All approved US embryonic stem cell lines may be contaminated
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《英国医生杂志》
The few stem cell lines approved in the United States are probably contaminated with a non-human molecule, says a study published online ahead of print publication in Nature Medicine (www.nature.com/nm/). The researchers recommend starting afresh with human embryonic stem cells that have never been exposed to animal products.
The authors, researchers at the University of California at San Diego and the Salk Institute in La Jolla, California, report that the human embryonic stem cells they studied are contaminated with non-human sialic acid that could cause rejection if the stem cells were transplanted into humans. "In effect, human embryonic stem cells seem like animal cells to the human immune system," they write.
The findings probably apply to all current stem cell lines produced in the same way, said the lead author, Ajit Varki, professor of medicine and cellular and molecular medicine at the University of California, San Diego, and codirector of the Glycobiology Research and Training Center. He said, "This mechanism is universal to all cell types we have studied. Thus, it is almost certain that all of the other embryonic stem cells grown in this manner would have the same contamination."
President Bush has limited federal funding for stem cell research just to stem cell lines in existence before 9 August 2001 (BMJ 2004;329:190). Several US states and universities are funding stem cell research that does not rely on government cash.
Dr Susan Fisher, professor of cell and tissue biology at the University of California, San Francisco, said that the new finding was worrying. "The previous concern was contamination with infectious agents such as viruses and bacteria or misfolded proteins such as prions that could be transferred from animals to people."
Stem cells are usually cultured on mouse feeder layers and use "serum replacements" derived from animals, Dr Varki said. He explained that sialic acids are sugar-like molecules found on the surfaces of all human and higher animal cells. Humans lack the gene, called Neu5Gc, for making one kind of sialic acid. Other mammals, such as mice, are able to make this sialic acid. Most normal healthy people have antibodies to Neu5Gc because they have been exposed to it in red meat.
Dr Varki抯 group found Neu5Gc in the H1 embryonic stem cell line from WiCell Research Institute, one of the approved stem cell lines. They reported that it must have originated elsewhere and been picked up by the stem cells during culture with the mouse feeder layers or serum replacements.
Because many people have antibodies to Neu5Gc, transplantation of current stem cell lines could lead to an immune response and rejection.
Dr Varki and Dr Fisher say that it may be possible to get around the problem. However, Dr Fisher said that the field is moving away from exposing people to animal cells and proteins and toward using only cultures and media derived from human tissue.(New York Janice Hopkins Tanne)
The authors, researchers at the University of California at San Diego and the Salk Institute in La Jolla, California, report that the human embryonic stem cells they studied are contaminated with non-human sialic acid that could cause rejection if the stem cells were transplanted into humans. "In effect, human embryonic stem cells seem like animal cells to the human immune system," they write.
The findings probably apply to all current stem cell lines produced in the same way, said the lead author, Ajit Varki, professor of medicine and cellular and molecular medicine at the University of California, San Diego, and codirector of the Glycobiology Research and Training Center. He said, "This mechanism is universal to all cell types we have studied. Thus, it is almost certain that all of the other embryonic stem cells grown in this manner would have the same contamination."
President Bush has limited federal funding for stem cell research just to stem cell lines in existence before 9 August 2001 (BMJ 2004;329:190). Several US states and universities are funding stem cell research that does not rely on government cash.
Dr Susan Fisher, professor of cell and tissue biology at the University of California, San Francisco, said that the new finding was worrying. "The previous concern was contamination with infectious agents such as viruses and bacteria or misfolded proteins such as prions that could be transferred from animals to people."
Stem cells are usually cultured on mouse feeder layers and use "serum replacements" derived from animals, Dr Varki said. He explained that sialic acids are sugar-like molecules found on the surfaces of all human and higher animal cells. Humans lack the gene, called Neu5Gc, for making one kind of sialic acid. Other mammals, such as mice, are able to make this sialic acid. Most normal healthy people have antibodies to Neu5Gc because they have been exposed to it in red meat.
Dr Varki抯 group found Neu5Gc in the H1 embryonic stem cell line from WiCell Research Institute, one of the approved stem cell lines. They reported that it must have originated elsewhere and been picked up by the stem cells during culture with the mouse feeder layers or serum replacements.
Because many people have antibodies to Neu5Gc, transplantation of current stem cell lines could lead to an immune response and rejection.
Dr Varki and Dr Fisher say that it may be possible to get around the problem. However, Dr Fisher said that the field is moving away from exposing people to animal cells and proteins and toward using only cultures and media derived from human tissue.(New York Janice Hopkins Tanne)