Regional-Controlled Tissue Expanders Increase Skin Expansion and Thickness Compared to Standard Tissue Expanders in a Rat Model

Background: Skin and soft-tissue expansion are widely used. However, the existing methods cannot expand targeted areas on the top flap. Thus, the authors developed a new expander with a partially thickened top. The authors hypothesized that pressure differences would lead to higher growth near nonthickened regions and lower growth near thickened regions, allowing targeted expansion. Methods: Eighteen male Sprague Dawley rats (8 weeks old) were used; 20-ml rectangular regional-controlled expanders (n = 12) and ordinary expanders (n = 6) were implanted. Flaps on regional-controlled expanders were divided into nonthickened and thickened regions and tattooed. Discontinuous inflation began 14 days postoperatively, 3 ml every 3 days, until the volume reached 50 ml. Tattooed skin area and thickness were measured. Immunofluorescence staining detected cell proliferation (proliferating cell nuclear antigen-positive) and vascular density (CD31(+)). Growth factors (transforming growth factor-beta, epidermal growth factor, vascular endothelial growth factor, and basic fibroblast growth factor) were assessed by enzyme-linked immunosorbent assay. Results: The expanded skin area of regional-controlled expansion nonthickened regions (396.2 +/- 41.4 mm(2)) was 33.8 +/- 10.0 percent larger than that of thickened regions (297.8 +/- 38.9 mm(2)). Thickened regions had a 28.9 +/- 14.6 percent thicker dermal layer (942.4 +/- 55.5 mu m) than nonthickened regions (737.1 +/- 64.5 mu m). Nonthickened regions had 295.0 +/- 145.0 percent more proliferating cell nuclear antigen-positive cells (92.4 +/- 16.2/mm(2)) than thickened regions (25.6 +/- 7.4/mm(2)). The vascular density was 133.0 +/- 61.7 percent higher in thickened regions (24.8 +/- 4.7/mm(2)) than in nonthickened regions (11.1 +/- 2.7/mm(2)) (all above, p < 0.05). Conclusions: Regional-controlled expansion specifically expands only the targeted area, causing thicker skin flaps with abundant vessels for defect repair. Although this technique has great clinical potential, it should be further validated with large animals and humans. Clinical Relevance Statement: This study presents the newly developed regional-controlled expansion technique that realized the targeted expansion. It is suitable for repairing defects and would contribute to shortening the expansion process and reducing complication rates.