Optimisation of a Carbohydrate-Functionalised Collagen Gel for Ventral Mesencephalic Cell Delivery

Parkinson’s Disease (PD) is a neurodegenerative disorder primarily characterised by the death of dopaminergic neurons in the substantia nigra, which relates to different movement disorders [1]. However, currently there are only symptomatic therapies available and none of these systems address the specific pathophysiology of the disease [2]. Hydrogels have shown potential as a vehicle for delivery of cells into the brain, namely ventral mesencephalic (VM) embryonic cells (recently used in PD clinical trials), protecting them from the host environment and maintaining their viability [3]. One biomaterial of interest is collagen since it has high compatibility with neural tissue [3] and is suitable for cell encapsulation. Additionally, the therapeutic potential of collagen can be further expanded by functionalising it to address a specific aspect of PD pathology, such as the glyco-signature and differently regulated sugars upon onset of the disease. The goal of this project is to develop and optimise a glycan-conjugated collagen-based hydrogel that will target the differently expressed carbohydrates in PD models, while encapsulating embryonic VM cells to replace the lost neurons.

In this study, collagen microgels were fabricated using different concentrations of polymer (2 and 3 mg/ml) and crosslinker (4S-StarPEG at 0.2 and 0.4mM) and their properties studied, such as their stability, complex viscosity and encapsulation profiles (Figure 1. A-C). Afterwards, the collagen was conjugated with different glycans (glucose, galactose, 3’-siallylactose, 2’-fucosyllactose) in order to expose gluco-, galacto-, 3’-sialylgalacto-, and 2’-fucosylgalactose. The functionalised compounds were analysed (Figure 1. D-F). These functionalised systems were used to fabricate gels and their biological properties assessed. The collagen microgels have high crosslinking efficiency and stability and were suitable to successfully encapsulate embryonic VM rat cells, showing high viability up to two weeks in 2mg/ml collagen and 0.4mM 4S-StarPEG microgels. In parallel, glycan expression was analysed in pre-clinical models of PD to choose the optimal for use in future in vivo studies.