​PhD student : Francesco Gubinelli

Abstract

Parkinson’s disease (PD) is the second most common neurodegenerative disease, affecting 0.3% of general population, with an increasing rate of 1 to 2% in persons over 65. At the moment the only available pharmacological treatment (L-Dopa) focuses on mitigating symptoms; nowadays treatments to slow down the disease’s progression, or suppress symptoms on the long term remain to be validated. Cellular transplantation had showed encouraging results, but it has some limitation, including the poor survival of the grafted cells, strong immune response and rejection of the graft. Biomaterials are materials used and adapted for medical applications and are designed to interact with different biological systems. Among them, collagen-based hydrogels recently gained attention in the field of regenerative medicine and cellular transplantation, being widely used for skin graft and wound healing, spinal cord regeneration, bones and tendon repair. To date, such promising approach has not been often investigated in vivo for neurodegenerative diseases as PD. In this work we developed a rodent relevant model of PD that is able to show a progressive neurodegeneration of DA neurons in the SNpc. Using adeno-associated viral vector (AAV), we overexpressed the C-terminal domain of mutated LRRK2 form (LRRK2G2019S) with or without mutant α-synuclein (α-synA53T) in the SNpc. Our results showed that, while LRRK2G2019S alone did not produce any toxicity, α-synA53T co-expressed with LRRK2 G2019S produced a greater loss of dopaminergic cells in the SNpc. α-synA53T toxicity is likely to be facilitated by the kinase activity of mutant LRRK2 through a cell autonomous mechanism. Once the neurodegenerative rat model of PD was developed and ready for testing the potential of the collagen scaffold as a delivery system, we proceeded with characterization of the hydrogel scaffold. Using high field (11.7T) magnetic resonance imaging (MRI), and histological analysis we characterized our collagen-based hydrogel after in vitro and, in vivo polymerization after intracerebral injection in rats. Our results indicate that collagen-based hydrogels can be safely injected into the brain without any major adverse effect and that MRI is a tool of choice for a direct and non-invasive in vivo follow-up of collagen hydrogel polymerization and grafting in the brain. The collagen scaffold showed a transitory and limited immune response localized around the site of injection. These results suggest that our in-situ polymerizing collagen-based hydrogel could be safely employed as a delivery system for cells and/or molecules during neuronal transplantation.