Memory Transplant
An Operation to move tissue or organ from one organism to another.
By transplanting neuronal precursor cells into the brains of mice, researcher have managed to reverse the learning and memory deficits in mouse models of Alzheimer’s disease and restore normal cognitive function. The study not only suggests a novel way to investigate how learning and memory is affected by certain disease, but also raises the possibility that cell replacement therapy could be used to treat Alzheimer’s in the future. The study has been published in the future. The study has been published in The journal of Neuroscience.
Memory Deficits Causes
In order for the brain to function, there need to be a balance between excitatory and inhibitory activity in neural networks. Too much excitation can damage cells and lead to cell death, whereas excess inhibition prevents the flow of information. This balance is disrupted in the brains of Alzheimer’s disease (AD) patients as inhibitory neurons in a region of the brain called the hippocampus become damaged and die, leading to learning and memory problems. Two factors that are known to heavily contribute to this are Apo lipoprotein (apo) E4 and amyloid-B (AB).
The study of Alzheimer’s has been facilitated by mouse models of the disease which allow researchers to examine disease progression and potential treatment avenues, amongst other things. In order to investigate whether replacing the lost or damaged neurons can improve brain signalizing and alleviate disease symptoms, scientists from the Gladstone Institutes and the University of California San Francisco transplanted progenitor inhibitory neurons into the hippocampus of aged mice expressing apoE4. These are early stage cells that are capable of maturing into inhibitory neurons. Using aged mice is important in the study of AD because it is more representative of the scenario in humans, since AD is a progressive disease that is predominantly diagnosed in those over the age of 65 unexpectedly, the grafted cells not only survived in the brains of mice and matured into inhibitory neurons, but they also functionally integrated into the neuronal circuit, restoring learning and memory. Furthermore, when they used apoE4 mice which also had excess levels of AB in their brains, similar to the brains of AD patients, the cognitive deficits displayed by the mice were once again alleviated. Interestingly the procedure left AB Levels unaltered in the brain, which implies that the improvements were not a result of amyloid reduction. While the researchers are a long way from being able to translate this into a treatment for humans, it remains an important proof of concept study and suggests that one day cell replacement therapy may help AD patients.
Memory T cells in Transplantation Memory T cells represent a great challenge in transplantation in that they are required for protection against invading pathogens, but their presence also endangers transplant survival. It is imperative that tolerization of memory T cells in transplant recipients should not drastically alter patient’s protective immunity. This is a significant issue in clinical transplantation, but resolving this issue have major impact on transplant outcomes. Knowledge gained through this inquiry will help not only the design of greatly improved tolerance induction protocols but also stratification
of donor recipient selection to reduce the risk of graft damage inflicted by alloreactive memory T cells.
References
Brain Transplant. (2009). Retrieved April 21, 2018 from http://www.washingtoncitypaper.com/articles/45154/what-would-happen-in-a-brain- transplant-personality-bodies-and/ Xian. C. Li, Malgosia & Rafik. M. (2013). Memory T cells in Transplantation-Progress and Challenges. Retrieved April 21, 2018 from http://www.ncbi.nlm.nih.gov/m/pubmed/15147417/
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