ed that many efforts have been made during the last few years to try to eliminate any animal-derived culture components in human stem cell culture. However, many of the specialized media used for growth and differentiation still contain materials from animal sources and are hence contaminated with Neu5Gc. In addition to using human serum, the researchers suggested the possibility of using what are called "feeder cells" from mice with a human-like defect in Neu5Gc production. They noted that they have recently produced such a mouse. Another possibility being attempted by groups in other parts of the world is to use human embryo-derived connective tissue cells as the feeder layer in the culture. A further solution might be a short-term culture in heat-inactivated serum from the actual patient who is going to receive the therapy, the scientists said. However, it may still prove difficult to completely eliminate the Neu5Gc, because is has become metabolically incorporated into the currently available, federally-funded human embryonic stem cell lines. "With this discovery, the preexisting general concern about using animal products for deriving human embryonic stem cells has become more specific, being defined in molecular terms," Varki said. "Such issues will, of course, become irrelevant if complete elimination of Neu5Gc can be achieved by deriving new human embryonic stem cells that have never been exposed to Neu5Gc-containing animal products of any kind," the researchers said in the Nature Medicine paper, noting that none of the suggested approaches guarantees the complete elimination of Neu5Gc from existing cultures. "Therefore, it would seem best to start over again with newly derived human embryonic stem cells that have never been exposed to any animal products, and ideally, only ever exposed to serum from the intended transplant recipient." "However, such an approach could not be pursued under existing rules for the use of federal grant dollars," Varki said. The
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Source:Eurekalert


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