miRNA‐23a/27a attenuates muscle atrophy and renal fibrosis through muscle‐kidney crosstalk

Abstract

BackgroundThe treatment of muscle wasting is accompanied by benefits in other organs, possibly resulting from muscle–organ crosstalk. However, how the muscle communicates with these organs is less understood. Two microRNAs (miRs), miR‐23a and miR‐27a, are located together in a gene cluster and regulate proteins that are involved in the atrophy process. MiR‐23a/27a has been shown to reduce muscle wasting and act as an anti‐fibrotic agent. We hypothesized that intramuscular injection of miR‐23a/27a would counteract both muscle wasting and renal fibrosis lesions in a streptozotocin‐induced diabetic model.MethodsWe generated an adeno‐associated virus (AAV) that overexpresses the miR‐23a∼27a∼24‐2 precursor RNA and injected it into the tibialis anterior muscle of streptozotocin‐induced diabetic mice. Muscle cross‐section area (immunohistology plus software measurement) and muscle function (grip strength) were used to evaluate muscle atrophy. Fibrosis‐related proteins were measured by western blot to monitor renal damage. In some cases, AAV‐GFP was used to mimic the miR movement in vivo, allowing us to track organ redistribution by using the Xtreme Imaging System.ResultsThe injection of AAV‐miR‐23a/27a increased the levels of miR‐23a and miR‐27a as well as increased phosphorylated Akt, attenuated the levels of FoxO1 and PTEN proteins, and reduced the abundance of TRIM63/MuRF1 and FBXO32/atrogin‐1 in skeletal muscles. It also decreased myostatin mRNA and protein levels as well as the levels of phosphorylated pSMAD2/3. Provision of miR‐23a/27a attenuates the diabetes‐induced reduction of muscle cross‐sectional area and muscle function. Curiously, the serum BUN of diabetic animals was reduced in mice undergoing the miR‐23a/27a intervention. Renal fibrosis, evaluated by Masson trichromatic staining, was also decreased as were kidney levels of phosphorylated SMAD2/3, alpha smooth muscle actin, fibronectin, and collagen. In diabetic mice injected intramuscularly with AAV‐GFP, GFP fluorescence levels in the kidneys showed linear correlation with the levels in injected muscle when examined by linear regression. Following intramuscular injection of AAV‐miR‐23a∼27a∼24‐2, the levels of miR‐23a and miR‐27a in serum exosomes and kidney were significantly increased compared with samples from control virus‐injected mice; however, no viral DNA was detected in the kidney.ConclusionsWe conclude that overexpression of miR‐23a/27a in muscle prevents diabetes‐induced muscle cachexia and attenuates renal fibrosis lesions via muscle–kidney crosstalk. Further, this crosstalk involves movement of miR potentially through muscle originated exosomes and serum distribution without movement of AAV. These results could provide new approaches for developing therapeutic strategies for diabetic nephropathy with muscle wasting.

Exosome-Mediated miR-29 Transfer Reduces Muscle Atrophy and Kidney Fibrosis in Mice

“…In our earlier publication we treated diabetic mice with a muscle injection of AAV-microRNA and observed that this microRNA was transported from muscle to kidney by exosomes. 27 The current study indicates that kidney fibrosis is reduced when muscle wasting is reduced following treatment using injected exosomes containing miR-29. The downstream kidney benefit suggests that the miR-29 in the injected exosomes is functional.…”

MicroRNAs in muscle wasting

“…7 The related proteins MuRF-2 and MuRF-3 bind to microtubules and are implicated in sarcomere formation with evident functional redundancy, which has proven to be important for the maintenance of skeletal muscle, as double knockout mice lead to myopathy, reduced fore generation, and fibre type shift. 15 Recently, the lncRNA MAR1 has been shown to act as a miR-487b scavenger to regulate Wnt5a protein expression leading to stimulated muscle differentiation and regeneration as well as increased strength in mice 16 making the already complex miR regulatory system even more complicated. 9 In a rat model of paralysed muscle by spinal cord injury, a down-regulation of miRs 23a, 23b, 27b, 145, and 206 was observed 56 days after injury, 10 while injection of 30 μg of mir-206 attenuated muscle loss in a rat denervation model.…”

“…14 Overexpression of miR-23a/27a in muscle attenuated diabetes-induced muscle cachexia and attenuates renal fibrosis lesions via muscle-kidney crosstalk in streptozotocin-induced diabetic mice. 15 Recently, the lncRNA MAR1 has been shown to act as a miR-487b scavenger to regulate Wnt5a protein expression leading to stimulated muscle differentiation and regeneration as well as increased strength in mice 16 making the already complex miR regulatory system even more complicated.…”

Mesenchymal stem cell-derived exosome miR-21-3p prevents renal fibrosis

“…Exosomes are a kind of nano-vesicle secreted by cells, which carry a large number of active substances and transmits communication between cells. Renal exosome participates in renal regeneration, repair, and communication between renal tubular cells, regulates the growth of osteocytes, plays a vital role in the progression and control of nephropathy and renal tumor, and has the potential to be used as a targeted therapeutic agent for the renal disease [27,28]. Recent studies have shown that, In UUO mice, tail vein injection of exosome secreted by MSCs overexpressing miRNA-let-7c can alleviate renal injury and down-expression in UUO kidney [29].…”