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Photopolymerized micropatterns with high feature frequencies overcome chemorepulsive borders to direct neurite growth.

ABSTRACT: Developing and regenerating neurites respond to a variety of biophysical and biochemical cues in their micro-environment to reach target cells and establish appropriate synapses. Defining the hierarchal relationship of both types of cues to direct neurite growth carries broad significance for neural development, regeneration, and, in particular, engineering of neural prostheses that improve tissue integration with native neural networks. In this work, chemorepulsive biochemical borders are established on substrates with a range of surface microfeatures to determine the potential of physical cues to overcome conflicting biochemical cues. Physical micropatterns are fabricated using photomasking techniques to spatially control photoinitiation events of the polymerization. Temporal control of the reaction allows for generation of microfeatures with the same amplitude across a range of feature frequencies or periodicities. The micropatterned substrates are then modified with repulsive chemical borders between laminin and either EphA4-Fc or tenascin C that compete with the surface microfeatures to direct neurite growth. Behaviour of neurites from spiral ganglion and trigeminal neurons is characterized at biochemical borders as cross, turn, stop, or repel events. Both the chemical borders and physical patterns significantly influence neurite pathfinding. On unpatterned surfaces, most neurites that originate on laminin are deterred by the border with tenascin C or EphA4-Fc. Importantly, substrates with frequent micropattern features overcome the influence of the chemorepulsive border to dominate neurite trajectory. Designing prosthesis interfaces with appropriate surface features may allow for spatially organized neurite outgrowth in vivo even in the presence of conflicting biochemical cues in native target tissues.

SUBMITTER: Tuft BW

PROVIDER: S-EPMC5787405 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Photopolymerized micropatterns with high feature frequencies overcome chemorepulsive borders to direct neurite growth.

Tuft Bradley W BW Xu Linjing L Leigh Braden B Lee Daniel D Guymon C Allan CA Hansen Marlan R MR

Journal of tissue engineering and regenerative medicine 20171123 3

Developing and regenerating neurites respond to a variety of biophysical and biochemical cues in their micro-environment to reach target cells and establish appropriate synapses. Defining the hierarchal relationship of both types of cues to direct neurite growth carries broad significance for neural development, regeneration, and, in particular, engineering of neural prostheses that improve tissue integration with native neural networks. In this work, chemorepulsive biochemical borders are estab ...[more]

PMID: 28753740

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Project description:Overcoming signal resolution barriers of neural prostheses, such as the commercially available cochlear impant (CI) or the developing retinal implant, will likely require spatial control of regenerative neural elements. To rationally design materials that direct nerve growth, it is first necessary to determine pathfinding behavior of de novo neurite growth from prosthesis-relevant cells such as spiral ganglion neurons (SGNs) in the inner ear. Accordingly, in this work, repeating 90° turns were fabricated as multidirectional micropatterns to determine SGN neurite turning capability and pathfinding. Unidirectional micropatterns and unpatterned substrates are used as comparisons. Spiral ganglion Schwann cell alignment (SGSC) is also examined on each surface type. Micropatterns are fabricated using the spatial reaction control inherent to photopolymerization with photomasks that have either parallel line spacing gratings for unidirectional patterns or repeating 90° angle steps for multidirectional patterns. Feature depth is controlled by modulating UV exposure time by shuttering the light source at given time increments. Substrate topography is characterized by white light interferometry and scanning electron microscopy (SEM). Both pattern types exhibit features that are 25 μm in width and 7.4 ± 0.7 μm in depth. SGN neurites orient randomly on unpatterned photopolymer controls, align and consistently track unidirectional patterns, and are substantially influenced by, but do not consistently track, multidirectional turning cues. Neurite lengths are 20% shorter on multidirectional substrates compared to unidirectional patterns while neurite branching and microfeature crossing events are significantly higher. For both pattern types, the majority of the neurite length is located in depressed surface features. Developing methods to understand neural pathfinding and to guide de novo neurite growth to specific stimulatory elements will enable design of innovative biomaterials that improve functional outcomes of devices that interface with the nervous system.

Dataset Information

Photopolymerized micropatterns with high feature frequencies overcome chemorepulsive borders to direct neurite growth.

Publications

Photopolymerized micropatterns with high feature frequencies overcome chemorepulsive borders to direct neurite growth.

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