Control of Retinal Ganglion Cell Positioning and Neurite Growth: Combining 3D Printing with Radial Electrospun Scaffolds

Abstract

Retinal ganglion cells (RGCs) are responsible for the transfer of signals from the retina to the brain. As part of the central nervous system, RGCs are unable to regenerate following injury, and implanted cells have limited capacity to orient and integrate in vivo. During development, secreted guidance molecules along with signals from extracellular matrix and the vasculature guide cell positioning, for example, around the fovea, and axon outgrowth; however, these changes are temporally regulated and are not the same in the adult. Here, we combine electrospun cell transplantation scaffolds capable of RGC neurite guidance with thermal inkjet 3D cell printing techniques capable of precise positioning of RGCs on the scaffold surface. Optimal printing parameters are developed for viability, electrophysiological function and, neurite pathfinding. Different media, commonly used to promote RGC survival and growth, were tested under varying conditions. When printed in growth media containing both brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), RGCs maintained survival and normal electrophysiological function, and displayed radial axon outgrowth when printed onto electrospun scaffolds. These results demonstrate that 3D printing technology may be combined with complex electrospun surfaces in the design of future retinal models or therapies.

Outlooks on Three-Dimensional Printing for Ocular Biomaterials Research

“…In both cases, this alignment was significantly improved compared to typical 2D culturing, which only showed 11% alignment. 54 In addition, their printed cells did not see a decrease in overall viability or reduced function when monitored by electrophysiology. In a promising study, Kador et al were able to achieve a printed density of about 30 cells/mm 2 as compared to the overall cell density in the human retina of about 2100 cells/mm 2 .…”

“…Three-dimensional bioprinting techniques have been used to deposit RGCs in an organized manner and represent the structure of the RGC layer in the retina. 36,54 Kador et al showed that a combined 3D printing approach that utilized both electrospinning of a polylactic acid scaffold and thermal inkjet printing with multiple nozzles using optimized media conditions could lead to significantly improved RGC orientation compared to traditional 2D culturing. Their 3Dprinted cells with axons were found to be 72% aligned with their radial scaffold with 49% of dendrites aligned as well.…”

“…In a promising study, Kador et al were able to achieve a printed density of about 30 cells/mm 2 as compared to the overall cell density in the human retina of about 2100 cells/mm 2 . 2,54 Other types of cells present in the retina, such as glial cells, have been printed along with RGC in an attempt to reproduce the whole retina. 36,59 Lorber et al published a study that attempted to print both RGCs and glial cells THREE-DIMENSIONAL PRINTING 13 together to evaluate the effects of a piezoelectric printing on the cellular viability.…”

“…Anatomical structure of the human eye, and 3D bioprinted parts: (B) 3D bioprinted cornea, (C) 3D bioprinted retinal ganglion cells. 53,54 Color images are available online.…”

Organ‐on‐chip models: Implications in drug discovery and clinical applications

“…In an effort to study this phenomenon, thermal inkjet printing has been used to study the electrophysiological function and axon patterning of printed retinal ganglion cells. A study printed on an electrospun scaffold embedded on hydrogel matrices to mimic the directionality of the nerve fiber layer of retinal cells in vivo (Kador et al, ). While retinal ganglion cell survival was not compromised, electrophysiological function was, as printed cells required higher injected current to elicit action potentials.…”