The TGF-β1 pathway is early involved in neurogenic bladder fibrosis of juvenile rats

A New Rat Model of Sacral Cord Injury Producing a Neurogenic Bladder and Its Functional and Mechanistic Studies

Sacral spinal cord injury (SSCI) can disrupt bladder neuromodulation and impair detrusor function. Current studies provide limited information on the histologic and genetic changes associated with SSCI-related neurogenic lower urinary tract dysfunction (NLUTD), resulting in few treatment options. This study aimed to establish a simple animal model of SSCI to better understand the disease progression. Ninety 8-week-old Sprague-Dawley (SD) rats were randomly separated into sham operation and SSCI groups. The SSCI group underwent sacral spinal cord injury, while the sham group did not. Urodynamic and histological assessments were conducted at various intervals (1, 2, 3, 4, and 6 weeks) post-injury to elucidate the disease process. Urodynamic examinations revealed significant bladder dysfunction in the SSCI group compared to the sham group, stabilizing around 3-4 weeks post-injury. Histological examination, including hematoxylin-eosin and Masson's trichrome staining, correlated these functional changes with bladder microstructural alterations. RNA-seq was performed on bladder tissues from the sham group and SSCI group at 6 weeks to identify differentially expressed genes and pathways. Selected genes were further analyzed using polymerase chain reaction (PCR). The findings indicated a pronounced inflammatory response in the first 2 weeks post-SSCI, progressing to bladder fibrosis at 3-4 weeks. In conclusion, this study presents a reliable, reproducible, and straightforward SSCI model, providing insights into bladder functional and morphological alterations post-SSCI and laying the groundwork for future therapeutic research.

Mechanosensitive Piezo1 channels promote neurogenic bladder fibrosis via regulating TGF-β1/smad and Hippo/YAP1 pathways

Bladder fibrosis is the final common pathway of neurogenic bladder (NB), and its underlying mechanisms are not fully understood. The current study aims to evaluate the involvement of Piezo1, a mechanosensitive channel, in bladder fibrosis. A full-thickness bladder specimen was taken during ileocystoplasty or ureteral reimplantation from the surgical cut's edge. By chopping off the bilateral lumbar 6 (L6) and sacral 1 (S1) spinal nerves, NB rat models were produced. Utilizing both pharmacological inhibition and Piezo1 deletion, the function of Piezo1 in the TGF-β1-induced fibrosis model of SV-HUC-1 cells was delineated. RNA-seq, immunofluorescence, immunohistochemistry (IHC), and Western blotting were used to evaluate the degrees of fibrosis and biochemical signaling pathways. Piezo1 protein expression was noticeably elevated in the human NB bladder. The abundance of Piezo1 protein in bladder of NB rats was significantly increased. RNA-seq analysis revealed that the ECM-receptor interaction signaling pathway and collagen-containing ECM were increased in spinal cord injury (SCI)-induced bladder fibrosis. Moreover, the bladder of the NB rat model showed activation of YAP1 and TGF-β1/Smad. In SV-HUC-1 cells, siRNA suppression of Piezo1 led to profibrotic responses and activation of the TGF-β1/Smad pathway. However, Yoda1, a Piezo1-specific agonist, significantly reduced these effects. TGF-β1 increased Piezo1 activation and profibrotic responses in SV-HUC-1 cells. In the TGF-β1-induced fibrosis model of SV-HUC-1 cells, the TGF-β1/Smad pathway was activated, whereas the Hippo/YAP1 signal pathway was blocked. Inhibition of Piezo1 further prevented this process. Piezo1 is involved in the progression of NB bladder fibrosis and profibrotic alterations in SV-HUC-1 cells, likely through regulating the TGF-β1/Smad and Hippo/YAP1 pathways.

ABT-263 exerts a protective effect on upper urinary tract damage by alleviating neurogenic bladder fibrosis

This study investigated the mechanism of action of ABT-263 in the treatment of neurogenic bladder fibrosis (NBF)and its protective effects against upper urinary tract damage (UUTD). Sixty 12-week-old Sprague-Dawley (SD) rats were randomly divided into sham, sham + ABT-263 (50 mg/kg), NBF, NBF + ABT-263 (25 mg/kg, oral gavage), and NBF + ABT-263 (50 mg/kg, oral gavage) groups. After cystometry, bladder and kidney tissue samples were collected for hematoxylin and eosin (HE), Masson, and Sirius red staining, and Western Blotting (WB) and qPCR detection. Primary rat bladder fibroblasts were isolated, extracted, and cultured. After co-stimulation with TGF-β1 (10 ng/mL) and ABT-263 (concentrations of 0, 0.1, 1, 10, and 100 µmol/L) for 24 h, cells were collected. Cell apoptosis was detected using CCK8, WB, immunofluorescence, and annexin/PI assays. Compared with the sham group, there was no significant difference in any physical parameters in the sham + ABT-263 (50 mg/kg) group. Compared with the NBF group, most of the markers involved in fibrosis were improved in the NBF + ABT-263 (25 mg/kg) and NBF + ABT-263 (50 mg/kg) groups, while the NBF + ABT-263 (50 mg/kg) group showed a significant improvement. When the concentration of ABT-263 was increased to 10 µmol/L, the apoptosis rate of primary bladder fibroblasts increased, and the expression of the anti-apoptotic protein BCL-xL began to decrease.ABT-263 plays an important role in relieving NBF and protecting against UUTD, which may be due to the promotion of myofibroblast apoptosis through the mitochondrial apoptosis pathway.

Activation of TRPA1 in Bladder Suburothelial Myofibroblasts Counteracts TGF-β1-Induced Fibrotic Changes

The activation of the transient receptor potential ankyrin 1 (TRPA1) channel has anti-fibrotic effects in the lung and intestine. Suburothelial myofibroblasts (subu-MyoFBs), a specialized subset of fibroblasts in the bladder, are known to express TRPA1. However, the role of the TRPA1 in the development of bladder fibrosis remains elusive. In this study, we use the transforming growth factor-β1 (TGF-β1) to induce fibrotic changes in subu-MyoFBs and assess the consequences of TRPA1 activation utilizing RT-qPCR, western blotting, and immunocytochemistry. TGF-β1 stimulation increased α-SMA, collagen type I alpha 1 chain(col1A1), collagen type III (col III), and fibronectin expression, while simultaneously suppressing TRPA1 in cultured human subu-MyoFBs. The activation of TRPA1, with its specific agonist allylisothiocyanate (AITC), inhibited TGF-β1-induced fibrotic changes, and part of these inhibition effects could be reversed by the TRPA1 antagonist, HC030031, or by reducing TRPA1 expression via RNA interference. Furthermore, AITC reduced spinal cord injury-induced fibrotic bladder changes in a rat model. The increased expression of TGF-β1, α-SMA, col1A1 and col III, and fibronectin, and the downregulation of TRPA1, were also detected in the mucosa of fibrotic human bladders. These findings suggest that TRPA1 plays a pivotal role in bladder fibrosis, and the negative cross talk between TRPA1 and TGF-β1 signaling may represent one of the mechanisms underlying fibrotic bladder lesions.

Neurogenic Lower Urinary Tract Dysfunction in Spinal Dysraphism: Morphological and Molecular Evidence in Children

Spinal dysraphism, most commonly myelomeningocele, is the typical cause of a neurogenic lower urinary tract dysfunction (NLUTD) in childhood. The structural changes in the bladder wall in spinal dysraphism already occur in the fetal period and affect all bladder wall compartments. The progressive decrease in smooth muscle and the gradual increase in fibrosis in the detrusor, the impairment of the barrier function of the urothelium, and the global decrease in nerve density, lead to severe functional impairment characterized by reduced compliance and increased elastic modulus. Children present a particular challenge, as their diseases and capabilities evolve with age. An increased understanding of the signaling pathways involved in lower urinary tract development and function could also fill an important knowledge gap at the interface between basic science and clinical implications, leading to new opportunities for prenatal screening, diagnosis, and therapy. In this review, we aim to summarize the evidence on structural, functional, and molecular changes in the NLUTD bladder in children with spinal dysraphism and discuss possible strategies for improved management and for the development of new therapeutic approaches for affected children.

Hypoxia-Induced HIF-1α Expression Promotes Neurogenic Bladder Fibrosis via EMT and Pyroptosis

BACKGROUND

Neurogenic bladder (NB) patients exhibit varying degrees of bladder fibrosis, and the thickening and hardening of the bladder wall induced by fibrosis will further affect bladder function and cause renal failure. Our study aimed to investigate the mechanism of bladder fibrosis caused by a spinal cord injury (SCI).

METHODS

NB rat models were created by cutting the bilateral lumbar 6 (L6) and sacral 1 (S1) spinal nerves. RNA-seq, Western blotting, immunofluorescence, cell viability and ELISA were performed to assess the inflammation and fibrosis levels.

RESULTS

The rats showed bladder dysfunction, upper urinary tract damage and bladder fibrosis after SCI. RNA-seq results indicated that hypoxia, EMT and pyroptosis might be involved in bladder fibrosis induced by SCI. Subsequent Western blot, ELISA and cell viability assays and immunofluorescence of bladder tissue confirmed the RNA-seq findings. Hypoxic exposure increased the expression of HIF-1α and induced EMT and pyroptosis in bladder epithelial cells. Furthermore, HIF-1α knockdown rescued hypoxia-induced pyroptosis, EMT and fibrosis.

CONCLUSION

EMT and pyroptosis were involved in the development of SCI-induced bladder fibrosis via the HIF-1α pathway. Inhibition of the HIF-1α pathway may serve as a potential target to alleviate bladder fibrosis caused by SCI.

Activation of the TGF-β1/Smads/α-SMA pathway is related to histological and functional changes in children with neurogenic bladder

This research is to investigate the expression of the TGF-β1/Smads/α-SMA pathway and its effect on bladder histology and function in children with neurogenic bladder (NB). The bladder specimens from 10 children with NB and 8 children with vesicoureteral junction obstruction were collected into the NB and control groups. The expression of TGF-β1, Smad2, Smad3, Smad4, Smad6, α-SMA, fibronectin, collagen I and collagen III in bladder tissues was detected. In addition, the histological characteristics of the bladder were evaluated. A preoperative urodynamic study was performed on all children with NB. We analysed the correlations among the expression of the marker protein a-SMA in myofibroblasts, effector cells of the pathway, and bladder function parameters. Compared with those in the control group, the expression of TGF-β1, Smad2, Smad3, Smad4, α-SMA, fibronectin, collagen I and collagen III was significantly increased in the NB group, while the expression of Smad6 was decreased (p < 0.01). HE and Masson staining in the NB group showed increased collagen levels and hypertrophy of smooth muscle cells. Children with NB had a low bladder volume ratio (BVR), low compliance (△C) and high maximum bladder pressure, low maximum flow rate, large postvoid residual volume, low bladder contraction index and low bladder voiding efficiency. The expression of α-SMA was negatively correlated with the BVR (r =  − 0.7066, P = 0.0223) and △C (r =  − 0.6516, P = 0.0412). We conclude that the TGF-β1/Smads/α-SMA pathway is activated in the bladder tissue of children with NB and may be involved in the processes causing histological and functional changes.

Telmisartan inhibits bladder smooth muscle fibrosis in neurogenic bladder rats

Hypertension is associated with bladder symptoms. The present study investigated whether an angiotensin receptor blocker could improve the symptoms and pathological changes associated with a neurogenic bladder (NB). A Sprague-Dawley rat model of NB was constructed. Rats in the sham and model groups were gavaged with saline, and rats in the treatment group were gavaged with telmisartan. Urodynamic parameters, including maximum cystometric capacity, residual urine volume, bladder wet weight, bladder compliance and detrusor pressure, were detected. Masson and H&E staining were performed to assess bladder fibrosis and histopathological changes. The expression levels of basic fibroblast growth factor (bFGF), TGF-β1, Collagen I, Collagen III, and α-smooth muscle actin (α-SMA) were also measured by reverse transcription-quantitative PCR, western blotting and immunohistochemistry. The model rats exhibited symptoms and pathological changes associated with NB. Treatment with telmisartan reduced maximum cystometric capacity, residual urine volume, bladder compliance and bladder wet weight, and increased detrusor pressure in model rats. The tissue staining results showed that telmisartan exerted an antifibrotic effect. In addition, telmisartan inhibited the expression of bFGF, TGF-β1, Collagen I, Collagen III and α-SMA in model rats. Therefore, the results of the present study indicated that telmisartan may serve as a potential therapeutic agent for NB.

Urinary exosomal vitronectin predicts vesicoureteral reflux in patients with neurogenic bladders and spinal cord injuries

Neurogenic bladder (NGB) is an important complication of urinary tract dysfunction after spinal cord injury (SCI). However, using urodynamics and urography to guide therapy remains invasive and complicated. Therefore, the present study aimed to identify potential noninvasive biomarkers from urinary exosomes that can facilitate diagnosis and guide prognosis of patients with NGB subsequent to SCI. Urinary exosomes were isolated, and their proteome profile was analyzed by mass spectrometry. Transmission electron microscopy and Nanoparticle Tracking Analysis confirmed the size and morphological characteristics of urinary exosomes. In addition, bioinformatics analysis and parallel reaction monitoring (PRM) were used to screen candidate biomarkers. The selected biomarkers were validated using western blotting and ELISA. Mass spectrometry identified 134 upregulated proteins and 99 downregulated proteins between the vesicoureteral reflux (VUR) and non-VUR groups. A total of 18 candidate proteins were selected for PRM validation, but only vitronectin (VTN) and α-1 type I collagen (COL1A1) demonstrated significant differences. In the validation experiments using western blotting and ELISA, VTN was exclusively highly expressed in VUR patients compared with non-VUR patients. However, the ELISA results of COL1A1 revealed no significant difference when a larger sample size was used. Furthermore, a receiver operating characteristic curve of ELISA-based VTN demonstrated an area under the curve of 0.795 and 80% sensitivity at a threshold set to give 82.9% specificity. Collectively, these results suggested that VTN in urinary exosomes may be used as a biomarker to predict the progression and guide the prognosis of NGB.

Upregulation of AQP2 mediated by transcription factor FOXO1 inhibits TGF-β-induced fibrosis in human urothelial cells

Bladder outlet obstruction (BOO) is a common urological disease, and inhibition of TGF-β-induced bladder tissue fibrosis may serve as an alternative strategy for BOO treatment. Aquaporin (AQP)2 was reported to be aberrantly expressed in rat BOO, but its specific role was not clarified. The aim of the present study was to explore the role of AQP2 in TGF-β-induced urothelial cell fibrosis and elucidate the potential underlying mechanism. The SV-HUC-1 human urinary tract epithelial cell line was treated with TGF-β1 to establish an in vitro model of bladder fibrosis. Cell Counting Kit-8 and wound healing assays were performed to measure cell viability and migration, respectively. Cell transfection was conducted to silence/overexpress AQP2 and Forkhead box O1 (FOXO1). Protein expression was measured using western blotting. Luciferase reporter and chromatin immunoprecipitation assays were used to verify the predicted interaction between AQP2 and FOXO1. The present study found that AQP2 expression was downregulated in TGF-β1-treated urothelial cells. Overexpression of AQP2 significantly suppressed cell viability, migration and epithelial-to-mesenchymal transition in TGF-β1-treated SV-HUC-1 cells. In addition, FOXO1 overexpression exerted similar effects as AQP2 overexpression on TGF-β-treated SV-HUC-1 cells, but these changes were partially abolished by AQP2 knockdown. It was also found that FOXO1 was able to bind to the AQP2 promoter and regulate AQP2 expression. In conclusion, the transcription factor FOXO1 may upregulate AQP2 expression, thereby inhibiting TGF-β-induced fibrosis in human urothelial cells. The findings of the present study may provide a novel potential strategy for the clinical treatment of BOO by targeting AQP2.