Renal tubular epithelial cell-derived Exosomal miR-330-3p plays a key role in fibroblast activation and renal fibrosis by regulating CREBBP.

Background: Renal tubular injury and activation of peripheral fibroblasts are hallmarks of chronic kidney disease (CKD), suggesting a close connection between the two cell types. Exosomes transport miRNAs and other substances to recipient cells. The involvement of exosome-mediated intercellular communication has been suggested in various diseases, including renal fibrosis. However, the underlying mechanisms remain to be determined.

Methods: Rab 27a-knockout mice were constructed to confirm the role of exosomes in mice with adenine-induced renal fibrosis. Exosome secretion from the kidneys of mice with adenine-induced renal fibrosis and UA-stimulated NRK-52E cells were investigated. Exosomes released from NRK-52E cells were harvested and incubated with NRK-49 F fibroblasts or injected intravenously into the mice via the tail vein. High-throughput miRNA sequencing was used to evaluate the miRNA profiles of UA-Exo. The roles of candidate miRNAs and their target genes and related pathways were predicted and evaluated in vitro and in vivo using specific miRNA mimics, miRNA inhibitors, siRNAs, and adeno-associated viruses (AAV).

Results: Inhibition of exosome secretion by Rab27a knockout or siRNA Rab27a treatment inhibited fibroblast activation and ameliorated renal fibrosis. Significantly increased renal fibrosis was seen in mice treated with adenine, and exosome release was increased after UA treatment of NRK-52E cells. Exosomes released from NRK-52E cells after UA stimulation activated fibroblasts and exacerbated renal fibrosis. The expression of miR-330-3p in exosomes was significantly increased in the UA-Exo group compared with the control group, suggesting the potential use of miR-330-3p as a marker of renal fibrosis. CREBBP was found to be a specific target of miR-330-3p. The stimulation or inhibition of exosomal miR-330-3p release from renal tubular epithelial cells thus promoted or blocked fibroblast activation in vitro, while miR-330-3p-deficient exosomes attenuated renal fibrosis by modulating CREBBP in vivo.

Conclusion: The findings suggest that exosomes play an important role in promoting renal fibrosis by mediating the communication between renal tubular epithelial cells and fibroblasts. This role is associated with inhibition of CREBBP activity by exosomal miR-330-3p in fibroblasts. Thus, the miR-330-3p/CREBBP axis is a promising target for the treatment and management of renal fibrosis.