The prospect of using stem cells for therapeutic purposes has been one of the most promising fields of science and medicine in recent years. Progress in this area has been substantial, including a better understanding of stem cell biology, the identification of new sources of stem cells, and encouraging therapeutic results in a variety of diseases. Neurological disorders remain one of the greatest challenges in medicine, with little or no effective treatments available. Preclinical studies using stem cells have been encouraging and have led to the initiation of a few clinical trials for Parkinson's disease, multiple sclerosis and stroke. Unfortunately, none of these trials demonstrated a satisfactory therapeutic outcome. There are many suggested reasons for that failure, with one of the primary reasons being an inefficient biodistribution and targeting of stem cells. Intraarterial delivery could potentially bypass this limitation, and a few attempts have been made to use this approach for direct targeting of brain lesions. The major obstacle limiting this approach is the lack of techniques tha enable efficient binding of cells to endothelium, as well as the risk of microembolism as a result of excessive cell binding. Our preliminary results indicate that overexpression of the docking receptor VLA-4 greatly improves the targeting efficiency of human, glial progenitors towards areas of inflammation. Using a microfluidics in vitro adhesion assay, cell binding to activated brain endothelial cells greatly increased as compared to non-VLA-4 controls (71.511.7 vs. 36.43.3 cells/FOV, respectively, p=0.045). In a LPS-induced rat global inflammatory brain model, cells containing the VLA-4 transgene demonstrated much enhanced homing in vivo following intraarterial injection. Real-time, quantitative serial whole brain MR imaging of magnetically labeled cells revealed that, VLA-4+ cells docked exclusively within the vascular bed of the ipsilateral carotid artery indicating a first pass adhesion mechanism. Pixel-by-pixel analysis revealed that injection of VLA-4+ cells in LPS-treated animals resulted in 3,979705 hypointense pixels as compared to 868317 in VLA-4- LPS-treated controls (p=0.014). With these encouraging results, the overall aim of this proposal is to induce pluripotent stem cells-derived glial precursors to overexpress the adhesion molecules VLA-4 and LFA-1 and the chemokine receptors CXCR-4 and CCR2. Combined with intracarotid delivery, we hypothesize that a highly efficient and specific engraftment within inflammatory brain lesions will occur. The ability of cells to bind to endothelium and extravasate into the brain parenchyma will be initially tested in vitro using a microfluidics model blood brain barrier. Experiments will then be performed in vivo in rat models of stroke and autoimmune encephalomyelitis. To ensure the safety of this approach, we will monitor cell delivery, cerebral blood flow, and oxygenation in real-time using MRI. Upon successful completion of our studies, this new targeting approach could significantly improve the efficacy of cell-based therapy with applications in many areas of medicine.
Efficient targeting of therapeutic cells to areas of brain damage continues to be a challenge. We hypothesized that genetic engineering of cells and overexpression of docking receptors such as VLA-4 combined with intraarterial approach would greatly improve targeting efficiency and would create a new paradigm for efficient cellular targeting. Magnetic resonance imaging will be used to monitor both in vivo cell binding and cerebral blood flow and oxygenation, in order to determine the efficiency and safety of this new approach non- invasively.
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