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Introduction

Previous studies have confirmed hypertrophy of extracellular matrix (ECM) can be found in bladder wall upon BOO, and muscarinic receptor antagonist can suspend the progression of bladder dysfunction caused by bladder outlet obstruction. However, the relationship between metabolism of ECM and muscarinic receptor activity remains unclear. Thus, we set up an animal experimental model of partial bladder outlet obstruction (PBOO) in female rat to explore how the muscarinic receptor antagonist affect extracellular matrix proteins, receptors and metabolism regulators in the pathological state.

Methods

Female Sprague-Dawley rats were used for the study. The rat was anesthetized and its proximal urethra were tied with 4-0 silk to create partial BOO. Tolterodine was used as the muscarinic receptor antagonist in the dosage of 0.36mg/kg/day from Day One after operation. Rats were randomly sub-divided into 3 groups: the sham group, the PBOO group and PBOO with tolterodine group. They were raised for 3 weeks and their bladder were harvested for further tests. Total bladder RNA was extracted according to the protocol, whole rat genome microarray and RT-PCR testing were performed to survey the gene expression of extracellular matrix proteins, receptors and metabolism regulators in rat bladder. The bladder specimens were fixed and paraffin-embedded, the slides were stained with Picrosirius red to examine the Integral Optical Density (IOD) of muscle and collage fiber. Those positive proteins in gene testing above were further tested with immunohistochemical staining following the protocol.

Results

Picrosirius red stain shows that, compared with the sham group, the IOD of muscle fiber was significantly increased in PBOO group and remained in PBOO with tolterodine group (p<0.05); while the collage fiber was significantly increased in PBOO group but decreased in PBOO with tolterodine group (p<0.05). The gene microarray and qPCR testing eventually revealed 34 significant genes related to extracellular matrix. None of collage gene subtypes exhibited significant change between groups. Yet, the matrix metalloproteinase (MMPs) exhibited significant decrease in PBOO group and increase in PBOO with tolterodine group (p<0.05). In addition, PBOO inhibited the expression of non-collagen ECM protein in rat bladder wall, while muscarinic receptor antagonist could promote the expression of non-collagen ECM protein and ECM receptor. The immunohistochemical staining supported above gene analysis.

Conclusions

Muscarinic receptor antagonist can decrease the volume fraction of collage via MMPs in rat bladder wall upon PBOO condition. Simultaneously, it can regulate the expression of extracellular matrix proteins and receptors. Such relationship between muscarinic receptor and extracellular matrix may associate with the improving effect of muscarinic receptor antagonist in bladder dysfunction caused by bladder outlet obstruction.

Funding

none