Regulation of matrix metalloproteinase-2 and-9 during healing of dermal wounds after incision using radiofrequency energy in neonatal and adult rats

Background: Radiofrequency energy (RFE) has many medical applications in the treatment of adults and children. The impact of RFE on healing-regulation systems in the developing tissues is not fully known. Matrix metalloproteinases (MMPs) are involved in the remodeling of the extracellular matrix and the inflammatory processes. MMPs are regulated differently among the different age groups. We evaluated possible changes in MMP activity after an incisional wound using a radiofrequency scalpel in neonatal and adult rats. Methods: In 30 Wistar rats [15 4-day-old (neonates) and 15 4-month-old (adults) rats], a ventral wound was created using a radiofrequency scalpel. Wounded areas and non-wounded tissues were harvested one, three and seven days after the intervention. Enzymatic activities of MMP-2 and MMP-9 were evaluated using gelatin zymography. Results: Adults expressed higher activity than neonates for MMP-2 on day 7 (Mann -Whitney U-test, p=0.009) and for MMP-9 on days one (p=1005) and three (p=0.005). MMP-9 was expressed in higher amounts in the wounded tissue in comparison with non-wounded tissue during days one and three (Wilcoxon signed rank test, p=0.028 and p=1043, respectively). MMP-2 was produced in equal amounts in the wounded and non-wounded tissue at all time-points. Only in the adult wounds at day seven, higher activity was noted compared with non-wounded skin (Wilcoxon signed rank test, p=3.043). Conclusions: RFE, despite its local burning effect, does not interfere with known patterns of MMP regulation. Neonates have lower activity of MMPs than adults. Energy conduction through adjacent non-wounded tissues does not have an impact upon MMP regulation.