Background & Aims
microRNAs (miRNAs) are non-coding RNAs that act as epigenetic modulators and affect the expression of their target genes. As a result, they have emerged as master switches of almost all processes in health and disease, including neuropathy and neuronal regeneration. After peripheral nerve injury, sensory neurons residing in the dorsal root ganglia (DRG) alter their excitability and cellular signaling programs including transcriptomic profiles indicative of processes related to neuropathic pain as well as axonal regeneration. The neurons’ responses are highly complex rendering distinguishing between the mechanisms involved in neuronal regeneration and neuropathy highly challenging.
Methods
In order to elucidate the role of miRNAs in these neuronal responses to injury, we utilized the spared nerve injury (SNI) model in mice. Paired miRNA:mRNA sequencing was performed on DRG of sham and SNI-treated animals, and the top differentially expressed miRNAs were further characterized by employing a combination of complementary methods, including bioinformatics, quantitative RT-PCR, fluorescent in situ hybridization in DRG sections, behavior phenotyping, cellular manipulations of microRNAs, RNA and protein expression analysis, outgrowth assays and the generation and assessment of microRNA deficient transgenic mice.
Results
In vivo inhibition of the top-upregulated miRNA miR-21a-5p using antisense oligonucleotides (ASO) alleviated SNI-induced mechanical hypersensitivity. On the other hand, ASO-inhibition as well as global depletion of the second most upregulated miRNA in a transgenic mouse model did not alleviate injury-induced pain-like behaviors. DRG neurons from these mice exhibited a significantly reduced neurite outgrowth in vitro, induction of this miRNA resulted in enhanced neuronal outgrowth. Furthermore, mRNA sequencing of DRG derived from transgenic mice revealed deregulated expression of neuroregeneration-related genes.
Conclusions
We propose that after peripheral nerve injury, specific miRNAs act as orchestrators of the expression of mRNA transcripts that are differentially implicated in pathways related to neuronal regeneration as well as neuropathic pain. By addressing the mechanistic aspects of the complex and diverging cellular responses that are initiated after peripheral nerve lesion, our study reveals the importance of dissecting the differential roles of miRNAs and introduces them as potential novel intervention strategies for neuronal regeneration as well as neuropathic pain treatment.
References
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Kalpachidou, T., K. K. Kummer and M. Kress (2020). “Non-coding RNAs in neuropathic pain.” Neuronal Signal 4(1): NS20190099.
López-González, M. J., M. Landry and A. Favereaux (2017). “MicroRNA and chronic pain: From mechanisms to therapeutic potential.” Pharmacology & Therapeutics 180: 1-15.
Sakai, A. and H. Suzuki (2013). “Nerve injury-induced upregulation of miR-21 in the primary sensory neurons contributes to neuropathic pain in rats.” Biochem Biophys Res Commun 435(2): 176-181.
Scholz, J. and C. J. Woolf (2007). “The neuropathic pain triad: neurons, immune cells and glia.” Nature Neuroscience 10: 1361.
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Presenting Author
Theodora Kalpachidou
Poster Authors
Theodora Kalpachidou
PhD
Medical University of Innsbruck
Lead Author
Maximilian Zeidler
PhD
Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
Lead Author
Viktor Lang
MSc
Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
Lead Author
Laura Castaldi
Lead Author
Paul Heppenstall
PhD
SISSA: Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea, 265, 34136 Trieste, Italy
Lead Author
Hermona Soreq
PhD
Edmond and Lily Safra Center for Brain Sciences, and Department of Biological Chemistry, The Hebrew
Lead Author
Kai Kummer
Mag.rer.nat.PhD
Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
Lead Author
Michaela Kress
Institute of Physiology, Medical University of Innsbruck, Innsbruck, Austria
Lead Author
Topics
- Models: Chronic Pain - Neuropathic