Stem Cell Therapy
Meanwhile, Myrtle Gordon, Ph.D., emeritus professor in experimental hematology, division of investigative science at Imperial College London, studies a population of stem cells called OmniCytes for treating liver damage. OmniCytes express CD34 and account for around 1% of CD34+ cells in bone marrow.
OmniCytes can become albumin-producing liver cells and have been transplanted into liver-damaged mice. “We now realize that mechanisms other than repopulation give functional improvement—there are secreted factors,” Dr. Gordon explained. OmniCytes inhibit cell death in rat liver cells, he added, as shown by biochemical and histological studies.
A large number of OmniCytes can be collected from leukapheresis, which is easier than bone marrow collection. There is no need for prolonged culture, and the required number of cells for transplant are available in less than three hours. “We are fairly encouraged by OmniCytes as a potential source for stem cell therapy. They can be useful in limiting damage and provide a bridge to liver transplantation.”
A Phase I trial administering OmniCytes into the portal vein or hepatic artery has been carried out as an autologous therapy with the aid of Hammersmith Hospital in London. A Phase II trial is under way with patients with alcoholic liver cirrhosis.
The next stage is to develop an off-the-shelf therapy and, for this, the researchers have optimized the expansion process. This will be applied in patients with liver failure. OmniCytes also differentiate into other cells; potential applications include diabetes, cardiovascular indications, and bone repair.
Finally, Clare Blackburn, Ph.D., head of thymus development and regeneration group at the MRC Centre for Regenerative Medicine at the University of Edinburgh, spoke about an approach to repair the immune system.
The thymus is one of the first organs to degenerate, with volume being lost early in life, which is reflected in a decrease of T-cell output. This increases susceptibility to infection and autoimmune disease and decreases response to vaccines. However, the thymus can regenerate, although attempts to do so have been fraught with drawbacks.
Dr. Blackburn’s group has identified the epithelial progenitor cells of the thymus which, when transferred to athymic mice, will make a functional thymus. “This raises the question of whether in vitro stem cells can break the bottleneck of the supply of tissue in thymus transplant.” For this, one would need to grow thymic cells in vitro or generate them from ES cells.
Dr. Blackburn is currently focused on discovering the cellular hierarchies of the cells that generate and maintain the fetal and mature thymus.