Stem cells in the treatment of neurodegenerative diseases (6)
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Multiple sclerosis and stem cells
One of the main features of multiple sclerosis, an autoimmune disease of the central nervous system, is a recurrent course in the early stages, followed by a transition to disease progression without remission [68]. The myelin sheath of nerve fibers, which is the main target in this disease, gradually degrades, which affects the condition of nerve cells [50]. Unlike Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis, multiple sclerosis develops mainly at a young age, and more often in women [50]. This disease is characterized by heterogeneity: its severity can vary from very mild to severe disability, and the stages of the disease can manifest as rare relapses and rapid progression of symptoms [68]. The currently used methods of treatment in this case are also extremely symptomatic.
Modern approaches to the treatment of multiple sclerosis include the use of monoclonal antibodies, chimeric molecules and hematopoietic stem cells (HSCs) [69]. The purpose of using hematopoietic cells in the treatment of multiple sclerosis is to completely replace the abnormally functioning immune system of the patient [69]. A study by Aharonowiz et al. [70] was devoted to the study of the possibility of using human neural progenitor cells derived from embryonic stem cells to inject a mouse model of multiple sclerosis into the ventricles of the brain. Transplanted human cells reduced the severity of clinical manifestations of the disease and had a neuroprotective effect through immunosuppression [70].
The possibility of transplantation of myelin-producing cells to restore myelin in damaged areas has been studied since the 70s of the last century [71]. However, the ability of differentiated cells to grow and regenerate myelin is very limited [71]. Therefore, the answer to the question of the feasibility of cell transplantation for the treatment of multiple sclerosis is the use of stem cells [71]. In 2009, Burt et al. [72] published the results of a study in which patients with recurrent multiple sclerosis were injected with autologous hematopoietic stem cells containing a population of myeloid progenitor cells. The result of transplantation was an improvement in neurological symptoms and a slowdown in the progression of the disease [72].
ConclusionThe clinical use of stem cells, both embryonic and fetal, as well as adult and induced pluripotent, is increasingly approaching reality.
However, this progress must be approached with extreme caution. In neurodegenerative diseases, the pathological changes associated with them should be evaluated, which can affect the transplanted stem cells. In addition, it is necessary to pay attention to the nature of the migration processes of transplanted stem cells and, possibly, manage them. As the moment of introduction of cell therapy methods using stem cells into clinical practice approaches, protocols for working with them will have to be thoroughly checked for preclinical safety, analysis of positive effects, proper planning of experiments and the availability of signed forms of informed consent [73].
In 2008, the International Society for Stem Cell Research published recommendations for the development of therapies based on the use of stem cells [74].
These recommendations include contacting experts in cell biology to conduct an expert assessment of research results, ranging from preclinical to clinical, focusing on the risks associated with the use of stem cells for therapeutic purposes, subject to voluntary informed consent, new criteria for control over an innovative treatment method that go beyond clinical studies, as well as comparability the results of therapy using stem cells in various medical institutions [74].
As for the number of ongoing clinical studies of new methods of treatment of neurodegenerative diseases, a significant preponderance falls on amyotrophic lateral sclerosis and multiple sclerosis. Most likely, this is due to the fact that after determining one of these diagnoses, the prognosis for patients is less favorable (in terms of life expectancy) than after confirming the diagnosis of Alzheimer's disease or Parkinson's disease. Due to the higher risk/benefit ratio, the U.S. Food and Drug Administration is more inclined to initiate clinical trials of treatments for amyotrophic lateral sclerosis and multiple sclerosis. However, an increase in the number of clinical trials of treatments for Alzheimer's disease and Parkinson's disease is inevitable both because of the large losses of human resources associated with these two diseases, and because of the huge financial costs for medical and social care of patients.
Despite the fact that before the introduction of therapeutic approaches based on the use of stem cells into clinical practice, the issues described above have yet to be resolved, the development of these technologies is proceeding at a rapid pace. The number of ongoing clinical trials inevitably increases, and the results of some of them eventually transform into routine clinical methods.
The list of references is given in a separate file.
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30.03.2012