Changes in the skeletal muscle transcriptome due to the intramuscular administration of lidocaine in wether lambs

Lidocaine is a commonly used local anesthetic that blocks sodium channels in nociceptor neurons, preventing the transmission of pain signals to the brain. Lidocaine can be administered to reduce discomfort during tissue biopsies. Biopsy tissue may then be used to study the transcriptome under the assumption that the genomic activity of lidocaine-treated tissue accurately reflects that of untreated tissue. This study investigated how intramuscular lidocaine injection influenced skeletal muscle gene expression in sheep, aiming to understand how transcriptomic changes could affect data interpretation. Approximately 10 min before euthanasia, the left biceps brachii muscle from each of 6 wether lambs (48.7 ± 0.8 kg) was injected (IM; 20G hypodermic needle) at a depth of 3 cm with 2 mL of 2% lidocaine (20 mg/mL); the right biceps brachii was untreated. At necropsy, muscle samples were collected from the injection sites and contralateral limbs and flash-frozen. In an additional set of lambs, lidocaine-treated and untreated samples were collected from the biceps brachii of 4 lambs, and the vastus intermedius of 4 other lambs. RNA was isolated and mRNA sequenced to a targeted depth of 20 million reads per sample. Sequences were mapped and quantified; matched-pair analysis was performed in EdgeR. No genes were consistently differentially expressed due to treatment in both muscle types, perhaps reflecting their distinct physiological roles. Lidocaine did influence the transcriptome with anti-inflammatory effects evident in both muscle types, including the downregulation of immune-associated transcription factors and other genes. Lidocaine's influence varied on other broad categories of genes, including those associated with muscle contractility, tissue repair, and structural integrity, which could affect the interpretation of transcriptome data in studies of muscle growth and development. Pathway analysis revealed that lidocaine impacted signaling mechanisms for cellular connectivity and structure. This study demonstrates that intramuscular administration of lidocaine results in the alteration of tissue's gene expression profiles, highlighting the importance of considering lidocaine's influence in transcriptome analyses. Thus, the use of complementary physiological measures to validate transcriptomic findings is recommended to ensure observed gene expression changes are accurately attributed to experimental conditions rather than the effects of lidocaine.