Immunohistochemical and radiological characterization of wound healing in porcine liver after radiofrequency ablation.

BACKGROUND: Radiofrequency ablation (RFA) is a minimal invasive therapeutic option for patients with hepatocellular carcinoma or liver metastases. We investigated RFA-induced cellular changes in the liver of pigs.

MATERIAL AND METHODS: Healthy pigs (n=18) were sacrificed between day 0 and 3 months after RFA. The wound healing process was evaluated by computed tomography (CT), chromotrope anilinblue (CAB) staining of large-scale and standard tissue sections. Immunohistochemistry (IHC) for heat shock protein 70, Caspase-3, Ki67, Reelin, Vinculin, Vimentin and α-SMA was perfomed.

RESULTS: One day after RFA, CAB staining showed cell damage and massive hyperaemia. All IHC markers were predominantly expressed at the outer borders of the lesion, except Reelin, which was mainly detected in untreated liver regions. By staining for Hsp70, the heat stress during RFA was monitored, which was most distinct 1-2 days after RFA. CT revealed decreased lesion size after one week. Development of a Vimentin and α-SMA positive fibrotic capsule was observed.

CONCLUSION: In the early phase signs of cell damage, apoptosis and proliferation are dominant. Reduced expression of Reelin suggests a minor role of hepatic stellate cells in the RFA zone. After one week myofibroblasts become prominent and contribute to the development of the fibrotic capsule. This elucidates the pathophysiology of RFA and could contribute to the future optimization of RFA procedures.