METHODS; EGF-F9 was prepared from cDNA of a mouse F9 deletion mutant and AP-tag 4 vector. This study used 8 male 7-week-old Sprague Dawley rats. A 2-cm incision was made at 2 places on the back of the rat to create a subcutaneous pocket. A 2 × 2 cm implant made from a smooth type tissue expander was inserted into the pocket. A control group (untreated) (n = 8) and a treated group (n = 8) were prepared. In the control group, 0.1 ml of phosphate buffered saline (PBS) was instilled into one pocket and 50 pM/0.1 ml of EGF-F9 was instilled into the other pocket. In both groups, PBS or EGF-F9 was injected into subcutaneous tissue overlying the implant three times a week. Tissue was collected on day 28 after surgery, and the thickness of the capsule was measured and histologically examined.
RESULTS: The mean thickness of the capsule in the control group and treated group was 95.3±47.8 μm and 48.1±12.8 μm, respectively. The capsule was significantly thinner in the treated group (p<0.05). In immunostaining, matrix metalloproteinase 9 (MMP 9) showed increased expression in the treated group and alpha smooth muscle actin (ASMA) showed increased expression in the control group.
CONCLUSIONS: The administration of EGF-F9 inhibited the formation of a capsule around the silicone implant. EGF is involved in the control of MMP expression and differentiation into myofibroblasts. It was suggested that administration of EGF-F9 suppressed the formation of the capsule by increasing local MMP 9 and regulating differentiation into myofibroblasts.