ChE PhD Dissertation Defense: Peng Zhao

Name:
Peng Zhao

Title:
Impact of ECM-Based Hydrogel Delivery Vehicle Properties on Cell Survival in a 3D In Vitro Injection Model for Retinal Progenitor Cell Transplantation

Date:
12/10/2024

Time:
2:00:00 PM

Committee Members:
Prof. Rebecca Carrier (Advisor)
Prof. Abigail Koppes
Prof. Sidi Bencherif
Prof. Michael Young

Location:
EXP 610-A

Abstract:
Age-related macular degeneration (AMD) is the leading cause of vision loss globally and a form of retinal degenerative (RD) disease. Current treatments, such as gene therapy, drugs, laser procedures, and neuroprotective approaches, cannot restore the photoreceptors lost in RD diseases. Cell transplantation into the subretinal space shows potential to enhance visual function, but low cell survival and efflux from the injection site present major obstacles. Mechanical forces during injection can severely damage cells, and the host microenvironment may further contribute to cell death. Following high-density subretinal injection, a compact cell bolus may form, resulting in nutrient depletion, low oxygen levels, pH imbalances, and waste accumulation—factors that exacerbate cell death.

Biomaterial scaffolds have been employed to improve cell survival and differentiation, though the ideal scaffold cues for supporting transplanted cell survival and integration remain undetermined. In this study, we developed a three-dimensional (3D) in vitro injection model to simulate subretinal bolus injection. Using this model, we found that the injection process and bolus microenvironment negatively impact human retinal progenitor cell (hRPC) viability, promoting apoptosis. Alginate-based hydrogels of varying stiffness and extracellular matrix (ECM) molecule compositions were created using factorial design. hRPC viability, apoptosis, and migration within the formed hydrogels were investigated through the 3D in vitro injection model and a 3D invasion assay. Factorial design analysis revealed that higher stiffness and the inclusion of laminin and hyaluronic acid enhance hRPC survival and 3D migration.

One challenge with studying cell responses in the context of cell transplantation is the inability to easily visualize cells at the transplantation site over time. Compared to traditional in vitro cultures, retinal explant models that retain native tissue structure and neuronal connections could provide physiologically relevant insights. Here, we developed a novel explant model for hRPC transplantation, wherein alginate-based hydrogels containing hRPCs were injected adjacent to cross-sectional retinal tissue slices. This setup allows visualization of the cells’ position relative to retinal tissue layers over time. Key cell behaviors, including migration, attachment, invasion, viability, and apoptosis, were tracked in real-time using confocal microscopy.