The Microphysiological Systems (MPS) World Summit 2023 took place from June 26 to 30, 2023, at the JW Marriott Hotel in Berlin, Germany. This premier event brought together academic researchers, industry professionals, and regulatory agencies to discuss the latest developments in MPS technology. The summit featured keynote presentations, scientific sessions, workshops, and networking opportunities, fostering collaboration and innovation in the field.
J. Lowry Curley1, Megan Terral1, Corey Rountree1, Eva Schmidt1, Monica Metea1, 2, Benjamin Cappiello1, and Michael J. Moore 1, 3
1 AxoSim Inc., New Orleans, LA, USA
2 PCE Consults, Boston, MA, USA
3 Department of Biomedical Engineering, Tulane University, New Orleans, LA, USA
Toxicity is a leading reason drugs are withdrawn from the market, with neurotoxicity responsible for 16%. Peripheral nerves (PNs) are particularly susceptible to off-target effects resulting in permanent sensory-motor deficits, and chemotherapy-induced peripheral neuropathy (CIPN) occurs with a 68% incidence rate and 30% retaining effects after 6 months. CIPN can also affect clinical outcomes, with 91% of cases leading to dose reduction and a 45% discontinuation rate. Preclinical animal models are historically expensive and low-throughput and have largely failed to deliver results that translate to success in the clinic. PNs, in particular, lack predictive human-relevant in vitro drug screening models, with less than 7% of neurological drug candidates reaching the marketplace. Microphysiological systems (MPS), including organs-on-chips, utilizing human induced pluripotent stem cell (iPSC)-derived cells to emulate specific organ systems, have emerged as promising screening platforms to bridge the gap between preclinical and clinical success.
Engineering 3D tissues relevant to the nervous system, particularly PNs, is challenging because of the complex ultrastructure and necessity of functional outputs. AxoSim has developed an all-human NerveSim® MPS, with human iPSC-derived sensory neurons and primary human Schwann cells for screening neurotoxic compounds using an embedded electrode array (EEA) to record compound action potentials (CAPs) from PNs cultures. The efficacy of this system was demonstrated by recording cultures exposed to Paclitaxel (PTX).
NerveSim® EEA cultures were stimulated in parallel at multiple distal sites with a stimulation current ramp while recording the CAPs at the cell body and axons. From these data, we collected conduction velocity (CV), peak response amplitude (AMP), and threshold stimulus strength (TSS). Histopathology shows phenotypic responses of peripheral neuropathy including decreased fiber densities and increased degenerated fibers. The ability to collect clinically relevant data is an effective tool for in vitro modeling of CIPN towards screening of therapeutics for neuroprotection and neuroregeneration. Current efforts are focused first on increasing the number of myelinated nerve fibers in the NerveSim® sample, and second, on quantifying the effects of well-known demyelinating compounds, such as Cuprizone, to further establish the efficacy of NerveSim® as a drug screening platform.
Microphysiological systems (MPS) have the potential to better inform preclinical stages of drug development by enabling toxicity screening with systems mimicking in vivo physiology. These systems are attracting attention from the pharmaceutical industry in hopes they will curb attrition rates, lower costs, and reduce reliance on animal models. AxoSim has developed an innovative MPS, NerveSim®, for screening neurotoxic compounds using an embedded electrode array (EEA) to record compound action potentials (CAPs) from peripheral nerve cultures. Bridging the gap between in vitro and in vivo, NerveSim® measures clinically relevant electrophysiological metrics using custom, automated hardware, and software.
The NerveSim® EEA platform is a custom 24-well tissue culture plate with an integrated circuit board for high-throughput electrophysiological recordings. Each well contains a cell-restrictive outer layer and a growth-permissive inner gel that guides axonal growth into a 3D nerve-like bundle. At the bottom of the inner gel are a series of microelectrodes that are used for recording or stimulation. Dissociated rat dorsal root ganglion (DRG) spheroids were cultured for four weeks to ensure growth along the EEA. A baseline electrophysiological recording was obtained four weeks before the cultures were exposed to multiple doses of Paclitaxel for seven days. After dosing, we recorded electrophysiology again to observe deviations from baseline caused by drug treatment.
Multiple NerveSim® EEA cultures were stimulated in parallel at distal sites with both a stimulation current and frequency ramp while recording the CAPs at the DRG body and axons. From these data, we collected the conduction velocity (CV), peak response amplitude (AMP), and threshold stimulus strength (TSS). Dosing with higher concentrations of PTX resulted in slower CV, lower AMP, and higher TSS compared to the vehicle control, consistent with peripheral neuropathy. Higher PTX concentrations had reduced when stimulated at distal location, confirming the axonal degeneration expected with high dose PTX. Stimulation current ramp allowed differentiation of the responses of C fiber subtypes based on the presence of activity-dependent slowing (ADS). Fluorescent microscopy confirmed that robust axonal growth was present for lower doses, suggesting that this system can detect subtle pathological changes in electrophysiology that occur before reductions in cell viability.
Lise Harbom1, Megan Terral1, Wesley Anderson1, and Michael J. Moore 1, 2, and J. Lowry Curley1
1 AxoSim Inc., New Orleans, LA, USA
2 Department of Biomedical Engineering, Tulane University, New Orleans, LA, USA
The translational gap between success in the lab versus success in clinical trials is an especially prevalent problem in neurological disease treatment, highlighting the need for novel model systems that allow drug testing in a human setting prior to patient exposure. Microphysiological systems containing human iPSC-derived cell lines provide this opportunity; however, it is important to ensure that these systems are comprised of cell types that accurately mimic an in vivo setting. In the central nervous system (CNS), glial cells, including astrocytes and oligodendrocytes, are integral to many aspects of neuronal function and can also be involved in neurological disease manifestation. To generate human BrainSim®, iPSC-derived neural stem cells (NSCs) are exposed to a variety of growth factors over a 12-week differentiation period. We tested a variety of media types to determine the optimal conditions for enhancing glial differentiation. By using qPCR, Western blot, immunohistochemistry (IHC), and other endpoints, we have generated compelling evidence that at 12 weeks of age, BrainSim® cultured under different media types consists not only of NSCs and neurons, but also astrocytes, oligodendrocyte precursor cells (OPCs), and oligodendrocytes with variable expression based on the media type. The appearance of markers such as GFAP, PDGFRα, and Olig2 make it possible to track the emergence of these cell types at 6 time points over the 12-week period. In the future, this will enable the testing of pharmaceutical drugs for their effects on glial development, proliferation, and differentiation, and due to the richer cellular landscape, allow for more thorough investigation of neuroprotective and neuroregenerative targets.
