A novel bioabsorbable pericardial membrane substitute to reduce postoperative pericardial adhesions in a rabbit model

In paediatric cardiac surgery, reoperations remain challenging since the injury and the formation of dense adhesions before reoperations can be life-threatening to the heart, bypass conduits or great vessels. To prevent the formation of dense adhesions, a variety of different types of pericardial membrane substitute have been employed. However, due to peel formation, calcification and infection, the routine application of these pericardial membrane substitute has not been achieved clinically. A novel bioabsorbable membrane has been developed from polylactic acid (PLA) to overcome these drawbacks. The purpose of this study was to assess the biosafety and the effectiveness of PLA membrane as a new bioabsorbable pericardial membrane substitute after pericardium replacement in a rabbit model.

A total of 33 rabbits underwent abrasion on the surface of the heart through right thoracotomy and were divided into a PLA membrane group (n = 17) and a control group (n = 16). Biosafety was assessed by comparing pre- and postoperative liver/kidney function and C-reactive protein levels. Subsequently, at 4 and 12 weeks postoperatively, the degree of reabsorption of the membrane and the intensity of adhesions were macroscopically assessed, followed by a microscopic evaluation for histological changes. Samples of the regenerated fibrous membranes that were harvested 12 weeks after implantation were used to perform immunostaining for cytokeratin and human bone marrow endothelial cell-1 (HBME-1).

The PLA membrane group exhibited a little inflammatory response (P > 0.05) and liver/kidney dysfunction (P > 0.05). The PLA membrane was mostly absorbed by 12 weeks with the replacement of loosely adherent tissue. Moderate adhesions were found between the pericardial membrane substitute and the epicardium at the 4-week postoperative inspection. After 12 weeks postoperatively, the adhesions were found to have resolved completely. The composite score, which combined the histological findings of inflammation and the tightness of adhesions, was graded on a scale of 0 to 3. Significant differences between the PLA and control groups were detected at 4 weeks (1.2 ± 0.4, 2.1 ± 0.6; P = 0.007, respectively) and 12 weeks (0.5 ± 0.5, 2.5 ± 0.7; P = 0.001, respectively). Twelve weeks after the replacement of the pericardium with the PLA membrane, as shown by the cells positively immunostained for cytokeratin and HBME-1, the regenerated membrane consisted of a bilayer structure mimicking the native pericardium.

To prevent the formation of adhesions after cardiac surgery, the bioabsorbable PLA membrane might serve as a promising substitute for the pericardium, which proved to be safe and efficacious in our study.