Translating Neuronal Responses From 2D to 3D Microenvironments to Improve The Design of Biomaterials
Creators: name: Ribeiro, Andreia Sofia Gaifem
Publisher: name: Maryland Shared Open Access Repository
Year: 2011
Subjects: 3D microenvironments
Biomaterials
integrin signaling
nerve repair
neural stem cells
sensory neurons

description: The major goal of this work was to examine the dynamic interactions between neurons and three-dimensional (3D) matrices in order to determine the impact of environment dimensionality in neuronal morphological responses and signaling programs. Current strategies for the replacement of organs and tissues rely on the design of components that replicate 3D structure and physiology. While great strides have been made in the development of new biomaterials and neural stem/progenitor cell (NPC) biology, efforts focused on nerve repair have been limited by a poor understanding of how neurons interact with their 3D microenvironment. Tissue engineering has provided numerous 3D substrates that promote neuronal survival and process outgrowth; however, intrinsic neuronal morphologies and the mechanisms regulating neuronal responses to biomaterials are generally overlooked. Therefore, in order to develop physiologically relevant cell culture environments and to ultimately engineer improved models for nerve repair applications, the overall goal of this work was to develop a deeper knowledge of the dynamic three-dimensional interactions between neurons and their extracellular milieu therefore eliciting the mechanisms that regulate neuronal behavior in 3D microenvironments. In this dissertation, we report that a 3D culture platform can invoke the characteristic transformation to the unipolar axonal arbor suffered by sensory neurons within a time frame similar to in vivo, overcoming the loss of this essential milestone in 2D substrates. Additionally, 3D substrates alone provided an environment that promoted growth cone and axonal branching features that reflect morphological patterns observed in vivo. We also demonstrate that microenvironment dimensionality plays a major role in sensory neuron development and regulation of signaling events controlling branching, polarization and outgrowth. We report &amp;beta1-integrin as a key mediator of morphogenic programs in sensory neurons cultured in 3D and in response to the interaction with a surrounding 3D matrix neurons alter &amp;beta1-integrin signaling transduction to the cytoskeleton.   All these differences summed together suggest the need for caution when applying conclusions from planar neuronal cell culture to in vivo 3D matrix signaling functions. Lastly, we present a promising strategy to pre-condition NPCs within a novel, hydrolytically degradable hydrogel scaffold based on cross-linked poly(ethylene glycol). This system offers the possibility of optimizing an array of gel bioactive and physical properties which may prove advantageous for future optimization of these scaffolds for specific clinical neurotransplantation applications. This work is major step forward in the understanding of key parameters that guide neuronal development and nerve regeneration and has the potential to lead in the development of novel and improved strategies to treat nerve injuries and neurodegenerative disorders.