Silicone Implants with Smooth Surfaces Induce Thinner but Denser Fibrotic Capsules Compared to Those with Textured Surfaces in a Rodent Model

Purpose Capsular contracture is the most frequent long-term complication after implant-based breast reconstruction or augmentation. The aim of this study was to evaluate the impact of implant surface properties on fibrotic capsule formation in an animal model. Materials and Methods Twenty-four rats received 1 scaled down silicone implant each; 12 of the rats received implants with textured surfaces, and the other 12 received implants with smooth surfaces. After 60 and 120 days, rats in each group underwent 7-Tesla Magnetic Resonance Imaging (MRI) and high-resolution ultrasound (HR-US), and specimens of the capsules were acquired and used to measure capsule thickness through histology, collagen density through picro sirius red staining, and analyses of expression of pro-fibrotic and inflammatory genes (Collagen1-4, TGFb1, TGFb3, Smad3, IL4, IL10, IL13, CD68) through qRT-PCR. Furthermore, MRI data were processed to obtain capsule volume and implant surface area. Results: On day 60, histology and HR-US showed that fibrotic capsules were significantly thicker in the textured implant group with respect to the smooth implant group (p<0.05). However, this difference did not persist on day 120 (p=0.56). Capsule thickness decreased significantly over the study period in both smooth and textured implant groups (p<0.05). Thickness measurements were substantiated by MRI analysis and volumes changed accordingly. Implant surface area did not vary between study dates, but it was different between implant types. On day 60, the density of collagen in the fibrotic capsules was significantly lower in the textured implant group with respect to the smooth group (p<0.05), but again this difference did not persist on day 120 (p=0.67). Collagen 1 and CD68 were respectively over- and under expressed in the textured implant group on day 60. Significant differences in the expression of other genes were not observed. Conclusion: Silicone implants with textured surfaces led to temporarily thicker but less dense fibrotic capsules compared with smooth surfaces. 7-Tesla MRI and HR-US are capable for non-invasive in-vivo assessment of capsular fibrosis in an animal model and can provide unique insights into the fibrotic process by 3D reconstruction and surface area measurement

Mean (+/- standard deviation) capsule volume in MRI of each study group.

<p>Results were not statistically significant.</p

Example pictures of picrosirius red staining under polarized light of both study groups on day 60.

<p>Example pictures of picrosirius red staining under polarized light of both study groups on day 60.</p

Example pictures of MR images for volumetric measurements.

<p>From top to bottom: Blank slides, complete capsule volume (green), implant volume (red) and complete minus implant volume (green margin). Volume calculations were performed via VOLUMEST and the scale was adjusted automatically by the software.</p

Mean (+/- standard deviation) capsule thickness in MRI of each study group.

<p>Results were not statistically significant.</p

Mean (+/- standard deviation) capsule thickness measurements in histology sections of each study group.

<p>P<0.05 and p<0.005 were considered statistically significant and highly significant.</p

Results of quantitative real time PCR for Collagen 1 (upper left), 2 (upper right), 3 (lower left) and 4 (lower right) given in fold change compared to textured implant group of day 60 or 120, respectively.

<p>Asterisks and brackets indicate statistical significance and P<0.05 was considered statistically significant.</p

Results of quantitative real time PCR for IL10, IL4, IL13, TGFb-1, TGFb-3 and Smad3 given in delta Ct (Ct gene—Ct housekeeping gene) for each study group and illustrated as heat map (Distance measure: Pearson’s Correlation; Clustering Method: Ave Linkage; Map Type: Global delta CT; Ct > 40,000 = not determined).

<p>Increasing positive or negative delta CT values are given in brighter green or red colors, respectively. Black indicates that either the gene is not expressed or is below the limit of detection.</p

3D reconstruction of 7-Tesla MRI scans of smooth implants on day 60 (60s, upper left), textured implants on day 60 (60t, upper right), smooth implants on day 120 (120s, lower left) and textured implants on day 120 (120t, lower right).

<p>3D reconstruction of 7-Tesla MRI scans of smooth implants on day 60 (60s, upper left), textured implants on day 60 (60t, upper right), smooth implants on day 120 (120s, lower left) and textured implants on day 120 (120t, lower right).</p