Abstract
Abstract: :
Purpose: Understanding how biomaterials may modulate neural cell behavior has relevance to the rational design of ocular prosthetics, evolving strategies in tissue engineering as well as to the interpretation of results from in vitro investigations. Contact guidance of neurites by topographic features is well known, but the role that topography plays in the modulation of neuritogenesis has not been addressed. To determine whether the scale of topographic features affects neurite formation by PC12 cells, we examined neuritogenesis under a range of culture conditions.Methods: X–ray lithography was used to pattern silicon wafers with six 2x2 mm areas with grooves and ridges ranging in pitch (groove width + ridge width) from 400nm to 4µm. PC12 cells were cultured with nerve growth factor (NGF) concentrations of 50, 25 or 5ng/ml for three days and then scored for neurite formation. Neurites were defined as process extensions of greater than one cell body diameter in length. Significance was determined by Χ–squared distribution tests. Results: Rates of neurite formation by PC12 cells cultured in 50ng/ml NGF was the similar regardless of feature size. NGF concentrations of 25 and 5ng/ml resulted in a decrease in overall neurite formation when compared to 50ng/ml. However, the resulting distribution of neuritogenesis among patterns of varying feature sizes was not random. Rather, cells show a biphasic response to topographic features where feature sizes ≤ 1200nm pitch augmented neuritogenesis and feature sizes ≥ 2,000nm pitch suppressed neuritogenesis compared to cells grown on flat surfaces. The transition occurred at 1600nm pitch, where neurite formation was similar to that on flat surfaces. Surprisingly, the greatest impact of topography was observed at 5ng/ml NGF suggesting that the influence of topography is greatest under culture conditions that are marginal for cell survival and neurite formation. Conclusions: These results show that the scale of topographic features can modulate neuritogenesis and suggest that surface topography should be considered in the design of ocular prosthetics. EY012253–05
Keywords: signal transduction • neuro–ophthalmology: cortical function/rehabilitation • wound healing