RNAscope^TM Technology for Cardiovascular and Skeletal Muscle Research

Heart and skeletal muscle are complex, heterogeneous tissues, comprised of multiple cell types. The RNAscope in situ hybridization (ISH) assay allows for precious insights into the complex spatial organization of gene expression within the heart and muscle. It is well-suited for the discovery and characterization of genes and pathways involved in normal cardiac and skeletal muscle processes as well as  in the development of cardiovascular and skeletal muscle diseases. The RNAscope assay enables (co)-localization and characterization of transcripts in the different heart & skeletal muscle cell types down to the single-cell level.

Several studies have been published demonstrating the application of the RNAscope ISH assay in cardiovascular and skeletal muscle research:

Cardiac Development

• Blood flow drives dynamic gene expression in developing heart valves
  How the cardiac cushions are remodeled into mature valve leaflets is not well understood. Goddard et al. found that hemodynamic forces drive expression of KLF2 by the cardiac endocardium by regulating Wnt9b. The RNAscope assay was used to detect the graded expression of Wnt9b in remodeling cardiac cushions.

Cardiomyopathy

• Nonmyocytes implicated in Marfan syndrome cardiomyopathy
  In children with Marfan syndrome (MFS), heart failure is the leading cause of death. Rouf et al. used an MFS mouse model (Fbn1C1039G/+) to determine that pathologic ERK activation and TGFβ3 signaling in nonmyocytes contribute to MFS disease pathogenesis. RNAscope ISH identified the specific cellular compartment that is the source of Tgfβ3 expression.

Cardiac Injury and Regeneration

• Upregulation of multiple Wnts during cardiac injury response
  While the adult injured heart forms a persistent fibrotic scar that leads to heart failure, the neonatal injured heart develops transient fibrotic tissue that gets replace by regenerated cardiomyocytes. To elucidate the molecular mechanisms of neonatal cardiac fibrosis, Mizutani et al. investigated Wnt signaling in the neonatal heart after cryoinjury. RNAscope™ ISH was used to survey the expression of 19 Wnt family members.

Cardiac Gene Therapy

• VEGF mRNA therapy improves cardiac function after myocardial infarction
  Manipulating cardiac gene expression without integrating into the genome, such as by mRNA therapy, could be a safe, clinical way to improve cardiac function. Carlsson et al. show that a VEGF-A mRNA improves cardiac function following myocardial infarction in pigs. RNAscope ISH demonstrated that the VEGF-A mRNA therapy localized to the interstitium prior to uptake by cardiomyocytes and confirmed degradation of the mRNA therapy after protein production.

Skeletal Muscle Injury and Regeneration

• Induction of Gm7325 in skeletal muscle following injury
  Gm7325 is a relatively uncharacterized gene whose expression is increased in several muscular dystrophy models. Takei et al. show that Gm7325 transcription is induced by skeletal myogenesis master transcription factor MyoD in activated satellite cells and may play an important role in skeletal muscle regeneration. RNAscope ISH revealed specific cellular localization of Gm7325 mRNA in injured skeletal muscle.

Genetic Animal Model Confirmation

• Confirmation of Fn1 downregulation in cardiac neural crest cells
  The role of Fibronectin 1 (Fn1) cardiac development has been precluded due to early embryonic lethality of the global deletion. Wang et al. conditionally inactivated Fn1 in the heart and used RNAscope ISH to confirm specific downregulation of Fn1 in neural crest cells.

 
Transcriptomic Validation

• Heterogeneity of cardiomyocyte transcriptomic response during heart failure
  Cardiac regeneration is a promising treatment for heart failure, but there are very few resident cardiomyocyte (CM) progenitor cells in the adult mammalian heart and differentiated adult CMs divide at very low rates. See et al. used single CM nuclear RNA-seq of healthy and injured mouse hearts to reveal subpopulations of adult CMs regulated by lincRNAs. RNAscope ISH confirmed the identity of Sca1+ CMs as adults CMs and not fibroblasts or endothelial cells.