Adherens junctions of the human detrusor

To immunohistochemically identify the protein composition of adherens junctions, which couple smooth muscle cells mechanically, and to confirm their decrease in different bladder dysfunctions, as studies in geriatric bladder dysfunction show fewer such junctions in patients with detrusor overactivity (DO) and bladder outlet obstruction (BOO).

Detrusor biopsies were obtained from video-urodynamically evaluated patients with neurogenic DO (NDO, 31 patients), BOO (six patients) and from six patients with stress urinary incontinence (SUI) with stable, unobstructed detrusors (serving as controls). Specimens were fixed, paraffin-embedded, sectioned, stained with a polyclonal pan-cadherin antibody, monoclonal alpha-, beta- and gamma-catenin antibodies, and a monoclonal integrin-beta1 antibody. All antibodies were known to react with proteins of adherens junctions. Two examiners unaware of sample origin evaluated the sections qualitatively and using a semiquantitative scale. The results were correlated with the patient groups.

Specific immunohistochemical staining of pan-cadherin, alpha-, beta- and gamma-catenin could not be detected in any detrusor smooth muscle compartment, but was present in the urothelium. There was integrin-beta1 reactivity in the basement membranes of bladder smooth muscle cells in 38 of 43 detrusor biopsies. There were no differences among the three groups.

The known proteins of cell-cell adherens junctions are not part of the cell-cell junctions of detrusor smooth muscle. The specific staining of integrin-beta1 indicates either the presence of cell-matrix junctions or of cell-cell junctions within the human detrusor. Further studies are needed to identify the complete protein composition of adherens junctions within smooth muscle cells.