Bladder Wall Stiffness after Cystectomy in Bladder Cancer Patients: A Preliminary Study

Bladder cancer (BlCa), specifically urothelial carcinomas, is a heterogeneous disease that

derives from the urothelial lining. Two main classes of BlCa are acknowledged: the non-muscle

invasive BlCa and the muscle-invasive BlCa; the latter constituting an aggressive disease which

invades locally and metastasizes systemically. Distinguishing the specific microenvironment that

cancer cells experience between mucosa and muscularis propria layers can help elucidate how these

cells acquire invasive capacities. In this work, we propose to measure the micromechanical properties

of both mucosa and muscularis propria layers of the bladder wall of BlCa patients, using atomic force

microscopy (AFM). To do that, two cross-sections of both the macroscopically normal urinary bladder

wall and the bladder wall adjacent to the tumor were collected and immediately frozen, prior to AFM

samples analysis. The respective “twin” formalin-fixed paraffin-embedded tissue fragments were

processed and later evaluated for histopathological examination. H&E staining suggested that tumors

promoted the development of muscle-like structures in the mucosa surrounding the neoplastic region.

The average Young’s modulus (cell stiffness) in tumor-adjacent specimens was significantly higher

in the muscularis propria than in the mucosa. Similarly, the tumor-free specimens had significantly

higher Young’s moduli in the muscularis propria than in the urothelium. Young’s moduli were

higher in all layers of tumor-adjacent tissues when compared with tumor-free samples. Here we

provide insights into the stiffness of the bladder wall layers, and we show that the presence of tumor

in the surrounding mucosa leads to an alteration of its smooth muscle content. The quantitative

assessment of stiffness range here presented provides essential data for future research on BlCa

and for understanding how the biomechanical stimuli can modulate cancer cells’ capacity to invade

through the different bladder layers.