Smooth muscle membrane organization in the normal and dysfunctional human urinary bladder: a structural analysis.
OBJECTIVE
The decline in contractile properties is a characteristic feature of the dysfunctional bladder as a result of infravesical outlet obstruction. During clinical progression of the disease, smooth muscle cells undergo structural modifications. Since adaptations to constant changes in length require a high degree of structural organization within the sarcolemma, we have investigated the expression of several proteins, which are involved in smooth muscle membrane organization, in specimens derived from normal and dysfunctional organs.


METHODS
Specimen from patients with urodynamically normal/equivocal (n = 4), obstructed (n = 2), and acontractile (n = 2) bladders were analyzed relative to their structural features and sarcolemmal protein profile.


RESULTS
Smooth muscle cells within the normal urinary bladder display a distinct sarcolemmal domain structure, characterized by firm actin-attachment sites, alternating with flexible "hinge" regions. In obstructed bladders, foci of cells displaying degenerative sarcolemmal changes alternate with areas of hypertrophic cells in which the membrane appears unaffected. In acontractile organs, the overall membrane structure remains intact, however annexin 6, a protein belonging to a family of Ca2+-dependent, "membrane-organizers," is downregulated.


CONCLUSIONS
Degenerative changes in smooth muscle cells, which are chronically working against high resistance, are preferentially located within the actin-attachment sites. In acontractile bladders, the downregulation of annexin 6 might have a bearing on the fine-tuning of the plasma membrane during contraction/relaxation cycles.
Burkhard
Fiona C
FC
Department of Urology, University of Bern, Bern, Switzerland. fiona.burkhard@insel.ch
Monastyrskaya
Katia
K
Studer
Urs E
UE
Draeger
Annette
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017302:Annexins / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D006801:Humans; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D012508:Sarcolemma / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D001745:Urinary Bladder Diseases / Q000473:pathology* / Q000503:physiopathology
D017302:Annexins; D002135:Calcium-Binding Proteins