gms | German Medical Science

Objectives: Abdominal trauma (AT) is of major importance worldwide especially since the civil and terroristic potential of blast injuries has increased. The consequences of blunt abdominal injuries are often underestimated or missed and the underlying pathomechanisms are still poorly defined. The underlying local and systemic alterations in the early innate immune response are also not well understood. Therefore, we investigated the temporo-spatial systemic and local effects of blunt AT on intestinal organs and innate immune response.

Methods: In the recently established blunt AT model (ethical approval no. 1345), n=68 male analgised C57Bl6 mice were anesthetized and fixed in a supine position and exposed to a single blast wave centred on the epigastrium, or control treatment. At 2, 6, or 24 h after trauma induction, mice were euthanised and intestinal organ damage was analysed macroscopically and microscopically.

By immunohistochemical staining of jejunum, ileum and colon tissue, complement protein C3c deposits and the complement system receptors C3aR and C5aR1, have been analysed. Jejunum and colon tissue homogenates were analysed for different complement factors by ELISA. To define the systemic immune response the concentrations of pro- and anti-inflammatory parameters and organ damage markers such as intestinal Fatty Acid Binding Protein (I-FABP) were measured in plasma. Statistical analysis were performed by One-Way-ANOVA and appropriate post hoc tests.

Results and Conclusion: In 36% of traumatized animals one or more visible injuries of the intestine were detected. Likewise, histologically epithelial damages were detected in jejunum and ileum tissue samples by using the Chiu-Score. An early intestinal tissue damage were also verified by significantly increased i-FABP plasma concentrations. In mucus of jejunum and colon C3 and C3a were detected and significantly altered after trauma. Significant correlations between various complement factors indicating complement modifications in the mucus after AT. While systemically C3a and C5a plasma concentrations increased, C3a and C5a in tissue homogenates revealed no significant alterations due to the AT. The comparing receptor for C5a remained unchanged whereas the C3aR revealed a tendency to increased expression patterns.

In conclusion, after AT there is an early intestinal damage reflected by enhanced i-FABP serum levels and an immune response with activation of the mucosal and systemic complement system both of which might be used for modern immune monitoring.