any proposed product; the uncertainty whether any products that may be generated in the future in the Company's stem cell programs will: (i) survive and persist in the desired locations, (ii) provide the therapeutic benefits intended, (iii) properly differentiate and integrate into existing tissue in the desired manner, or (iv) not cause tumors or other side effects; and others that are described in Exhibit 99 to the Company's Annual Report on Form 10-K entitled "Cautionary Factors Relevant to Forward Looking Statements."

    CONTACT:  StemCells, Inc./CytoTherapeutics, Inc. 
              George Dunbar, Acting President and CEO, 408/731-8670
                 or
              IR PR Strategies, LLC
              Anette Breindl, 858/860-0266

Scientists at StemCells California, Inc. Report the First Identification of Purified Blood Stem Cells as a Source of Mature Liver Cells

Liver Function Restored in Mutant Mice Injected With Bone Marrow Cells

Potential future applications

Liver Function Restored in Mutant Mice Injected
With Bone Marrow Cells