Plastic Surgery Research Council
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Presenter: Stephanie D Malliaris, MD
Co-Authors: Brazin J; Groh B; Otterburn DM; Hidalgo D; Mehrara BJ; Silver RB; Spector JA
New York Presbyterian Hospital

BACKGROUND: Capsular contracture occurs after 5-15% of primary breast augmentations and 19-67% of prosthetic breast reconstruction. Despite this frequency, the etiology remains poorly understood. Mast cells, traditionally associated with immune response and inflammation, have been linked by our lab and others to pathologic fibrosis in kidney and lung especially with regard to the release of mast cell renin and local formation of profibrotic ANG II. We analyzed the mast cell population in breast capsular tissue.

METHODS: Tissue was collected from patients undergoing implant exchange or revision. Chart review provided implant duration/indication and the Baker class. Specimens were fixed and stained for mast cells and fibroblasts. Fresh specimens were used to measure collagen content and to isolate mast cells for analysis of lysates for ANG I forming activity.

RESULTS: Mast cells were visualized in sections of capsule tissue by staining with tryptase and heparin antibodies. The average number of mast cells per section was 91 mast cells/mm2 (n=22); however the distribution within tissue varied. Significantly more mast cells were found in the posterior capsule than the anterior (61 vs 122,p<0.01). Fibroblasts were abundant in the capsule averaging 3310 fibroblasts/mm2 (n=22) and distribution within tissue was constant. Capsule collagen content measured with picrosirius red dye was 1259200 ?g/g tissue (n=10). Capsular mast cells immuno-express renin, the rate-limiting enzyme in the renin-ANG II cascade. The mast cell renin is active, having ANG I forming activity. Mast cells were also found in close proximity to fibroblasts expressing the ANG II AT1 receptor subtype.

CONCLUSIONS: These are the first data to quantify the presence of mast cells in breast capsular tissue and suggest mast cells play an important role in pathologic peri-prosthetic capsule formation by secreting profibrotic mediators in close proximity to fibroblasts. A more thorough understanding of the mast cell role in the formation of peri-prosthetic capsule formation may lead to novel therapies to prevent and treat capsular contracture.

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