From Bone to Body: Qualitative Evaluation of Collagenous Tissues Using JFRL Staining in Normal and Pathological...

Join of the five dyes revealing collagenous tissue (JFRL) staining was originally developed for osteochondral tissues, enabling the discrimination between mineralized bone and unmineralized osteoids based on distinct color tones. Given the abundance of collagen in the body, we hypothesized that JFRL staining could be extended to systemic organs using a collagen-oriented histological approach. In the present study, we optimized and applied JFRL staining to diverse normal and pathological tissues using quantitative red, green, and blue color analysis. In normal tissues, JFRL staining generated characteristic red-green color balances in collagen-rich regions, whereas noncollagenous protein components exhibited distinct yellow-greenish tones. In contexts associated with diseased models such as wound healing, structural heterogeneity is reflected by a red-dominant coloration, whereas fibrous capsules surrounding inflammatory biomaterials shift toward green-dominant staining. In contrast, renal fibrotic lesions exhibit extensive collagen accumulation and markedly reduced chromatic variation. The tumor-associated stroma exhibited heterogeneous red-green patterns, reflecting qualitative differences in collagen organization. Together, these findings demonstrate that JFRL staining enables both visualization and qualitative assessment of collagen architecture across physiological and pathological states, providing a practical histological tool for research and diagnostic applications related to remodeling-associated structural changes.