A recent initiative by Organogenesis Inc. of Cambridge Massachusetts, is the production of living organ equivalents from human cells. Known as TESTORGANS, they are intended to promote extended organ-like function in vitro for use in studying the effects of pharmaceuticals, pesticides, cosmetics, detergents and other substances on human organ systems. By 1989 TESTORGANS included TESTSKIN, TESTLUNG, TESTINTESTINE and a living artery equivalent test system. Organogenesis believes that its test organ systems will have applications not only in toxicity testing but in other areas such as investigating how drugs can be delivered through the skin, wound healing research and the study of specific diseases like psoriasis and atherosclerosis.(37) The company's most developed product is TESTSKIN, a full-thickness skin replacement consisting of two layers - a living dermal layer and a multi-layered epidermis. Unfortunately, part of the skin model is currently built up on collagen of bovine origin. TESTSKIN is already being used by some cosmetic companies.
Another company, the La Jolla-based Marrow Tech Inc. in California, has recently developed complete culture systems for human bone marrow, liver, oral mucosa and skin for in vitro safety tests. In the case of the human skin model, the different layers of cells which form normal skin are placed in layers on a nylon mesh producing a full-thickness skin equivalent. Unlike the Organogenesis product, no collagen extracted from another species is used to form Marrow Tech's simulated skin product.
The company feels that its skin equivalent will be useful in detecting potential skin irritants.(37) This would be a considerable advance over the traditional use of animals who are widely acknowledged as poor models for human skin tests.(39)
With their obvious advantage in overcoming species variations, the potential of human tissue tests should have been appreciated long ago. Yet only a handful of researcher appear to have recognized their importance: for instance, in 1952 Britain's Industrial Medicine and Burns Research Unit at Birmingham's Accident Hospital was using cultures of human skin to assess the relative toxicity of antibiotics;(40) in 1962 researchers using human bone marrow cells predicted that griseofulvin, an antibiotic, might damage the blood,(41) a finding subsequently confirmed by clinical experience; in 1966 scientists were comparing the toxic effects of various anaesthetics on human liver cells(42) and three years later they reported similar studies with kidney tissue;(43) and in 1971 Lash and Saxen showed how human cells could be used to investigate the harmful effects of thalidomide.(44)
Today, the overwhelming emphasis is still on animal experiments and even those using in vitro techniques rely heavily on animal cells rather than human tissues: at the 7th Scandinavian Society for Cell Toxicology Congress held in Denmark in 1989, only three of the 18 papers studying the toxicity of chemicals to people actually employed human cells. Most of the remainder used tissues from rats and mice.
|More >>||1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19|