Human amnion as a bioprosthesis for bile duct reconstruction in the pig

Advances in the generation of bioengineered bile ducts

The generation of bioengineered biliary tissue could contribute to the management of some of the most impactful cholangiopathies associated with liver transplantation, such as biliary atresia or ischemic cholangiopathy. Recent advances in tissue engineering and in vitro cholangiocyte culture have made the achievement of this goal possible. Here we provide an overview of these developments and review the progress towards the generation and transplantation of bioengineered bile ducts. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni and Peter Jansen.

Comparison of equine amnion and a nonadherent wound dressing material for bandaging pinch-grafted wounds in ponies

OBJECTIVE

To evaluate healing of pinch-grafted wounds on the distal aspect of the limbs of ponies bandaged with equine amnion or a standard nonadherent wound dressing material.

ANIMALS

6 ponies.

PROCEDURE

A 2.5x2.5-cm full-thickness section of skin was removed from the dorsal aspect of each limb at the midpoint of the metacarpus or metatarsus. Six days later, wounds were grafted with partial-thickness pinch grafts. Half the wounds were bandaged with amnion, and the other half were bandaged with a nonadherent dressing. Bandages were changed every 3 days until wound healing was complete. At each bandage change, numbers of grafts lost were recorded, and wounds were measured.

RESULTS

Percentage of grafts lost from wounds bandaged with amnion was not significantly different from percentage lost from wounds bandaged with the nonadherent dressing. Median healing time for wounds bandaged with amnion (30 days) was significantly less than median healing time for wounds bandaged with the nonadherent dressing (39 days). All wounds were healed by day 45.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that amnion can be used for bandaging pinch-grafted wounds on the distal aspect of the limbs of ponies.

Construction of peritoneal venous valves: an experimental study in rats and piglets

In the search for new techniques to improve venous valve insufficiency, a peritoneal patch with a mesothelial layer on either side was employed in the venous circulation to construct a venous valve de novo. This material was used because of the resemblance in fibrinolytic activity of mesothelial cells to endothelium. The behavior of double-sided flaps of peritoneum was first studied on only one side in the caval vein wall of 10 rats. All veins remained open, and smooth incorporation of the patch into the vein wall was observed. It was therefore decided to use the same material for construction of a cusp blade in the venous circulation. This venous reconstruction was microsurgically performed in 21 rats and 4 piglets. In our hands, intramuscular anesthesia proved superior to intraperitoneal analgesia in rats. For the piglets mechanical ventilation and general anesthesia were used. In 9 of 21 rats a fair or good result was observed, although it did not seem possible to create a fully competent valve with only one cusp blade in the 1.5-mm-diam caval veins. The same fact evolved from the study using four 7-mm-diam piglet veins. All peritoneal flaps in the venous circulation demonstrated rebuilding of their structure, perhaps induced by the relatively exaggerated central venous flow. To our knowledge, this technique has never been used before. It seems to offer many advantages in the venous circulation, where hardly any thrombogenic surface is tolerated in contrast to the arterial circulation. Application in humans is yet premature, but future research may resolve several problems that occurred in this study.

The use of an amniotic membrane graft to prevent postoperative adhesions

Grafts of trypsin-treated, gamma-irradiated human amniotic membranes were used to cover injured uterine horns of nulliparous female rabbits to prevent adhesions. In this study, the gradual integration of the membranes into the serosal layer of the uterus, together with marked neovascularization, was observed. By the 30th postoperative day, the grafts had been completely integrated, with little evidence of rejection and no evidence of infection at the graft sites. Of 30 uterine horns treated with membrane grafts, only 4 (13.4%) showed any adhesion formation at or among the graft sites. All of the 24 untreated controls showed adhesion formation at the site of injury. Furthermore, whatever adhesions were found in membrane-treated horns could be graded as thin and filmy, accounting for less than 10% of the surface area of the graft, whereas the controls showed dense, thick adhesions covering 50% to 100% of the injured areas. We conclude that these specially prepared amniotic membranes are safe and effective in dramatically reducing postoperative adhesion formation in this animal model.