在有液相置换流时培养在坚附基质上的肾脏器官样品，比起静态对照组，生成了更多的血管网络，并展现出更加成熟的足细胞和小管区间（文献：Homan等人，2019年；Takasato等人，2015年）。然而，它们的生理功能还未被系统地研究。本研究通过利用负载fura-2测量器官样品中的小管，研究了21-64天培养的器官样品中[Ca2+]i的机械诱导响应。通过在离体器中微灌流或将其安置在样品池底部，以测量[Ca2+]i。当经过>40天的培养的器官样品中的微灌流小管受到腔内流体的冲击时，[Ca2+]i快速从195.0±22.1 nM（n=9；p≤0.001）的基线升高到2.5倍以上。然而，在<30天的培养的器官样品中的小管中，则未检测到这种反应。未进行收集流的小管（41天的培养）在施加了十倍的流量之后，其[Ca2+]i从基线值（p<0.001）增加了三倍。在老鼠近曲小管中，Piezo1通道对流体诱导的[Ca2+]i反应起到作用（文献：Carrisoza-Gaytan等人，EB 2019）。在培养21天后的小管结构中，可以检测到可免疫识别的顶级和底部的PIEZO1。底部的PIEZO1似乎是功能性的，因为在器官样品培养了>30天后，暴露于PIEZO1激活剂Yoda 1的底部的小管，[Ca2+]i（p≤0.001）也增加了，且峰值[Ca2+]i随着培养时间的推进而增加。这些结果与在静态培养器官样品中的小管中，流变/拉伸敏感的Ca2+通道数量和/或活性的成熟增加有关，其中包括PIEZO1。

Kidney organoids cultured on adherent matrices in the presence of superfusate flow generate vascular networks and exhibit more mature podocyte and tubular compartments compared to static controls (Homan et al., 2019; Takasato et al., 2015). However, their physiological function has yet to be systematically investigated. Here, we measured mechanoinduced changes in intracellular Ca2+ concentration ([Ca2+]i) in tubules isolated from organoids cultured for 21-64 d, microperfused in vitro or affixed to the base of a specimen chamber, and loaded with fura-2 to measure [Ca2+]i. A rapid >2.5-fold increase in [Ca2+]i from a baseline of 195.0±22.1 nM (n=9; p≤0.001) was observed when microperfused tubules from organoids >40 d in culture were subjected to luminal flow. In contrast, no response was detected in tubules isolated from organoids <30 d in culture. Nonperfused tubules (41 d) subjected to a 10-fold increase in bath flow rate also exhibited a 3-fold increase in [Ca2+]i from baseline (p<0.001). Mechanosensitive Piezo1 channels contribute to the flow-induced [Ca2+]i response in mouse distal tubule (Carrisoza-Gaytan et al., EB 2019). Immunodetectable apical and basolateral PIEZO1 was identified in tubular structures by 21 d in culture. Basolateral PIEZO1 appeared to be functional as basolateral exposure of nonperfused tubules to the PIEZO1 activator Yoda 1 increased [Ca2+]i (p≤0.001) in segments from organoids cultured for >30 d, with peak [Ca2+]i increasing with advancing days in culture. These results are consistent with a maturational increase in number and/or activity of flow/stretch-sensitive Ca2+ channels, including PIEZO1, in tubules of static organoids in culture.