Partial replacement of left hemidiaphragm in dogs by either cryopreserved or decellularized heterograft patch

Large diaphragmatic defects are still a challenging issue for reconstruction using either synthetic prosthesis or bioprosthesis. To evaluate the possibility of using diaphragm allograft as a natural bioprosthesis in humans, we conducted a two-group study and compared cryopreserved and decellularized diaphragmatic heterograft patched in a canine model.

At the end of organ harvesting from a human donor, the left hemidiaphragm was taken to the laboratory in phosphate-buffered saline solution. The next step was freezing the grafts at -80°C, and preserving them for up to 2 months in Group 1. It was subjected to a detergent-enzymatic method (containing sodium deoxycholate/DNase lavations) of decellularization for 25 cycles in Group 2. Through left thoracotomy in the eighth intercostal space, cryopreserved patches in six dogs and decellularized patches in five dogs replaced the diaphragm. During the follow-up, sonography was done in all animals, but three and two dogs in Group 1 and 2 underwent computed tomography (CT) scan, respectively. The animals were euthanized after 6 months.

There was no mortality. Sonography showed only motion impairment of the patches in all cases. In Group 1, CT scan showed mild atelectasis and scattered infiltration in the left lower lobe, fibrotic bands and minimal fluid collection under the diaphragm. In Group 2, CT scan showed scattered fibrotic bands and mild to moderate elevation of the left hemidiaphragm. There was no evidence of gross disruption and complete healing of the suture line. Necropsy in both groups showed patches were completely replaced with a dense fibrous tissue. In Group 1, focal calcification was noticeable in every case and foreign body-type granulomas were clearly seen all over the grafted tissue. Histology in Group 2 animals showed less inflammatory cell infiltration and scattered foreign body granulomas in comparison with the cryopreserved patch graft.

The gross healing process in the decellularized heterograft is similar to the cryopreserved diaphragm but with fewer inflammatory cells and foreign body granulomas on histology. Both of them can be used instead of bioprostheses with regard to the fact that the decellularized patch technique is more complex and expensive. It is recommended to compare them with commercial bioprostheses.