Competitive Guidance Cues Affect Fibroblast Cell Alignment: Electric Fields vs. Contact Guidance
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Competitive Guidance Cues Affect Fibroblast Cell Alignment: Electric Fields vs. Contact Guidance
Iain R. Gibson and Colin D. McCaig School of Medical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD, UK. ABSTRACT When bovine ligament fibroblast cells were cultured on parallel micro-grooved surfaces, they aligned their long axes parallel to the groove direction. This alignment was dependent on the groove depth, with increasing groove depth increasing guided cell alignment. When cells were cultured in a physiological dc electric field (EF) on non-grooved, flat surfaces, the cells aligned in response to the EF, with their long axes perpendicular to the EF vector. This response was EF strength dependent, increasing EF strength (from 20 to 200mV/mm) increased cell alignment, perpendicular to the EF vector. These two guidance cues were applied simultaneously, so that the EF vector was parallel to the groove direction. At high but still physiological EF strengths (200mV/mm) cells ignored the topography and were guided by the EF alone, aligning perpendicular to the EF vector, as on non-grooved surfaces. At low field strengths (20mV/mm) cells responded only to the topographic guidance cue, with cells aligning parallel to the grooves and therefore also to the EF vector. Intermediate field strengths (50 to 100mV/mm) produced a mixed response, with cells responding to both guidance cues. The effect of removing serum from the culture medium on the EF and topographical guidance of fibroblast cells was studied and the results were compared to cells on non-grooved surfaces. Removal of serum produced a small but significant decrease in the angle of cell alignment for cells on nongrooved surfaces, from 78 to 63 degrees, relative to the EF vector, but did not completely suppress the EF guidance cue. In contrast, the EF guidance of cells on grooved substrates was suppressed almost completely by the absence of serum, with cells responding only to the grooved topography, aligning their long axis parallel to the grooves and the EF vector. These results imply that alignment of fibroblasts by topography is serum-independent, but alignment by EFs is serum-dependent. In addition they demonstrate that the alignment of fibroblast cells can be tailored by the dual guidance cues of topography and electric fields.
INTRODUCTION The morphology of fibroblasts can be directed by various guidance cues. The control of cell alignment is important in the design of tissue-engineered implants to replace tendons and ligaments, which naturally exhibit alignment of cells in parallel to collagen fibres. Of the various guidance cues, contact guidance, whereby cells respond to nano- and micro-scale topography, has been studied most extensively [1,2], and is possibly the most relevant to tissue engineering. In general, cells become highly oriented along grooves with widths between 1 and 10 µm. There is some disagreement, however, as to whether groove depth is the most significant factor in guiding cell al
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