# Construction of a Novel 3D Urinary Bladder Mucosa Model and Its Application in Toxicity Assessment of Arsenicals

## TL;DR

Researchers created a 3D model of the human bladder lining to study how arsenic compounds cause toxicity and damage.

## Contribution

A novel 3D urinary bladder mucosa model was developed for toxicity assessment of arsenicals.

## Key findings

- The 3D-UBMM closely resembles human bladder epithelium in morphology and marker protein expression.
- Exposure to arsenic compounds caused dose-dependent urothelial necrosis and reduced P63-positive cells.
- The model can be used for evaluating bladder toxicants and identifying mechanisms of carcinogenesis.

## Abstract

The urinary bladder is a primary target organ for environmental toxicants such as arsenic. The objects of this study were two-fold. First, we constructed a novel 3D urinary bladder mucosa model (3D-UBMM) composed of an overlying epithelium and a supporting subepithelial layer. Primary human bladder urothelial and fibroblast cells were immortalized by introducing the human CDK4R24C and TERT genes. The construction of the 3D-UBMM involved incorporating immortalized fibroblast cells into a collagen raft, while immortalized urothelial cells were cultured at the air-liquid interface. This 3D-UBMM closely resembles the human bladder epithelium in terms of morphology and marker protein expression, including uroplakin 1b, P63, and cytokeratin 5. Second, using the 3D-UBMM we investigated the cytotoxicity of sodium arsenite (iAsIII) and dimethylarsenic acid (DMAV). Exposure to iAsIII and DMAV resulted in increased urothelial necrosis, increased γ-H2AX-positive cells, and reduced P63-positive cells, all in a dose–response manner. These findings affirm that this novel 3D-UBMM resembles the human bladder epithelium and offers a practical in vitro model for evaluating bladder toxicants and carcinogens, identifying mechanisms of carcinogenesis, and supporting hazard identification and risk assessment.