OBJECTIVETo evaluate the efficacy of acellular dermal matrix(ADM) in the closure of anal fistula in an experimental porcine model, and to explore its healing mechanism.

METHODSThe fistula-in-ano model was created and treated with ADM in the porcine model (n=14). Fistula specimens were obtained at hour 12, 24 and day 3, 7, 14, 28, 60 respectively with 2 pigs in each time point. Hematoxylin and eosin staining and immunohistochemical staining for the alpha smooth muscle actin (α-SMA) were performed.

RESULTSAt 12 hours after implantation, neutrophils and scattered cells with a fibroblastic appearance were present at the interface and began to infiltrate into the ADM. The cell density increased from hour 12 (218.2±58.2) to day 7(998.7±128.0) (P<0.01), and decreased from day 7 to day 28. Mature vessels and myofibroblasts stained with α-SMA were identified at the edge of ADM at day 7. The density of vessels (11.2±3.3 vs. 30.5±5.2, P<0.01) and myofibroblasts (3.8±0.8 vs. 6.8±0.4, P<0.01) increased from day 7 to day 14. Partially organized bundles of muscle were found at day 60.

CONCLUSIONSADM is a reasonable new option for the closure of anal fistula. The ability of ADM to become vascularized and remodeled by autologous cells may be advantageous for anal fistula healing and other chronic septic wound.