No Sex Differences in the Amount of Type IV Collagen in Wistar Rats Regardless of Sampling Strategy.

Serum collagen IV (Col IV) is an important marker for staging liver fibrosis, but histological baselines in healthy tissue are often lacking or biased. This study applied unbiased stereological sampling to quantify liver Col IV in healthy adult Wistar rats and assess sex differences. No significant differences were observed between sampling strategies (simple, systematic, or stratified random) or between males (4.26% ± 0.93%) and females (3.71% ± 1.27%), yielding a pooled mean of 3.96% ± 1.11%. The Col IV-positive area (3.62% ± 1.29%) did not differ significantly from the total collagen area measured by Sirius red (3.06% ± 1.72%), although a statistical trend was noted (R2 = 0.5845, p = 0.0767). These data indicate that IHC-based area measurements capture a larger structural footprint of the mesh-like Col IV network than biochemical mass-based methods, and that 58% of the variance in Col IV area is explained by Sirius red-positive area, suggesting a regulated spatial balance. The absence of sex effects on Col IV implies that previously reported sex-related differences in total liver collagen likely involve other collagen types. Unbiased Col IV quantification may support validation of minimally invasive methods for staging liver fibrosis.