Speaker
Description
Introduction
Neurodegenerative diseases (NDs) are a group of chronic disorders (e.g. Alzheimer’s disease, Parkinson’s disease and multiple sclerosis -MS) characterized by progressive neurological dysfunction. Despite different neuronal populations can be affected, NDs share major clinical manifestations, namely motor impairment, cognitive disability and/or dementia. Effective treatments do not exist, but stem cell therapies emerged as treatment modalities with potential to cure NDs. However, despite high initial expectations, their clinical use is still limited. To overcome their crucial limitations, such as poor cell survival and low penetration into the central nervous system (CNS), we designed a hydrogel to deliver bone marrow mesenchymal stem cells (BMSCs) intrathecally or intracerebroventricularly.
Methodology
The hydrogel physically crosslinked with liposomes was based on biomolecules (phospholipids and hyaluronic acid-HA) naturally present in the CNS. The characterization comprised the determination of size, polydispersity index (PDI), surface charge and temperature transition of large unilamellar liposomes (LUVs) and their distribution in the HA matrix as well as the assessment of the gel’s thermal and rheological behaviors. Hydrogel cytocompatibility was assessed using BMSCs isolated from healthy rats. To determine biocompatibility and efficacy two rat strains were used, namely Wistar Han rats and Lewis rats, respectively. This choice was based on their ideal use for testing the formulations’ safety and therapeutic efficacy in experimental autoimmune encephalomyelitis (EAE). The assessment of the hydrogel’s in vivo compatibility was performed through its direct injection into the rat’s ventricular space. Moreover, a fluorescent-labeled hydrogel was used to investigate its brain distribution. To determine the efficacy of the developed formulation, containing a significantly lower number of cells than previously reported, the daily body weight, clinical score, and neuropathology levels were assessed in EAE rat models.
Results
LUVs presented a homogeneous (PDI=0.088+0.022) size of 115.7+3.5 nm and a significant negative surface charge (-33.4+3.7 mV). Hydrogels with LUVs displayed a rougher surface than the glycosaminoglycan hydrogel. The shift to a lower value of the temperature of the endothermic peak of HA also confirmed the presence of liposomes. Moreover, liposomes increased the elastic and viscous moduli of the HA matrix as well as the viscosity of the formulation. The encapsulation of BMSCs in the 3D matrix demonstrated they were able to adhere to, survive and proliferate within the hydrogels to a higher extent than in 2D cultures. In vivo studies confirmed hydrogel safety. Moreover, the hydrogel diffused into the corpus callosum, which is ideal for NDs treatment, as the damage of this white matter structure is responsible for important neuronal deficits. The BMSCs-laden hydrogel significantly decreased the maximum mean clinical score and average mean clinical score when compared with the control group of EAE and eliminated the relapse.
Conclusions
The developed formulation was more efficacious in reducing disease severity and maximum clinical score in EAE rats than cells suspensions, demonstrating the added value of cell incorporation in the hydrogel. Therefore, the engineering of stem cells therapies using this natural carrier can result in efficacious treatments for MS and related debilitating conditions.
Acknowledgements: FCT-Cells4_IDs-PTDC/BTM-SAL/28882/2017, IF/003472015, FROnTHERA-NORTE-01-0145-FEDER-000023 and NORTE2020 Structured Project
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