Cross-linked poly(gamma-glutamic acid) attenuates pleural and chest wall adhesions in a mouse thoracotomy model

Background: Cross-linked poly(gamma-glutamic acid) (XL) is derived from a naturally occurring biodegradable polymer produced by Bacillus subtilis. In the present study, we compared the efficacy of XL in preventing adhesion formation after thoracotomy in mice with Seprafilm (SEP), which is currently the most commonly applied adhesion prevention material. Methods: Left thoracotomy was done. Adhesion between the lung and the thoracotomy site (Lu groups), or between the thoracotomy site and the overlying chest muscles (Mu groups), was evaluated in separate groups of animals. In the Lu-XL group (n = 12) and the Mu-XL group (n = 12), approximately 20 mg of XL was applied as powder. In the Lu-SEP group (n = 12) and Mu-SEP group (n = 12), a 5 × 3 mm SEP sheet was applied. Nothing was applied in the Lu-NON group (n = 12) and the Mu-NON group (n = 12). After 7 and 14 days, the respective adhesions were scored and compared. Results: The adhesion score was significantly lower in the Lu-XL group (0.5 ± 0.9) in comparison to the Lu-NON group (3.8 ± 0.5) and the Lu-SEP group (2.2 ± 0.8; p < 0.002), and in the Mu-XL group (0.8 ± 0.7) in comparison to the Mu-NON group (3.8 ± 0.4) and the Mu-SEP group (2.5 ± 0.8; p < 0.001). These differences were similar also at 14 days. Conclusion: It was suggested that the antiadhesive effect of XL was superior to SEP in this particular model of thoracotomy in mice.