Objective: To compare the impact of different methods of ablation, i.e. cryotherapy,argon plasma coagulation (APC) and radiofrequency, when applied to the skin of rats, on the systemic inflammatory response and local tissue damage.
Methods: Forty-eight healthy male SD rats were randomly divided into 4 groups: cryotherapy, APC, radiofrequency, and sham procedure. Cryotherapy, APC and catheter ablation were applied to the skin of the rats in the 3 groups respectively, while the sham-operated animals underwent shaving only. The animals were assessed after 1,3,5,7, and 28 days. The serum level of TNF-α was measured. TGF-β1 positive cells in the skin and the thickness of the scar tissue were assessed at the corresponding times, while HE-stained sections collected on the 5th day were examined.
Results: When the levels of serum TNF-α were compared after 24h, there were no significant differences among the cryotherapy, APC, and radiofrequency groups(cryotherapy and APC, cryotherapy and radiofrequency, APC and radiofrequency, t values were 0.23, 0.22, and 1.53, respectively, all P>0.05), but the levels in each of these 3 groups were significantly higher than that in the sham-operated group ( t values were -4.83, -4.63, and -3.24, respectively, all P<0.05). When the levels of TNF-α were compared after 7d, the cryotherapy group showed the highest (146 ± 8 ng/L), significantly higher than that in the sham-operated group (t value 3.88, P<0.05). The multiplication values of the average optical density and TGF-β1 positive cells in the rat skin among the radiofrequency (105.3 ± 16.4), APC(58.8 ± 12.8), and cryotherapy (36.4 ± 2.8) groups were significantly different (all P<0.05). The difference was also significant between the APC and the radiofrequency groups compared to the sham operation (34.1 ± 1.7) group (t values were 6.02 and 8.81, respectively, both P<0.05). HE staining of sections of the rat skin after 5 days showed that, radiofrequency resulted in the most serious injury to the skin, while the damage resulting from APC and cryotherapy varied, but was not significantly different (t value 0.91, P>0.05). The radiofrequency group showed the highest value (612 ± 98 µm) in the thickness of the scar tissue on the skin, which was significantly higher than that of the APC group (362 ± 120 µm, t value 4.54, P<0.05), while there was no scar formation in response to cryotherapy or sham operation.
Conclusion: Cryotherapy, APC and radiofrequency, when applied locally to the skin, caused different types of injury and had different effects on inflammation. The response of inflammation varied with different processing methods. Cryotherapy resulted in significantly lower response compared to either radiofrequency or APC when the inflammatory response was assessed after 5 days and the scar formation after 28 days.