Identification of PDGFRα Positive Populations of Interstitial Cells in Human and Guinea Pig Bladders

Abstract

The bladder wall comprises a complex array of cells, including urothelium, smooth muscle, nerves and interstitial cells. Interstitial cells have several subtypes based on site, morphology and differential expression of markers such as anti-vimentin and anti-KIT. We examined whether a subpopulation of interstitial cells immunopositive for PDGFRα exists in human and guinea pig bladders. Human and guinea pig bladder tissues were processed for immunohistochemistry and examined by bright field or confocal microscopy. Whole mount tissues and paraffin sections were labeled with antibodies to PDGFRα, vimentin, KIT and PGP9.5. Protein expression was assessed by Western blot. PDGFRα(+) cells were present in human and guinea pig bladders. In the guinea pig PDGFRα(+) cells had a branched stellate morphology and formed networks in the lamina propria. In human and guinea pig detrusors PDGFRα(+) cells were elongated on the boundary of smooth muscle bundles or were seen as groups of stellate cells in the interbundle spaces. PDGFRα(+) cells were located close to nerves labeled by PGP9.5. Double labeling revealed that PDGFRα(+) cells were a subgroup of the vimentin(+) population. A significant proportion of PDGFRα(+) cells were also KIT(+). Bands corresponding to PDGFRα, KIT and vimentin proteins were detected on Western blot. To our knowledge this study is the first to identify PDGFRα(+)/KIT(+) cells in the bladder lamina propria and detrusor layers. These cells are a subgroup of the vimentin(+) population, showing the complexity of bladder interstitial cells. PDGFRα(+) cells are apparently structurally associated with intramural nerves, indicating integration with bladder control mechanisms.