Pentachroma O-H: A Five-Color Histological Staining Method for Enhanced Intestinal Tissue Analysis.

Current histological staining methods for intestinal tissue analysis face limitations in simultaneously visualizing multiple tissue components, often requiring multiple sequential stains that increase processing time and tissue consumption. This proof-of-concept study aimed to define and develop a pentachromatic staining method for enhanced visualization of gastrointestinal tissue architecture. We developed the Pentachroma O-H method, an original protocol using readily available histological reagents (Alcian Blue pH 2.5, Weigert's resorcin-fuchsin, Mayer's hematoxylin, and Van Gieson's solution) applied in an optimized sequence. The protocol was tested on healthy human ileum tissue obtained from surgical specimens as proof of concept. Thirty serial sections were stained with Pentachroma O-H and compared to adjacent sections stained with conventional hematoxylin-eosin (H&E) to document the emerging morphological characteristics of this original stain. Pentachroma O-H achieved distinct five-color differentiation in approximately 45 min: acidic mucins appeared turquoise-blue, collagen fibers red, elastic fibers black-purple, smooth muscle and erythrocyte cytoplasm yellow, and nuclei blue-black. The method clearly delineated intestinal architecture, including mucosal goblet cells, muscularis mucosae, connective tissue vasculature (parietal smooth muscle and elastic laminae), fibers, and cellular components, as well as lymphoid tissue aggregates and infiltrates, with improved contrast compared to H&E. All tissue components were simultaneously visualized in single sections with excellent morphological preservation. This first description of Pentachroma O-H demonstrates its capability to provide comprehensive ileum tissue visualization equivalent to multiple traditional special stains in a single, efficient protocol, offering significant potential advantages for gastrointestinal pathology assessment and warranting future validation studies across diverse tissue types and pathological conditions.