Aberrant Ca2+ oscillations in smooth muscle cells from overactive human bladders

Area of Science:

• Urology
• Cell Biology
• Physiology

Background:

• Overactive bladder (OAB) syndrome is common and expensive, but its causes, particularly involuntary detrusor muscle activity, are not fully understood.
• Identifying the cellular mechanisms behind OAB is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the role of intracellular Ca(2+) oscillations in smooth muscle cells from human bladders exhibiting pathological overactivity.
• To determine the cellular origins of involuntary detrusor muscle contractions in OAB.

Main Methods:

• Examined intracellular Ca(2+) oscillations in detrusor smooth muscle cells from overactive human bladders.
• Assessed the Ca(2+)-dependence and pharmacological sensitivity of spontaneous Ca(2+) oscillations.
• Measured spontaneous action potentials and depolarizing oscillations in relation to Ca(2+) transients.

Main Results:

• Smooth muscle cells from overactive bladders showed elevated basal Ca(2+) and unprovoked spontaneous Ca(2+) oscillations.
• These oscillations were Ca(2+)-dependent, verapamil-sensitive, and affected by SR Ca(2+) reuptake.
• A higher proportion of cells from overactive bladders exhibited spontaneous activity with greater oscillation magnitude.
• Spontaneous electrical and Ca(2+) activity was attenuated by NiCl(2).

Conclusions:

• This study provides the first evidence of spontaneous, autonomous cellular activity (Ca(2+) and membrane potential oscillations) originating from detrusor smooth muscle in human bladders.
• This cellular activity, mediated by Ca(2+) influx and release, underlies spontaneous muscle contractions in OAB.
• Defective Ca(2+) handling in detrusor smooth muscle contributes to the increased contractile activity observed in overactive bladders.