Peptide growth factors and myofibroblasts in capsules around human breast implants

Peptide growth factors were mapped immunohistochemically for assessment of their presumed relation to the cells in capsules enveloping gel-filled, smooth-surfaced silicone mammary implants (12 capsules from 11 women). The implant capsules were dominated by fibroblast-like cells, but there were as well macrophages, inflammatory cells, and vascular cells. These cells expressed immunoreactivity for TGF-beta, IGF-II, IGF-I, and, to a lesser extent, PDGFB, NGF, and TNF-alpha. The numerous spindle-shaped cells in the contracted capsules displayed several distinct cytoplasmic actin bundles and fulfilled ultrastructural criteria for myofibroblasts. In contrast, myofibroblasts were recognized in low frequencies in the noncontracted capsules. Mature skin scar tissue did not show any peptide growth factor immunoreactivity, and myofibroblasts were absent. It is postulated that the low-grade chronic inflammatory foreign-body reaction, aggravated by mechanical stress and possible leakage of irritants, stimulates capsule cells to form peptide growth factors, reflecting that extended healing processes prevail in both noncontracted and contracted capsules. We propose that the local enrichment of peptide growth factors, beneficial for acute wound healing, in the chronically irritated tissue around implants provides trophic support for the contractile cells in the implant capsules.