Surgical adhesions: Evidence for adsorption of surfactant to peritoneal mesothelium

Background: It has been speculated that the formation of surgical adhesions must be preceded by physical adhesion of the two surfaces, a process normally prevented by a lining of adsorbed surface-active phospholipid (surfactant) acting as both a superb boundary (solid-to-solid) lubricant and a release (antistick) agent. Animal trials administering exogenous surfactant as a dry powder (ALEC(TM)) have previously demonstrated a reduction of 80% in abdominal adhesions. Methods: Incubation of rat peritoneum (both live and excised) with radiolabelled dipalmitoyl phosphatidylcholine (DPPC) has been used to demonstrate adsorption; while the normal lining of surfactant in the human abdominal cavity has been confirmed by epifluorescence microscopy using Phosphin E as the hydrophobic probe. Aims: The overall aim is to confirm that peritoneal mesothelium has a lining of surfactant known for its lubricating and release properties, and that this lining can be enhanced by the adsorption of exogenous material. Results: Adsorption of DPPC to peritoneal mesothelium was 470 ng/cm(2) (n = 8) ex vivo and 598 ng/cm(2) (n = 18) in vivo, these rates being enhanced by EggPG by 62% ex vivo and 47% in vivo to reach the equivalent of almost three close-packed monolayers. Conclusions: These results can explain the reduction in surgical adhesions previously reported in animals by administering ALEC(TM) (7:3 DPPC:EggPG) as a highly surface-active dry powder, although it is now used in saline suspension to treat respiratory distress syndrome in newborns, in whom it has no side-effects. These findings would appear to justify clinical trials for dry ALEC(TM) in suppressing surgical adhesions with minimal risk of an adverse reaction. The results of these trials are also discussed and found to be compatible with the known ability of surfactant to resist physical adhesion by fibronectin, the tacky 'glue' by which fibroblasts attach to surfaces as the first step in formation of fibrinous adhesions.