Optimizing a Hyaluronic Acid-Based Hydrogel for Delivery of Neural Progenitor Cells for Ischemic Stroke Treatment

Stroke is one of the leading causes of disability and mortality worldwide. A stroke occurs when brain tissue is locally deprived of oxygen and nutrients through ischemic or hemorrhagic stroke. Current treatment options for stroke patients aim to restore blood flow to brain tissue within a brief therapeutic time window. As a result of the limited time span of reperfusion, the only remaining treatment option for 90% of stroke patients is rehabilitation, with no currently approved treatments to regenerate and replace damaged tissue. Preclinical studies have shown promising results after cell transplantation in stroke models, yet, cell survival remains poor. Delivering cells in a compatible and suitable delivery vehicle could enhance cell survival and improve stroke outcomes.

Hyaluronic Acid (HA), a primary component of the brain extracellular matrix (ECM), is an ideal candidate for cell delivery to the brain of stroke patients. HA-based self-polymerizing hydrogels serve as a platform for the adhesion of structural motifs and a depot release for growth factors to promote transplant stem cell survival and differentiation of human neural progenitor cells (iPS-NPCs). Moreover, HA hydrogels are a biocompatible and biodegradable material that degrades as encapsulated cells move within the gel.

Here, we synthesized a defined, biomimetic hydrogel composed of HA and a 4-arm Poly(ethylene glycol) (PEG) crosslinker using oxyamine chemistry to ensure tunability of the resulting HA-PEG hydrogel. The physical properties of the gel were assessed through rheology and optimized by changing the ratios of the gel components. The gel was further optimized by the incorporation of the cell-adhesion peptide PHSRN-RGD. Peptide concentration was evaluated using a fluorometric assay.

To assess the feasibility of the gels, human iPSC-derived neural progenitor cells (NPCs) were encapsulated in the optimized HA-PEG hydrogels and cultured for 5 days in vitro. Cells were then stained and imaged using confocal microscopy to assess cell viability and distribution throughout the gel. The stability of the HA-PEG hydrogel was tested in the absence or presence of the HA-degrading enzyme hyaluronidase.

Current work involves further optimization of the hydrogel with the laminin-derivatives IKVAV and YIGSR peptides, which have been shown to enhance attachment and neuronal differentiation. Overall, the results of this study will enable the delivery of NPCs in the optimized hydrogel in preclinical studies.