Methods for Assessing Lower Urinary Tract Function in Animal Models

Research and progress on the mechanism of lower urinary tract neuromodulation: a literature review

The storage and periodic voiding of urine in the lower urinary tract are regulated by a complex neural control system that includes the brain, spinal cord, and peripheral autonomic ganglia. Investigating the neuromodulation mechanisms of the lower urinary tract helps to deepen our understanding of urine storage and voiding processes, reveal the mechanisms underlying lower urinary tract dysfunction, and provide new strategies and insights for the treatment and management of related diseases. However, the current understanding of the neuromodulation mechanisms of the lower urinary tract is still limited, and further research methods are needed to elucidate its mechanisms and potential pathological mechanisms. This article provides an overview of the research progress in the functional study of the lower urinary tract system, as well as the key neural regulatory mechanisms during the micturition process. In addition, the commonly used research methods for studying the regulatory mechanisms of the lower urinary tract and the methods for evaluating lower urinary tract function in rodents are discussed. Finally, the latest advances and prospects of artificial intelligence in the research of neuromodulation mechanisms of the lower urinary tract are discussed. This includes the potential roles of machine learning in the diagnosis of lower urinary tract diseases and intelligent-assisted surgical systems, as well as the application of data mining and pattern recognition techniques in advancing lower urinary tract research. Our aim is to provide researchers with novel strategies and insights for the treatment and management of lower urinary tract dysfunction by conducting in-depth research and gaining a comprehensive understanding of the latest advancements in the neural regulation mechanisms of the lower urinary tract.

Automated identification and segmentation of urine spots based on deep-learning

Micturition serves an essential physiological function that allows the body to eliminate metabolic wastes and maintain water-electrolyte balance. The urine spot assay (VSA), as a simple and economical assay, has been widely used in the study of micturition behavior in rodents. However, the traditional VSA method relies on manual judgment, introduces subjective errors, faces difficulty in obtaining appearance time of each urine spot, and struggles with quantitative analysis of overlapping spots. To address these challenges, we developed a deep learning-based approach for the automatic identification and segmentation of urine spots. Our system employs a target detection network to efficiently detect each urine spot and utilizes an instance segmentation network to achieve precise segmentation of overlapping urine spots. Compared with the traditional VSA method, our system achieves automated detection of urine spot area of micturition in rodents, greatly reducing subjective errors. It accurately determines the urination time of each spot and effectively quantifies the overlapping spots. This study enables high-throughput and precise urine spot detection, providing important technical support for the analysis of urination behavior and the study of the neural mechanism underlying urination.

Targeted Delivery of Catalase and Photosensitizer Ce6 by a Tumor-Specific Aptamer Is Effective against Bladder Cancer In Vivo

Photodynamic therapy (PDT) is often applied in a clinical setting to treat bladder cancer. However, current photosensitizers report drawbacks such as low efficacy, low selectivity, and numerous side effects, which have limited the clinical values of PDT for bladder cancer. Previously, we developed the first bladder cancer-specific aptamer that can selectively bind to and be internalized by bladder tumor cells versus normal uroepithelium cells. Here, we use an aptamer-based drug delivery system to deliver photosensitizer chlorine e6 (Ce6) into bladder tumor cells. In addition to Ce6, we also incorporate catalase into the drug complex to increase local oxygen levels in the tumor tissue. Compared with free Ce6, an aptamer-guided DNA nanotrain (NT) loaded with Ce6 and catalase (NT-Catalase-Ce6) can specifically recognize bladder cancer cells, produce oxygen locally, induce ROS in tumor cells, and cause mitochondrial apoptosis. In an orthotopic mouse model of bladder cancer, the intravesical instillation of NT-Catalase-Ce6 exhibits faster drug internalization and a longer drug retention time in tumor tissue compared with that in normal urothelium. Moreover, our modified PDT significantly inhibits tumor growth with fewer side effects such as cystitis than free Ce6. This aptamer-based photosensitizer delivery system can therefore improve the selectivity and efficacy and reduce the side effects of PDT treatment in mouse models of bladder cancer, bearing a great translational value for bladder cancer intravesical therapy.

Minimizing the variables of voiding spot assay for comparison between laboratories

The voiding spot assay (VSA) is increasingly being adopted as a standard method for assessing mouse urinary function. However, VSA outcomes are highly sensitive to housing environment and procedural parameters. Many variables exist among laboratories, including analytical software, type of daily housing cage, transportation, and the time of the day. Some of these variables, such as the time of VSA and analytical software, have been shown to result in inconsistency and incomparability of data. In this study, we evaluated whether the results of VSA can be compared across laboratories by minimizing these variables. We found that analytical tools between Fiji and MATLAB are in good agreement in the quantification of VSA parameters, especially primary voiding spot (PVS) parameters. Unexpectedly, we found that mice housed in different daily home cages did not alter voiding patterns in a standard VSA cage. Nonetheless, we still recommend acclimation when performing VSA in unfamiliar cages. Notably, mice are highly sensitive to transportation and the time in the morning versus afternoon, which can induce significant changes in voiding patterns. Therefore, a standardized period among laboratories and allowing 2-3 days of rest for mice acclimation after transportation are necessary for VSA. Finally, we performed VSA using identical procedural parameters in two laboratories from two geographical locations to compare the results of VSA and concluded that it is possible to generate limited comparable VSA data, such as PVS volume.

Molecular Mechanism Operating in Animal Models of Neurogenic Detrusor Overactivity: A Systematic Review Focusing on Bladder Dysfunction of Neurogenic Origin

Neurogenic detrusor overactivity (NDO) is a severe lower urinary tract disorder, characterized by urinary urgency, retention, and incontinence, as a result of a neurologic lesion that results in damage in neuronal pathways controlling micturition. The purpose of this review is to provide a comprehensive framework of the currently used animal models for the investigation of this disorder, focusing on the molecular mechanisms of NDO. An electronic search was performed with PubMed and Scopus for literature describing animal models of NDO used in the last 10 years. The search retrieved 648 articles, of which reviews and non-original articles were excluded. After careful selection, 51 studies were included for analysis. Spinal cord injury (SCI) was the most frequently used model to study NDO, followed by animal models of neurodegenerative disorders, meningomyelocele, and stroke. Rats were the most commonly used animal, particularly females. Most studies evaluated bladder function through urodynamic methods, with awake cystometry being particularly preferred. Several molecular mechanisms have been identified, including changes in inflammatory processes, regulation of cell survival, and neuronal receptors. In the NDO bladder, inflammatory markers, apoptosis-related factors, and ischemia- and fibrosis-related molecules were found to be upregulated. Purinergic, cholinergic, and adrenergic receptors were downregulated, as most neuronal markers. In neuronal tissue, neurotrophic factors, apoptosis-related factors, and ischemia-associated molecules are increased, as well as markers of microglial and astrocytes at lesion sites. Animal models of NDO have been crucial for understanding the pathophysiology of lower urinary tract (LUT) dysfunction. Despite the heterogeneity of animal models for NDO onset, most studies rely on traumatic SCI models rather than other NDO-driven pathologies, which may result in some issues when translating pre-clinical observations to clinical settings other than SCI.

Tissue-engineered autologous peritoneal grafts for bladder reconstruction in a porcine model

Ileal neobladder construction is a common treatment for patients with bladder cancer after radical cystectomy. However, metabolic disorders caused by transposed bowel segments occur frequently. Bladder tissue engineering is a promising alternative approach. Although numerous studies have reported bladder reconstruction using acellular and cellular scaffolds, there are also disadvantages associated with these methods, such as immunogenicity of synthetic grafts and incompatible mechanical properties of the biomaterials. Here, we engineered an autologous peritoneal graft consisting of a peritoneal sheet and the seromuscular layer from the ileum. Three months after the surgery, compared with the neobladder made from the ileum, the reconstructed neobladder using our new method showed normal function and better gross morphological characteristics. Moreover, histopathological and transcriptomic analysis revealed urothelium-like cells expressing urothelial biomarkers appeared in the neobladder, while no such changes were observed in the control group. Overall, our study provides a new strategy for bladder tissue engineering and informs a variety of future research prospects.