Mesenchymal stem cells ameliorate partial bladder outlet obstruction-induced epithelial-mesenchymal transition type II independent of mast cell recruitment and degranulation

Mast cell distribution and prevalence in the murine urinary bladder

BACKGROUND

Mast cells have been implicated in the pathology of various urinary bladder disorders. However, the distribution of mast cells throughout urinary bladder tissue remains uncertain despite mast cell prevalence being relatively well-defined. Using a mouse tissue model, this study aims to characterise the prevalence and distribution of mast cells throughout the urinary bladder.

METHODS

Bladder tissues were collected from six C57BL/6J female mice. Mast cell prevalence was quantified by flow cytometry, based on the expression of the following characteristic markers: CD45, CD117 and FcɛRIα. The toluidine blue stain assessed mast cell distribution, size, and proximity to vasculature. A repeated measures one-way ANOVA was used to evaluate the density of mast cells between the discrete layers of the urinary bladder, and an ordinary one-way ANOVA was used to assess potential differences between mast cell size across the urinary bladder wall.

RESULTS

It was determined that mast cells compose less than 4% of all live leukocytes in the urinary bladder. They were also found to be more prominent in the lamina propria and detrusor muscle layers, compared to the urothelium and adventitia. In addition, 20.89% of mast cells were located near vasculature, which may be an important factor in consideration of their function and potential to contribute to various bladder pathologies, such as cystitis or overactive bladder.

CONCLUSION

These findings provide a baseline understanding of mast cell prevalence and distribution throughout the urinary bladder.

The PI3K-AKT-mTOR signaling pathway mediates the cytoskeletal remodeling and epithelial-mesenchymal transition in bladder outlet obstruction

Objective

Partial bladder outlet obstruction(pBOO) is the most common cause of lower urinary tract symptoms (LUTS) and significantly affects the quality of life. Long-term pBOO can cause changes in bladder structure and function, referred to as bladder remodeling. The pathogenesis of pBOO-induced bladder remodeling has yet to be fully understood, so effective treatment options are lacking. Our study aimed to explore how pBOO-induced bladder remodeling brings new strategies for treating pBOO.

Methods

A rat model of pBOO was established by partial ligation of the bladder neck, and the morphological changes and fibrosis changes in the bladder tissues were detected by H&E and Masson trichrome staining. Furthermore, EMT(epithelial-mesenchymal transition) related indicators and related pathway changes were further examined after TGF- β treatment of urothelial cells SV-HUC-1. Finally, the above indicators were tested again after using the PI3K inhibitor. Subsequently, RNA sequencing of bladder tissues to identify differential genes and related pathways enrichment and validated by immunofluorescence and western blotting analysis.

Results

The pBOO animal model was successfully established by partially ligating the bladder neck. H&E staining showed significant changes in the bladder structure, and Masson trichrome staining showed significantly increased collagen fibers. RNA sequencing results significantly enriched in the cytoskeleton, epithelial-mesenchymal transformation, and the PI3K-AKT-mTOR signaling pathway. Immunofluorescence and western blotting revealed EMT and cytoskeletal remodeling in SV-HUC-1 cells after induction of TGF- β and in the pBOO bladder tissues. The western blotting showed significant activation of the PI3K-AKT-mTOR signaling pathway in SV-HUC-1 cells after induction of TGF-β and in pBOO bladder tissues. Furthermore, EMT and cytoskeletal damage were partially reversed after PI3K pathway inhibition using PI3K inhibitors.

Conclusions

In the pBOO rat model, the activation of the PI3K-AKT-mTOR signaling pathway can mediate the cytoskeletal remodeling and the EMT to induce fibrosis in the bladder tissues. PI3K inhibitors partially reversed EMT and cytoskeletal damage.

BOO induces fibrosis and EMT in urothelial cells which can be recapitulated in vitro through elevated storage and voiding pressure cycles

PURPOSE

To determine the unique contributions from elevated voiding and storage pressures in the development of fibrosis and the epithelial-to-mesenchymal transition (EMT) in urothelial cells, and how progressive BOO pressure cycling is an important mechanical cue leading to these pathological changes.

MATERIALS AND METHODS

Urothelial cells isolated from control, SHAM, 2 (acute)- or 6 (chronic)-week BOO rats treated with an inflammasome inhibitor or no drug. Total RNA was isolated and RT-PCR was conducted with custom primers for pro-fibrotic and EMT genes. In separate experiments, a rat urothelial cell line was exposed to cyclic pressure regimes characteristic of acute and chronic BOO in the presence or absence of an inflammasome inhibitor. Following exposure, RT-PCR was conducted, collagen content was determined and intracellular caspase-1 activity was measured.

RESULTS

Urothelial cells isolated from acute and chronic BOO rat models demonstrated expression of pro-fibrotic and EMT genes. Similarly, MYP3 rat urothelial cells subjected to pressure cycling regimes that reflect intravesical pressures in the acute or chronic BOO bladder also demonstrated increased expression of pro-fibrotic and EMT genes, along with elevated soluble collagen. Treatment with inflammasome inhibitors reduced expression of pro-fibrotic genes in the rat model and pressure cycling model but had a limited effect on EMT.

CONCLUSION

These results indicate that acute and chronic BOO pressure cycling are essential in the initiation and progression of fibrosis in the bladder via the NLRP3 inflammasome, but also provide new evidence that there is also an alternative NLRP3-independent pathway leading to EMT and fibrosis.