Light irradiation of peripheral nerve cells: Wavelength impacts primary sensory neuron outgrowth in vitro

• Published in: Journal of photochemistry and photobiology. B, Biology Vol. 215; p. 112105
• Main Authors: Diaz Vera, David, Soucy, Jonathan R., Lee, Audrey, Koppes, Ryan A., Koppes, Abigail N.
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 01.02.2021; Elsevier BV
• Subjects: Apoptosis; Axonogenesis; c-Jun protein; Cell death; Cell proliferation; Dorsal root ganglia; Dorsal root ganglion neurons; Genetics; Information processing; Irradiance; Irradiation; Krox-20 protein; Light; Light irradiation; Metabolism; Morphology; Nervous system; Neurons; Opsins; Optics; Optogenetics; Peripheral nerves; Peripheral nervous system; Photo stimulation; Radiation; Schwann cells; Stimulation; Transcription factors; Visible spectrum; Wavelengths; Optogenetics; Light irradiation; Photo stimulation; Dorsal root ganglion neurons; Schwann cells
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2020.112105

The expansion of optogenetics via the development and application of new opsins has opened a new world of possibilities as a research and therapeutic tool. Nevertheless, it has also raised questions about the innocuity of using light irradiation on tissues and cells such as those from the Peripheral Nervous System (PNS). Thus, to investigate the potential of PNS being affected by optogenetic light irradiation, rat dorsal root ganglion neurons and Schwann cells were isolated and their response to light irradiation examined in vitro. Light irradiation was delivered as millisecond pulses at wavelengths in the visible spectrum between 627 and 470 nm, with doses ranging between 4.5 and 18 J/cm2 at an irradiance value of 1 mW/mm2. Results show that compared to cultures kept in dark conditions, light irradiation at 470 nm reduced neurite outgrowth in dissociated dorsal root neurons in a dose dependent manner while higher wavelengths had no effect on neuron morphology. Although neurite outgrowth was limited by light irradiation, no signs of cell death or apoptosis were found. On the other hand, peripheral glia, Schwann cells, were insensitive to light irradiation with metabolism, proliferation, and RNA levels of transcription factors c-Jun and krox-20 remaining unaltered following stimulation. As the fields of photostimulation and optogenetics expand, these results indicate the need for consideration to cell type response and stimulation parameters for applications in vitro and further investigation on specific mechanisms driving response. •Visible spectrum irradiation of single sensory neurons impacts neurite growth in vitro.•Irradiation effects are dose dependent with effects apparent at 470 nm.•Irradiation does not impact proliferation or apoptosis.•No irradiation effects are reported with longer wavelengths.•Whole dorsal root ganglia containing glia do not show light sensitive effects.