A tunable synthetic hydrogel system for culture of retinal ganglion cells and amacrine cells

Abstract

The central nervous system (CNS) consists of complex groups of individual cells that receive electrical, chemical, and physical signals from their local environment. Standard in vitro cell culture methods rely on two-dimensional (2D) substrates that poorly simulate in vivo neural architecture. Neural cells grown in three-dimensional (3D) culture systems may provide an opportunity to study more accurate representations of the in vivo environment than 2D cultures. Furthermore, each specific type of neuron depends on discrete compositions and physical properties of their local environment. Previously, we developed a library of hydrogels composed of poly(ethylene glycol) (PEG) and poly(L-lysine) (PLL) which exhibit a wide range of mechanical properties. Here, we identified specific scaffolds from this library that readily support the survival, migration and neurite outgrowth of purified retinal ganglion cells (RGCs) and amacrine cells (ACs). These data address important biological questions about the interaction of neurons with the physical and chemical properties of their local environment and provide further insight for engineering neural tissue for cell-replacement therapies following injury.

Hydrogels in ophthalmic applications

“…Furthermore, natural polymers often 141 interact with proteins and cells through non-specific or specific 142 binding, which can be desired in hydrogel-based sustained release 143 systems or cell carriers. However, hydrogels made from natural 144 polymers may suffer from weak mechanical strength, high 145 batch-to-batch variability, and immunogenicity. Synthetic poly- 146 mers, on the other hand, allow for the preparation of hydrogels 147 with well-defined network architecture, tunable mechanical prop- 148 erties, and prolonged stability.…”

Retinal ganglion cell polarization using immobilized guidance cues on a tissue-engineered scaffold

“…[12] However, RGC transplantation is inherently more difficult than photoreceptor transplantation, as it requires the transplanted cells to integrate dendritically with their amacrine or bipolar cell presynaptic partners in the inner plexiform layer, extend their axons radially through the retina to the optic nerve, grow down the optic nerve and find their appropriate targets in the brain. Previously, we investigated the use of both PLL-PEG hydrogels [26] and PLA electrospun scaffolds [27] to study RGC survival and neurite growth and as a potential cell delivery vehicle. Unlike hydrogels, PLA electrospun scaffolds allowed RGC axons to replicate the radial organization of native RGCs in the retina, but they did not promote the polarization or centripetally directed growth seen in the retina in vivo.…”

“…[28] Future experiments will be designed to determine whether these RGC-seeded scaffolds are able to enhance guidance towards, and into, the optic nerve head. The incorporation of Netrin-1 did require a fibronectin coating of PLA fibers rather than the laminin coating used previously[19, 26] as laminin has been shown to alter Netrin-1 from an attractive to a repulsive guidance factor. [11] This use of Netrin-1 was also compatible with scaffolding purified RGCs from early postnatal rats, an age at which the DCC Netrin-1 receptor is expressed.…”

Synthesis and characterization of a pH-responsive poly(ethylene glycol)-based hydrogel: acid degradation, equilibrium swelling, and absorption kinetic characteristics

“…Hydrogels may be prepared so that their physical-chemical characteristics (e.g., equilibrium swelling and absorption kinetic) respond to changes in their external environment, such as temperature [3], pH [4,5], ionic strength [6], and so on. These materials show a wide variety of applications such as drug delivery [7], membranes for (bio)separation process [8], substrate for cell culture [9], and mucosal vaccines [10].…”