While most human tissues for research and testing can be obtained from volunteers, biopsies, surgical operations and post mortem samples, a much neglected source is the normally discarded human placenta. Many studies of placental structure and function continue to use animals but as Joseph Dancis of the New York University School of Medicine has explained, "of all mammalian organs, the placenta shows the greatest variation in structure among the species ... One cannot be confident that an observation made with animal placenta is pertinent to the human, unless it is tested in the human."(54) The placenta may have other important applications. Since it comes from the same single fertilized human egg as the baby, it can almost be seen as a scaled-down human being. Testing the action of drugs on placental biochemistry could therefore eliminate many tests currently performed on animals. Soli Contractor of London's Charing Cross and Westminster Medical School argues that:
"The human placenta has enormous potential for studying metabolic processes without recourse to animal experimentation. Its greatest advantage lies in eliminating the necessity for extrapolating results from animal experiments and trying to interpret them in terms of the human situation.”(55)
The placenta contains tiny vessels and has been suggested by surgeons at Britain's Frenchay Hospital in Bristol as an alternative to animals for practicing microsurgery.(56)
In many cases it is advantageous for human cells to be cultured to allow their continuous growth. Such "tissue cultures" allow researchers to increase the number of cells available for study. It also enables the effect of drugs on cell growth to be monitored, providing scientists with a measure of toxicity. To enable cells to grow effectively, they are kept in a nutrient medium usually derived from fetal calf serum. But there may often be advantages in using synthetic growth media where the exact composition of nutrients is known, or indeed human sera. Researchers at the University of British Columbia compared the growth of human breast cancer cells incubated with either human or fetal calf sera. As might be anticipated, they found that use of human serum most closely resembled the clinical situation not only in the growth of cancer cells but also their sensitivity to chemotherapeutic drugs.(57) The results have important implications for the development of anticancer drugs.
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