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Published on: September 14, 2019
Efficient Downregulation of Alk4 in Skeletal Muscle After Systemic Treatment with Conjugated siRNAs in a Mouse Model
Sarah Engelbeen1, Svetlana Pasteuning-Vuhman1, Joke Boertje-van der Meulen1
1Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
Abstract:
Downregulation of genes involved in the secondary pathology of Duchenne muscular dystrophy, for example, inflammation, fibrosis, and adiposis, is an interesting approach to ameliorate degeneration of muscle and replacement by fibrotic and adiposis tissue. Small interfering RNAs (siRNAs) are able to downregulate target genes, however, delivery of siRNAs to skeletal muscle still remains a challenge. We investigated delivery of fully chemically modified, cholesterol-conjugated siRNAs targeting Alk4, a nontherapeutic target that is expressed highly in muscle. We observed that a single intravenous or intraperitoneal (IP) injection of 10 mg/kg resulted in significant downregulation of Alk4 mRNA expression in skeletal muscles in both wild-type and mdx mice. Treatment with multiple IP injections of 10 mg/kg led to an overall reduction of Alk4 expression, reaching significance in tibialis anterior (39.7% ± 6.2%), diaphragm (32.7% ± 5.8%), and liver (41.3% ± 29.9%) in mdx mice. Doubling of the siRNA dose did not further increase mRNA silencing in muscles of mdx mice. The chemically modified conjugated siRNAs used in this study are very promising for delivery to both nondystrophic and dystrophic muscles and could have major implications for treatment of muscular dystrophy pathology.
Insights
Chemically modified cholesterol-conjugated small interfering RNAs (siRNAs) effectively deliver to skeletal muscles. This offers a promising strategy for treating Duchenne muscular dystrophy by downregulating target genes.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Duchenne muscular dystrophy (DMD) pathology involves muscle degeneration, inflammation, fibrosis, and adiposis.
- Small interfering RNAs (siRNAs) can downregulate disease-associated genes, but effective skeletal muscle delivery remains a challenge.
Purpose of the Study:
- To investigate the delivery and efficacy of chemically modified, cholesterol-conjugated siRNAs targeting Alk4 in skeletal muscles of wild-type and mdx mice.
- To assess the potential of this siRNA delivery system for treating muscular dystrophy.
Main Methods:
- Administered single intravenous or intraperitoneal (IP) injections of 10 mg/kg of cholesterol-conjugated siRNAs targeting Alk4.
- Performed multiple IP injections of 10 mg/kg and a doubled dose in mdx mice.
- Quantified Alk4 mRNA expression in skeletal muscles and liver.
Main Results:
- A single injection of siRNAs significantly downregulated Alk4 mRNA in skeletal muscles of both wild-type and mdx mice.
- Multiple IP injections reduced Alk4 expression in tibialis anterior, diaphragm, and liver of mdx mice.
- Doubling the siRNA dose did not enhance mRNA silencing in mdx mouse muscles.
Conclusions:
- Chemically modified, cholesterol-conjugated siRNAs demonstrate effective delivery to skeletal muscles, including dystrophic muscles.
- This siRNA delivery approach holds significant promise for the therapeutic management of Duchenne muscular dystrophy.
