Bridging the translational gap: Critical TME differences between human PDAC and mouse models

Background: Pancreatic ductal adenocarcinoma (PDAC) develops within a dense, heterogeneous tumor microenvironment (TME) in which collagen and hyaluronic acid (HA) shape tissue architecture, biomechanics, and therapeutic response. Although mouse PDAC models are widely used, their ability to recapitulate human extracellular matrix (ECM) organization remains uncertain. This study aimed to quantitatively compare ECM composition and spatial topology in human PDAC versus a commonly used mouse model. Methods: Tissue sections from primary human PDAC (n=6) and a syngeneic PDAC mouse model (n=3) were stained with H&E and a dual Picrosirius Red (collagen) and Alcian Blue (HA) protocol. The mouse model was generated by subcutaneous implantation of 2838c3 cells into C57BL/6 mice under approved protocols, with tumors resected at ~100 mm³. High-resolution brightfield images were acquired under identical conditions using Agilent Lionheart. Quantitative analyses across 63 histomorphometric and spatial parameters, including area fractions, edge-to-core localization, and texture, were performed using the CerFlux PEER AI/ML imaging and analytics platform and cross-validated in Fiji. Texture and spatial order were quantified using gray-level co-occurrence matrix features and Moran's I. Results: Human PDAC exhibited balanced ECM composition (collagen=0.16±0.04; HA=0.18±0.04), whereas mouse tumors showed HA enrichment and collagen depletion (collagen=0.04±0.002; HA=0.26±0.09). Edge mapping revealed proportionate collagen and HA in human samples (edge ratio=0.9±0.46) but 4-fold peripheral collagen enrichment in mouse tumors (edge ratio=4.3±1.3). Human tumors demonstrated higher entropy (collagen=8.1±0.2; HA=7.9±0.2) and substantial HA autocorrelation (Moran's I=0.58±0.22; 0.60±0.42), reflecting heterogeneous, regionally clustered desmoplasia. Mouse tumors displayed reduced entropy (~7.8) and lower Moran's I (0.32±0.05; 0.17±0.01), indicative of ordered, capsule-like ECM organization. Principal component analysis distinctly segregated species: PC1 (42%) collagen-HA balance, with human samples scoring positive and mouse samples negative; PC2 (21%) textural heterogeneity versus edge-localized order. Conclusions: These findings show that the murine PDAC model fails to reproduce the balanced collagen-HA composition and spatially disordered desmoplasia of human PDAC, instead forming an HA-rich, collagen-depleted core encased in an ordered collagen capsule with markedly lower stromal entropy and autocorrelation. These findings highlight the limitations of mouse models, particularly subcutaneous tumor models, and underscores the need for human-relevant new approach methods (NAMs) for translational therapeutic studies.