Normative nerve conductions in the tail of rhesus macaques (Macaca mulatta)

STEER: 3D Printed Guide for Nerve Regrowth Control and Neural Interface in Non-Human Primate Model

OBJECTIVE

Peripheral neural interface (PNI) with a stable integration of synthetic elements with neural tissue is key for successful neuro-prosthetic applications. An inevitable phenomenon of reactive fibrosis is a primary hurdle for long term functionality of PNIs. This proof-of-concept study aimed to fabricate and test a novel, stable PNI that harnesses fibro-axonal outgrowth at the nerve end and includes fibrosis in the design.

METHODS

Two non-human primates were implanted with Substrate-guided, Tissue-Electrode Encapsulation and Integration (STEER) PNIs. The implant included a 3D printed guide that strove to steer the regrowing nerve towards encapsulation of the electrodes into a fibro-axonal tissue. After four months from implantation, we performed electrophysiological measurements to test STEERs functionality and examined the macro and micro- morphology of the outgrowth tissue.

RESULTS

We observed a highly structured fibro-axonal composite within the STEER PNI. A conduction of intracranially generated action potentials was successfully recorded across the neural interface. Immunohistology demonstrated uniquely configured laminae of myelinated axons encasing the implant.

CONCLUSION

STEER PNI reconfigured the structure of the fibro-axonal tissue and facilitated long-term functionality and stability of the neural interface.

SIGNIFICANCE

The results point to the feasibility of our concept for creating a stable PNI with long-term electrophysiologic functionality by using simple design and materials.

Dorsal caudal tail and sciatic motor nerve conduction studies in adult mice: technical aspects and normative data

Mice provide an important tool to investigate human neuromuscular disorders. The variability of electrophysiological techniques limits direct comparison between studies. The purpose of this study was to establish normative motor nerve conduction data in adult mice. The dorsal caudal tail nerve and sciatic nerve motor conduction studies were performed bilaterally on restrained anesthetized adult mice. The means and standard deviations for each electrophysiological parameter were determined in normal mice. Data were compared with inflammatory demyelinating polyneuropathy mice to determine whether these parameters discriminate between normal and abnormal peripheral nerves. Normal adult mice had a distal latency of 0.89 (+/-0.17) ms and 0.75 (+/-0.09) ms, distal compound motor unit action potential amplitude of 13.2 (+/-5.9) mV and 28.1 (+/-8.3) mV, and conduction velocity of 74.6 (+/-9.0) m/s and 76.5 (+/-8.3) m/s, respectively. These data were validated by the finding of statistically significant differences in several electrophysiological parameters that compared normal and polyneuropathy-affected mice. A standardized method for motor nerve conduction studies and associated normative data in mice should facilitate comparisons of disease severity and response to treatment between studies that use similar models. This would assist in the process of translational therapeutic drug design in neuromuscular disorders.