# Novel Insights on Plant Extracts to Prevent and Treat Recurrent Urinary Tract Infections
## 4 In Vitro Urinary Tract Models  
To develop new plant-based treatment strategies, it is imperious to improve our knowledge about UTI pathogenesis using different model systems that will provide practical information about the host-pathogen interaction and unique aspects of the urinary tract environment [17]. The mechanism of rUTI is complex, and over the last decades, several hypotheses have emerged based on animal models or advanced human cell-based in vitro models. A recent exhaustive review discussed the importance of model systems in revealing the crucial insights about UTI pathogenesis, including their strengths and limitations [2]. Further progress in improving the plant-based strategies to cure rUTI will be supported by advances in human-based models that are more accurate and controllable than animal models and can reveal bottleneck points of UTI pathogenesis [18; 19].  
In general, in vitro urinary tract infection models are based on the cells in static culture; however, the intricacy and antibiotic resistance of these infections have necessitated the need to expand these studies to include the characteristics of the bladder's physiological conditions (e.g., urine and fluid flow). Advanced in vitro human cell-based models that provide a complementary platform (along with animals) for drug detection and alternative treatment strategies are directly proportional to studies on the complexity of recurrent urinary tract infections [2].  
Some models were based on a virulent bacterium colonizing a bladder in vitro at the laboratory level. These models were created based on research about preventing symptomatic urinary tract infection caused by aggressive bacteria by colonizing the bladder with strains that cause asymptomatic bacteriuria (ABU), which are less virulent bacteria. These asymptomatic _E. coli_ strains were created by comparing isolated ABUs from diabetic patients in terms of their virulence-associated phenotypes and virulence in an in vitro model with murine sepsis (from laboratory rats) and the content of their genome [20; 21].  
Generalized Lotka-Volterra modeling (gLVM) has revealed the protective role of two taxonomic classes of bacteria, _Actinobacteria_ and _Bacteroides_, which appear to suppress pathogen growth. For longitudinal data, the original BEEM approach (biomass estimation and model inference with a maximizing of expectancies) was utilized to simulate the microbiota shift after 24 h of antibiotic therapy [22].  
These models are highly desirable because of their advantages compared to animal models and their potential to study a wide variety of conditions, such as UTI in bladder cancer, tissue regeneration/transplantation, and the effect of xenobiotics that come into contact with the urine, in vitro in the human bladder environment and reconstitution of the urothel (or even organ) [2; 23].  
While the procedure can preserve a precise 3D cell architecture, layering, and differentiation, it is time-consuming, requires quick access to fresh tissue, and may show variability between samples [20]. There is also a growing chance that stromal and urothelial cells will come into contact with undesired combinations during cultivation, with stromal cells outgrowing the urothel [24; 25].  
Because the existing experimental models have flaws and only provide partial results, new tactics have been created, including new experimental 3D bladder models that strive to reproduce/imitate the human urothel employing stem cells or stem cells that have been propagated, expanded, and stratified/differentiated. Some are even protected by patents [26].