Proteomic Characterization of Senescent Laryngeal Adductor and Plantaris Hindlimb Muscles

Transcriptome Analysis of Left Versus Right Intrinsic Laryngeal Muscles Associated with Innervation

OBJECTIVES/HYPOTHESIS

Recurrent laryngeal nerve injury diagnosed as idiopathic or due to short-term surgery-related intubation exhibits a higher incidence of left-sided paralysis. While this is often attributed to nerve length, it is hypothesized there are asymmetric differences in the expression of genes related to neuromuscular function that may impact reinnervation and contribute to this laterality phenomenon. To test this hypothesis, this study analyzes the transcriptome profiles of the intrinsic laryngeal muscles (ILMs), comparing gene expression in the left versus right, with particular attention to genetic pathways associated with neuromuscular function.

STUDY DESIGN

Laboratory experiment.

METHODS

RNA was extracted from the left and right sides of the rat posterior cricoarytenoid (PCA), lateral thyroarytenoid (LTA), and medial thyroarytenoid (MTA), respectively. After high-throughput RNA-Sequencing, 88 samples were organized into 12 datasets according to their age (P15/adult), sex (male/female), and muscle type (PCA/LTA/MTA). A comprehensive bioinformatics analysis was conducted to compare the left-right ILMs across different conditions.

RESULTS

A total of 774 differentially expressed genes were identified across the 12 experimental groups, revealing age, sex, and muscle-specific differences between the left versus right ILMs. Enrichment analysis of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways implicated several genes with a left-right laryngeal muscle asymmetry. These genes are associated with neuronal and muscular physiology, immune/inflammatory response, and hormone control.

CONCLUSION

Bioinformatics analysis confirmed divergent transcriptome profiles between the left-right ILMs. This preliminary study identifies putative gene targets that will characterize ILM laterality.

LEVEL OF EVIDENCE

N/A Laryngoscope, 134:3741-3753, 2024.

Fiber-Type Shifting in Sarcopenia of Old Age: Proteomic Profiling of the Contractile Apparatus of Skeletal Muscles

The progressive loss of skeletal muscle mass and concomitant reduction in contractile strength plays a central role in frailty syndrome. Age-related neuronal impairments are closely associated with sarcopenia in the elderly, which is characterized by severe muscular atrophy that can considerably lessen the overall quality of life at old age. Mass-spectrometry-based proteomic surveys of senescent human skeletal muscles, as well as animal models of sarcopenia, have decisively improved our understanding of the molecular and cellular consequences of muscular atrophy and associated fiber-type shifting during aging. This review outlines the mass spectrometric identification of proteome-wide changes in atrophying skeletal muscles, with a focus on contractile proteins as potential markers of changes in fiber-type distribution patterns. The observed trend of fast-to-slow transitions in individual human skeletal muscles during the aging process is most likely linked to a preferential susceptibility of fast-twitching muscle fibers to muscular atrophy. Studies with senescent animal models, including mostly aged rodent skeletal muscles, have confirmed fiber-type shifting. The proteomic analysis of fast versus slow isoforms of key contractile proteins, such as myosin heavy chains, myosin light chains, actins, troponins and tropomyosins, suggests them as suitable bioanalytical tools of fiber-type transitions during aging.

Larynx proteomics after jellyfish collagen IL : Increased ECM /collagen and suppressed inflammation

Objectives/Hypothesis

Compare proteomic profiles of rabbit vocal folds (VFs) injected with micronized cross‐linked jellyfish collagen “collagen Type 0” (MX‐JC) against two clinical products for injection medialization laryngoplasty (IL).

Study Design

Animal model.

Methods

Left recurrent laryngeal nerve sectioning and IL were performed in New Zealand White rabbits (N = 6/group). Group 1 received (MX‐JC) and adipose‐derived stem cells (ADSCs), Group 2, MX‐JC alone; Group 3, cross‐linked hyaluronic acid; and Group 4, micronized acellular dermis. Animals were sacrificed at 4 and 12 weeks. Proteomic profiling of injected versus noninjected VFs by nano‐liquid chromatography, tandem mass spectrometry, and reactome gene ontology analysis was performed.

Results

Overall, 37–61 proteins were found to be upregulated and 60–284 downregulated in injected versus non‐injected VFs (>1.5 fold, false discovery rate‐adjusted p < .05). Over‐representation analysis (% of total) revealed top up‐regulated pathways at 4 and 12 weeks, respectively: Group 1, keratan sulfate metabolism (46%) and cellular processes (29%); Group 2, extracellular matrix (ECM)/collagen processes (33%) and beta oxidation (39%); Group 3, cellular processes (50%) and energy metabolism (100%); and Group 4, keratan sulfate metabolism (31%) and inflammation (50%). Top downregulated pathways were: Group 1, Inflammation (36%) and glucose/citric acid metabolism (42%); Group 2, cell signaling (38%) and glucose/citric acid metabolism (35%); Group 3, keratan sulfate metabolism (31%) and ECM/collagen processes (48%); and Group 4, glucose/citric acid metabolism (33%) and ECM/collagen processes (43%).

Conclusions

MX‐JC “collagen Type 0” upregulates pathways related to ECM/collagen formation and downregulates pathways related to inflammation suggesting that it is promising biomaterial for IL.

Level of Evidence

NA

Potential Biophysiological Mechanisms Underlying Vocal Demands and Vocal Fatigue

Patients with complaint of vocal fatigue have perceptual, acoustic, and aerodynamic outcomes that are heterogeneous in nature. One reason may be due to different underlying biophysiological mechanisms that lead to these heterogeneous clinical presentations. Five potential mechanisms are proposed: neuromuscular, metabolic, vocal tissue, afferent, and central neural. Analytical frameworks and study designs to study these mechanisms are also addressed. A better understanding of biophysiological mechanisms of vocal fatigue can improve precision of therapeutic approaches. It can also help shift management from symptom-based to etiology-focused approaches for vocal fatigue.