Section of Nephrology, Yale University School of Medicine, New Haven, Connecticut.
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut.
Am J Physiol Renal Physiol. 2022 Mar 1;322(3):F322-F334. doi: 10.1152/ajprenal.00284.2021. Epub 2022 Jan 31.
Renal tubular casts originating from detached epithelial cells after ischemia-reperfusion injury (IRI) can obstruct tubules and negatively impact glomerular filtration rate. Using multiphoton imaging of 400-μm-thick kidney sections, the distribution of casts and morphometric measurement of tubules was performed along the entire nephron for the first time. Tubular nuclei are shed before cell detachment, and visually occlusive casts () appeared at 12 h after IRI at the S3/thin descending limb (tDL) junction. casts peaked at 24 h after injury [present in 99% of S3, 78% of tDL, 76% of thin ascending limb (tAL), 60% of medullary thick ascending limb (mTAL), and 10% of connecting tubule segments]. Cast formation in the S3 correlated with selective loss of cell numbers from this tubule segment. By , most mTALs and connecting tubules were cast free, whereas 72% of S3 tubules and 58% of tDLs still contained casts. Although bulk phagocytosis of cast material by surviving tubular cells was not observed, mass spectrometry identified large numbers of tryptic peptides in the outer medulla, and trypsin levels were significantly increased in the kidney and urine 24 h after IRI. Administration of either antipain or camostat to inhibit trypsin extended cast burden to the S2, led to sustained accumulation of S3 casts after IRI, but did not affect cast burden in the mTAL or renal function. Our data provide detailed and dynamic mapping of tubular cast formation and resolution after IRI that can inform future interventions to accelerate cast clearance and renal recovery. This detailed characterization of the dynamic distribution of dead cell debris in ischemically injured kidney tubules reveals which cells in the kidney are most severely injured, when and where tubular casts form, and when (and to a lesser extent, how) they are cleared.
缺血再灌注损伤 (IRI) 后脱落的上皮细胞形成的肾小管管型可阻塞小管并对肾小球滤过率产生负面影响。本研究通过对 400μm 厚的肾脏切片进行多光子成像，首次沿整个肾单位对管型的分布和肾小管的形态测量进行了研究。在细胞脱落之前，肾小管核就已经脱落，在 IRI 后 12 小时，在 S3/薄降支 (tDL) 交界处就可以看到管型完全阻塞 ()。24 小时后损伤时出现峰值 [在 S3 中占 99%，tDL 中占 78%，薄升支 (tAL) 中占 76%，髓质厚升支 (mTAL) 中占 60%，连接小管段中占 10%]。S3 中的管型形成与该管段细胞数量的选择性丢失相关。到 72 小时，大多数 mTAL 和连接小管没有管型，但 72%的 S3 管和 58%的 tDL 仍含有 casts。尽管没有观察到存活的肾小管细胞对管型物质的大量吞噬，但质谱分析在外髓质中鉴定出大量胰蛋白酶肽，IRI 后 24 小时肾脏和尿液中的胰蛋白酶水平显著升高。给予安痛定或卡莫司他抑制胰蛋白酶可将管型负担扩展到 S2，导致 IRI 后 S3 管型持续积聚，但不影响 mTAL 中的管型负担或肾功能。本研究提供了 IRI 后肾小管管型形成和消退的详细和动态图谱，为未来加速管型清除和肾脏恢复的干预措施提供了信息。这项对缺血性肾损伤肾小管中死细胞碎片动态分布的详细描述揭示了肾脏中哪些细胞受到最严重的损伤，管型何时以及在何处形成，以及何时（以及在较小程度上，如何）清除。
