Peripheral nerve injuries present challenges to regeneration. Currently, the gold standard for nerve repair is an autograft that results in another region of the body suffering nerve damage. Previously, bioactive borate glass (BBG) has been studied in clinical trials to treat patients with non-healing wounds, and we have reported that BBG is conducive for soft tissue repair. BBG provides structural support, degrades in a non-cytotoxic manner, and can be chemically doped. Here, we tested a wide range of chemical compounds that are reported to have neuroprotective characteristics to promote regeneration of peripheral neurons after traumatic injury. We hypothesized that chemical dopants added in trace amounts to BBG would improve neuronal survival and neurite outgrowth from dorsal root ganglion (DRG) explants. We measured neurite outgrowth from whole DRG explants, and survival rates of dissociated neurons and support cells that comprise the DRG. Results show that chemically doped BBGs have differentially variable effects on neuronal survival and outgrowth, with iron, gallium, and zinc improving outgrowth of neurons, and iodine causing the most detriment to neurons. Because chemically doped BBGs support increased nerve regrowth and survival, they show promise for use in peripheral nerve regeneration.

Peripheral nerve injury can be disabling. Regeneration is limited by the rate of axonal extension, and proximal injury to peripheral nerves can take over a year to reach target organs. Electrical stimulation (ES) has been shown to increase the rate of neurite growth, though the mechanism is not yet well understood. In our prior manuscript, we developed a computational model that demonstrates how ES can functionally elevate intracellular calcium concentration ([Ca]) based on ES intensity and duration. In this article, we validate the computation model for the [Ca] changes in neuron soma. Embryonic chicken dorsal root ganglion cells were suspended in 3-dimensional collagen scaffolds. Fura-2 was used to measure [Ca] in response to biphasic ES pulses ranging from 70 to 60,000 V/m in intensity and from 10 µs to 100 ms in duration. The computational model most closely matched the experimental data of the neurons with the highest [Ca] elevation for ES pulses 100 µs or greater in duration. Nickel (200 µM) and cadmium (200 µM) blocked 98-99% of the [Ca] rise, indicating that the rise in [Ca] in response to ES is via voltage-dependent calcium channels. The average [Ca] rise in response to ES was about one-tenth of the peak rise. Therefore, the computational model is validated for elevating [Ca] of neurons and can be used as a tool for designing efficacious ES protocols for improving neuronal regeneration. Electrical stimulation is used to enhance neuron growth, and the role of neuronal intracellular calcium concentration ([Ca]) is an area of research interest. Widely varying stimulation parameters in the literature make it difficult to compare stimulation protocols. The results in this manuscript are the first to show neuronal [Ca] in response to a broad and defined range of electrical pulse durations and intensities. These results validate our previously published novel computational model of [Ca].