Circadian regulation of bladder capacity and extracellular matrix variation independent of central clock–driven behavioral rhythms

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Mammals exhibit a circadian rhythm of bladder capacity, but whether this rhythm can be maintained through intrinsic bladder mechanisms independently of central clock-driven behavioral rhythms remains unclear. Here, we addressed this question using Bmal1 conditional knockout mice lacking central clock function in the brain. Under constant darkness, these mice lost behavioral rhythmicity but largely retained circadian variation in bladder capacity together with bladder clock gene expression. Transcriptomic analyses further identified diurnal variation in bladder extracellular matrix–related factors, suggesting a potential molecular basis for bladder capacity rhythmicity. These findings indicate that the bladder harbors a peripheral circadian mechanism that contributes to the circadian regulation of bladder capacity and provides insight into the role of peripheral clock mechanisms in bladder pathophysiology. The bladder largely preserves bladder capacity rhythms despite disrupted central clock-driven behavioral rhythms, suggesting potential roles for the peripheral bladder clock and extracellular matrix variation in temporal storage regulation.