Plastic Surgery Research Council
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PSRC 60th Annual Meeting
Program and Abstracts

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A Novel Peripheral Nerve Injury Model: Lab on a Chip
Jason Meierhenry, BA1, Yalda Toofan, BA1, David Boudreault, MD1,2, David Sahar, MD1,2, Aijun Wang, PhD1.
1Surgical Bioengineering Laboratory, Department of Surgery, UC Davis Medical Center, Sacramento, CA, USA, 2Division of Plastic Surgery, Department of Surgery, UC Davis Medical Center, Sacramento, CA, USA.

Purpose:
The purpose of this device is to create an in vitro microfluidics model to study the effects of electric stimulation on axon regeneration after peripheral nerve injury. Published in vitro studies in this field have presented inconclusive results regarding the effect of electric stimulation on the directional growth and rate of axon regeneration. In vivo studies have shown more consistent results; however, the use of animal models adds significant time, cost, and complications to the experiments over in vitro models. Our novel in vitro microfluidics model allows for more streamlined and efficient peripheral nerve injury experiments, while recreating the unidirectional poly-axonal structure seen in vivo.
Methods:
The PDMS (polydimethylsiloxane) device is fixed upon a glass substrate to be used as a microscope slide. The device consists of four microchannels in parallel (for running multiple trials), with each channel containing four different wells. The leftmost well is meant for the placement of a DRG (dorsal root ganglion), and neuron-growth medium. The wells are coated with poly-d-lysine and laminin, and the DRGs will adhere to the channel and sprout axons after plating. Once the axons have grown the entire length the channel, electrodes will be inserted into two of the remaining wells. A physical injury is induced to the axon by carefully placing a scalpel in the fourth well, and then an electric field of 1Hz will be applied for one hour. A potentiostat is used to regulate the strength and duration of the electric fields (Figure 1). The device is then placed upon an inverted microscope, and recording software is used with the microscope to compile a time-lapse video for measuring the rate of axon regeneration growth of the axon and measuring any directional biases of the axons. Throughout the experiment, transparent heating plates are used to maintain a constant temperature throughout the channel, and HEPES is used to control CO2 concentration (Figure 2).
Results:
Preference of nerve regeneration towards the cathode at 250mVolts over 6 hours, shown through time lapsed photography (Figure 3). Over time and higher voltage, axons regressed towards the DRG cell clump, further experiments showed death at 39°C (Figure 4). Our preliminary work shows promise and has helped us redesign our experimental model depicted (Figure2). A larger data series is being collected.
Conclusion:
The use of this model has significant implication for the study of peripheral nerves and would lead to novel therapies and a better understanding of nerve injury and regeneration. Electric fields show promise in guiding nerve regeneration, but heat must be controlled, as it plays a critical role. Our microfluidics model could also be used to measure the effect of other stimuli or insults to peripheral nerve.


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