Effects of aging on thyroarytenoid muscle regeneration

Comparison Between Patient-Perceived Voice Changes and Quantitative Voice Measures in the First Postoperative Year After Thyroidectomy: A Secondary Analysis of a Randomized Clinical Trial

Importance

Voice changes after thyroidectomy are typically attributed to recurrent laryngeal nerve injury. However, most postoperative voice changes occur in the absence of clinically evident vocal fold paralysis. To date, no study has compared the prevalence, duration, and consequences of voice-related disability from the patient perspective with use of quantitative vocal measures.

Objectives

To assess the quality-of-life consequences of postthyroidectomy voice change from the perspective of patients with thyroid cancer and to compare patient-perceived voice changes with changes in quantitative vocal variables at 5 time points in the first postoperative year.

Design, Setting, and Participants

This prospective mixed methods observational study within a randomized clinical trial occurred at the University of Wisconsin Hospital and Clinics. Participants were 42 patients with clinically node-negative papillary thyroid cancer without a preexisting vocal cord paralysis who were recruited and enrolled from outpatient clinics between June 6, 2014, and March 6, 2017, as part of the ongoing randomized clinical trial.

Intervention

Total thyroidectomy.

Main Outcomes and Measures

Semistructured interviews, symptom prevalence, and instrumental voice evaluations (laryngoscopy, phonation threshold pressure, Dysphonia Severity Index, and Voice Handicap Index) occurred at baseline (n = 42) and 2-week (n = 42), 6-week (n = 39), 6-month (n = 35), and 1-year (n = 30) postoperative time points.

Results

Participants had a mean age of 48 years (interquartile range, 38-58 years; age range, 22-70 years) and were mostly female (74% [31 of 42]) and of white race/ethnicity (98% [41 of 42]). Impaired communication was the primary theme derived from patient interviews from before thyroidectomy to after thyroidectomy. Voice changes were perceived by 24 participants at 2 weeks after thyroidectomy. After surgery, voice symptoms were prevalent and persisted for 50% (21 of 42) of participants out to at least 1 year of follow-up. Quantitative vocal perturbations were detected in the Dysphonia Severity Index and Voice Handicap Index at the 2-week follow-up but returned to baseline levels by the 6-week follow-up visit.

Conclusions and Relevance

Voice changes are common after surgery for papillary thyroid cancer and affect quality of life for many patients out to 1 year of follow-up. Directly querying patients about postoperative voice changes and questioning whether commonly used aerodynamic and acoustic variables detect meaningful voice changes are important in identifying patients whose quality of life has been affected by postthyroidectomy dysphonia.

Trial Registration

ClinicalTrials.gov Identifier: NCT02138214.

Enhancement of aging rat laryngeal muscles with endogenous growth factor treatment

Clinical evidence suggests that laryngeal muscle dysfunction is associated with human aging. Studies in animal models have reported morphological changes consistent with denervation in laryngeal muscles with age. Life-long laryngeal muscle activity relies on cytoskeletal integrity and nerve-muscle communication at the neuromuscular junction (NMJ). It is thought that neurotrophins enhance neuromuscular transmission by increasing neurotransmitter release. We hypothesized that treatment with neurotrophin 4 (NTF4) would modify the morphology and functional innervation of aging rat laryngeal muscles. Fifty-six Fischer 344xBrown Norway rats (6- and 30-mo age groups) were used to evaluate to determine if NTF4, given systemically (n = 32) or directly (n = 24), would improve the morphology and functional innervation of aging rat thyroarytenoid muscles. Results demonstrate the ability of rat laryngeal muscles to remodel in response to neurotrophin application. Changes were demonstrated in fiber size, glycolytic capacity, mitochondrial, tyrosine kinase receptors (Trk), NMJ content, and denervation in aging rat thyroarytenoid muscles. This study suggests that growth factors may have therapeutic potential to ameliorate aging-related laryngeal muscle dysfunction.

A muscle stem cell for every muscle: variability of satellite cell biology among different muscle groups

The human body contains approximately 640 individual skeletal muscles. Despite the fact that all of these muscles are composed of striated muscle tissue, the biology of these muscles and their associated muscle stem cell populations are quite diverse. Skeletal muscles are affected differentially by various muscular dystrophies (MDs), such that certain genetic mutations specifically alter muscle function in only a subset of muscles. Additionally, defective muscle stem cells have been implicated in the pathology of some MDs. The biology of muscle stem cells varies depending on the muscles with which they are associated. Here we review the biology of skeletal muscle stem cell populations of eight different muscle groups. Understanding the biological variation of skeletal muscles and their resident stem cells could provide valuable insight into mechanisms underlying the susceptibility of certain muscles to myopathic disease.

The effects of treadmill running on aging laryngeal muscle structure

OBJECTIVES/HYPOTHESIS

Age-related changes in laryngeal muscle structure and function may contribute to deficits in voice and swallowing observed in elderly people. We hypothesized that treadmill running, an exercise that increases respiratory drive to upper airway muscles, would induce changes in thyroarytenoid muscle myosin heavy chain (MHC) isoforms that are consistent with a fast-to-slow transformation in muscle fiber type.

STUDY DESIGN

Randomized parallel group controlled trial.

METHODS

Fifteen young adult and 14 old Fischer 344/Brown Norway rats received either treadmill running or no exercise (5 days/week/8 weeks). Myosin heavy chain isoform composition in the thyroarytenoid muscle was examined at the end of 8 weeks.

RESULTS

Significant age and treatment effects were found. The young adult group had the greatest proportion of superfast-contracting MHCIIL isoform. The treadmill running group had the lowest proportion of MHCIIL and the greatest proportion of MHCIIx isoforms.

CONCLUSION

Thyroarytenoid muscle structure was affected both by age and treadmill running in a fast-to-slow transition that is characteristic of exercise manipulations in other skeletal muscles.

LEVEL OF EVIDENCE

NA. Laryngoscope, 126:672-677, 2016.

Aging and regeneration in vertebrates

Aging is marked by changes that affect organs and resident stem cell function. Shorting of telomeres, DNA damage, oxidative stress, deregulation of genes and proteins, impaired cell-cell communication, and an altered systemic environment cause the eventual demise of cells. At the same time, reparative activities also decline. It is intriguing to correlate aging with the decline of regenerative abilities. Animal models with strong regenerative capabilities imply that aging processes might not be affecting regeneration. In this review, we selectively present age-dependent changes in stem/progenitor cells that are vital for tissue homeostasis and repair. In addition, the aging effect on regeneration following injury in organs such as lung, skeletal muscle, heart, nervous system, cochlear hair, lens, and liver are discussed. These tissues are also known for diseases such as heart attack, stroke, cognitive impairment, cataract, and hearing loss that occur mostly during aging in humans. Conclusively, vertebrate regeneration declines with age with the loss of stem/progenitor cell function. Future studies on improving the function of stem cells, along with studies in fish and amphibians where regeneration does not decline with age, will undoubtedly provide insights into both processes.