Abstract
Neurological disorders are devastating and affect the daily activities of millions of people globally. A number of neurological diseases lead to neurodegeneration characterized by irreversible damage or loss of neurons located in the central nervous system. Over 100 million Americans suffer from neurological diseases. The United States spends an estimated $789 billion every year for the care of individuals with neurological diseases. Current treatment options can only help manage the symptoms due to the complexity of neurological diseases. Treatments fall short of halting or reversing the sequential neuronal damage, thus warranting the need for other effective treatments. Recent advances in stem cell therapy have received increased attention due to their potential to mitigate the symptoms of neurological disorders. Mesenchymal stromal cells (MSCs) are extensively studied due to proven self-renewal and immunomodulatory, angiogenic and neuroprotective properties. Analyses of MSC secretion attributed these properties to paracrine secretions such as unique cytokines, growth factors and extracellular vesicles, including exosomes. Human placental-derived MSCs (hPMSCs) secrete significant levels of paracrine factors such as hepatocyte growth factor, brain-derived neurotropic factor and vascular endothelial growth factors. Treatment of surgically created fetal lamb myelomeningocele with hPMSCs hPMSCs preserved motor neurons and improved their ambulatory functions through paracrine secretion mechanisms. Studies have shown that exosomes secreted by hPMSC, present in the conditioned medium, are effective in alleviating the severity of neuronal damage. Since the membrane composition is similar to that of the plasma membrane, exosomes are an excellent candidate for cell-free therapy as it is biocompatible and facilitates targeted delivery. Although exosomes have the potential to be effective therapeutic agents, their composition is variable, their isolation process is time-consuming and their yields are often low. Therefore, an alternative solution to overcome the aforementioned challenges is necessary. This project was focused on the synthesis of stem cell derived exosome-mimicking nanovesicles (EMNs) that were similar to native exosomes in size, composition and biological function. The synthesis of EMNs involved encapsulating concentrated exosome-free conditioned medium into hPMSC-derived lipid rafts. These EMNs were hypothesized to have the therapeutic potential to rescue apoptotic neurons in culture. We hypothesized that the hPMSC-derived EMNs would have the therapeutic potential to rescue apoptotic neurons in culture. The results of this study indicated that the EMNs were successfully loaded with hPMSC secretions and formed spherical vesicles with a size range of 50-200 nm. A total of 3.78 ×109 EMNs were produced from 10 million cells, thus overcoming the low yields of collection seen with native exosomes. Additionally, the EMNs could rescue the neurons that were undergoing apoptosis when compared PBS-treated neurons, thus corroborating the fact that they are not only similar to native exosomes in terms of their size and membrane composition, but are also able to function similar to native exosomes. Overall, this project is a proof-of-concept study of using hPMSC-derived lipid rafts to produce exosome-mimicking nanovesicles to deliver neuroprotective secretome. This project has been able to address the need for an effective system to facilitate the delivery of stem cell paracrine secretions and neuroprotective agents in a scalable manner.