Engineering a 3D functional human peripheral nerve in vitro using the Nerve-on-a-Chip platform

June 20, 2019

Development of “organ-on-a-chip” systems for neuroscience applications are lagging due in part to the structural complexity of the nervous system and limited access of human neuronal & glial cells. In addition, rates for animal models in translating to human success are significantly lower for neurodegenerative diseases. Thus, a preclinical in vitro human cell-based model capable of providing critical clinical metrics such as nerve conduction velocity and histomorphometry are necessary to improve prediction and translation of in vitro data to successful clinical trials. To answer this challenge, we present an in vitro biomimetic model of all-human peripheral nerve tissue capable of showing robust neurite outgrowth (~5 mm), myelination of hNs by primary human Schwann cells (~5%), and evaluation of nerve conduction velocity (0.13–0.28 m/sec), previously unrealized for any human cell-based in vitro system. To the best of our knowledge, this Human Nerve-on-a-chip (HNoaC) system is the first biomimetic microphysiological system of myelinated human peripheral nerve which can be used for evaluating electrophysiological and histological metrics, the gold-standard assessment techniques previously only possible with in vivo studies.

In this study, we describe an in vitro, microengineered, biomimetic, all-human peripheral nerve (HNoaC) comprised of induced pluripotent stem cell (iPSC)-derived neurons (hNs) and primary human Schwann cells (hSCs) that can provide data suitable for integrated nerve conduction velocity (NCV) and histopathological assessments. This all-human system is a significant extension of our in vitro “Nerve-on-a-chip” (NoaC) platform previously developed using embryonic rat dorsal root ganglion (DRG) neurons and rat SCs. Most of the previous work done in this field is largely based on animal cells and uses a similar strategy to meticulously isolate somas from the axons in order to measure the electrical function of the cells. However, these systems were either developed in two dimensions or represented excised nerves, and thus were not capable of providing conventional histological data, which is important for understanding the neuronal function. To our knowledge, this combination of hNs and hSCs has not previously been achieved for any other 3D human stem cell-based in vitro neural system. This all human nerve model showed, for the first time, numerous aspects of peripheral nerve physiology including robust defined axonal outgrowth (~5 mm), evidence of human Schwann cell myelination of human iPSC-derived neurons, and evaluation of NCV testing in an in vitro system, similar to in vivo animal testing. This innovative HNoaC platform can be used to create a variety of nerves (motor, sensory etc.) in the future and has the potential to accelerate the field of human disease modeling, drug discovery, toxicity screening, and precision medicine.

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