Saeed Shahbeigi
Stem Cells (SC) therapy emerges as a potential new hope for neurological patients as it could accomplish the immunomodulatory as well as the neuroprotective functions. There is a growing body of literature that supports the potential of the SC for immunomodulation and re-myelination. Here we focus on examining the registered published and on-going clinical trials using stem cells especially the Mesenchymal Stem Cell therapy in neurological disorders such as MS, ALS, Stroke, spinal cord injuries and also some types of devastating neuropathies like POEMS. There are evidence showing that the MSC can alter the phenotype of NK cells and suppress proliferation, cytokine secretion, and cytotoxicity against HLA-class Iexpressing targets. Some of these effects require cell-to-cell contact, whereas others are mediated by soluble factors, including transforming growth factor-beta1 and prostaglandin E2, pointing to the existence of diverse mechanisms for the MSC-mediated NK-cell suppression . The MSC have been reported to block the differentiation of monocytes into dendritic cells and impair antigen presentation as well as IL-12 production. Also the human MSC alter cytokine secretion and induce more anti-inflammatory responses. Specifically, the hMSC by induction of mature dendritic cells (DC) decrease tumor necrosis factor alpha (TNF-alpha) secretion and increase IL-10 secretion . The hMSC inhibit Th1 cells, decrease interferon gamma, and affect Th2 cells by increasing secretion of IL-4. This causes an increase in the proportion of T- Regulatory cell switches the CD4+ T cell responses from a Th1 to a Th2 polarized phenotype resulting in a decrease secretion of IFN-gamma from NK cells. Generally speaking we are going to discuss the immunomodulatory effects of the mesenchymal stem cells and finally to review some interested data from our experience and other papers around the world. The positive outcomes of the transplantation of fetal neural tissue in adult rat models of a variety of neurological disorders, particularly Parkinson's disease, in the 1970s, and its translation to humans in the 1980s, raised great hopes for patients suffering from these incurable disorders. This resulted in a frantic research globally to find more suitable, reliable, and ethically acceptable alternatives. The discovery of adult stem cells, embryonic stem cells, and more recently, the induced pluripotent cells further raised our expectations. The useful functional recovery in animal models using these cell transplantation techniques coupled with the desperate needs of such patients prompted many surgeons to “jump from the rat-to-man” without scientifically establishing a proof of their utility. Each new development claimed to overcome the limitations, shortcomings, safety, and other technical problems associated with the earlier technique, yet newer difficulties prevented evidence-based acceptance of their clinical use. However, thousands of patients across the globe have received these therapies without a scientifically acceptable proof of their reliability. The present review is an attempt to summarize the current status of cell therapy for neurological disorders.