The Use of Stem Cells in Regenerative Medicine for Parkinson’s and Huntington’s Diseases

MSC-Derived Exosomes can Enhance the Angiogenesis of Human Brain MECs and Show Therapeutic Potential in a Mouse Model of Parkinson's Disease

Parkinson’s disease (PD) is the second most widespread neurodegenerative disorder in the world. It has been reported that exosomes derived from mesenchymal stem cells (MSCs) can contribute to the recovery of PD. However, the underlying mechanism remains poorly defined. In this study, proteomics and time-series analysis showed that exosomes derived from MSCs can keep human brain microvascular endothelial cells (HBMECs) in a transcriptionally active state, which may be beneficial for angiogenesis. Next, we found that MSC-derived exosomes can promote the angiogenesis of HBMECs by increasing the expression of ICAM1, and alleviate the damage caused by 1-methyl-4-phenylpyridinium (MPP+) in these cells. Accordingly, when ICAM1 was knocked down, the tube formation ability of HBMECs was obviously decreased. In addition, ICAM1 was found to promote the angiogenesis of HBMECs by activating the SMAD3 and P38MAPK signaling pathways. In a PD mouse model, MSC-derived exosomes were found to contribute to the recovery of PD by promoting ICAM1-related angiogenesis. These findings demonstrate that the exosome-ICAM1-SMAD3/P38MAPK axis can promote the angiogenesis of HBMECs, with possible therapeutic potential for PD.

Is the Immunological Response a Bottleneck for Cell Therapy in Neurodegenerative Diseases?

Neurodegenerative disorders such as Parkinson's (PD) and Huntington's disease (HD) are characterized by a selective detrimental impact on neurons in a specific brain area. Currently, these diseases have no cures, although some promising trials of therapies that may be able to slow the loss of brain cells are underway. Cell therapy is distinguished by its potential to replace cells to compensate for those lost to the degenerative process and has shown a great potential to replace degenerated neurons in animal models and in clinical trials in PD and HD patients. Fetal-derived neural progenitor cells, embryonic stem cells or induced pluripotent stem cells are the main cell sources that have been tested in cell therapy approaches. Furthermore, new strategies are emerging, such as the use of adult stem cells, encapsulated cell lines releasing trophic factors or cell-free products, containing an enriched secretome, which have shown beneficial preclinical outcomes. One of the major challenges for these potential new treatments is to overcome the host immune response to the transplanted cells. Immune rejection can cause significant alterations in transplanted and endogenous tissue and requires immunosuppressive drugs that may produce adverse effects. T-, B-lymphocytes and microglia have been recognized as the main effectors in striatal graft rejection. This review aims to summarize the preclinical and clinical studies of cell therapies in PD and HD. In addition, the precautions and strategies to ensure the highest quality of cell grafts, the lowest risk during transplantation and the reduction of a possible immune rejection will be outlined. Altogether, the wide-ranging possibilities of advanced therapy medicinal products (ATMPs) could make therapeutic treatment of these incurable diseases possible in the near future.

Advances in Monitoring Cell-Based Therapies with Magnetic Resonance Imaging: Future Perspectives

Cell-based therapies are currently being developed for applications in both regenerative medicine and in oncology. Preclinical, translational, and clinical research on cell-based therapies will benefit tremendously from novel imaging approaches that enable the effective monitoring of the delivery, survival, migration, biodistribution, and integration of transplanted cells. Magnetic resonance imaging (MRI) offers several advantages over other imaging modalities for elucidating the fate of transplanted cells both preclinically and clinically. These advantages include the ability to image transplanted cells longitudinally at high spatial resolution without exposure to ionizing radiation, and the possibility to co-register anatomical structures with molecular processes and functional changes. However, since cellular MRI is still in its infancy, it currently faces a number of challenges, which provide avenues for future research and development. In this review, we describe the basic principle of cell-tracking with MRI; explain the different approaches currently used to monitor cell-based therapies; describe currently available MRI contrast generation mechanisms and strategies for monitoring transplanted cells; discuss some of the challenges in tracking transplanted cells; and suggest future research directions.