Cytoprotection and neural regeneration in peripheral nerve injury

Abstract

Neural injuries are some of the most common ailments presented in the clinic, affecting up to 20 million Americans. While a number of treatments have been studied, many of their drawbacks outweigh their advantages, so new solutions are still needed. Simple signaling molecules (SSMs), very small agents that govern bioactivity, offer an exciting approach to traditional approaches due to their small size, availability, and influence on cellular pathways. In this research, I evaluated the cytoprotective and neuroinductive capacity of three SSMs: hydrogen sulfide (H2S), n-acetyl cysteine (NAC), and glutathione (GSH). To investigate each molecule's cytoprotective effect, neural stem cells (NE-4Cs) were exposed to a toxic level of a known reactive oxygen species (ROS) - hydrogen peroxide (H2O2) - while supplemented with various concentrations of H2S, NAC, or GSH. In this model of oxidative stress, H2S did not exhibit significant cytoprotective effects, however, NAC and GSH both demonstrated considerable promise. In specific, therapeutic ranges of 2 - 8 mM NAC and 2 - 12 mM GSH were established as cytoprotective against H2O2-mediated cellular insult. To study the neuroinductivity of H2S, NAC, and GSH in NE-4Cs, immunofluorescence microscopy for an early neuronal marker, [beta]3 tubulin, was employed to assess stem cell neural differentiation. This evaluation revealed that H2S presented the most neuroinductive potential, while NAC and GSH showed little capacity to facilitate neuronal differentiation. A neuroinductive window of 3.9 - 250 [mu]M H2S was established through this study. With the neuroinductive range of H2S and the cytoprotective ranges of NAC and GSH identified, this research paves the way for future controlled drug delivery systems of these molecules to be developed and implemented for peripheral nerve injury applications.