Researchers at Progenitor Inc. believe they have found aforerunner of the stem cell that creates the blood and immunesystems.
The Columbus, Ohio, company, a majority-owned subsidiary ofInterneuron Pharmaceuticals Inc. (NASDAQ:IPIC), reportedMonday at the Federation of American Societies forExperimental Biology in New Orleans that transplantation ofthese cells allows mice whose immune systems are seriouslyinsufficient to survive.
"We believe the progenitor stem cell is unique and differentfrom the adult bone marrow stem cell previously described inthe scientific literature," said Glenn Cooper, Progenitor'spresident and chief executive officer. The cells are initiallyinvisible to the immune system, he said, lacking markersrecognized by the thymus or the major histocompatibilitycomplex, so they are not likely to be rejected as "foreign"after implantation.
Derived from the yolk sac, which grows rapidly early in thedevelopment of an embryo, the "naive" cells' offspringeventually specialize to become mature cells of the blood andimmune systems.
"Unlike the adult stem cell," Cooper said, "we are able toculture these cells, expand their numbers and subsequentlydifferentiate them upon demand into mature blood cells. In thefuture it may be possible to use human progenitor stem cellsfor a broad range of therapeutic applications, including asuniversal donor cells for bone marrow transplantation, carriercells for gene therapy and a source for red blood celltransfusion."
He told BioWorld that Progenitor has been issued a patentcovering the use of these cells in gene transfer. Because theydivide much more rapidly than adult bone marrow cells, Coopersaid, it is "trivial" to put new genes into the progenitor stemcells and transplant them into mice.
Gene transfer applications might include correcting blooddisorders such as sickle cell anemia, thalassemia andhemophilia, he said, and could also be considered in suchmetabolic defects as Gaucher's disease.
Proteins produced by the gene inserted into the stem cell couldcirculate to exert effects elsewhere. Inhibition might becreated by introducing antisense genes into the transplantedcells, too.
Progenitor is exploring whether its method of deriving yolksac stem cells will be applicable to stem cells of othertissues. The study presented Monday described using cellsurface markers to identify the progenitor stem cells.Tracking the markers with immunophenotyping showed thecells were progenitors of hematopoietic cells that lackedmature immune characteristics.
Cooper said the yolk sac progenitor cells, which are onlypresent for a couple of weeks during development of anembryo, divide about every 24 hours and can be expanded inquantity and maintained in an undifferentiated state, thendifferentiated "on demand."
Other companies, such as Systemix Inc. of Palo Alto, Calif., areworking on early adult bone marrow cells, which divide moreslowly and carry tissue type markers that could raise concernsof rejection.
-- Nancy Garcia Associate Editor
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