Elsevier

Kidney International

Volume 97, Issue 6, June 2020, Pages 1181-1195
Kidney International

Basic Research
Tubule-derived exosomes play a central role in fibroblast activation and kidney fibrosis

https://doi.org/10.1016/j.kint.2019.11.026Get rights and content

Extracellular vesicles such as exosomes are involved in mediating cell-cell communication by shuttling an assortment of proteins and genetic information. Here, we tested whether renal tubule-derived exosomes play a central role in mediating kidney fibrosis. The production of exosomes was found to be increased in the early stage of unilateral ureteral obstruction, ischemia reperfusion injury or 5/6 nephrectomy models of kidney disease. Exosome production occurred primarily in renal proximal tubular epithelium and was accompanied by induction of sonic hedgehog (Shh). In vitro, upon stimulation with transforming growth factor-β1, kidney proximal tubular cells (HKC-8) increased exosome production. Purified exosomes from these cells were able to induce renal interstitial fibroblast (NRK-49F) activation. Conversely, pharmacologic inhibition of exosome secretion with dimethyl amiloride, depletion of exosome from the conditioned media or knockdown of Shh expression abolished the ability of transforming growth factor-β1-treated HKC-8 cells to induce NRK-49F activation. In vivo, injections of tubular cell-derived exosomes aggravated kidney injury and fibrosis, which was negated by an Shh signaling inhibitor. Blockade of exosome secretion in vivo ameliorated renal fibrosis after either ischemic or obstructive injury. Furthermore, knockdown of Rab27a, a protein that is essential for exosome formation, also preserved kidney function and attenuated renal fibrotic lesions in mice. Thus, our results suggest that tubule-derived exosomes play an essential role in renal fibrogenesis through shuttling Shh ligand. Hence, strategies targeting exosomes could be a new avenue in developing therapeutics against renal fibrosis.

Section snippets

Increased biogenesis of exosomes and microvesicles in various models of CKD

We first examined the production of extracellular vesicles in various models of CKD induced by unilateral ureteral obstruction (UUO), ischemia-reperfusion injury (IRI), and 5/6 nephrectomy, respectively. As shown in Figure 1a to d, renal expression of CD63, a marker of exosomes that is associated with membranes of intracellular vesicles,16 was upregulated after UUO or IRI. Time-course studies revealed that CD63 started to increase as early as day 1 and continued to increase along with the

Discussion

Kidney tubular epithelium is vulnerable to various metabolic, ischemic, and toxic insults. The injured and/or stressed tubular epithelial cells often engage multiple intercellular crosstalks with interstitial fibroblasts, leading to their activation and expansion.4,36 Such epithelial-mesenchymal communication (EMC) has become a new paradigm in renal fibrogenesis.27,37 In the present study, we show that extracellular vesicles, particularly exosomes, play an essential role in mediating EMC in

Animal model

Male C57BL/6 mice were purchased from Vital River Laboratory (Beijing, China) and housed with free access to water and chow diet. For the UUO model, mice were subjected to double-ligating left ureter following a midline abdominal incision. UIRI was established as described.26 Briefly, left renal pedicles were clipped for 35 minutes using microaneurysm clamps. The intact right kidney was removed at 10 days post-UIRI, and then mice were sacrificed a day after.46 The kidney tissues were collected

Disclosure

All the authors declared no competing interests.

Acknowledgments

This work was supported by the National Natural Science Foundation of China grants 81521003, 81700652, and 81722011 and Guangzhou Regenerative Medicine and Health Guangdong Laboratory grants 2018GZR110104001, 2018GZR0202003, and 2018GZR110102004.

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