Restoring the Mechanosensation in Engineered Skin using Controllable Cellular and Extracellular Cues

Mechanosensation is essential for perceiving the external world and social exchange. The skin is our largest sensory organ and is densely populated with nerve endings responsible for senses, such as touch, pain, pressure, and vibration. The long-term goal of this project is to integrate sensory neurons into bioengineered 3D skin constructs (BESCs) to enable studying skin mechanosensation and regeneration using human cells. The growth, location, and type of sensory neurons in BESCs will be controlled by locally providing specialized proteins secreted by specific cell types of the skin, as well as through localized electrical stimulation. This project will make a positive societal impact in the long term by 1) providing a physiologically-relevant in vitro model to a broader research community to study the innervation dynamics of sensory neurons during development and wound healing; and 2) evaluating the efficacy/toxicity of drug candidates using human cells. In addition, this project will contribute to STEM education and workforce development by providing research training and professional opportunities for students at all levels and will significantly benefit students pursuing a career in the fields of biomaterials, tissue engineering, and neuroscience. Training activities include: a 4-week summer boot camp for graduate student training; a graduate-level course; a Vertically Integrated Program (VIP) to integrate undergraduate research; a 2-week summer research experience involving K-12 students; and a 2-day-long virtual summer symposium for training young researchers.The molecular and cellular mechanisms underlying the specific types of mechanosensation are well-characterized. Yet, there is limited knowledge about what determines and instructs the branching patterns and proper innervation of somatosensory neurons (SSN) and sensory end-organs in the skin to mediate mechanosensation. The goal of this project is to induce and control the level of innervation in engineered skin through spatially-controlled microenvironmental cues, including 3D-patterned dermal extracellular matrix (ECM) conduits, follicular epidermal signals (e.g., hair follicles), and Schwann cells (SCs) differentiated via wireless electrical stimulation in defined patterns. Studies in Goal 1 will identify the ECM molecules that promote or prevent SSN outgrowth and employ the identified attractive/repulsive ECM cues in BESCs to guide the nerve endings to their final destination. Studies in Goal 2 will use a hair-bearing BESC model and determine the preferential innervation of the follicular (hairy) and interfollicular (non-hairy) epidermis by different subtypes of SSNs. Studies in Goal 3 will leverage electrical differentiation approaches to spatially control the Schwann cell fate commitment in the 3D dermis to regulate local myelination and function of SSNs. The key intellectual merit of this project for biomedical sciences is to decipher the individual effects of cellular and extracellular cues on the innervation and pattern formation of sensory neurons in the context of a 3D skin microenvironment using human cells. This study will also contribute to engineering by addressing a prevailing tissue engineering challenge of controlling innervation in 3D skin models. The cue-driven strategy involving environmental guidance signals and integrated wireless electrical biointerfaces can further be adapted for spatially-controlled innervation and engineering of other organs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.