Extracellular matrix gene expression during wound healing of the injured rat vocal fold

Cryotherapy Modifies Extracellular Matrix Expression of Vocal Fold in Rat Models

OBJECTIVES

Vocal fold (VF) scarring is the major cause of voice disorders. Cryotherapy is an effective anti-scarring therapy for skin lesions. The aim of this study was to explore the anti-scarring potential of cryotherapy in vocal folds.

METHODS

The extracellular matrix (ECM) mRNA expression of cryotherapy on normal VF tissue and the histologic results of cryotherapy on vocal fold healing were studied. Fifteen rats were introduced cryotherapy on the normal VF bilaterally and were harvested for real-time polymerase chain reaction (RT-PCR) analysis for collagen I, collagen III, TGFβ1, decorin, fibronectin and HAS1 at 1 day, 3 days and 7 days. Ten rats were unilaterally injured by stripping lamina propria and immediately treated with or without cryotherapy and were harvested at 2 months for histological and immunohistochemical analysis.

RESULTS

Regenerative effect of cryotherapy was validated of ECM gene expression. Histological and immunohistochemical analysis showed significantly increased hyaluronan, decreased collagen, and increased decorin deposition in injury-cryotherapy cohort compared with injury control cohort and normal control cohort.

CONCLUSIONS

Cryotherapy may provide an optimal environment for vocal fold tissue regeneration. The results of the present investigation suggest that cryotherapy has therapeutic potential in prevention and treatment of vocal fold scarring.

Antifibrotic effects of eupatilin on TGF-β1-treated human vocal fold fibroblasts

Vocal fold scarring is a major cause of dysphonia. Vocal fold fibroblasts (VFFs) and the TGF-β signaling pathway play important roles in scar formation. Eupatilin, a chromone derivative of the Artemisia species, is a traditional folk remedy for wound healing. However, until recently, few studies investigated the therapeutic effects of eupatilin. We investigated the antifibrogenic effects of eupatilin on TGF-β1-treated human vocal fold fibroblasts (hVFFs). The optimal concentration of eupatilin was determined by a cell viability assay. Western blotting was used to measure the expression of alpha-smooth muscle actin during myofibroblast differentiation, fibronectin (FN), collagen type I (Col I), and collagen type III (Col III) extracellular matrix proteins, and Smad2, Smad3, and p38 in the fibrotic pathway. Measurements were made before and after eupatilin treatment. Eupatilin at 100 nM was shown to be safe for use in hVFFs. TGF-β1 induced hVFFs to proliferate and differentiate into myofibroblasts and increased Col III and FN synthesis in a time- and dose-dependent manner. Eupatilin suppressed TGF-β1-induced hVFF proliferation and differentiation into myofibroblasts through the Smad and p38 signaling pathways. Furthermore, eupatilin inhibited TGF-β1-induced FN, Col I, and Col III synthesis in hVFFs. Our in vitro findings show that eupatilin effectively suppressed TGF-β1-induced fibrotic changes in hVFFs via the Smad and p38 signaling pathways. Thus, eupatilin may be considered a novel therapeutic agent for the treatment of vocal fold fibrosis.

Cryotherapy has antifibrotic and regenerative effects on human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Vocal fold scarring remains a major treatment challenge, and scar prevention without residual lesions remains a dilemma. Cryotherapy has shown cosmetic outcomes on skin lesions with minimal scarring. The aim of this study was to clarify the beneficial effects of cryotherapy for the prevention and the treatment of vocal fold scarring.

STUDY DESIGN

In vitro.

METHODS

Primary cultures of human vocal fold fibroblasts (VFFs) were used in this study. Myofibroblast differentiation was stimulated by transforming growth factor β1 (TGF-β1). We mimicked the cryotherapy effect on vocal fold healing in vivo by freezing VFFs ± TGF-β1 in vitro. The influence of freezing on cell viability, proliferation, migration, and contractile properties were analyzed. The expression of collagen I, collagen III, fibronectin, TGF-β1, matrix metallopeptidase 1 (MMP1), hyaluronan synthase 1 (HAS1) were investigated by real-time polymerase chain reaction (RT-PCR), and the expression of alpha smooth muscle actin (α-SMA) and decorin were investigated by RT-PCR and Western blot.

RESULTS

Freezing was found to modify extracellular matrix (ECM) synthesis and differentiation of VFFs. Expression of collagen I, collagen III, fibronectin, α-SMA, and TGF-β1 was downregulated, and MMP1 was upregulated in VFFs + TGF-β1 (myofibroblast) by freezing. HAS1 and decorin were upregulated in both VFFs ± TGF-β1 by freezing. Freezing VFFs + TGF-β1 (myofibroblast) with fast thawing had a lower expression of α-SMA when compared with slow thawing. Freezing reduced the migration and collagen contraction of VFFs + TGF-β1 (myofibroblast).

CONCLUSION

Cryotherapy induces antifibrotic and regenerative ECM alterations in VFFs. These data provide insight into the prevention and the treatment of vocal fold scarring with cryotherapy in phonomicrosurgery.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:E143-E150, 2019.

The Ability of Human Nasal Inferior Turbinate-Derived Mesenchymal Stem Cells to Repair Vocal Fold Injuries

Objective This study investigated the ability of implanted human nasal inferior turbinate-derived mesenchymal stem cells (hTMSCs) to repair injured vocal folds. To this end, we used quantitative real-time polymerase chain reaction (PCR) to analyze the early phase of wound healing and histopathological analysis to explore the late phase of wound healing in xenograft animal models. Study Design Prospective animal study. Setting Research laboratory. Subjects and Methods The right-side lamina propria of the vocal fold was injured in 20 rabbits and 30 rats. Next, hTMSCs were implanted into half of the injured vocal folds (hTMSC groups). As a control, phosphate-buffered saline (PBS) was injected into the other half of the injured vocal folds (PBS groups). Rat vocal folds were harvested for polymerase chain reaction (PCR) at 1 week after injury. Rabbit vocal folds were evaluated endoscopically and the larynges harvested for histological and immunohistochemical examination at 2 and 8 weeks after injury. Results In the hTMSC group, PCR showed that hyaluronan synthase ( HAS) 1, HAS 2, and transforming growth factor ( TGF)-β1 were significantly upregulated compared with the PBS group. Procollagen type III ( COL III) messenger RNA expression was significantly upregulated in the PBS group compared with the normal group. Histological analyses showed that hTMSC administration afforded more favorable collagen and hyaluronic acid deposition than was evident in the controls. Implanted hTMSCs were observed in injured vocal folds 2 weeks after implantation. Conclusions Our results show that hTMSCs implantation into injured vocal folds facilitated vocal fold regeneration, with presenting antifibrotic effects.

Biochemical basis of vocal fold mobilization after microflap surgery in a rabbit model

OBJECTIVES/HYPOTHESIS

To investigate phonation-related extracellular matrix (ECM) changes in the vocal fold lamina propria after microflap surgery using an in vivo rabbit phonation model.

STUDY DESIGN

Prospective animal study.

METHODS

Twenty-four New Zealand White rabbits were used in this study. Quantitative polymerase chain reaction and immunohistochemistry were used to investigate alterations in vocal fold ECM proinflammatory and profibrotic gene, and protein expression from a control group of animals receiving a microflap without phonation and a separate group of animals receiving experimentally induced phonation on postmicroflap days 0, 3, and 7.

RESULTS

IHC demonstrated the highest concentration of CD45 in vocal folds on postoperative day 0. Staining for CD45 was absent by postoperative day 7, with no differences in CD45 staining between groups. Fibronectin gene expression increased significantly on postoperative day 3 in the control and experimentally induced phonation groups, with maximal staining of fibronectin around the microflap incision on postoperative day 7. No alterations in cyclooxygenase-2, interleukin-1β, and transforming growth factor-β1 gene expression were observed between groups.

CONCLUSIONS

Results of the present study revealed an acute inflammatory response in the vocal fold at the time of microflap (day 0) and up to 3 days post-microflap. By post-operative day 3, staining of CD45 positive cells decreased, with essentially no evidence of inflammation by post-operative day 7. With the end of the acute inflammatory response occurring around day 3, these data may provide support for mobilizing tissue after inflammation has subsided and the process of active tissue remodeling has ensued (days 3-7).

LEVEL OF EVIDENCE

N/A.

Bone marrow-derived clonal mesenchymal stem cells as a source of cell therapy for promoting vocal fold wound healing

OBJECTIVES

We investigated whether mouse bone marrow-derived clonal mesenchymal stem cells (BM-cMSCs) could promote vocal fold (VF) wound healing by using a xenograft animal model.

METHODS

Homogeneous BM-cMSCs isolated by a subfractionation culturing method from the bone marrow aspirates of green fluorescent protein transgenic mice were injected into the VFs of rabbits immediately after direct mechanical injury. Macroscopic, biomechanical (rheometric), histologic, immunohistochemical, and transcriptional evaluations were performed on the scarred VFs 1 to 3 months after injury. Engraftment of the implanted BM-cMSCs was determined by detection of green fluorescent protein cells in the recipient VF by confocal microscopy.

RESULTS

The BM-cMSC-treated VFs showed improved morphological properties and viscoelasticity as compared to control VFs injected with phosphate-buffered saline solution. Histologic and immunohistochemical evaluations showed less excessive collagen deposition and increased density of glycosaminoglycans in the BM-cMSC-treated VFs as compared to the control VFs at 3 months after injury (p = 0.003 and p = 0.037, respectively). BM-cMSC transplantation led to a significant attenuation of fibronectin (p = 0.036) and transforming growth factor beta1 (p = 0.042) messenger RNA expression at 1 month after injury. Green fluorescent protein-expressing BM-cMSCs engrafted in recipient VFs were found at 1 month after implantation.

CONCLUSIONS

BM-cMSCs appeared to survive in the injured xenogeneic VFs after transplantation for up to 1 month and favorably enhanced the wound healing of VFs after injury. We conclude that BM-cMSCs are a possible source of cell therapy for vocal fold regeneration.

Feasibility and acute healing of vocal fold microflap incisions in a rabbit model

OBJECTIVES/HYPOTHESIS

The purpose of this study was to investigate the feasibility of performing mucosal elevation of a vocal fold microflap in a rabbit model and to measure the acute healing of rabbit microflap incisions compared to control vocal folds.

STUDY DESIGN

Prospective animal study.

METHODS

Ten New Zealand white rabbits were used in this study. All rabbits received a 3-mm incision through the epithelium of one vocal fold using a sickle knife and mucosal elevation through this incision using a microlaryngeal fine-angled spatula. The contralateral vocal fold was left intact to serve as an internal control. Student t tests were used to investigate differences in epithelial thickness, immunohistochemical staining of CD45, and inflammatory and profibrotic gene expression between vocal folds undergoing microflap and control.

RESULTS

Exposure of the rabbit larynx was achieved, allowing for the identification of a surgical plane and the creation of a microflap and elevation of the vocal fold mucosa. Hematoxylin-and-eosin staining revealed no significant differences in epithelial thickness, immunohistochemistry for CD45 showed no significant differences in CD45-positive cells, and quantitative polymerase chain reaction revealed no significant differences in interleukin-1β, transforming growth factor β-1, or cyclooxygenase-2 gene expression between vocal folds undergoing microflap and control.

CONCLUSIONS

We demonstrate the feasibility of vocal fold microflap surgery in a rabbit model. With the advantage of greater access to primers and antibodies for molecular biologic studies, the application of the microflap technique in a small-animal model such as rabbit has broad implications for future experimental investigations in laryngology.

Effects of raised-intensity phonation on inflammatory mediator gene expression in normal rabbit vocal fold

OBJECTIVE

To investigate the hypothesis that a transient episode of raised-intensity phonation causes a significant increase in vocal fold inflammatory messenger RNA (mRNA) expression in vivo.

STUDY DESIGN

Prospective animal study.

SETTING

Laboratory.

SUBJECTS AND METHODS

Ten New Zealand White breeder rabbits received 30 minutes of experimentally induced modal or raised-intensity phonation, followed by a 30-minute recovery period. A separate group of five rabbits served as sham controls. Real-time polymerase chain reaction was performed to investigate the mRNA expression of interleukin 1beta (IL-1beta), transforming growth factor beta-1 (TGFbeta1), and cyclooxygenase-2 (COX-2). Separate one-way analysis of variance (ANOVA) tests were used to investigate differences in gene expression across groups, with an appropriate alpha correction of 0.016 to control for type I error. Significant main effects were further examined using Fisher's least significant difference.

RESULTS

ANOVA revealed that there were differences for IL-1beta, TGFbeta1, and COX-2 between sham control, modal phonation, and raised-intensity phonation (P 0.0001). Pairwise comparisons revealed that the expression of IL-1beta, COX-2, and TGFbeta1 increased significantly during raised-intensity phonation, compared to modal phonation and sham control (P 0.0001).

CONCLUSION

Results provided support for the hypothesis that a transient episode of raised-intensity phonation causes a significant increase in vocal fold inflammatory mRNA expression. Future studies will investigate the signal transduction pathways and mechanisms regulating the vocal fold inflammatory response. The long-term goal of these studies is to advance understanding of the molecular and cellular events underlying phonation-related tissue alterations.

Microarray-driven validation of reference genes for quantitative real-time polymerase chain reaction in a rat vocal fold model of mucosal injury

Relative quantification by normalization against a stably expressed reference gene is a widely used data analysis method in microarray and quantitative real-time polymerase chain reaction (qRT-PCR) platforms; however, recent evidence suggests that many commonly utilized reference genes are unstable in certain experimental systems and situations. The primary aim of this study, therefore, was to screen and identify stably expressed reference genes in a well-established rat model of vocal fold mucosal injury. We selected and evaluated the expression stability of nine candidate reference genes. Ablim1, Sptbn1, and Wrnip1 were identified as stably expressed in a model-specific microarray dataset and were further validated as suitable reference genes in an independent qRT-PCR experiment using 2(-DeltaCT) and pairwise comparison-based (geNorm) analyses. Parallel analysis of six commonly used reference genes identified Sdha as the only stably expressed candidate in this group. Sdha, Sptbn1, and the geometric mean of Sdha and Sptbn1 each provided accurate normalization of target gene Tgfb1; Gapdh, the least stable candidate gene in our dataset, provided inaccurate normalization and an invalid experimental result. The stable reference genes identified here are suitable for accurate normalization of target gene expression in vocal fold mucosal injury experiments.

Alteration in cellular morphology, density and distribution in rat vocal fold mucosa following injury

The vocal fold mucosa plays an important role in voice production. Its cellular composition and density frequently change under various pathological conditions, often contributing to altered extracellular matrix production, tissue viscoelasticity, and voice quality. In this study, cellular changes in the rat mucosa following a unilateral stripping injury were investigated and analyzed semi-quantitatively. Distinctive and sequential changes in cellular morphology, composition, and density were observed in the mucosa post-injury. Cellular recruitment was a major event during the early stage of injury and reached its peak level by day 5 post-injury. Several types of cells, including neutrophil-like cells, epithelial cells, and fibroblast-like cells, were sequentially recruited. The sequential emergence of reactive cell populations following injury and subsequent reconstruction of the mucosa suggests their involvement in vocal fold tissue repair and scar formation processes.