Cleaning Up Engineered Tissue
A lesser but still important detail in tissue engineering is given some thought: "scientists are seemingly approaching a day when they will be able to make nearly any type of tissue from human embryonic stem cells. You need nerves or pancreas, bone or skin? With the right combination of growth factors, skill and patience, a laboratory tissue culture dish promises to yield therapeutic wonders. But within these batches of newly generated cells lurks a big potential problem: Any remaining embryonic stem cells - those that haven't differentiated into the desired tissue - can go on to become dangerous tumors called teratomas when transplanted into patients. Now researchers [have] developed a way to remove these pluripotent human embryonic stem cells from their progeny before the differentiated cells are used in humans. ... We've used a combination of antibodies to weed out the few undifferentiated cells that could be left in the 10 or 100 million differentiated cells that make up a therapeutic dose. ... The researchers studied two sets of antibodies - one commercially available and one they generated themselves - to identify which among them bound most strongly to pluripotent, but not differentiated, cells. They found one newly generated antibody that was highly specific for a previously unknown marker on undifferentiated cells that they termed stage-specific embryonic antigen-5, or SSEA-5. The cells bound by this antibody, anti-SSEA-5, expressed high levels of pluripotent-specific genes and resembled embryonic stem cells in appearance. Anti-SSEA-5 also bound strongly to the inner cell mass of an early human embryo, the group of cells from which embryonic stem cell lines are derived. ... anti-SSEA-5 recognizes and binds to a cell-surface carbohydrate structure called a glycan. As the pluripotent cell differentiates, this glycan is modified to other glycan structures not recognized by the antibody."
Link: http://www.eurekalert.org/pub_releases/2011-08/sumc-sdm081211.php