Competitive Guidance Cues Affect Fibroblast Cell Alignment: Electric Fields vs. Contact Guidance

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.

Cell Orientation by a Microgrooved Substrate Can Be Predicted by Automatic Control Theory

“…The predicted angle-dependence as well as the predicted addition of normalized guiding signals (Eq. C8) is verified for fibroblasts exposed to electric field and grooved surfaces (data from (33)). For single cues one gets K hL ¼ 12 and K E ¼ 0.025 mm/mV.…”

“…The signal strength characteristics, g(signal), predicted by the symmetry properties of the system, is the square of the cellular input signals: (hL) 2 , a strong indication that the symmetries are fulfilled. The measured general guiding coefficient K hL G is 24 for melanocytes and 12 for fibroblasts (33). Both cell types have a comparable cell size but the coefficient differs significantly.…”

Conducting Polymer-Based Multilayer Films for Instructive Biomaterial Coatings

“…We observed that HDFs displayed a moderate preference for aligning with the direction in which the slides were dipped during the dip coating process (Figures 3B & 4). Cells without any preferential alignment would be expected to have an average orientation of 45° (Figures 3B & 4 & Supplementary Figure 2); however, we saw that HDFs on PEDOT-PSS-based multilayer films had an average orientation of 38.6° ± 1.5° (Figure 4A & E), whereas HDFs on PEDOT-S-based multilayer films had an average orientation of 35.3° ± 1.8° (Figure 4B & E), which is likely to be because the polymer chains were aligned during the dip coating process as is commonly observed for multilayer films prepared in this fashion [34], and fibroblasts are known to respond to features on such length scales [35,36]. Interestingly, electrical stimulation of HDFs on the conductive substrates led to an increase in their propensity to align with the direction of the DC current passed through the substrate (akin to their behavior when a DC current is passed through the culture medium) [37], and we found that HDFs on PEDOT-PSS-based multilayer films had an average orientation of 27.7° ± 1.7° (Figure 4C & E), whereas HDFs on PEDOT-S-based multilayer films had an average orientation of 32.1° ± 1.1° (Figure 4C & E).…”

Electric field stimulation for tissue engineering applications

“…To assist cell adhesion, surfaces used as channels for cell seeding are often coated with ECM proteins (e.g. laminin, fibronectin, collagen) [65][66][67][68][69][70] and to improve cell motility and alignment, microgrooves are etched onto glass / quartz slides [71][72][73].…”