Abdominal wall thickness as a means of assessing peritoneal fibrosis in mice.

Herein we describe a method for the quantitative assessment of connective tissue deposition within the peritoneal cavity. Female C57BL/6 mice (8-10 weeks) were given a single intraperitoneal injection of varying concentrations of talc (100 mg, 50 mg, 30 mg, 20 mg) in 1 ml of PBS or PBS alone. After 14 days, animals were killed. Adhesion formation was measured by the standard method of Myllârniemi et al. (1966), namely a gross visual inspection of the peritoneal cavity. This analysis gave a crude assessment of connective tissue deposition in the abdominal cavity but did not allow one to distinguish more subtle differences between intermediate dosage groups. In addition, a histological evaluation was performed. For the latter method, portions of the abdominal wall of mice were fixed and processed for histological analysis using Masson's Trichrome stain which allows for differentiation of connective tissue components. The thickness of connective tissue between the parietal peritoneum and the underlying abdominal wall muscle was measured. A dose-dependent increase in connective tissue deposition was observed in talc-treated animals compared to saline control animals. A differential cell count of the peritoneal exudate cells (PEC) showed that there was no change in cell populations in talc treated animals (compared to control animals). Given the above results, the measurement of connective tissue thickness was found to give the most accurate assessment of peritoneal fibrosis than other previously used methods.