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When Cells Dispense By Flora Mauch, Checkbiotech Thursday, December 1, 2005 Imagine a machine whose most important component is a bunch of living cells. Nature and technology – what might seem like opposites to many of us, have actually been made to work hand in hand by researchers. Recently, a team in California developed a process utilizing a commercially available membrane bioreactor, in which rice cells produce substances that can be subsequently used as health care products. There are several methods that use genetic engineering to encourage cells to produce a desired substance. In such cases, cells are provided with a special piece of DNA, which contains the recipe for the desired substance. Under ideal circumstances, the cell starts to read off the DNA and to produce the product. In order to maximize yields and facilitate harvesting the product, a research team headed by Dr. Karen A. McDonald, at the University of California Davis, developed a process which utilizes a special type of bioreactor. A bioreactor is a container in which special cells or microorganisms are cultivated in ideal conditions to gain their metabolites. The membrane bioreactor from Dr. McDonald’s laboratory consists of two separate compartments – one contains the cells, and the other the nutrients. The distinct arrangement allows nutrients to reach cells more easily, and the product, which is excreted from the cells into the medium, can be easily retrieved. To improve the efficiency of the bioreactor, the UC Davis research team utilized rice cells. Dr. McDonald chose to work with rice cells, because they have certain characteristics allow them to grow rapidly in culture, read the DNA especially well, excrete products into the culture medium, which translates into a higher level of product. With the new rice bioreactor system, Dr. McDonald’s group succeeded in producing alpha-1-antitrypsin (AAT), which is normally made by human liver cells. AAT is of great importance in medicine. Its task is to inhibit protein- degrading substances – also known as proteases – in blood and other bodily fluids. Between proteases and their antagonists (most important the AAT) there exists a subtle balance. In case of a AAT deficiency, an excess of proteases results. As protein is one of the main components in almost all tissues, severe tissue damages is often the consequence of AAT deficiencies, because the proteases are no longer kept in check. In the future, the AAT produced by the rice bioreactor could be administered to patients suffering from a genetic disorder that does not allow their body to produce AAT on its own. However, it will still take some time until rice-produced AAT will be commercially produced. Dr. McDonald told Checkbiotech, “Currently, plant cell culture produced AAT has not been tested for use in humans, and therefore has not been approved for use in patients. We have purified AAT from our rice cell cultures so that we can further characterize it.” Characterizing the protein, will allow Dr. McDonald to look at how the rice-produced AAT compares to AAT produced in human cells. The closer the match, the sooner rice-produced AAT will appear on the market. Currently, the team from UC Davis is also trying to improve the rice bioreactor in terms of productivity. When asked what the next stage of her research will be, Dr. McDonald said, “For the plant cell culture membrane bioreactor system, there are a number of variables that we would like to study to allow us to further optimize the production system.” “Other members of our group are investigating the production of AAT as well as other human proteins from other plant cell hosts using different expression systems and different bioreactor designs.” For further information contact: Full article in: Production of Human alpha-1-Antitrypsin from Transgenic Rice Cell Culture in a Membrane Bioreactor. Biotechnol. Prog. 2005, 21, 728-734. Copyright CheckBiotech Source |