Hyperdry Human Amniotic Membrane as a Protective Dressing for Open Wounds With Exposed Bowel in Mice

Introduction: An enteroatmospheric fistula forms when the exposed bowel is perforated with chronic enteric fistula formation. Currently, there is no established preventative method for this condition. Hyperdry (HD) amniotic membrane (AM) can promote early granulation tissue formation on the exposed viscera and is suitable for dressing intractable wounds as it possesses anti-inflammatory, antibacterial, and immunomodulatory properties. This study investigated whether HD-AM promotes early formation of blood vessel–containing granulation tissue for enteroatmospheric fistula treatment. Methods: An experimental animal model of an open wound with exposed bowel was developed. A 15 × 20 mm wound was prepared on the abdomen of Institute of Cancer Research mice, and the HD-AM was placed. The mice were assigned to one of the following groups: HD-AM group, in which the stromal layer of the HD-AM was placed in contact with the exposed bowel; HD-AM UD group, in which the epithelial layer of the HD-AM was placed in contact with the exposed bowel; and the HD-AM (-) or control group, in which the HD-AM was not used. Results: On postoperative days 7 and 14, granulation tissue thickness significantly increased in the HD-AM and HD-AM UD groups compared with that in the HD-AM (-) group. Macrophages accumulated in the HD-AM epithelium only in the HD-AM group. During HD-AM contact, a subset of invading macrophages switched from M1 to M2 phenotype. Conclusions: HD-AM is a practical wound dressing with its scaffolding function, regulation of TGF β-1 and C-X-C motif chemokine 5 (CXCL-5), and ability to induce M1-to-M2 macrophage conversion.