Traumatic injury to the spinal cord often results in irreversible loss of function as the central nervous system fails to spontaneously regenerate. The application of molecular and topographical guidance cues has been shown to direct neurite growth. Biomaterial platforms incorporating chemotropic, topographic and physical cues allow the investigation of how neurons integrate complex guidance information to make growth decisions.

Microfluidic and micropatterning methods described provide a valuable tool towards fabricating these in vitro platforms. Adsorbed laminin (LN) and chondroitin sulfate proteoglycan (CSPG) gradients demonstrate that neurites extend toward regions of lower CSPG and higher LN concentrations. When the two contrasting cues were presented together, neurites responded differently depending on the directions of the gradients. The methods of circular statistical analysis that have been developed allow more accurate evaluation of neurite directional data.

A three-dimensional approach to studying guidance cues was applied to biological matrices to identify the mechanisms involved in the regulation of neurite outgrowth. By comparing gene expression of neuroblastoma cells cultured in collagen or Matrigel, genomic profiles were screened using DNA microarrays. Selected genes were further evaluated by reverse-transcriptase polymerase chain reaction. Complex cell–material interactions were observed in 3D, where the dimension of the culture material influenced gene expression and cell spreading, while the structural and mechanical properties of the culture material influenced gene expression and neurite outgrowth.

Growth and morphology of Schwann cell (SC) cultures on microgrooved topography were also studied. The dynamics of SC bridging was observed and analyzed under timelapse microscopy. Highly motile SCs were observed and trajectories included a climbing phase and a stabilization phase. Combining molecular and topographical guidance information by selectively coating LN on microgrooves showed that protein coating of walls and grooves was essential for SC bridging. The combination of LN and topography yielded a synergistic effect between the guidance cues.

The platforms and studies described herein allow us to investigate interactions between neurons, glia and their microenvironment and to understand the molecular basis for these interactions that regulate neurite outgrowth.