Highly Effective Photonic Cue for Repulsive Axonal Guidance

Bryan J Black,Ling Gu,Samarendra K Mohanty,Nic D Leipzig

doi:10.1371/journal.pone.0086292

Abstract

In vivo nerve repair requires not only the ability to regenerate damaged axons, but most importantly, the ability to guide developing or regenerating axons along paths that will result in functional connections. Furthermore, basic studies in neuroscience and neuro-electronic interface design require the ability to construct in vitro neural circuitry. Both these applications require the development of a noninvasive, highly effective tool for axonal growth-cone guidance. To date, a myriad of technologies have been introduced based on chemical, electrical, mechanical, and hybrid approaches (such as electro-chemical, optofluidic flow and photo-chemical methods). These methods are either lacking in desired spatial and temporal selectivity or require the introduction of invasive external factors. Within the last fifteen years however, several attractive guidance cues have been developed using purely light based cues to achieve axonal guidance. Here, we report a novel, purely optical repulsive guidance technique that uses low power, near infrared light, and demonstrates the guidance of primary goldfish retinal ganglion cell axons through turns of up to 120 degrees and over distances of ∼90 µm.

Highlights

It is well known that axonal pathfinding [1,2] is paramount to an organism’s nervous system development [3,4], and that, during this development, functional connections must be made across the entire organism [5,6,7]
These cues can effectively induce or inhibit axonal growth [12] by affecting actin filament polymerization processes. If such gradients are asymmetrically positioned along the axonal growth axis, they result in growth cone turning and short-to-long-range axonal guidance
Efficient optical guidance of axons using laser as repulsive cue For optical guidance of axons, in vitro experiments were conducted on goldfish retinal ganglion cell (RGC) axons emerging from retina explants in petridish

Summary

Introduction

It is well known that axonal pathfinding [1,2] is paramount to an organism’s nervous system development [3,4], and that, during this development, functional connections must be made across the entire organism [5,6,7]. It has been shown that axonal growth rates and direction are primarily determined by environmental cues [11] which are ‘sensed’ by the axon’s filopodia [1] These filopodia are finger-like growth cone extensions which sample the surroundings for attractive or repulsive growth and guidance cues, which may be mechanical, electrical, or chemical in nature. These cues can effectively induce or inhibit axonal growth [12] by affecting actin filament polymerization processes. If such gradients are asymmetrically positioned along the axonal growth axis, they result in growth cone turning and short-to-long-range axonal guidance. The development of selective, minimally-invasive methods of axonal guidance is of considerable importance in the fields of neuroscience and neuroengineering

Methods

Results

Conclusion