Since 1958, about 30 000 people worldwide, mostly children, were given hormone injections of human growth extracted from the pituitary gland of human corpses for treat their small size. The procedure was halted in 1985 when researchers found that a small percentage of the beneficiaries had received contaminated injections have been the development of Creutzfeldt-Jakob disease (CJD), a fatal neurodegenerative disease caused by poorly protein folded called prions.
Now, a new study of brain dead eight people who contracted CJD from these injections suggests that injections may also have spread amyloid-β, the neuron-clogging protein that is a feature of Alzheimer's disease. The study is the first evidence in humans that the amyloid-β could be transmitted through medical procedures such as brain surgery, the researchers said. Skeptics, however, note that the CJD prion often triggers unusual amyloid deposits; epidemiological studies, they say, found no link between the injections and an increased risk of developing Alzheimer's disease.
Outside of CJD and mad cow tied, kuru is perhaps the most famous prion disease. Endemic to Papua New Guinea and now essentially eradicated, kuru is transmitted by the ritual consumption of human brain tissue at funerals. Increasingly, however, scientists recognize that a number of other neurodegenerative diseases, including Alzheimer's disease, Huntington's disease and Parkinson's disease, also involve aberrant proteins that act as "seeds "in the brain. They turn otherwise normal protein fibers "break form more seeds, pause, and form more seeds," says John Collinge, a neuropathologist at University College London and lead author of the new study.
Still unknown Alzheimer's disease is the role of proteins such as amyloid-β and tau play in the misfolded disease, and whether they are transmitted by direct contact with the consumer or contaminated brain tissue. Although scientists have managed to induce amyloid-β transmission in rodents, these experiments relied on "massive" overexpression of the protein, said Samuel Gandy, neuropathologist at the medical School Icahn Mount Sinai in New York City. "Exhaustive" tent reproduce such transmission in primates have failed, he said, led many to doubt whether such propagation is possible.
in the current study, Collinge and colleagues examined brain tissue eight people aged 36 to 51, who died of CJD approximately 30 to 40 years after receiving the growth hormone injections. Four had an amyloid-β because pathologists treat moderate to severe in people with Alzheimer's, but they did not have a second type of protein, tau, which is considered an important feature of the disease as well, today, reports the online team Nature . Two had softer deposits, more unequal; it was free-amyloid. "It is a very unusual finding," said Collinge. "In this age group, you really do not see this kind of pathology, unless you have a genetic predisposition to Alzheimer's disease," none of them did, he said.
However, scientists have known since the 190s that prion protein that causes CJD can "cross-grain" amyloid-β, which causes abnormal deposits to form, and vice versa, said Gandy. In such small, observational study, it is impossible to determine whether CJD became the β-amyloid seen in the brain tissue of deceased or protein seeds subjects were transmitted by injection, he said. None of the subjects showed signs of tau, another protein associated with Alzheimer's disease, he and others point.
to explore the possibility that CJD, not the seeds of amyloid-β, was the culprit, Collinge and also examined the brains of 116 people colleagues with a range of prion diseases unrelated to hormone injections. They found little to no β-amyloid pathology in this group, suggesting that CJD alone was not responsible for the disease, they say. It is an "argument" in favor of the group, said Claudio Soto, a neuroscientist at the University of Texas Health Science Center at Houston. Since prions come in many different forms, however, it is still possible that beta-amyloid deposits found in the brains of injection beneficiaries were actually caused by CJD, whereas the controls were without plate he notes.
then Collinge's team plans to test for growth hormone vials archived original treatments to see if they can detect the amyloid β-protein "seeds." One obstacle, however, is that scientists do not know exactly what constitutes these seeds at the molecular level, Collinge said.
Though provocative, the new study can not answer the question of whether pathogenic amyloid-beta "seeds" can be transmitted from person to person through contaminated surgical instruments or blood, and Collinge Soto suitable. There is no epidemiological evidence to support this possibility, and an alarm on the contagiousness of Alzheimer's disease is premature, they said. Still, "which is something that should be studied," says Soto
* Updated, September 11, 9:30. Two authors of the study, John Collinge and Jonathan DF Wadsworth said a conflict of interest in the online version of the paper. Collinge is a director and both are shareholders of the D-Gen biopharmaceutical company Limited, which provides antibodies against prion proteins and developed a product prion decontamination, in collaboration with Du Pont Corporation.
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