Mast Cell Accumulation and Degranulation in Rat Bladder with Partial Outlet Obstruction

Area of Science:

• Urology
• Cell Biology
• Pharmacology

Background:

• Benign prostatic hyperplasia (BPH) leads to partial bladder outlet obstruction (pBOO), causing both voiding and storage symptoms.
• Enhanced 5-hydroxytryptamine (5-HT)-induced bladder contraction in pBOO bladders is a potential cause of storage symptoms.
• The presence and source of 5-HT in rat bladders, particularly in the context of pBOO, remain largely uncharacterized.

Purpose of the Study:

• To investigate the hypothesis that mast cells are a source of 5-HT in rat bladders.
• To examine the distribution of mast cells and 5-HT in the bladders of rats with pBOO.
• To correlate mast cell presence and degranulation with 5-HT localization in pBOO models.

Main Methods:

• Partial bladder outlet obstruction (pBOO) and sham operations were performed on female Sprague-Dawley rats.
• Bladders were isolated and processed for light and electron microscopy.
• Mast cells were identified using toluidine blue staining, and 5-HT was detected via immunohistochemical staining.

Main Results:

• Mast cells were found in the mucosa/submucosa of sham bladders and increased in the detrusor muscle/subserosa/serosa of pBOO bladders, particularly in the subserosal layer.
• The distribution of mast cells closely matched that of 5-HT-positive cells in consecutive sections.
• While degranulated mast cells were present in both groups, their proportion was significantly elevated in all regions of pBOO rat bladders.

Conclusions:

• Mast cells in rat bladders contain 5-HT and are more numerous in the subserosal layer of pBOO bladders.
• Increased release of 5-HT from mast cells in pBOO bladders may stimulate 5-HT2 receptors on detrusor muscle.
• This mechanism involving mast cell-derived 5-HT is suggested as a potential contributor to storage symptoms in pBOO.