Can molecular hydrogen supplementation reduce exercise-induced oxidative stress in healthy adults? A systematic review and meta-analysis

Objective

Exercise-induced oxidative stress affects multiple neurophysiological processes, diminishing the exercise performance. Hydrogen (H2) can selectively reduce excessive free radicals, but studies observed its "dual effects" on exercise-induced oxidative stress, that is, increasing or decreasing the oxidative stress. Therefore, we here conducted a systematic review and meta-analysis to quantitatively assess the influence of H2 on exercise-induced oxidative stress in healthy adults.

Methods

We conducted a systematic review of publications across five databases. The following keywords were used for search strategy: ["hydrogen"[Mesh] or "molecular hydrogen" or "hydrogen rich water" or "hydrogen-rich water" or "hydrogen rich saline"] and ["Oxidative Stress"[Mesh] or "Antioxidative Stress" or "Oxidative Damage" or "Oxidative Injury" or "Oxidative Cleavage"] and ["randomized controlled trial"[Mesh] or "randomized" or "RCT"]. We included trials reporting the effects of H2 on exercise-induced oxidative stress and potential antioxidant capacity post-exercise in healthy adults. Additionally, subgroup analyses were conducted to explore how various elements of the intervention design affected those outcomes.

Results

Six studies, encompassing seven experiments with a total of 76 participants, were included in our analysis. Among these studies, hydrogen-rich water, hydrogen bathing, and hydrogen-rich gas were three forms used in H2 administration. The H2 was applied in different timing, including before, during, or after exercise only, both before and after exercise, and repeatedly over days. Single-dose, multi-dose within 1 day and/or multiple-dose over days were implemented. It was observed that compared to placebo, the effects of H2 on oxidative stress (diacron-reactive oxygen metabolites, d-ROMs) was not significant (SMD = -0.01, 95%CI-0.42 to 0.39, p = 0.94). However, H2 induced greater improvement in antioxidant potential capacity (Biological Antioxidant Potential, BAP) (SMD = 0.29, 95% CI 0.04 to 0.54, p = 0.03) as compared to placebo. Subgroup analyses revealed that H2 supplementation showed greater improvement (SMD = 0.52, 95%CI 0.16 to 0.87, p = 0.02) in the antioxidant potential capacity of intermittent exercises than continuous exercise.

Conclusion

H2 supplementation can help enhance antioxidant potential capacity in healthy adults, especially in intermittent exercise, but not directly diminish the levels of exercise-induced oxidative stress. Future studies with more rigorous design are needed to examine and confirm these findings.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=364123, Identifier CRD42022364123.

Concentration Effects of Methylprednisolone in Human Vocal Fold Fibroblast-Macrophage Co-Culture

OBJECTIVE

The diversity of glucocorticoid (GC) properties may underlie variability of clinical efficacy for vocal fold (VF) disease. Optimized therapeutic approaches must account for tissue complexity as well as interactions between cell types. We previously reported that reduced GC concentrations inhibited inflammation without eliciting fibrosis in mono-cultured VF fibroblasts and macrophages. These data suggested that a refined approach to GC concentration may improve outcomes. In the current study, co-culture of VF fibroblasts and macrophages was employed to investigate the effects of different concentrations of methylprednisolone on fibrotic and inflammatory response genes in VF fibroblasts to optimize management paradigms.

STUDY DESIGN

In vitro.

METHODS

THP-1 monocyte-derived macrophages were stimulated with interferon-γ (IFN-γ), lipopolysaccharide (LPS), or transforming growth factor-β (TGF-β) to induce inflammatory (M(IFN/LPS)) and fibrotic (M(TGF)) phenotypes. Macrophages were then co-cultured with a human VF fibroblast cell line using a 0.4 μm pore membrane with or without 0.1-3000 nM methylprednisolone. Inflammatory (CXCL10, TNF, and PTGS2) and fibrotic (ACTA2, CCN2, and COL1A1) gene expression was quantified in fibroblasts.

RESULTS

Incubating VF fibroblasts with M(IFN/LPS) macrophages increased expression of TNF and PTGS2, and this effect was inhibited by methylprednisolone. Incubation of VF fibroblasts with M(TGF) macrophages increased expression of ACTA2, CCN2, and COL1A1, and this effect was enhanced by methylprednisolone. The concentration of methylprednisolone required to downregulate inflammatory genes (TNF and PTGS2) was lower than that to upregulate fibrotic genes (ACTA2, CCN2, and COL1A1).

CONCLUSION

Reduced concentration of methylprednisolone effectively suppressed inflammatory genes without enhancing fibrotic genes, suggesting that a refined approach to GC concentration may improve clinical outcomes.

LEVEL OF EVIDENCE

N/A Laryngoscope, 133:3116-3122, 2023.

A Novel Method for Thyroarytenoid Myofiber Culture

OBJECTIVES/HYPOTHESIS

Myofiber culture has been employed to investigate muscle physiology in vitro and is well-established in the rodent hind limb. Thyroarytenoid (TA) myofiber culture has not been described, providing an opportunity to employ this method to investigate distinct TA myofiber functions. The purpose of this study was to assess the feasibility of a TA myofiber culture model.

STUDY DESIGN

In vitro.

METHODS

TA muscles from five Sprague Dawley rats were independently isolated and digested for 90 min. A smooth-tip, wide-bored pipette dissociated TA myofibers from cartilage, and the fibers were distributed on collagen-coated dishes and incubated at 37°C, 5% CO2 for 2 h. Myofiber specificity was determined via immunolabeling for desmin and myosin heavy chain (MHC). Myofibers viability was assessed over 7 days via esterase assay. Additional myofibers were immunolabeled for satellite cell marker Pax-7. Glucocorticoid (GC) receptor (GR) was immunolabeled following GC treatment.

RESULTS

The harvest technique yielded ~120 myofibers per larynx. By day 7, ~60% of the fibers remained attached and were calcein AM-positive/ethidium homodimer-negative, indicating viability. Myofibers were positive for desmin and MHC, indicating muscle specificity. Cells surrounding myofibers were positive for Pax-7, indicating the presence of myogenic satellite cells. Myofibers also responded to GC treatment as determined by GR nuclear translocation.

CONCLUSION

TA myofibers remained viable in culture for at least 7 days with a predictable response to exogenous stimuli. This technique provides novel investigative opportunities regarding TA structure and function.

LEVEL OF EVIDENCE

N/A Laryngoscope, 133:3109-3115, 2023.

Dose-Dependent Glucocorticoid Regulation of Transcription Factors in Vocal Fold Fibroblasts and Macrophages

OBJECTIVE

Variable outcomes of glucocorticoid (GC) therapy for laryngeal disease are putatively due to diverse interactions of the GC receptor (GR) with cell signaling pathways, limited consideration regarding concentration-dependent effects, and inconsistent selection of GCs. In the current study, we evaluated the concentration-dependent effects of three frequently administered GCs on transcription factors with an emphasis on the phosphorylation of GR at Ser203 and Ser211 regulating the nuclear translocation of GR. This study provides foundational data regarding the diverse functions of GCs to optimize therapeutic approaches.

STUDY DESIGN

In vitro.

METHODS

Human vocal fold fibroblasts and THP1-derived macrophages were treated with different concentrations of dexamethasone, methylprednisolone, and triamcinolone in combination with IFN-γ, TNF-α, or IL4. Phosphorylated STAT1, NF-κB family molecules, and phosphorylated STAT6 were analyzed by Western blotting. Ser211-phosphorylated GR (S211-pGR) levels relative to GAPDH and Ser203-phosphorylated GR (S203-pGR) were also analyzed.

RESULTS

GCs differentially altered phosphorylated STAT1 and NF-κB family molecules in different cell types under IFN-γ and TNF-α stimuli. GCs did not alter phosphorylated STAT6 in IL4-treated macrophages. The three GCs were nearly equivalent. A lower concentration of dexamethasone increased S211-pGR/GAPDH ratios relative to increased S211-pGR/S203-pGR ratios regardless of cell type and treatment.

CONCLUSION

The three GCs employed in two cell lines had nearly equivalent effects on transcription factor regulation. Relatively high levels of Ser203-phosphorylation at low GC concentrations may be related to concentration-dependent differential effects of GCs in the two cell lines.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:2704-2711, 2023.

Acute In Vitro and In Vivo Effects of Dexamethasone in the Vocal Folds: a Pilot Study

OBJECTIVES/HYPOTHESIS

Glucocorticoids (GC)s are commonly employed to treat vocal fold (VF) pathologies. However, VF atrophy has been associated with intracordal GC injections. Dexamethasone-induced skeletal muscle atrophy is well-documented in other tissues and believed to be mediated by increased muscle proteolysis via upregulation of Muscle Ring Finger (MuRF)-1 and Atrogin-1. Mechanisms of dexamethasone-mediated VF atrophy have not been described. This pilot study employed in vitro and in vivo models to investigate the effects of dexamethasone on VF epithelium, thyroarytenoid (TA) muscle, and TA-derived myoblasts. We hypothesized that dexamethasone will increase atrophy-associated gene expression in TA muscle and myoblasts and decrease TA muscle fiber size and epithelial thickness.

STUDY DESIGN

In vitro, pre-clinical.

METHODS

TA myoblasts were isolated from a female Sprague-Dawley rat and treated with 1 μM dexamethasone for 24-h. In vivo, 15 New Zealand white rabbits were randomly assigned to three treatment groups: (1) bilateral intracordal injection of 40 μL dexamethasone (10 mg/ml; n = 5), (2) volume-matched saline (n = 5), and (3) untreated controls (n = 5). Larynges were harvested 7-days post-injection. Across in vivo and in vitro experimentation, MuRF-1 and Atrogin-1 mRNA expression were measured via RT-qPCR. TA muscle fiber cross-sectional area (CSA) and epithelial thickness were also quantified in vivo.

RESULTS

Dexamethasone increased MuRF-1 gene expression in TA myoblasts. Dexamethasone injection, however, did not alter atrophy-associated gene expression, TA CSA, or epithelial thickness in vivo.

CONCLUSION

Dexamethasone increased atrogene expression in TA myoblasts, providing foundational insight into GC induced atrophic gene transcription. Repeated dexamethasone injections may be required to elicit atrophy in vivo.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:2264-2270, 2023.

Glucocorticoid Dose Dependency on Gene Expression in Vocal Fold Fibroblasts and Macrophages

OBJECTIVE

Glucocorticoids (GCs) modulate multiple cellular activities including inflammatory and fibrotic responses. Outcomes of GC treatment for laryngeal disease vary, affording opportunity to optimize treatment. In the current study, three clinically employed GCs were evaluated to identify optimal in vitro concentrations at which GCs mediate favorable anti-inflammatory and fibrotic effects in multiple cell types. We hypothesize a therapeutic window will emerge as a foundation for optimized therapeutic strategies for patients with laryngeal disease.

STUDY DESIGN

In vitro.

METHODS

Human vocal fold fibroblasts and human macrophages derived from THP-1 monocytes were treated with 0.03-1000 nM dexamethasone, 0.3-10,000 nM methylprednisolone, and 0.3-10,000 nM triamcinolone in combination with interferon-γ, tumor necrosis factor-α, or interleukin-4. Real-time polymerase chain reaction was performed to analyze inflammatory (CXCL10, CXCl11, PTGS2, TNF, IL1B) and fibrotic (CCN2, LOX, TGM2) genes, and TSC22D3, a target gene of GC signaling. EC50 and IC50 to alter inflammatory and fibrotic gene expression was calculated.

RESULTS

Interferon-γ and tumor necrosis factor-α increased inflammatory gene expression in both cell types; this response was reduced by GCs. Interleukin-4 increased LOX and TGM2 expression in macrophages; this response was also reduced by GCs. GCs induced TSC22D3 and CCN2 expression independent of cytokine treatment. EC50 for each GC to upregulate CCN2 was higher than the IC50 to downregulate other genes.

CONCLUSION

Lower concentrations of GCs repressed inflammatory gene expression and only moderately induced genes involved in fibrosis. These data warrant consideration as a foundation for optimized clinical care paradigms to reduce inflammation and mitigate fibrosis.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:1169-1175, 2023.

Sex-differences in oral anticoagulation therapy in patients hospitalised with atrial fibrillation: a nationwide cohort study

Background

Important disparities in the treatment and outcomes of women and men with atrial fibrillation are well recognized. Whether introduction of direct oral anticoagulants has reduced disparities in treatment is uncertain.

Methods

All patients who had an incident hospitalization from 2010 to 2019 with non-valvular atrial fibrillation in Scotland were included in this cohort study. Community drug dispensing data were used to determine prescribed oral anticoagulation therapy and comorbidity status. Logistic regression modelling was used to evaluate patient factors associated with treatment with vitamin K antagonists and direct oral anticoagulants.

Results

A total of 172,989 patients (48% women [82,833/172,989]) had an incident hospitalization with non-valvular atrial fibrillation in Scotland between 2010 and 2019. The proportion of patients with thromboembolic risk factors (CHA2DS2VASc score >0 in men and >1 in women) treated with oral anticoagulation therapy increased from 36.8% to 66.3% over this 10-year period. By 2019, factor Xa inhibitors accounted for 83.6% of all oral anticoagulants prescribed, while treatment with vitamin K antagonists and direct thrombin inhibitors declined to 15.9% and 0.6%, respectively. Women were less likely to be prescribed any oral anticoagulation therapy compared to men (adjusted odds ratio, aOR 0.68 [95% CI, CI 0.67–0.70]). This disparity was mainly attributed to vitamin K antagonists (aOR 0.68 [95% CI 0.66–0.70]), whilst there was less disparity in use of factor Xa inhibitors between women and men (aOR 0.92 [95% CI 0.90–0.95]). At 1 year following hospitalization with atrial fibrillation, patients not prescribed oral anticoagulation therapy were more likely to have subsequent major adverse cardiovascular events compared to those prescribed with oral anticoagulation therapy (38.8% [15,380/39,608] versus 17.0% [6,761/39,671] in women and 35.2% [12,977/36,868] versus 16.4% [7,395/45,093] in men).

Conclusions

Women with non-valvular atrial fibrillation were significantly less likely to be prescribed vitamin K antagonists compared to men. Most patients admitted to hospital in Scotland with incident non-valvular atrial fibrillation are now treated with factor Xa inhibitors and this is associated with less treatment disparities between women and men.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): This study was supported by the British Heart Foundation through a Clinical Research Training Fellowship (FS/18/25/33454), Intermediate Clinical Research Fellowship (FS/19/17/34172), Senior Clinical Research Fellowship (FS/16/14/32023) and a Research Excellence Award (RE/18/5/34216), and a research grant to NHS Lothian from Bristol Myers Squibb Pharmaceuticals Ltd and Pfizer UK Ltd.

Novel contrast-computed tomography method based on a Gaussian Mixture Model for assessment of fibrocalcific volume in aortic valve stenosis

Background

Discordant echocardiography is observed in up to one third of patients with aortic stenosis (AS), in whom computed tomography (CT) derived aortic valve calcium scoring is now recommended. However, CT calcium scoring only assesses calcific valve thickening and ignores non-calcific fibrotic thickening, which could be an important contributor of AS.

Purpose

To generate a quick and robust contrast-CT method based on a gaussian mixture model (GMM) for assessment of fibro-calcific aortic valve thickening in patients with AS, and to investigate its reproducibility and associations with echo parameters of AS severity and disease progression.

Methods

A post-hoc analysis of 136 patients with calcific AS (24 with severe, 81 moderate and 31 mild AS) enrolled in the SALTIRE2 trial (NCT-02132026) was performed. Aortic valve fibrocalcific volume was calculated using a GMM applied on contrast-CT at baseline and at 1-year follow up. The software estimated the Hounsfield Units (HU) distribution of 3 compartments (blood pool, non-calcific and calcific tissue) within the aortic valve volume of interest, automatically generating thresholds for non-calcific and calcific tissue, respectively computed as the lower 99.7 and the upper 99.7 percentile of the blood pool HU distribution (Figure 1). Fibrocalcific volume was measured as the sum of calcific and non-calcific volumes, indexed for CT annulus area and compared to echo parameters of AS severity. Evaluation of scan-rescan reproducibility and AS progression were also assessed.

Results

Image analysis took 5.8±1.0 minutes per scan and showed excellent scan-rescan reproducibility (mean difference −1%, limits of agreement −9% to 7%). Indexed-fibrocalcific volume correlated well with echocardiographic aortic peak velocity (rho=0.70, p<0.0001), better than non-calcific and calcific volumes alone (rho=0.30 and rho=0.61 respectively, both p<0.0001) and Agatston calcium score (rho=0.63, p<0.0001). Baseline indexed-fibrocalcific volume was also the strongest predictor of subsequent AS progression in terms of change in aortic valve peak velocity (rho=0.29, p=0.006) and mean gradient (rho=0.39, p<0.0001). Progression-to-noise ratio for fibrocalcific volume was favourable (Cohen's statistic d=0.62), indicating that groups sizes of 21, 46 and 170 participants would be required to demonstrate 30%, 20% and 10% reductions in fibro-calcific volume progression with a novel drug respectively (alpha=0.05, power=80%).

Conclusions

This novel contrast CT-based approach can provide robust and rapid assessment of fibrocalcific thickening in AS patients. Fibrocalcific volume measured using this technique, correlates well with other markers of AS severity, predicts disease progression and holds promise in tracking disease progression and response to novel therapies.

Funding Acknowledgement

Type of funding sources: None.

Macrophages alter inflammatory and fibrotic gene expression in human vocal fold fibroblasts

Macrophage phenotypes are simplistically classified as pro-inflammatory (M1) or anti-inflammatory/pro-fibrotic (M2). Phenotypically different macrophages are putatively involved in vocal fold (VF) fibrosis. The current study investigated interactions between macrophages and VF fibroblasts. THP-1 monocyte-derived macrophages were treated with interferon-gamma (IFN-γ), lipopolysaccharide (LPS)/IFN-γ, interleukin-10 (IL10), transforming growth factor-β1 (TGF-β), or interleukin-4 (IL4) for 24 h (M(IFN), M(IFN/LPS), M(IL10), M(TGF), and M(IL4), respectively; M(-) denotes untreated macrophages). Differentially activated macrophages and human VF fibroblasts were co-cultured ± direct contact. Expression of CXCL10, CCN2, ACTA2, FN1, TGM2, and LOX was quantified by real-time polymerase chain reaction. Type I collagen and smooth muscle actin (SMA) were observed by immunofluorescence. CXCL10 and PTGS2 were upregulated in fibroblasts indirectly co-cultured with M(IFN) and M(IFN/LPS). M(TGF) stimulated CCN2, ACTA2, and FN1 in fibroblasts. Enzymes involved in extracellular matrix crosslinking (TGM2, LOX) were increased in monocultured M(IL4) compared to M(-). Direct co-culture with all macrophages increased type I collagen and SMA in fibroblasts. Macrophage phenotypic shift was consistent with stimulation and had downstream differential effects on VF fibroblasts. Direct contact with macrophages, regardless of phenotype, stimulated a pro-fibrotic response in VF fibroblasts. Collectively, these data suggest meaningful interactions between macrophages and fibroblasts mediate fibrosis.

In vivo coronary artery thrombus imaging with 18F-GP1 PET-CT

Background

Coronary artery thrombus is typically present in type 1 myocardial infarction, but small volumes in the setting of an uncertain culprit lesion may be beyond the detection limit of current imaging modalities.

Purpose

Using a novel glycoprotein IIb/IIIa-receptor radiotracer, 18F-GP1, we investigated whether positron emission tomography-computed tomography (PET-CT) could detect thrombus formation in coronary arteries.

Methods

In a single centre cross-sectional study, patients over 40 years of age with myocardial infarction were recruited after myocardial infarction and underwent underwent CT angiography and 18F-GP1 PET-CT. Stable patients with and without coronary artery disease formed a control cohort. Coronary artery 18F-GP1 uptake was visually assessed and quantified using maximum target-to-background ratios (TBRmax).

Results

Ninety-four (44 post-myocardial infarction and 50 control patients) were included in the cross-sectional analysis. The mean age of the post-myocardial infarction group was 61±9 years, three-quarters were male and two thirds had presented with ST elevation on electrocardiography. 34 (80%) patients post-myocardial infarction, but none of the control patients, demonstrated focal 18F-GP1 uptake in the coronary arteries.

Of 42 vessels with an angiographic culprit lesion, 35 (83%) had 18F-GP1 uptake which was significantly higher than non-culprit vessels (p<0.0001) as well as control vessels (p<0.0001), while non-culprit vessel uptake was similar to control vessel uptake (p=0.567): culprit vessel median TBRmax 1.2 [interquartile range 0.96–1.44], non-culprit vessel TBRmax 0.96 [0.84–1.03] and control vessel TBRmax 0.9 [0.76 to 0.94]. Linear regression models demonstrated univariable associations between coronary 18F-GP1 TBRmax and time from myocardial infarction, male sex and presence of culprit vessel. On multivariable analysis, only culprit vessel status was associated with TBRmax (adjusted R2= 0.22, P<0.001). Based on the Youden's index of the ROC curves, the optimal cut-off of predicting the presence of a culprit vessel was 1.20 with a specificity of 97%, accuracy of 83%, sensitivity (60%) and c-statictic of 0.74.

A patient with ectatic vessel and visual thrombus demonstrated the most intense 18F-GP1 uptake (TBRmax 2.0, highest in the cohort) in the region of heaviest thrombus burden (Figure 2). Extra-coronary uptake was seen in regions of left ventricular thrombus, left atrial appendage thrombus, pulmonary thromboembolism and intramyocardial microvascular obstruction.

Conclusions

18F-GP1 PET-CT is able to detect coronary artery thrombus in culprit lesions following myocardial infarction, as well as extra-coronary thrombotic pathologies that may be important in guiding patient management. 18F-GP1 is highly specific in recognising a culprit lesion from a non-culprit lesion both visually as well as quantitatively.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Figure 1Figure 2

18F-Sodium fluoride positron emission tomography, aortic disease activity and ischaemic stroke risk

Background

Arterial 18F-sodium fluoride (18F-NaF) activity on positron emission tomography (PET) is a marker of active microcalcification and atherosclerosis. Coronary 18F-NaF activity (CMA) predicts coronary artery disease progression and subsequent myocardial infarction.

Objective

To investigate whether aortic 18F-NaF activity (AMA) predicts thoracic aortic atherosclerotic disease progression and subsequent ischaemic stroke or myocardial infarction in patients with established cardiovascular disease.

Methods

In a post-hoc observational cohort study, we evaluated AMA and CMA in patients with stable coronary artery disease (n=239) or aortic stenosis (n=158) who had underwent thoracic 18F-NaF PET and computed tomography (CT). We assessed the associations between AMA or CMA and progression of calcified atherosclerotic plaque in both thoracic aortic and coronary territories on follow up CT, as well as subsequent ischaemic stroke or myocardial infarction.

Results

In 141 and 231 patients with repeat aortic and coronary CT imaging respectively at 12.7±2.7 months, AMA correlated with log progression of thoracic aortic calcium scores (r=0.21, p=0.011), volume (r=0.29, p<0.01) and mass (r=0.29, P<0.01) as well as log coronary calcium score progression (r=0.21, p=0.03). CMA correlated with log coronary (r=0.42, p<0.01), but not log aortic (p>0.80) calcium score progression. In 397 patients, 16 had an ischaemic stroke and 25 had a myocardial infarction after 4.7±1.6 years. After adjusting for clinical risk factors, CMA and calcium scoring, AMA was associated with stroke (hazard ratio, 1.71 [95% confidence interval 1.00–2.90], p=0.048]). AMA was superior to clinical risk and calcium scores in identifying patients with stroke (c-statistic 0.76 versus 0.58 versus 0.63 respectively, p<0.05). Survival analysis demonstrated that AMA was associated with ischaemic stroke (p<0.001) but not myocardial infarction (p=0.45), whereas CMA was associated with myocardial infarction (p<0.001) but not stroke (p=0.39).

Conclusions

In patients with established cardiovascular disease, AMA is associated with progression of aortic atherosclerosis and future ischaemic stroke. Arterial 18F-NaF identifies localised areas of atherosclerotic disease activity that relate to regional atherothrombotic events.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): British Heart Foundation AMA, disease progression and outcomesVariables associated with stroke

Preliminary Investigation of In vitro, Bidirectional Vocal Fold Muscle-Mucosa Interactions

OBJECTIVE

Oversimplified clinical dogma suggests that laryngeal diseases fall into two broad, mutually exclusive diagnostic categories-mucosal injury or neuromuscular/functional disorders. Extensive investigation in the lower airway as well as other organ systems suggest complex interactions between tissue types underlying both tissue health and pathological states. To date, no such relationship has been described in the vocal folds, likely the most bioactive organ in the body. We hypothesize interactions between the vocal fold muscle and mucosa likely contribute to aberrant phonatory physiology and warrant further investigation to ultimately develop novel therapeutic strategies.

METHODS

Primary culture of myoblasts from rat thyroarytenoid muscle and fibroblasts from the vocal fold mucosa were established. Co-culture and conditioned media experiments were performed to established bidirectional interactions between cell types. Transforming Growth Factor (TGF)-β was employed to stimulate a fibrotic phenotype in culture. In addition to quantitative PCR, standard migration and proliferation assays were performed as well as immunocytochemistry.

RESULTS

Bidirectional cell-cell interactions were observed. Without TGF-β stimulation, myoblast conditioned media inhibited fibroblast migration, but enhanced proliferation. Conversely, fibroblast conditioned media increased both myoblast proliferation and migration. Myoblast conditioned media decreased TGF-β-mediated gene expression and of particular interest, ACTA2 mRNA expression. In both co-culture and in response to fibroblast conditioned media, myosin heavy chain (Myh2) mRNA expression decreased in myoblasts.

CONCLUSIONS

These data are the first to describe interactions between cell types within the vocal fold. The implications for these interactions in vivo warrant further investigation to develop and refine optimal treatment strategies.

Glucocorticoids activate Yes-associated protein in human vocal fold fibroblasts

Fibrosis of the vocal folds poses a substantive clinical challenge potentially underlying the rapid proliferation of direct steroid injections into the upper airway. The variable clinical response to glucocorticoids (GCs) in the vocal folds is likely related to diversity inherent to GCs and patient-specific, and upstream, cell-specific responses to GCs. Broadly, we hypothesize the disparity in clinical outcomes are due to undesirable effects of GCs on resident fibroblasts. Transcriptome analysis identified significant GC-mediated modulation of Hippo signaling, a known regulator of fibrotic gene expression. Subsequent analysis confirmed GC-mediated YAP activation, a transcriptional co-factor in the Hippo signaling pathway. YAP inhibition attenuated ACTA2 expression in GC-treated human vocal fold fibroblasts. Nuclear localization and phosphorylation at Ser211, however, was not affected by YAP inhibition, suggesting nuclear translocation of YAP is indirectly driven by GR. RNA-seq analysis confirmed the influence of GCs on Wnt signaling, and canonical Wnt signaling target genes were upregulated by GCs. These data implicate YAP and its downstream targets as putative mediators of a pro-fibrotic response to GCs. Therapeutic YAP inhibition may ultimately be clinically relevant and warrants further consideration.

Mycoplasma affects baseline gene expression and the response to glucocorticoids in vocal fold fibroblasts

Introduction. In vitro experimentation is intentionally contrived to isolate specific phenomena in the context of profound biological complexity. Mycoplasmas in the upper airway likely contribute to this complexity and play a largely unknown role in both health and disease. Similarly, the presence and role of mycoplasma in in vitro investigation are largely unknown.Hypothesis. We hypothesize mycoplasma in human vocal fold fibroblasts (VFF) will affect both basal gene-expression patterns as well as the cell response to exogenous stimuli.Aim. We sought to determine mycoplasma presence across vocal fold fibroblast cultures, basal transcriptional changes as a function of mycoplasma, and responsiveness to exogenous glucocorticoids in mycoplasma-positive and -negative VFF.Methodology. PCR-based mycoplasma detection was performed in an immortalized human VFF line as well as rat and rabbit primary VFF cultures and extracted rat laryngeal tissue. RNA sequencing was performed in mycoplasma-positive and -negative human cells at baseline and in response to dexamethasone.Results. Mycoplasma was identified in the human cell line as well as primary culture from rabbits. Mycoplasma was not detected in tissue or primary culture from rat vocal folds. Basal mRNA expression in human VFF differed significantly following mycoplasma treatment. In addition, differential responses to dexamethasone were observed across multiple pathways as a function of mycoplasma presence in these cells. Pathways including apoptosis, DNA damage repair, and G1 to S cell cycle signalling were significantly enriched in mycoplasma-positive cells.Conclusion. Variability of mycoplasma presence across culture conditions and differential responses to exogenous stimuli as a function of mycoplasma presence are potentially problematic for the translation of in vitro experimentation in the upper aerodigestive tract. It remains unclear if these findings represent contamination or the baseline state of this specialized tissue.

Complex fibroblast response to glucocorticoids may underlie variability of clinical efficacy in the vocal folds

Similar to the hypertrophic scar and keloids, the efficacy of glucorticoids (GC) for vocal fold injury is highly variable. We previously reported dexamethasone enhanced the pro-fibrotic effects of transforming growth factor (TGF)-β as a potential mechanism for inconsistent clinical outcomes. In the current study, we sought to determine the mechanism(s) whereby GCs influence the fibrotic response and mechanisms underlying these effects with an emphasis on TGF-β and nuclear receptor subfamily 4 group A member 1 (NR4A1) signaling. Human VF fibroblasts (HVOX) were treated with three commonly-employed GCs+ /-TGF-β1. Phosphorylation of the glucocorticoid receptor (GR:NR3C1) and activation of NR4A1 was analyzed by western blotting. Genes involved in the fibrotic response, including ACTA2, TGFBR1, and TGFBR2 were analyzed by qPCR. RNA-seq was performed to identify global changes in gene expression induced by dexamethasone. GCs enhanced phosphorylation of GR at Ser211 and TGF-β-induced ACTA2 expression. Dexamethasone upregulated TGFBR1, and TGFBR2 in the presence of TGF-β1 and increased active NR4A1. RNA-seq results confirmed numerous pathways, including TGF-β signaling, affected by dexamethasone. Synergistic pro-fibrotic effects of TGF-β were observed across GCs and appeared to be mediated, at least partially, via upregulation of TGF-β receptors. Dexamethasone exhibited diverse regulation of gene expression including NR4A1 upregulation consistent with the anti-fibrotic potential of GCs.

Thrombus formation on bioprosthetic aortic valves

Background

18F-GP1 is a novel radiotracer with a high affinity for the platelet glycoprotein IIb/IIIa receptor. Subclinical bioprosthetic valve thrombus has been postulated as a trigger for accelerated valve degeneration.

Purpose

To determine the feasibility of 18F-GP1 positron-emission tomography-computed tomography (PET-CT) for the detection of subclinical bioprosthetic aortic valve thrombus.

Methods

(i) Explanted degenerated aortic valve prostheses underwent histology and imaging. (ii) In a prospective observational study, patients with bioprosthetic aortic valve replacement (AVR) underwent echocardiography and 18F-GP1 PET-CT. Valves were assessed for hypoattenuating leaflet thickening (HALT), hypo-attenuation affection leaflet motion (HAM) and GP1 uptake.

Results

(i) GP1 correlated with thrombus on explanted valves (Figure). (ii) The first 6 patients (Table) were asymptomatic and had normally functioning surgical bioprostheses on echocardiography. At a median of 166 (range 122–189) days post-AVR, no patients had HALT or HAM on CT. There was avid focal GP1 uptake on the leaflets of all 6 patients which appeared most prominent along the leaflet edges (Figure). Only one patient had focal uptake in the valve frame, remote from the leaflets. In a separate cohort undergoing 18F-GP1 PET-CT for other conditions, there was no uptake on normal, native aortic valves (n=8).

Conclusion

For the first time, we demonstrate that 18F-GP1 PET-CT is a highly sensitive method of assessing platelet activation on bioprosthetic aortic valves. Despite the absence of CT evidence, early thrombus appeared to be a universal finding on recently implanted valve prostheses. The biological and clinical implications of subclinical bioprosthetic aortic valve thrombus have yet to be established.

GP1 uptake in AVR

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): British Heart Foundation

Implementing Efficient Peptoid-Mediated Delivery of RNA-Based Therapeutics to the Vocal Folds

Objective

We hypothesize that Smad3 is a master regulator of fibrosis in the vocal folds (VFs) and RNA-based therapeutics targeting Smad3 hold therapeutic promise. Delivery remains challenging. We previously described a novel synthetic peptoid oligomer, lipitoid L0, complexed with siRNA to improve stability and cellular uptake. An advantage of these peptoids, however, is tremendous structural and chemical malleability to optimize transfection efficiency. Modifications of L0 were assayed to optimize siRNA-mediated alteration of gene expression.

Methods

In vitro, Smad3 knockdown by various lipitoid variants was evaluated via quantitative real-time polymerase chain reaction in human VF fibroblasts. Cytotoxicity was quantified via colorimetric assays. In vivo, a rabbit model of VF injury was employed to evaluate the temporal dynamics of Smad3 knockdown following injection of the L0-siRNA complex.

Results

In vitro, similar reductions in Smad3 expression were established by all lipitoid variants, with one exception. Sequence variants also exhibited similar nontoxic characteristics; no statistically significant differences in cell proliferation were observed. In vivo, Smad3 expression was significantly reduced in injured VFs following injection of L0-complexed Smad3 siRNA at 1 day postinjection. Qualitative suppression of Smad3 expression persisted to 3 days following injury, but did not achieve statistical significance.

Conclusions

In spite of the chemical diversity of these peptoid transfection reagents, the sequence variants generally provided consistently efficient reductions in Smad3 expression. L0 yielded effective, yet temporally limited knockdown of Smad3 in vivo. Peptoids may provide a versatile platform for the discovery of siRNA delivery vehicles optimized for clinical application.

Level of Evidence

NA.

P5013Trends in hospitalised cardiac arrest outcomes over 25 years in Scotland

Introduction

Cardiac arrest is a major healthcare burden; survival has historically been poor. Contemporary therapies have been associated with improvements in out-of-hospital cardiac arrest survival in other healthcare systems.

Purpose

To determine temporal trends and predictors of 30-day and overall survival in patients with cardiac arrest who survive to hospital admission in Scotland.

Methods

We conducted a consecutive individual patient linkage study using data from the Scottish Morbidity Records held by the Information Services Division, National Health Service Scotland. We identified all patients who had an index cardiac arrest hospitalisation from 1st January 1990 to 31st December 2014. The primary outcome was 30-day mortality. Generalised additive models were used to estimate temporal trends. Year of admission was the primary explanatory variable, adjusted for age, sex, comorbidities (stroke, myocardial infarction, heart failure), Scottish Index of Multiple Deprivation (SIMD, a national deprivation score), and angiography within 30 days of admission. Cox regression models were constructed for overall mortality, adjusting for the above variables.

Results

In total, 47,692 patients had an index hospitalisation with cardiac arrest in Scotland between 1990 and 2014. The mean age was 69±16 years; 45% (n=21,257) were female. Most patients (n=24,867, 52.4%) were in top two SIMD quintiles (greater deprivation). Incidence was lowest in 1990 (27 per 100,000 population), rising until 1998 (47 per 100,000) before declining (mean 30 per 100,000 for 2010–2014) (Figure 1A). Overall rates of angiography and PCI at 30 days were low (5.4% and 3.1% respectively), albeit higher in more recent years (14.1% and 9.6% respectively for 2010–2014).

Thirty-day mortality was high but decreased over time (73.7% from 1990–1994 to 63.1% from 2010–2014, p<0.001). This effect persisted after adjustment for covariates. The predicted 30-day mortality for a 69 year old patient was highest in 1990 (75%, 95% confidence interval [CI] 73–77%) and lowest in 2014 (66%, 95% CI 64–68%) (Figure 1B). Age, heart failure and greater deprivation were other independent predictors of 30-day mortality. In contrast, previous myocardial infarction and angiography within 30 days were predictors of reduced 30-day mortality. On Cox regression analysis, age (hazard ratio [HR] 1.15, 95% CI 1.14–1.16 per 10 years) and heart failure (HR 1.11, 95% CI 1.08–1.14) were independent predictors of overall mortality. Thirty-day angiography (HR 0.29, 95% CI 0.28–0.31) was the strongest independent predictor of survival, likely reflecting selection bias, in addition to year of admission, previous myocardial infarction and less deprivation.

Temporal trends in cardiac arrest

Conclusions

Hospital episodes with cardiac arrest in Scotland peaked in the late 1990s and have since fallen. Thirty-day mortality remains high, with an improvement over time that is independent of baseline patient characteristics.

3325Incidence, outcomes and microbiology in patients with infective endocarditis

Introduction

Despite recent improvements in management, infective endocarditis remains associated with high morbidity and mortality. Over the last few decades, several factors have impacted on both the incidence and outcomes following infective endocarditis.

Purpose

Using a national linkage approach, we describe the changing age- and sex-stratified incidence and outcomes of infective endocarditis in Scotland over the last 25 years.

Methods

We conducted a consecutive retrospective individual patient linkage study across multiple national databases. Using data extracted from the Scottish hospital discharge dataset held by the Information Services Division of NHS National Services Scotland, we extracted episodes for all patients aged 20 years or older who were admitted with infective endocarditis between January 1, 1990, and December 31, 2014 in Scotland, UK. Patient episodes with infective endocarditis were linked to national prescribing and microbiology databases. The primary outcome was 1-year mortality following the index presentation. Generalised additive models were constructed to estimate the crude and age- and sex-stratified incidence rates (using a poison distribution) as well as trends in mortality (using a binomial distribution) adjusted for age, sex and comorbidity.

Results

Across 12,446 individual patients, there were a total of 12,667 hospitalisations (mean age 68±17 years, 55% females) with infective endocarditis using a 5-year look back period. The estimated crude rate of hospitalisation increased from 7.38 per 100,000 (95% CI 6.58 to 8.28) in 1990 to 15.09 per 100,000 (95% CI 13.90 to 16.39) in 2014 (p<0.001). Over the period of the study, 31% (3,877/12,667) of people admitted to hospital with infective endocarditis died within one year of admission. Case fatality fell markedly in both men and women from 1990 to 2014 (Figure). Microbiology was status was available for 34% of all hospitalisations with staphylococcus cultures associated with worse outcomes.

Conclusions

Despite the crude incidence of infective endocarditis doubling over the last 25 years and case fatality remaining high, the risk of death has markedly fallen over the last two decades. Staphylococcus cultures remain an independent marker of poor prognosis in this cohort.

Acknowledgement/Funding

British Heart Foundation

1269Dual antiplatelet therapy to inhibit myocardial injury in patients with high-risk coronary artery plaque: a randomized controlled trial

Background

High-risk coronary atherosclerotic plaque is associated with higher plasma troponin concentrations suggesting ongoing myocardial injury that may be a target for dual antiplatelet therapy.

Purpose

To determine whether ticagrelor reduces high-sensitivity troponin I concentrations in patients with established coronary artery disease and high-risk coronary plaque with 18F-fluoride uptake.

Methods

In a randomized double-blind placebo-controlled trial, patients with multivessel coronary artery disease underwent coronary 18F-fluoride positron emission tomography-computed tomography and measurement of high-sensitivity cardiac troponin I and were randomized (1:1) to ticagrelor 90 mg twice daily or matched placebo. The primary endpoint was troponin I concentration at 30 days in patients with increased coronary 18F-fluoride uptake.

Results

In total, 202 patients were randomized and 191 met the pre-specified criteria for inclusion in the primary analysis. In patients with increased coronary 18F-fluoride uptake (n=120/191) there was no evidence that ticagrelor had an effect on plasma troponin concentrationsat 30 days (ratio of geometric means for ticagrelor versusplacebo, 1.11, [95% confidence interval 0.90 to 1.36], p=0.32) (Table 1). Over 1 year, ticagrelor had no effect on troponin concentrations in patients with increased coronary 18F-fluoride uptake (ratio of geometric means, 0.86, 95% confidence interval 0.63 to 1.17, p=0.33).

Table 1 Adjusted Geometric Mean (GSE) Ratio of Geometric Means p-value Ticagrelor Placebo (95% CI) Cardiac troponin I, ng/L (18F-fluoride activity) 3.8 (1.1) 3.4 (1.1) 1.11 (0.90 to 1.36) 0.32 Cardiac Troponin I, ng/L (No 18F-fluoride activity) 2.4 (1.1) 2.3 (1.1) 1.02 (0.80 to 1.31) 0.87 Plasma high-sensitivity cardiac troponin I concentration (ng/L) at 30 days for the per-protocol population.Estimates are back transformed estimates from analysis of log transformed values at 30 days adjusting for age, sex and log transformed baseline troponin. Ratio of geometric means is Ticagrelor divided by Placebo. GSE, geometric standard error.

Conclusions

Dual antiplatelet therapy with ticagrelor does not reduce plasma troponin concentrations in patients with coronary 18F-fluoride uptake. This suggests that subclinical plaque thrombosis does not contribute to ongoing myocardial injury in this setting.

Clinical Trials Study ID: NCT02110303Study ID: NCT02110303

Acknowledgement/Funding

Wellcome Trust Senior Investigator Award WT103782AIA

Quantifying vocal fold wound-healing biomechanical property changes

OBJECTIVES

Development of novel vocal fold (VF) therapeutics is limited by a lack of standardized, meaningful outcomes. We hypothesize that automated microindentation-based VF biomechanical property mapping matched to histology permits quantitative assessment.

STUDY DESIGN

Ex vivo.

METHODS

Twelve anesthetized New Zealand white rabbits underwent endoscopic right VF injury. Larynges were harvested/bisected day 7, 30, or 60 (n = 4/group), with four uninjured controls. Biomechanical measurements (normal force, structural stiffness, and displacement at 1.96 mN) were calculated using automated microindentation mapping (0.3 mm depth, 1.2 mm/s, 2 mm spherical indenter) with a grid overlay (>50 locations weighted toward VF edge, separated into 14 zones). Specimens were marked/fixed/sectioned, and slides matched to measurement points.

RESULTS

In the injury zone, normal force/structural stiffness (mean, standard deviation [SD]/mean, SD) increased from uninjured (2.2 mN, 0.64/7.4 mN/mm, 2.14) and day 7 (2.7 mN, 0.75/9.0 mN/mm, 2.49) to day 30 (4.3 mN, 2.11/14.2 mN/mm, 7.05) and decreased at 60 days (2.7 mN, 0.77/9.1 mN/mm, 2.58). VF displacement decreased from control (0.28 mm, 0.05) and day 7 (0.26 mm, 0.05) to day 30 (0.20 mm, 0.05), increasing at day 60 (0.25 mm, 0.06). A one-way ANOVA was significant; Tukey's post hoc test confirmed day-30 samples differed from other groups (P < 0.05), consistent across adjacent zones. Zones far from injury remained similar across groups (P = 0.143 to 0.551). These measurements matched qualitative histologic variations.

CONCLUSION

Quantifiable VF biomechanical properties can be linked to histology. This technological approach is the first to simultaneously correlate functional biomechanics with histology and is ideal for future preclinical studies.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:454-459, 2020.

The effects of cytosporone-B, a novel antifibrotic agent, on vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Our laboratory recently described NR4A1 as an endogenous inhibitor of TGF-β-induced vocal fold (VF) fibrosis. Our prior report described the temporal expression of NR4A1 during VF healing in vivo and the effects of NR4A1 knockdown on fibroplastic cell activities in vitro. Based on these findings, we hypothesized that cytosporone-B (Csn-B), an NR4A1 agonist, may hold significant therapeutic potential.

STUDY DESIGN

In vitro.

METHODS

Human VF fibroblasts were exposed to TGF-β1+/-Csn-B. Expression of genes related to fibrosis were quantified. In addition, contraction was assayed as a surrogate for the fibrotic phenotype in our cell line.

RESULTS

TGF-B1 stimulated COL1A1 and ACTA2, as expected. Csn-B significantly downregulated TGF-β1-mediated upregulation of these genes (P = .009, P = .03, respectively). Csn-B had no effect on genes related to TGF-β/Smad signaling. Csn-B also decreased the TGF-β1-mediated contractile phenotype in our cells (P = .004).

CONCLUSIONS

NR4A1 is an endogenous inhibitor of fibrosis in the vocal folds and Csn-B, as an NR4A1 agonist, may evolve as an ideal, therapeutic candidate for this challenging condition.

LEVEL OF EVIDENCE

NA Laryngoscope, 128:E425-E428, 2018.

Phosphorylation of the glucocorticoid receptor alters SMAD signaling in vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Direct glucocorticoid (GC) injection for vocal fold (VF) scarring has evolved as a therapeutic strategy, but the mechanisms underlying the antifibrotic effects remain unclear. GCs act via the glucocorticoid receptor (GR), which is phosphorylated at multiple serine residues in a hormone-dependent manner to affect bioactivity. We hypothesize that GCs regulate SMAD signaling via GR phosphorylation in vocal fold fibroblasts (VFFs).

STUDY DESIGN

In vitro.

METHODS

Human VFFs were treated with dexamethasone (DM; 10^-5 -10^-7 M) ± transforming growth factor (TGF)-β1 (10 ng/mL). RU486 (10^-6 M) was employed to isolate the regulatory effects of GR. Total GR, Ser²¹¹ , and Ser²⁰³ phosphorylation was examined via sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunocytochemistry. Quantitative polymerase chain reaction was employed to determine GR-mediated effects of DM on genes related to fibrosis.

RESULTS

Total GR and Ser²¹¹ phosphorylation was observed predominantly in the nucleus 1 hour after DM administration. DM decreased total GR expression, but Ser²⁰³ and Ser²¹¹ phosphorylation increased. RU486 limited the effects of DM. SMAD3 and SMAD7 mRNA expression significantly decreased 4 hours after DM administration (P < 0.05); this response was negated by RU486. COL1A1 remained unchanged, and ACTA2 significantly increased following 24 hours of DM treatment (P < 0.05).

CONCLUSION

DM regulated TGF-β1 signaling via altered SMAD3 and SMAD7 expression. This response was associated with altered GR phosphorylation. These findings provide insight into the mechanisms of steroidal effects on vocal fold repair; ultimately, we seek to enhance therapeutic strategies for these challenging patients.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E187-E193, 2019.

The effects of concurrent chemoradiation therapy to the base of tongue in a preclinical model

OBJECTIVES/HYPOTHESIS

To develop a clinically relevant model of oropharyngeal concurrent chemoradiation therapy (CCRT) in order to quantify the effects of CCRT on tongue function and structure. CCRT for advanced oropharyngeal cancer commonly leads to tongue base dysfunction and dysphagia. However, no preclinical models currently exist to study the pathophysiology of CCRT-related morbidity, thereby inhibiting the development of targeted therapeutics.

STUDY DESIGN

Animal model.

METHODS

Twenty-one male Sprague-Dawley rats were randomized into three groups: 2 week (2W), 5 month (5M), and control (C). The 2W and 5M animals received cisplatin, 5-fluorouracil, and five fractions of 7 Gy to the tongue base; the C animals received no intervention. In vivo tongue strength and displacement, as well as hyoglossus muscle collagen content, were assessed. Analyses were conducted 2 weeks or 5 months following completion of CCRT in the 2W and 5M groups, respectively.

RESULTS

Peak tetanic and twitch tongue forces were significantly reduced in both 2W and 5M animals compared to controls (tetanic: P = .0041, P = .0089, respectively; twitch: P = .0201, P = .0020, respectively). Twitch half-decay time was prolonged in 2W animals compared to controls (P = .0247). Tongue displacement was significantly reduced across all testing parameters in 5M animals compared to both the C and 2W groups. No differences in collagen content were observed between experimental groups.

CONCLUSIONS

The current study is the first to describe a preclinical model of CCRT to the head and neck with an emphasis on clinical relevance. Tongue strength decreased at 2 weeks and 5 months post-CCRT. Tongue displacement increased only at 5 months post-CCRT. Fibrosis was not detected, implicating alternative causative factors for these findings.

LEVEL OF EVIDENCE

NA Laryngoscope, 1783-1790, 2018.

Nanoparticle delivery of RNA-based therapeutics to alter the vocal fold tissue response to injury

OBJECTIVES/HYPOTHESIS

Our laboratory and others hypothesized that Smad3 is a principle mediator of the fibrotic phenotype in the vocal folds (VFs), and we further posited that alteration of Smad3 expression through short interfering (si)RNA holds therapeutic promise, yet delivery remains challenging. To address this issue, we employed a novel synthetic oligomer, lipitoid, complexed with siRNA to improve stability and cellular uptake with the goal of increased efficiency of RNA-based therapeutics.

STUDY DESIGN

In vitro study and in vivo animal model.

METHODS

In vitro, lipitoid cytotoxicity was quantified via colorimetric and LIVE/DEAD assays in immortalized human VF fibroblasts and primary rabbit VF fibroblasts. In addition, optimal incubation interval and solution for binding siRNA to lipitoid for intracellular delivery were determined. In vivo, a rabbit model of VF injury was employed to evaluate Smad3 knockdown following locally injected lipitoid-complexed siRNA.

RESULTS

In vitro, lipitoid did not confer additional toxicity compared to commercially available reagents. In addition, 20-minute incubation in 1× phosphate-buffered saline resulted in maximal Smad3 knockdown. In vivo, Smad3 expression increased following VF injury. This response was significantly reduced in injured VFs at 4 and 24 hours following injection (P = .035 and .034, respectively).

CONCLUSIONS

The current study is the first to demonstrate targeted gene manipulation in the VFs as well as the potential utility of lipitoid for localized delivery of genetic material in vivo. Ideally, these data will serve as a platform for future investigation regarding the functional implications of therapeutic gene manipulation in the VFs.

LEVEL OF EVIDENCE

NA. Laryngoscope, 128:E178-E183, 2018.

Preliminary study of a novel transfection modality for in vivo siRNA delivery to vocal fold fibroblasts

OBJECTIVE

An obstacle to clinical use of RNA-based gene suppression is instability and inefficiency of current delivery modalities. Nanoparticle delivery likely holds great promise, but the kinetics and transfection conditions must be optimized prior to in vivo utility. We investigated a RNA nanoparticle complex incorporating a lipitoid transfection reagent in comparison to a commercially available reagent.

STUDY DESIGN

In vitro.

METHODS

We investigated which variables influence transfection efficiency of lipitoid oligomers and a commercially available reagent across species, in vitro. These variables included duration, dose, and number of administrations, as well as serum and media conditions. The target gene was Smad3, a signaling protein in the transforming growth factor-β cascade implicated in fibroplasia in the vocal folds and other tissues.

RESULTS

The two reagents suppressed Smad3 mRNA for up to 96 hours; lipitoid performed favorably and comparably. Both compounds yielded 60% to 80% mRNA knockdown in rat, rabbit, and human vocal fold fibroblasts (P < 0.05 relative to control). Dose and number of administrations played a significant role in gene suppression (P < 0.05). Suppression was more dose-sensitive with lipitoid. At a constant siRNA concentration, a 50% decrease in gene expression was observed in response to a five-fold increase in lipitoid concentration. Increased number of administrations enhanced gene suppression, ∼45% decrease between one and four administrations. Neither serum nor media type altered efficiency.

CONCLUSION

Lipitoid effectively knocked down Smad3 expression across multiple transfection conditions. These preliminary data are encouraging, and lipitoid warrants further investigation with the goal of clinical utility.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E231-E237, 2017.

Stem Cell-Mediated Paracrine Signaling Alters Fibroplasia in Human Vocal Fold Fibroblasts in Vitro

OBJECTIVES

Interactions between mesenchymal stem cells (MSCs) and native vocal fold fibroblasts (VFFs) have not been described in spite of promising preliminary data regarding the effects of MSCs on vocal fold repair in vivo. The current study employed a conditioned media (CM) model to investigate the paracrine effects of bone marrow-derived mesenchymal stem cells (BMSCs) on VFFs.

METHODS

Human VFFs were treated with transforming growth factor-β1 (TGF-β1; 10 ng/mL), CM from human BMSCs following 48 hours of TGF-β1 stimulation, or CM+TGF-β1. Proliferation, immunocytochemistry for alpha smooth muscle actin (αSMA), migration, and collagen gel contraction were quantified as well as transcription of components of the TGF-β signaling pathway.

RESULTS

Transforming growth factor-β1 accelerated proliferation and induced αSMA in VFFs; these effects were suppressed with CM ( P = .009, P < .001, respectively). The CM+TGF-β1 condition increased cell migration ( P = .02) and decreased gel contraction; CM+TGF-β1 also inhibited TGF-β signaling via significant upregulation of NR4A1 as well as downregulation of S MAD3 and TGF-β1 relative to TGF-β1 stimulation in the absence of CM ( P = .002, P < .001, and P = .005, respectively).

CONCLUSIONS

Conditioned media affected many profibrotic cell activities in TGF-β1-stimulated VFFs, likely related to altered TGF-β signaling. These data provide preliminary insight regarding the antifibrotic effects of MSCs and further support their progression to clinical utility.

NR4A1 is an endogenous inhibitor of vocal fold fibrosis

OBJECTIVES/HYPOTHESIS

NR4A1 was recently identified as an endogenous inhibitor of transforming growth factor (TGF)-β-induced fibrosis, and the role of this nuclear receptor has not been elucidated in tissue health or the response to injury in the vocal folds. Given the clinical implications of vocal fold fibrosis, we investigated NR4A1 expression during vocal fold wound healing in vivo and the regulatory roles of NR4A1 on vocal fold fibroblasts (VFFs) in vitro with the ultimate goal of developing targeted therapies for this challenging patient population.

STUDY DESIGN

In vivo and in vitro.

METHODS

In vivo, the temporal pattern of NR4A1 mRNA expression was quantified following rat vocal fold injury. In vitro, the role of NR4A1 on TGF-β1-mediated transcription of genes underlying fibrosis as well as myofibroblast differentiation and collagen gel contraction was quantified in our human VFF line. Small interfering RNA was employed to alter NR4A1 expression to further elucidate this complex system.

RESULTS

Nr4a1 mRNA increased 1 day after injury and peaked at 7 days. Knockdown of NR4A1 resulted in upregulation of COL1A1 and TGF-β1, with TGF-β1 stimulation (both P < .001) in VFFs. NR4A1 knockdown also resulted in increased α-smooth muscle actin-positive cells (P = .013) and contraction (P = .002) in response to TGF-β1.

CONCLUSIONS

NR4A1 has not been described in vocal fold health or disease. Upregulation of TGF-β following vocal fold injury was concurrent with increased NR4A1 expression. These data provide a foundation for the development of therapeutic strategies given persistent TGF-β signaling in vocal fold fibrosis.

LEVEL OF EVIDENCE

N/A Laryngoscope, 127:E317-E323, 2017.

SMAD3 expression and regulation of fibroplasia in vocal fold injury

OBJECTIVE

Recent reports highlight the efficacy of small interfering RNA (siRNA) targeting SMAD3 to regulate transforming growth factor β (TGF-β)-mediated fibroplasia in vocal fold fibroblasts. The current study sought to investigate SMAD3 expression during wound healing in vivo and quantify the downstream transcriptional events associated with SMAD3 knockdown in vitro.

STUDY DESIGN

In vivo and in vitro.

METHODS

Unilateral vocal fold injury was created in a rabbit model. SMAD3 and SMAD7 mRNA expression was quantified at 1 hour and 1, 3, 7, 14, 30, 60, and 90 days following injury. In vitro, multi-gene analysis technology was employed in our immortalized human vocal-fold fibroblast cell line following TGF-β1 stimulation ± SMAD3 knockdown across time points.

RESULTS

SMAD3 mRNA expression increased following injury; upregulation was significant at 3 and 7 days compared to control (both P < 0.001). SMAD7 mRNA was also upregulated at 3, 7, and 14 days (P = 0.02, P < 0.001, and P < 0.001, respectively). In vitro, SMAD3 knockdown reduced the expression of multiple profibrotic, TGF-β signaling, and extracellular matrix metabolism genes at 6 and 24 hours following TGF-β1 stimulation.

CONCLUSION

Cumulatively, these data support SMAD3 as a potential master regulator of TGF-β-mediated fibrosis. SMAD3 transcription peaked 7 days following injury. Multi-gene analysis indicated that the therapeutic effectiveness of SMAD3 knockdown may be related to regulation of downstream mediators of fibroplasia and altered TGF-β signaling.

LEVEL OF EVIDENCE

NA. Laryngoscope, 127:E308-E316, 2017.

Mesenchymal stem cells have antifibrotic effects on transforming growth factor-β1-stimulated vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Mesenchymal stem cells (MSCs) hold therapeutic promise for vocal fold scar, yet the precise mechanism(s) underlying tissue level changes remain unclear. We hypothesize that MSCs interact with native fibroblasts to favorably affect healing. Furthermore, we hypothesize that these interactions vary based on MSC source.

METHODS

Vocal fold fibroblasts (VFFs), adipose-derived stem cells, and bone marrow-derived stem cells (BMSCs) were extracted from Sprague-Dawley rats; and a coculture model was employed culturing VFFs ± transforming growth factor (TGF-β1) (10 ng/mL) ± MSCs. Monoculture MSCs were also prepared as a control. Both extracellular matrix (ECM) and components of the TGF-β signaling pathway were analyzed via polymerase chain reaction and western blotting.

RESULTS

Significantly decreased TGF-β1 mRNA and α-smooth muscle actin protein was observed in VFFs in response to TGF-β1 in the coculture with both MSCs (P < 0.05, P < 0.01). BMSCs significantly downregulated collagen I (P < 0.05), collagen III (P < 0.05), Smad3 (P < 0.01), and TGF-β1 receptor I (P < 0.01) mRNA in VFFs. Hyaluronic synthase-1 and 2 increased in cocultured BMSCs when compared with monocultured BMSCs at baseline and in response to TGF-β1 (P < 0.01).

CONCLUSION

MSCs had a favorable effect on ECM regulation as well as suppression of TGF-β1 signaling in VFF. Bidirectional paracrine signaling was also observed as VFFs altered ECM regulation in MSCs. These data provide insight into the regenerative effects of MSCs and provide a foundation for clinical application.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E35-E41, 2017.

The role of Smad3 in the fibrotic phenotype in human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

To investigate the role of Smad3 as a regulator of transforming growth factor (TGF)-β1-mediated cell activities associated with fibrosis in normal human vocal fold fibroblasts. We also sought to confirm the temporal stability of Smad3 knockdown via small inhibitor ribonucleic acid (siRNA). Vocal fold fibroblasts were employed to determine the effects of Smad3 knockdown on TGF-β1-mediated migration and contraction, as well as regulation of connective tissue growth factor (CTGF). We hypothesized that Smad3 is an ideal candidate for therapeutic manipulation in vivo based on its role in fibrosis.

STUDY DESIGN

In vitro.

METHODS

Knockdown of Smad3 via siRNA was performed in our normal human vocal fold cell line. Three-dimensional collagen gel contraction and scratch assays were employed to determine the role of Smad3 on TGF-β1-mediated contraction and migration, respectively. The role Smad3 in the induction of CTGF was characterized via sodium dodecyl sulfate polyacrylamide gel electrophoresis. The effects of Smad3 signaling on Smad7 messenger (m)RNA and protein were also quantified.

RESULTS

Smad3 knockdown was temporally-stable up to 72 hours (P < 0.001), diminished TGF-β1-mediated collagen gel contraction and migration, and blunted induction of CTGF, but it had no effect on TGF-β1-mediated Smad7 mRNA or protein induction.

CONCLUSION

Transforming growth factor-β1 stimulated profibrotic cell activities in our cell line and these actions were largely reduced with Smad3 knockdown. These data provide continued support for therapeutic targeting of Smad3 for vocal fold fibrosis because it appears to regulate the fibrotic phenotype.

LEVEL OF EVIDENCE

N/A. Laryngoscope, 126:1151-1156, 2016.

Concurrent oral human papilloma virus infection in patients with recurrent respiratory papillomatosis: a preliminary study

OBJECTIVES/HYPOTHESIS

To determine oral human papilloma virus (HPV) colonization in patients with adult-onset recurrent respiratory papillomatosis (AO-RRP) and their long-term partners.

STUDY DESIGN

Prospective, cohort study

METHODS

Patients with pathology-confirmed AO-RRP and a small cohort of their long-term partners were subjected to a standardized oral rinse and swab protocol to obtain oral epithelial cells. DNA from these samples was extracted and subjected to both qualitative analyses via multiplex polymerase chain reaction as well as to a commercially available linear array assay for the determination of specific HPV subtypes.

RESULTS

Samples were collected from 27 patients with AO-RRP and six long-term sexual partners. Qualitative analysis of agarose gel products using a multiple genotype primer cocktail suggested the presence of HPV DNA in oral rinse or swabs in 26 patients (96%) and four partner samples (67%). A subset of these positive patient samples was then subjected to genotyping; a spectrum of HPV subtypes was observed. Interestingly, HPV81 was identified in many samples.

CONCLUSION

Recent data suggest that less than 7% of the general population is HPV positive in the oral cavity. Our data suggest that the oral colonization rate is much higher in patients with AO-RRP. Additionally, long-term sexual partners of patients with RRP had a much higher rate of HPV positivity. These preliminary data may have implications for viral transmission and provide a framework for enhanced patient education as well as further investigation.

LEVEL OF EVIDENCE

4.

Smad3: an emerging target for vocal fold fibrosis

OBJECTIVES/HYPOTHESIS

To determine the efficacy of small interfering RNA (siRNA) targeting Smad3 to mediate fibroplasia in vitro, to investigate the temporal regulation of Smad3 following vocal fold (VF) injury, and to determine the local and distal effects of Smad3 siRNA VF injection.

STUDY DESIGN

In vitro and in vivo.

METHODS

In vitro, Smad3 regulation was examined at both the level of transcription and translation in a human VF cell line in response to Smad3 siRNA ± transforming growth factor β (TGF-β). Collagen transcription was also examined. In vivo, Smad3 messenger RNA (mRNA) expression was quantified as a function of time following rabbit VF injury. Also, the effects of injected Smad3 siRNA were assessed at local and distal sites.

RESULTS

Smad3 siRNA knocked down Smad3 transcription and translation and limited TGF-β-mediated collagen mRNA expression with minimal cytotoxicity in vitro. In vivo, Smad3 mRNA increased 1 day following VF injury and remained elevated through day 7. Smad3 siRNA injection into the uninjured vocal fold had no local or distant effect on Smad3 mRNA at multiple organ sites.

CONCLUSIONS

These data provide a foundation for further investigation regarding the development of novel RNA-based therapeutics for the VF, specifically locally delivered siRNA for challenging fibrotic conditions of the VF.

The utility of the potassium titanyl phosphate laser in modulating vocal fold scar in a rat model

OBJECTIVES/HYPOTHESIS

We hypothesize that the KTP laser has the potential to augment wound healing in a rat model, and this modality may serve as a therapeutic tool for the management of vocal fold fibrosis.

STUDY DESIGN

Prospective, laboratory animal study.

METHODS

Rats were subjected to either vocal fold injury ± KTP laser treatment at low energy to simulate clinically relevant endpoints. In addition, cohorts were subjected to therapeutic KTP laser alone. Endpoints included the analyses of gene expression data related to the acute inflammatory response and extracellular matrix deposition and organization.

RESULTS

Therapeutic KTP treatment was associated with an additive effect on inflammatory gene expression in the context of the injured rat vocal fold mucosa. A similar additive effect was observed for matrix metalloproteinase gene expression, similar to data previously reported in the dermatology literature. However, histologically, the KTP had little effect on established vocal fold fibrosis.

CONCLUSIONS

These data are the first to attempt to provide mechanistic insight into the clinical utility of angiolytic lasers for vocal fold scar. Similar to previous data obtained in the skin, it appears that these effects are mediated by MMPs.

Alpha 1E subunit of the R-type calcium channel is associated with myelinogenesis

During myelinogenesis, we found an exceedingly strong, transient expression of the alpha(1E) gene for the R-type voltage-gated calcium channel in CNS white matter. This immunoreactivity appeared in glial cells along specific pathways of the brainstem, cerebellum, and telencephalon. The reactivity followed a wave that progressed from the brainstem at P5, to the cerebellar peduncles by P8, the arbor vitae by P14, and the granular layer by P17. The reactivity-peaked about 3-4 days later and decreased gradually to become negligible in all areas before adulthood. Ultrastructural analysis confirmed that alpha(1E) immunoreactivity was located in oligodendroglial somata, their projections, paranodal wraps and loose myelin sheaths. There was a distinct association of the channel protein reactivity on oligodendroglial membranes in contact with the axon. We propose that glial projections, contacting axons, sense axonal firing through small K(+) currents and open the high voltage R-type calcium channels to signal myelination.

A single dose of kainic acid elevates the levels of enkephalins and activator protein-1 transcription factors in the hippocampus for up to 1 year

Neuronal plasticity plays a very important role in brain adaptations to environmental stimuli, disease, and aging processes. The kainic acid model of temporal lobe epilepsy was used to study the long-term anatomical and biochemical changes in the hippocampus after seizures. Using Northern blot analysis, immunocytochemistry, and Western blot analysis, we have found a long-term elevation of the proconvulsive opioid peptide, enkephalin, in the rat hippocampus. We have also demonstrated that an activator protein-1 transcription factor, the 35-kDa fos-related antigen, can be induced and elevated for at least 1 year after kainate treatment. This study demonstrated that a single systemic injection of kainate produces almost permanent increases in the enkephalin and an activator protein-1 transcription factor, the 35-kDa fos-related antigen, in the rat hippocampus, and it is likely that these two events are closely associated with the molecular mechanisms of induction of long-lasting enhanced seizure susceptibility in the kainate-induced seizure model. The long-term expression of the proenkephalin mRNA and its peptides in the kainate-treated rat hippocampus also suggests an important role in the recurrent seizures of temporal lobe epilepsy.

Plasmalemmal ATPase calcium pump localizes to inner and outer hair bundles

Recent studies demonstrate calcium ion influx at the tips of hair cell stereocilia during mechano-transduction. These ions must be either pumped from the cytosol into the extracellular space or endoplasmic envelope, or else sequestered by binding to specific proteins. A plasma membrane calcium pump (ATPase-type) was analysed in whole-mounts of rat organ of Corti using a monoclonal antibody to a large cytoplasmic loop of this protein. The reactivity was particularly high on the tips of longer stereocilia and was found along the shafts. Inner hair cell stereocilia had much less reactivity than outer hair cells. The reactivity lined the plasma membrane of inner hair cell bodies while a higher reactivity appeared in the cytoplasm of outer hair cells. Supporting cells were unreactive. Ultrastructural examination confirmed the plasma membrane calcium pump location on stereocilia and along the endolymph surface of receptor cells. Reaction product lined the plasma membrane of stereocilia as intense puncta. More reactive puncta occurred near the distal ends of stereocilia and the number decreased toward the ciliary base. The endolymph plasma membrane over the cuticular notch was especially reactive. The finding of more intense pump reactivity at the tips of stereocilia than the base is consistent with the hypothesis that during transduction, calcium ions enter stereocilia, distally, and the ATPase plasma membrane calcium pump rapidly extrudes these ions to the extracellular space.

Long-term expression of Fos-related antigen and transient expression of delta FosB associated with seizures in the rat hippocampus and striatum

Systemic administration of kainic acid (KA), an analogue of glutamic acid, causes limbic seizures and pathophysiological changes in adult rats that are very similar to human temporal lobe epilepsy. One of the earliest changes in gene expression after treatment with KA is the induction of immediate-early genes. The fos and jun families are frequently studied immediate-early genes that are induced by KA. Several groups, including ours, have recently reported that a 35-kDa Fos-related antigen (FRA) is induced for a protracted time by various stimuli. It has been suggested that this FRA is delta FosB, which has a molecular mass of approximately 35 kDa. The present study characterizes the long-term expression of FRA and delta FosB after systemic treatment with KA. Immunocytochemistry and western blot analysis using an antibody that cross-reacts with all known FRAs showed that a 35-kDa FRA was induced at high levels in both the hippocampus and striatum for up to 1 month by KA. A semiquantitative PCR analysis showed that delta FosB was induced by KA, but its expression lasted for only 6 h. This result was also verified by northern blot analysis. These results suggested that the 35-kDa FRA with long-term elevated levels seen with western blot analysis and immunocytochemistry is a new species of the FRA and not delta FosB. The long-term expression of FRA in both the hippocampus and striatum may be associated with the pathophysiological changes after KA administration.

Ultrastructural localization of the plasmalemmal calcium pump in cerebellar neurons

In a previous study, fluorescence labeling of a plasmalemmal ATPase protein with the 5F10 monoclonal antibody revealed prominent antigen in the cerebellar molecular layer surrounding the somata and dendrites of Purkinje cells. In the present study, this antibody labeled with silver enhanced nano-sized gold particles on semithin plastic sections revealed a clearly demarcated plasma membrane outlining the somata and entire dendritic arbors of Purkinje cells including their spines. Ultrastructural analysis of horseradish peroxidase preparations showed reaction product along the plasmalemma and extending on to the sub-plasmalemmal endoplasmic reticulum. In the granular layer, somata of granule cells were reactive, as were their dendritic extensions into glomeruli where reactive claws surrounded voids formed by mossy fiber rosettes. Somata and dendrites of cerebellar nuclear cells also had reactive zones that were limited to the plasma membrane and a narrow zone of the sub-plasmalemmal endoplasmic reticulum. Comparative labeling of this protein and P channel protein revealed similar plasmalemmal locations. This study shows that a specific calcium ATPase pump protein is located on the plasmalemma of certain types of cerebellar neurons. The ultrastructural distribution of calcium pump and P channel antibodies occurred in punctate sites along the plasma membrane of dendrites and spines of Purkinje cells. The close association between P-type calcium channels and the plasma membrane calcium pump is consistent with rapid extrusion of intracellular calcium from neurons endowed with large numbers of voltage-gated calcium channels.

Immunohistochemical localization of Lyn (p56) protein in the adult rat brain

Expression of a sarcoma proto-oncogene, c-lyn, was mapped in the adult rat brain using immunohistochemistry. Lyn protein was prevalent in restricted cell populations of the olfactory bulb and the basal forebrain which included nuclei of accumbens, fundal striatum, bed stria, ventral pallidum and central amygdala as well as deep entorhinal and pyriform cortices. Tightly packed Lyn-positive cells formed discrete multiple stripes crossing perpendicular to the rostral limb of the anterior commissure, and intense masses surrounding the caudal limb. In the thalamus, the habenula, anterodorsal nucleus and medial geniculate body, together with the paraventricular hypothalamic nuclei, had prominent reactive neuronal somata and dendrites in the neuropil. The lateral septal nucleus also had intense Lyn-positive neurons with overlapping dendritic fields. In addition, scattered neurons were evenly distributed throughout the striatum. The red, interpeduncular, auditory and trigeminal tract nuclei were intensely reactive. The cerebellar molecular layer was uniformly labeled except for a few isolated fiber bundles in the lowest part of this layer. The granule cells adjacent to the Purkinje cell layer appeared in reactive patches. In the spinal cord, the posteromarginal nucleus had intense labeling. The significance of this highly localized distribution pattern of Lyn protein may be related to connections forming functional compartments serving signal transduction within specific central nervous system circuitry.