Quantitative photoacoustic endoscopy reveals early microvascular biomarkers of endometrial fibrosis in a rat model.

Endometrial fibrosis, the core pathological feature of intrauterine adhesion, lacks effective early assessment methods. This study used a quantitative photoacoustic endoscopy (PAE) method to assess the relationship between early PAE-derived features and late-stage fibrosis by characterizing microvascular and inflammatory dynamics in the injured endometrium. PAE captured dynamic endometrial microvascular perfusion changes post-injury, with distinct late vascular remodeling patterns under mild and severe injury. PAE-derived vessel area and mean E lacunarity correlated strongly with histologically validated vascular density (r = 0.90 and -0.84, respectively), and at mid-to-later stages, PAE features correlated with inflammatory cell counts. Day 7 post-injury emerged as a key evaluation window, with vessel area showing AUCs of 0.938 for distinguishing mild fibrosis and 0.946 for severe fibrosis. These findings suggest that quantitative PAE provides high-resolution, biopsy-free monitoring of the endometrial microenvironment and may offer microvascular biomarkers that link early imaging changes to subsequent fibrosis progression.