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Electron microscopic evaluation of guinea pig skin and soft tissues "expanded" with a self-inflating silicone implant.

An electron microscopic study of guinea pig skin and soft tissue after expansion by self-inflating silicone implant for periods of 7 weeks to 8 months revealed definite ultrastructural changes. In the epidermis, the cells of the malpighian layer contained larger groups of tonofilaments forming tonofibrils. Intercellular spaces in all layers of expanded epidermis were much more reduced than in normal epidermis. The basal lamina and the laminar surfaces of the basal cells demonstrated more undulation than those of the controls. The expanded dermis contained large bundles of compacted collagen fibers, as well as thin collagen fibers, active fibroblasts, and a few myofibroblasts. The subcutaneous tissue contained a paucity of adipose tissue and thickened collagen fibers in the interlobular spaces. The skeletal muscle showed larger amounts of sarcoplasm in relation to myofibrils. An increased number and size of mitochondria were found with sarcomeres abnormally arranged. The capsule around the implant was composed of active, elongated, and flattened fibroblasts and bundles of collagen fibers with variable fiber width. Intracellular collagen fibers were found in the cytoplasm of the fibroblasts. Myofibroblasts in the capsule were observed more often in early expanded tissue. Small blood vessels in the capsule showed multiplication of the basal lamina or were surrounded by a very wide, homogenous material. Inflammatory cells were not found in the capsule. Such findings are important in developing and evaluating future skin-expansion research in humans and animals.