Cyclic Stretch Promotes Proliferation and Contraction of Human Bladder Smooth Muscle Cells by Cajal-Mediated c-kit Expression in Interstitial Cells

Background

The present study was performed to assess the effect of mechanical stretch on the proliferation and contractile function of hBSMCs.

Material/Methods

hBSMCs and ICCs were seeded at 8×10⁴ cells/well in 6-well silicone elastomer-bottomed culture plates coated with type I collagen, and grown to 80% confluence in DMEM/10% FBS and a 5% CO₂ humidified atmosphere at 37°C. Cells of hBSMCs and hBSMCs/ICCs of co-culture were then subjected to continuous cycles of stretch-relaxation using a computer-driven, stretch-inducing device. The treated concentration of imatinib was 10 μM. Mechanisms underlying observed hBSMCs contraction were examined using Western blotting and RT-PCR. The 0.1 μM carbachol was separately added to the experimental groups, and 300 s was recorded by laser scanning confocal microscope.

Results

We found that mechanical stretch increased contraction and proliferation of hBSMCs. Calcium ion activity increased significantly after mechanical stretch. The number of hBSMCs was significantly increased after the combination mechanical stretch with ICCs treatment. After combination mechanical stretch with hBSMCs/ICCs treatment, the mRNA and protein level of M2, M3, and c-kit were significantly increased. After combination of mechanical stretch with no imatinib treatment, the proliferation of hBSMCs was higher than others, and the mRNA and protein level of M2 and M3 were significantly increased.

Conclusions

We revealed that ICCs could promote hBSMC proliferation and contraction, and cyclic stretch could promote acetylcholine receptor M2 and M3 caused by c-kit in the ICCs, which promoted the contraction of hBSMCs.

Progressive bladder remodeling due to bladder outlet obstruction: a systematic review of morphological and molecular evidences in humans

BACKGROUND

Bladder outlet obstruction is a common urological condition. We aimed to summarize available evidences about bladder outlet obstruction-induced molecular and morphological alterations occurring in human bladder.

METHODS

We performed a literature search up to December 2017 including clinical and preclinical basic research studies on humans. The following search terms were combined: angiogenesis, apoptosis, bladder outlet obstruction, collagen, electron microscopy, extracellular matrix, fibrosis, hypoxia, histology, inflammation, innervation, ischemia, pressure, proliferation, remodeling, suburothelium, smooth muscle cells, stretch, urothelium.

RESULTS

We identified 36 relevant studies. A three-stages model of bladder wall remodeling can be hypothesized involving an initial hypertrophy phase, a subsequent compensation phase and a later decompensation. Histological and molecular alterations occur in the following compartments: urothelium, suburothelium, detrusor smooth muscle cells, detrusor extracellular matrix, nerves. Cyclic stretch, increased hydrostatic and cyclic hydrodynamic pressure and hypoxia are stimuli capable of modulating multiple signaling pathways involved in this remodeling process.

CONCLUSIONS

Bladder outlet obstruction leads to progressive bladder tissue remodeling in humans. Multiple signaling pathways are involved.

MicroRNA 4323 induces human bladder smooth muscle cell proliferation under cyclic hydrodynamic pressure by activation of erk1/2 signaling pathway

We cultivated human bladder smooth muscle cells (HBSMCs) under pressures of 0 or 200 cm H₂O pressure for 24 h, before using microarray technology to extract and analyze the different expressions of miRNAs and mRNAs in the two groups. We also predicted the target mRNA of the miDNA and performed functional forecasting. Changes in miRNA were identified by quantitative real-time polymerase chain reaction (qRT-PCR) after overexpressing miRNA by transfection. We used flow cytometry to examine HBSMC proliferation, and we used qRT-PCR and Western blot analyses to quantify the expression and activation of mRNAs and proteins. There were nine upregulated and four downregulated miRNAs involved in cell proliferation, including miR 4323, which was identified by qRT-PCR ( p = 0.027). In addition, miR 4323 was shown to inhibit LYN ( p = 0.031), decrease lyn kinase ( p = 0.037), and promotes the phosphorylation of extracellular regulated protein kinases 1 and 2 (Erk1/2) ( p = 0.004). Moreover, overexpression of miR 4323 activated the proliferation pathway regulated by Erk1/2. Then, miR 4323 was shown to stimulate the proliferation of HBSMCs, with the proliferation index improving from 30.84 ± 4.57 to 52.13 ± 3.41 ( p = 0.001). In summary, when the miRNA miR 4323 was overexpressed under cyclic hydrodynamic pressure, LYN is decreased and the Erk1/2 signaling pathway is activated; in addition, miR 4323 is involved in HBSMC proliferation when under hydrodynamic pressure.