Cancer-mediated Axonal Guidance of Sensory Neurons in a Microelectrode-based Innervation MPS
Despite recent advances in the field of microphysiological systems (MPS), availability of models capable of mimicking the interactions between the nervous system and innervated tissues is still limited. This represents a significant challenge in identifying the underlying processes of various pathological conditions, including neuropathic, cardiovascular and metabolic disorders. In this study, we introduce a compartmentalized 3D coculture system that enables physiologically relevant tissue innervation while recording neuronal excitability. By integrating custom microelectrode arrays into tailored glass chips microfabricated via selective laser-etching, we developed an entirely novel class of innervation MPSs (INV-MPS). This INV-MPS allows for manipulation, visualization, and electrophysiological analysis of individual axons innervating complex 3D tissues. Here, we focused on sensory innervation of 3D tumor tissue as a model case study since cancer-induced pain represents a major unmet medical need. The system was compared with existing nociception models and successfully replicated axonal chemoattraction mediated by nerve growth factor (NGF). Remarkably, in the absence of NGF, 3D cancer spheroids cocultured in the adjacent compartment induced sensory neurons to consistently cross the separating barrier and establish fine innervation. Moreover, we observed that crossing sensory fibers could be chemically excited by distal application of known pain-inducing agonists only when cocultured with cancer cells. To our knowledge, this is the first system showcasing morphological and electrophysiological analysis of 3D-innervated tumor tissue in vitro, paving the way for a plethora of studies into innervation-related diseases and improving our understanding of underlying pathophysiology. Significance StatementMPSs integrating innervated tissues are crucial as alternatives to animal models and to enhance the translation of non-clinical research to humans, as nerve fibers play a pivotal role in many organs. To address this need, we developed the INV-MPS, enabling parallelized electro-physiological recording from 3D cocultures of peripheral neurons with complex tissues. We demonstrate the ability of cancer spheroids to direct axonal growth and modulate excitability of nociceptive fibers in a 3D setting. We anticipate that this model will be applicable for closely monitoring innervation in various tissues, including somatic and visceral organs. The INV-MPS, hence, has tremendous potential for human-relevant drug discovery, creating opportunities for more ethical and clinically translatable approaches to study innervation in disease.