Injection of human mesenchymal stem cells improves healing of scarred vocal folds: analysis using a xenograft model

Vocal fold restoration after scarring: biocompatibility and efficacy of an MSC-based bioequivalent

BACKGROUND

There is growing interest to application of regenerative medicine approaches in otorhinolaryngological practice, especially in the framework of the therapy of vocal fold (VF) scar lesions. The used conservative and surgical methods, despite the achieved positive outcomes, are frequently unpredictable and do not result in the restoration of the VF's lamina propria's structure, which provides the mechanical properties necessary for vibration. In this connection, the aim of this study was to ascertain the safety and efficacy of a bioequivalent in the treatment of VF scars using a rabbit model of chronic damage.

METHODS

The bioequivalent consisted of a hydrogel system based on a PEG-fibrin conjugate and human bone marrow-derived MSC. It was characterized and implanted heterotopically into rats and orthotopically into rabbits after VF scar excision.

RESULTS

We showed that the fabricated bioequivalent consisted of viable cells retaining their metabolic and proliferative activity. While being implanted heterotopically, it had induced the low inflammatory reaction in 7 days and was well tolerated. The orthotopic implantation showed that the gel application was characterized by a lower hemorrhage intensity (p = 0.03945). The intensity of stridor and respiratory rate between the groups in total and between separate groups had no statistically significant difference (p = 0.96 and p = 1; p = 0.9593 and p = 0.97…1, respectively). In 3 days post-implantation, MSC were detected only in the tissues closely surrounding the VF defect. The bioequivalent injection caused that the scar collagen fibers were packed looser and more frequently mutually parallel that is inherent in the native tissue (p = 0.018). In all experimental groups, the fibrous tissue's ingrowth in the adjacent exterior muscle tissue was observed; however, in Group 4 (PEG-Fibrin + MSC), it was much less pronounced than it was in Group 1 (normal saline) (p = 0.008). The difference between the thicknesses of the lamina propria in the control group and in Group 4 was not revealed to be statistically significant (p = 0.995). The Young's modulus of the VF after the bioequivalent implantation (1.15 ± 0.25 kPa) did not statistically significantly differ from the intact VF modulus (1.17 ± 0.45 kPa); therefore, the tissue properties in this group more closely resembled the intact VF.

CONCLUSIONS

The developed bioequivalent showed to be biocompatible and highly efficient in the restoration of VF's tissue.

Stem cell therapy for vocal fold regeneration after scarring: a review of experimental approaches

This review aims at becoming a guide which will help to plan the experimental design and to choose adequate methods to assess the outcomes when testing cell-based products in the treatment of the damaged vocal folds. The requirements to preclinical trials of cell-based products remain rather hazy and dictated by the country regulations. Most parameters like the way the cells are administered, selection of the cell source, selection of a carrier, and design of in vivo studies are decided upon by each research team and may differ essentially between studies. The review covers the methodological aspects of preclinical studies such as experimental models, characterization of cell products, assessment of the study outcome using molecular, morphological and immunohistochemical analyses, as well as measuring the tissue physical properties. The unified recommendations to perform preclinical trials could significantly facilitate the translation of cell-based products into the clinical practice.

Peroxisome Proliferator-Activated Receptor-γ Agonist Attenuates Vocal Fold Fibrosis in Rats via Regulation of Macrophage Activation

Macrophages aid in wound healing by changing their phenotype and can be a key driver of fibrosis. However, the contribution of macrophage phenotype to fibrosis following vocal fold injury remains unclear. Peroxisome proliferator-activated receptor-γ (PPARγ) is expressed mainly by macrophages during early wound healing and regulates the macrophage phenotype. This study aimed to evaluate the effects of pioglitazone (PIO), a PPARγ agonist, on the macrophage phenotype and fibrosis following vocal fold injury in rats. PIO was injected into the rat vocal folds on days 1, 3, 5, and 7 after injury, and the vocal fold lamina propria was evaluated on days 4 and 56 after injury. Moreover, THP-1-derived macrophages were treated with PIO, and the expression of proinflammatory cytokines under lipopolysaccharide/interferon-γ stimulation was analyzed. PIO reduced the expression of Ccl2 both in vivo and in vitro. Furthermore, PIO decreased the density of inducible nitric oxide synthase⁺ CD68⁺ macrophages and inhibited the expression of fibrosis-related factors on day 4 after injury. On day 56 after injury, PIO inhibited fibrosis, tissue contracture, and hyaluronic acid loss in a PPARγ-dependent manner. These results indicate that PPARγ activation could inhibit accumulation of inflammatory macrophages and improve tissue repair. Taken together, these findings imply that inflammatory macrophages play a key role in vocal fold fibrosis.

Achievements and Challenges in Transplantation of Mesenchymal Stem Cells in Otorhinolaryngology

Otorhinolaryngology enrolls head and neck surgery in various tissues such as ear, nose, and throat (ENT) that govern different activities such as hearing, breathing, smelling, production of vocal sounds, the balance, deglutition, facial animation, air filtration and humidification, and articulation during speech, while absence of these functions can lead to high morbidity and even mortality. Conventional therapies for head and neck damaged tissues include grafts, transplants, and artificial materials, but grafts have limited availability and cause morbidity in the donor site. To improve these limitations, regenerative medicine, as a novel and rapidly growing field, has opened a new therapeutic window in otorhinolaryngology by using cell transplantation to target the healing and replacement of injured tissues. There is a high risk of rejection and tumor formation for transplantation of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs); mesenchymal stem cells (MSCs) lack these drawbacks. They have easy expansion and antiapoptotic properties with a wide range of healing and aesthetic functions that make them a novel candidate in otorhinolaryngology for craniofacial defects and diseases and hold immense promise for bone tissue healing; even the tissue sources and types of MSCs, the method of cell introduction and their preparation quality can influence the final outcome in the injured tissue. In this review, we demonstrated the anti-inflammatory and immunomodulatory properties of MSCs, from different sources, to be safely used for cell-based therapies in otorhinolaryngology, while their achievements and challenges have been described too.

Culture of Mesenchymal Stem Cells in a Hydrogel Model of Vocal Fold Lamina Propria

Stem cell injection has been proposed as an alternative approach for the restoration of vocal fold (VF) function in patients with VF scarring. To assess the therapeutic efficacy of this treatment strategy, we evaluated the behaviors of human mesenchymal stem cells (hMSCs) in hydrogels derived from thiolated hyaluronic acid (HA-SH) and poly(ethylene glycol) diacrylate (PEG-DA) entrapping assembled collagen fibrils (abbreviated as HPC gels). Three hydrogel formulations with varying amounts of collagen (0, 1 and 2 mg/mL) but a fixed HA-SH (5 mg/mL) and PEG-DA (2 mg/mL) concentration, designated as HPC0, HPC1 and HPC2, were investigated. The HPC gels exhibit similar pore sizes (35-50 nm) and AFM indentation moduli (~175 Pa), although the elastic shear modulus for HPC1 (~32 Pa) is lower than HPC0 and HPC2 (~55 Pa). Although HPC1 and HPC2 gels both promoted the development of an elongated cell morphology, greater cell spreading was observed in HPC2 than in HPC1 by day 7. At the transcript level, cells cultured in HPC1 and HPC2 gels had an increased expression of fibronectin and integrin β1, but a decreased expression of tissue inhibitor of metalloproteinase-1, collagen types I/III and HA synthase-1 when compared to cells cultured in HPC0 gels. Cellular expression of connective tissue growth factor was also elevated in HPC1 and HPC2 cultures. Importantly, the HPC2 hydrogels promoted a signficant up-regulation of matrix metalloproteinase 1, transforming growth factor β1, and epithelial growth factor receptor, indicating an increased tissue turnover. Overall, hMSCs cultured in HPC2 gels adopt a phenotype reminiscent of cells involved in the wound healing process, providing a platform to study the effectiveness of therapeutic stem cell treatments for VF scarring.

HGF and bFGF Secreted by Adipose-Derived Mesenchymal Stem Cells Revert the Fibroblast Phenotype Caused by Vocal Fold Injury in a Rat Model

OBJECTIVE

To investigate how adipose-derived mesenchymal stem cells (ADSCs), secreted hepatocyte growth factor (HGF), and basic fibroblast growth factor (bFGF) affect the fibroblast phenotype after vocal fold injury.

METHODS

We cultured primary normal (uninjured) and injured vocal fold fibroblasts (VFFs). A transwell co-culture system of ADSCs and injured VFFs was constructed in vitro, then the effects of HGF or bFGF were inhibited. The proliferation, extracellular matrix (ECM) secretion and transformation of VFFs were observed.

RESULTS

Compared with uninjured VFFs, the secretion of collagen by injured VFFs increased significantly, hyaluronan synthase 1 (HAS1) secretion decreased, and VFF transformation increased significantly. After co-culture with ADSCs, the proliferation of VFFs was accelerated and the transformation was inhibited. Co-culture inhibited the expression of type I and III collagen and promoted the expression of HAS1. When HGF or bFGF secretion was inhibited, the proliferation of injured VFFs was inhibited. The inhibitory effect on collagen was reduced by both groups, but this was more obvious with the anti-HGF group. The anti-bFGF group had a more prominent effect on HAS1 secretion after injury than the anti-HGF group but the difference was not statistically significant. The inhibition of the transformation of injured VFFs was reduced while α-smooth muscle actin was upregulated, which was more obvious with the anti-HGF group.

CONCLUSIONS

ADSCs and secreted HGF and bFGF can revert the fibroblast phenotype caused by vocal fold injury. The effects of HGF are more significant than bFGF on collagen secretion and the transformation of VFFs into myofibroblasts. However, bFGF is more effective than HGF in upregulating HAS1.

Characterizing Vocal Fold Injury Recovery in a Rabbit Model With Three-Dimensional Virtual Histology

OBJECTIVES/HYPOTHESIS

In animal studies of vocal fold scarring and treatment, imaging-based evaluation is most often conducted by tissue slicing and histological staining. Given variation in anatomy, injury type, severity, and sacrifice timepoints, planar histological sections provide limited spatiotemporal details of tissue repair. Three-dimensional (3D) virtual histology may provide additional contextual spatial information, enhancing objective interpretation. The study's aim was to evaluate the suitability of magnetic resonance imaging (MRI), microscale computed tomography (CT), and nonlinear laser-scanning microscopy (NM) as virtual histology approaches for rabbit studies of vocal fold scarring.

METHODS

A unilateral injury was created using microcup forceps in the left vocal fold of three New Zealand White rabbits. Animals were sacrificed at 3, 10, and 39 days postinjury. ex vivo imaging of excised larynges was performed with MRI, CT, and NM modalities.

RESULTS

The MRI modality allowed visualization of injury location and morphological internal features with 100-μm spatial resolution. The CT modality provided a view of the injury defect surface with 12-μm spatial resolution. The NM modality with optical clearing resolved second-harmonic generation signal of collagen fibers and two-photon autofluorescence in vocal fold lamina propria, muscle, and surrounding cartilage structures at submicrometer spatial scales.

CONCLUSIONS

Features of vocal fold injury and wound healing were observed with MRI, CT, and NM. The MRI and CT modalities provided contextual spatial information and dissection guidance, whereas NM resolved extracellular matrix structure. The results serve as a proof of concept to motivate incorporation of 3D virtual histology techniques in future vocal fold injury animal studies.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:1578-1587, 2021.

Treatment of vocal fold scarring with autologous bone marrow-derived human mesenchymal stromal cells-first phase I/II human clinical study: commentary to response

We would like to thank for the interest for the article and comments in the response. We believe that cell therapy may offer a treatment for severe voice problems in patients with vocal fold scarring and MSC treatment is a valuable alternative.

Regulation of Stem Cell Function in an Engineered Vocal Fold-Mimetic Environment

Human mesenchymal stem cells (hMSCs) have been proposed as therapeutic cells for the treatment of vocal fold (VF) scarring. Although functional recovery was observed in animal models after stem cell injection, it is not clear how injected stem cells interact locally with the extracellular matrix (ECM) of the lamina propria (LP) and how such interactions affect stem cell behaviors to improve function. Herein, we developed an in vitro cell culture platform where hMSCs were encapsulated in a LP-mimetic matrix, derived from hyaluronic acid (HA), poly(ethylene glycol) (PEG) and collagen, and cultured dynamically in a custom-designed VF bioreactor. The cell culture system was characterized by oscillatory shear rheology, laser doppler vibrometry (LDV), and digital image correlation (DIC). A constitutive finite element analysis (FEA) model was further developed to predict vibratory responses of the hydrogel. LDV analysis demonstrated an average displacement of 47 μm in the center of the hydrogel construct at 200 Hz applied frequency without any harmonics. The predicted strains throughout the hydrogel ranged from 0 to 0.03, in good agreement with reported values for the VF. The 3D cellular construct was subjected to vibrational stimulations at 200 Hz for an optimized duration of 1 h, as confirmed by a maximal c-Fos upregulation at the transcript level. Vibrational culture over a 3-day period with a 1h-on/1h-off pattern did not compromise the overall cell viability, but resulted in a significant downregulation of fibrogenic markers and diminished staining for alpha smooth muscle actin (αSMA). Collectively, high frequency mechanical loading resulted in the loss of myofibrogenic potential and a shift away from a fibrotic phenotype.

Advances in regenerative medicine for otolaryngology/head and neck surgery

Head and neck structures govern the vital functions of breathing and swallowing. Additionally, these structures facilitate our sense of self through vocal communication, hearing, facial animation, and physical appearance. Loss of these functions can lead to loss of life or greatly affect quality of life. Regenerative medicine is a rapidly developing field that aims to repair or replace damaged cells, tissues, and organs. Although the field is largely in its nascence, regenerative medicine holds promise for improving on conventional treatments for head and neck disorders or providing therapies where no current standard exists. This review presents milestones in the research of regenerative medicine in head and neck surgery.

Treatment of vocal fold scarring with autologous bone marrow-derived human mesenchymal stromal cells-first phase I/II human clinical study

Background

Vocal fold (VF) scarring, caused by surgery or inflammation, often results in severe voice problems or aphonia. Effective lasting treatment is lacking. Previous in vitro and in vivo animal studies reported positive effects on VF scar resolution with mesenchymal stromal cell (MSC) implantation. The principal aim of this study was to examine safety aspects and secondly treatment efficacy vocal fold function in patients with VF scarring and severe voice problems.

Methods

In this open-label phase I/II study, 16 patients were treated with surgical scar resection followed by injection of autologous MSCs (0.5–2 × 10⁶ MSCs/patient). Patients were monitored 1 year for serious adverse events (SAE) or minor complications. Therapeutic efficacy on treated VFs was evaluated by measurement of VF vibrations using high-speed laryngoscopy (HSL) and phonation pressure threshold (PTP) for elasticity and VF function. Patients self-reported voice change using the Voice Handicap Index (VHI).

Results

No SAE or minor side effects were reported. Video ratings of VF vibrations and digitized analysis of HSL and PTP were significantly improved for 62–75% of the patients (depending on parameter). Two patients showed deteriorated VF vibrations, but improved PTP. VHI was significantly improved in 8 patients, with the remaining experiencing no significant change.

Conclusions

The results indicate that local injection of autologous MSC into scarred VFs with severe voice problems may offer a safe and feasible therapeutic option. VF vibration and elasticity were improved in approximately two thirds of treated patients.

This clinical study is registered in clinicaltrials.gov (ID: NCT01981330). Retrospective registration of first patient (20130511). https//: register.clinicaltrials.gov/.

Hyaluronan Hydrogels for the Local Delivery of Mesenchymal Stromal Cells to the Injured Vocal Fold

Mesenchymal stromal cells (MSCs) promote wound healing by expediting the inflammatory phase. Local injection of MSCs into injured vocal folds (VFs) is effective in animal models, suggesting suitability for clinical translation. Despite their therapeutic potential, MSCs do not persist within the VF. This study evaluates whether hyaluronan (HA) hydrogels offer a safe delivery vehicle for local injection of MSCs into VFs, and increase longevity of the cells within the injured tissue. MSCs ± HA hydrogel were exposed to interleukin (IL)1β, IL8, and chemokine (C-C motif) ligand 4, and evaluated for mRNA expression of matrix remodeling genes and secretion of immunomodulatory/prohealing factors. Chemotaxis/invasion in response to inflammation was evaluated. A lapin model of VF injury evaluated in vivo effects of MSCs ± HA hydrogel on enhancing VF healing. Histological evaluation of inflammation, type I collagen expression, HA hydrogel resorption, and MSC persistence was evaluated at 3 and 25 days after injury. MSCs within HA hydrogel were responsive to their extracellular environment, upregulating immunomodulatory factors when exposed to inflammation. Despite delayed migration out of the gel in vitro, the MSCs did not persist longer within the injured tissue in vivo. MSCs ± HA hydrogel exerted equivalent dampening of inflammation in vivo. The gel was resorbed within 25 days and no edema was evident. HA hydrogels can be safely used in the delivery of MSCs to injured VFs, minimizing leakage of administered cells. MSCs within the HA hydrogel did not persist longer than those in suspension, but did exert comparable therapeutic effects.

Mesenchymal stromal cells modulate tissue repair responses within the injured vocal fold

OBJECTIVES/HYPOTHESIS

This study aimed to determine whether local injection of human mesenchymal stromal cells (MSC) could modulate the early inflammatory response within injured vocal folds (VFs) to promote wound-healing processes.

STUDY DESIGN

Experimental xenograft model.

METHODS

VF injury was surgically induced by bilateral resection of the lamina propria of rabbits, and MSC were immediately injected into the injured area of both VFs. Animals were sacrificed on days 2, 4, and 24. Histological analyses were performed by hematoxylin and eosin, Masson's Trichrome, and elastin staining. Cell death was visualized by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and the M2 macrophage marker, CD163, detected by immunohistochemistry. Persistence of injected MSC was evaluated by fluorescent in situ hybridization (FISH). Quantitative polymerase chain reaction was performed on the contralateral VF.

RESULTS

Histological examination at days 2 and 4 indicated that MSC were able to reduce tissue inflammation, with gene expression analysis confirming a significant reduction of proinflammatory markers, interleukin (IL)-1β, and IL-8. FISH demonstrated low-level persistence of injected MSC at both time points, and TUNEL confirmed localized cell death at the injury site. Increased levels of CD163+ anti-inflammatory macrophages indicated a change in the immune milieu, supporting wound resolution. Evidence of a more organized collagen matrix suggests that MSC may enhance the production of a functional repair tissue after injury, despite their low-level persistence within the tissue.

CONCLUSIONS

This study demonstrates that MSC are able to positively modulate the early wound-healing response through resolution of the inflammatory phase and promotion of tissue repair.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:E21-E29, 2020.

Collagen fibrillar structures in vocal fold scarring and repair using stem cell therapy: a detailed histological, immunohistochemical and atomic force microscopy study

Regenerative medicine opens new opportunities in the repair of cicatricial lesions of the vocal folds. Here, we present a thorough morphological study, with the focus on the collagen structures in the mucosa of the vocal folds, dedicated to the effects of stem cells on the vocal folds repair after cicatricial lesions. We used a conventional experimental model of a mature scar of the rabbit vocal folds, which was surgically excised with a simultaneous implantation of autologous bone marrow-derived mesenchymal stem cells (MSC) into the defect. The restoration of the vocal folds was studied 3 months postimplantation of stem cells and 6 months after the first surgery. The collagen structure assessment included histology, immunohistochemistry and atomic force microscopy (AFM) studies. According to the data of optical microscopy and AFM, as well as to immunohistochemical analysis, MSC implantation into the vocal fold defect leads not only to the general reduction of scarring, normal ratio of collagens type I and type III, but also to a more complete restoration of architecture and ultrastructure of collagen fibres in the mucosa, as compared to the control. The collagen structures in the scar tissue in the vocal folds with implanted MSC are more similar to those in the normal mucosa of the vocal folds than to those of the untreated scars. AFM has proven to be an instrumental technique in the assessment of the ultrastructure restoration in such studies. LAY DESCRIPTION: Regenerative medicine opens new opportunities in the repair of the vocal fold scars. Because collagen is a main component in the vocal fold mucosa responsible for the scar formation and repair, we focus on the collagen structures in the mucosa of the vocal folds, using a thorough morphological study based on histology and atomic force microscopy (AFM). Atomic force microscopy is a scanning microscopic technique which allows revealing the internal structure of a tissue with a resolution up to nanometres. We used a conventional experimental model of a mature scar of the rabbit vocal folds, surgically excised and treated with a mesenchymal stem cells transplant. Our morphological study, primarily AFM, explicitly shows that the collagen structures in the scarred vocal folds almost completely restore after the stem cell treatment. Thus, the modern microscopic methods, and especially AFM are instrumental tools for monitoring the repair of the vocal folds scars.

Mechanotransduction of vocal fold fibroblasts and mesenchymal stromal cells in the context of the vocal fold mechanome

The design of cell-based therapies for vocal fold tissue engineering requires an understanding of how cells adapt to the dynamic mechanical forces found in the larynx. Our objective was to compare mechanotransductive processes in therapeutic cell candidates (mesenchymal stromal cells from adipose tissue and bone marrow, AT-MSC and BM-MSC) to native cells (vocal fold fibroblasts-VFF) in the context of vibratory strain. A bioreactor was used to expose VFF, AT-MSC, and BM-MSC to axial tensile strain and vibration at human physiological levels. Microarray, an empirical Bayes statistical approach, and geneset enrichment analysis were used to identify significant mechanotransductive pathways associated with the three cell types and three mechanical conditions. Two databases (Gene Ontology, Kyoto Encyclopedia of Genes and Genomes) were used for enrichment analyses. VFF shared more mechanotransductive pathways with BM-MSC than with AT-MSC. Gene expression that appeared to distinguish the vibratory strain condition from polystyrene condition for these two cells types related to integrin activation, focal adhesions, and lamellipodia activity, suggesting that vibratory strain may be associated with cytoarchitectural rearrangement, cell reorientation, and extracellular matrix remodeling. In response to vibration and tensile stress, BM-MSC better mimicked VFF mechanotransduction than AT-MSC, providing support for the consideration of BM-MSC as a cell therapy for vocal fold tissue engineering. Future research is needed to better understand the sorts of physical adaptations that are afforded to vocal fold tissue as a result of focal adhesions, integrins, and lamellipodia, and how these adaptations could be exploited for tissue engineering.

Adipose-Derived Mesenchymal Stromal Cells Persist in Tissue-Engineered Vocal Fold Replacement in Rabbits

OBJECTIVES:

Cell therapies using mesenchymal stromal cells (MSCs) have been proposed as a promising new tool for the treatment of vocal fold scarring. However, the mechanisms by which MSCs promote healing as well as their duration of survival within the host vocal fold have yet to be defined. The aim of this work was to assess the persistence of embedded MSCs within a tissue-engineered vocal fold mucosal replacement in a rabbit model of vocal fold injury.

METHODS:

Male rabbit adipose-derived MSCs were embedded within a 3-dimensional fibrin gel, forming the cell-based outer vocal fold replacement. Four female rabbits underwent unilateral resection of vocal fold epithelium and lamina propria and reconstruction with cell-based outer vocal fold replacement implantation. Polymerase chain reaction and fluorescent in situ hybridization for the sex-determining region of the Y chromosome (SRY-II) in the sex-mismatched donor-recipient pairs sought persistent cells after 4 weeks.

RESULTS:

A subset of implanted male cells was detected in the implant site at 4 weeks. Many SRY-II-negative cells were also detected at the implant site, presumably representing native female cells that migrated to the area. No SRY-II signal was detected in contralateral control vocal folds.

CONCLUSIONS:

The emergent tissue after implantation of a tissue-engineered outer vocal fold replacement is derived both from initially embedded adipose-derived stromal cells and infiltrating native cells. Our results suggest this tissue-engineering approach can provide a well-integrated tissue graft with prolonged cell activity for repair of severe vocal fold scars.

Mesenchymal stromal cell injection promotes vocal fold scar repair without long-term engraftment

BACKGROUND

Regenerative medicine holds promise for restoring voice in patients with vocal fold scarring. As experimental treatments approach clinical translation, several considerations remain. Our objective was to evaluate efficacy and biocompatibility of four bone marrow mesenchymal stromal cell (BM-MSC) and tunable hyaluronic acid based hydrogel (HyStem-VF) treatments for vocal fold scar using clinically acceptable materials, a preclinical sample size and a dosing comparison.

METHODS

Vocal folds of 84 rabbits were injured and injected with four treatment variations (BM-MSC, HyStem-VF, and BM-MSC in HyStem-VF at two concentrations) 6 weeks later. Efficacy was assessed with rheometry, real-time polymerase chain reaction (RT-PCR) and histology at 2, 4 and 10 weeks following treatment. Lung, liver, kidney, spleen and vocal folds were screened for biocompatibility by a pathologist.

RESULTS AND DISCUSSION

Persistent inflammation was identified in all hydrogel-injected groups. The BM-MSC alone treatment appeared to be the most efficacious and safe, providing an early resolution of viscoelasticity, gene expression consistent with desirable extracellular matrix remodeling (less fibronectin, collagen 1α2, collagen 3, procollagen, transforming growth factor [TGF]β1, alpha smooth muscle actin, interleukin-1β, interleukin-17β and tumor necrosis factor [TNF] than injured controls) and minimal inflammation. Human beta actin expression in BM-MSC-treated vocal folds was minimal after 2 weeks, suggesting that paracrine signaling from the BM-MSCs may have facilitated tissue repair.

Cell therapy and vocal fold scarring

Vocal fold microstructure is complex and can be affected by laryngeal microsurgery, inducing scarring that prevents mechanical uncoupling of epithelium and muscle, leading to vibration disorder and disabling dysphonia. Treatment options presently are few, and often without efficacy for vibration, having only an impact on volume to reduce glottal closure defect. The present review of the literature had two aims: (i) to report the current state of the literature on cell therapy in vocal fold scarring; and (ii) to analyze the therapeutic interest of the adipose-derived stromal vascular fraction in the existing therapeutic armamentarium. A PubMed^® search conducted in September 2016 retrieved English or French-language original articles on the use of stem cells to treat vocal fold scarring. Twenty-seven articles published between 2003 and 2016 met the study selection criteria. Mesenchymal stem cells were most widely used, mainly derived from bone marrow or adipose tissue. Four studies were performed in vitro on fibroblasts, and 18 in vivo on animals. End-points comprised: (i) scar analysis (macro- and micro-scopic morphology, viscoelastic properties, extracellular matrix, fibroblasts); and (ii) assessment of stem cell survival and differentiation. The studies testified to the benefit of mesenchymal stem cells, and especially those of adipose derivation. The stromal vascular fraction exhibits properties that might improve results by facilitating production logistics.

Mesenchymal Stem Cell Therapy for the Treatment of Vocal Fold Scarring: A Systematic Review of Preclinical Studies

Objectives

Therapy with mesenchymal stem cells exhibits potential for the development of novel interventions for many diseases and injuries. The use of mesenchymal stem cells in regenerative therapy for vocal fold scarring exhibited promising results to reduce stiffness and enhance the biomechanical properties of injured vocal folds. This study evaluated the biomechanical effects of mesenchymal stem cell therapy for the treatment of vocal fold scarring.

Data Sources

PubMed, Embase, the Cochrane Library and Google Scholar were searched.

Methods

Controlled studies that assessed the biomechanical effects of mesenchymal stem cell therapy for the treatment of vocal fold scarring were included. Primary outcomes were viscoelastic properties and mucosal wave amplitude.

Results

Seven preclinical animal studies (n = 152 single vocal folds) were eligible for inclusion. Evaluation of viscoelastic parameters revealed a decreased dynamic viscosity (η’) and elastic modulus (G’), i.e., decreased resistance and stiffness, in scarred vocal folds treated with mesenchymal stem cells compared to non-treated scarred vocal folds. Mucosal wave amplitude was increased in scarred vocal folds treated with mesenchymal stem cells vs. non-treated scarred vocal folds.

Conclusion

The results from these studies suggest an increased regenerative effect of therapy with mesenchymal stem cells for scarred vocal folds and are encouraging for further clinical studies.

Stem cell approaches for vocal fold regeneration

OBJECTIVES/HYPOTHESIS

Current interventions in the management of vocal fold (VF) dysfunction focus on conservative and surgical approaches. However, the complex structure and precise biomechanical properties of the human VF mean that these strategies have their limitations in clinical practice and in some cases offer inadequate levels of success. Regenerative medicine is an exciting development in this field and has the potential to further enhance VF recovery beyond conventional treatments. Our aim in this review is to discuss advances in the field of regenerative medicine; that is, advances in the process of replacing, engineering, or regenerating the VF through utilization of stem cells, with the intention of restoring normal VF structure and function.

DATA SOURCES

English literature (1946-2015) review.

METHODS

We conducted a systematic review of MEDLINE for cases and studies of VF tissue engineering utilizing stem cells.

RESULTS

The three main approaches by which regenerative medicine is currently applied to VF regeneration include cell therapy, scaffold development, and utilization of growth factors.

CONCLUSION

Exciting advances have been made in stem cell biology in recent years, including use of induced pluripotent stem cells. We expect such advances to be translated into the field in the forthcoming years. Laryngoscope, 126:1865-1870, 2016.

Adipose-Derived Mesenchymal Stem Cells in the Regeneration of Vocal Folds: A Study on a Chronic Vocal Fold Scar

Background. The aim of the study was to assess the histological effects of autologous infusion of adipose-derived stem cells (ADSC) on a chronic vocal fold scar in a rabbit model as compared to an untreated scar as well as in injection of hyaluronic acid. Study Design. Animal experiment. Method. We used 74 New Zealand rabbits. Sixteen of them were used as control/normal group. We created a bilateral vocal fold wound in the remaining 58 rabbits. After 18 months we separated our population into three groups. The first group served as control/scarred group. The second one was injected with hyaluronic acid in the vocal folds, and the third received an autologous adipose-derived stem cell infusion in the scarred vocal folds (ADSC group). We measured the variation of thickness of the lamina propria of the vocal folds and analyzed histopathologic changes in each group after three months. Results. The thickness of the lamina propria was significantly reduced in the group that received the ADSC injection, as compared to the normal/scarred group. The collagen deposition, the hyaluronic acid, the elastin levels, and the organization of elastic fibers tend to return to normal after the injection of ADSC. Conclusions. Autologous injection of adipose-derived stem cells on a vocal fold chronic scar enhanced the healing of the vocal folds and the reduction of the scar tissue, even when compared to other treatments.

Stem Cell Therapy in Injured Vocal Folds: A Three-Month Xenograft Analysis of Human Embryonic Stem Cells

We have previously shown that human embryonic stem cell (hESC) therapy to injured rabbit vocal folds (VFs) induces human tissue generation with regained VF vibratory capacity. The aims of this study were to test the sustainability of such effect and to what extent derivatives of the transplanted hESCs are propagated in the VFs. The VFs of 14 New Zealand rabbits were injured by a localized resection. HESCs were transplanted to 22 VFs which were analyzed for persistence of hESCs after six weeks and after three months. At three months, the VFs were also analyzed for viscoelasticity, measured as dynamic viscosity and elastic modulus, for the lamina propria (Lp) thickness and relative content of collagen type I. Three months after hESC cell therapy, the dynamic viscosity and elastic modulus of the hESC treated VFs were similar to normal controls and lower than untreated VFs (p ≤ 0.011). A normalized VF architecture, reduction in collagen type I, and Lp thickness were found compared with untreated VFs (p ≤ 0.031). At three months, no derivatives of hESCs were detected. HESCs transplanted to injured rabbit VFs restored the vibratory characteristics of the VFs, with maintained restored function for three months without remaining hESCs or derivatives.

Biomechanical Screening of Cell Therapies for Vocal Fold Scar

Candidate cell sources for vocal fold scar treatment include mesenchymal stromal cells from bone marrow (BM-MSC) and adipose tissue (AT-MSC). Mechanosensitivity of MSC can alter highly relevant aspects of their behavior, yet virtually nothing is known about how MSC might respond to the dynamic mechanical environment of the larynx. Our objective was to evaluate MSC as a potential cell source for vocal fold tissue engineering in a mechanically relevant context. A vibratory strain bioreactor and cDNA microarray were used to evaluate the similarity of AT-MSC and BM-MSC to the native cell source, vocal fold fibroblasts (VFF). Posterior probabilities for each of the microarray transcripts fitting into specific expression patterns were calculated, and the data were analyzed for Gene Ontology (GO) enrichment. Significant wound healing and cell differentiation GO terms are reported. In addition, proliferation and apoptosis were evaluated with immunohistochemistry. Results revealed that VFF shared more GO terms related to epithelial development, extracellular matrix (ECM) remodeling, growth factor activity, and immune response with BM-MSC than with AT-MSC. Similarity in glycosaminoglycan and proteoglycan activity dominated the ECM analysis. Analysis of GO terms relating to MSC differentiation toward osteogenic, adipogenic, and chondrogenic lineages revealed that BM-MSC expressed fewer osteogenesis GO terms in the vibrated and scaffold-only conditions compared to polystyrene. We did not evaluate if vibrated BM-MSC recover osteogenic expression markers when returned to polystyrene culture. Immunostaining for Ki67 and cleaved caspase 3 did not vary with cell type or mechanical condition. We conclude that VFF may have a more similar wound healing capacity to BM-MSC than to AT-MSC in response to short-term vibratory strain. Furthermore, BM-MSC appear to lose osteogenic potential in the vibrated and scaffold-only conditions compared to polystyrene, potentially attenuating the risk of osteogenesis for in vivo applications.

Single injection of basic fibroblast growth factor to treat severe vocal fold lesions and vocal fold paralysis

Objectives/Hypothesis

Severe vocal fold lesions such as vocal fold sulcus, scars, and atrophy induce a communication disorder due to severe hoarseness, but a treatment has not been established. Basic fibroblast growth factor (bFGF) therapies by either four‐time repeated local injections or regenerative surgery for vocal fold scar and sulcus have previously been reported, and favorable outcomes have been observed. In this study, we modified bFGF therapy using a single of bFGF injection, which may potentially be used in office procedures.

Study Design

Retrospective chart review.

Methods

Five cases of vocal fold sulcus, six cases of scars, seven cases of paralysis, and 17 cases of atrophy were treated by a local injection of bFGF. The injection regimen involved injecting 50 µg of bFGF dissolved in 0.5 mL saline only once into the superficial lamina propria using a 23‐gauge injection needle. Two months to 3 months after the injection, phonological outcomes were evaluated.

Results

The maximum phonation time (MPT), mean airflow rate, pitch range, speech fundamental frequency, jitter, and voice handicap index improved significantly after the bFGF injection. Furthermore, improvement in the MPT was significantly greater in patients with (in increasing order) vocal fold atrophy, scar, and paralysis. The improvement in the MPT among all patients was significantly correlated with age; the MPT improved more greatly in younger patients.

Conclusions

Regenerative treatments by bFGF injection—even a single injection—effectively improve vocal function in vocal fold lesions.

Level of Evidence

4 Laryngoscope, 125:E338–E344, 2015

Airway tissue engineering: an update

INTRODUCTION

Prosthetic materials, autologous tissues, cryopreserved homografts and allogeneic tissues have thus far proven unsuccessful in providing long-term functional solutions to extensive upper airway disease and damage. Research is therefore focusing on the rapidly expanding fields of regenerative medicine and tissue engineering in order to provide stem cell-based constructs for airway reconstruction, substitution and/or regeneration.

AREAS COVERED

Advances in stem cell technology, biomaterials and growth factor interactions have been instrumental in guiding optimization of tissue-engineered airways, leading to several first-in-man studies investigating stem cell-based tissue-engineered tracheal transplants in patients. Here, we summarize current progress, outstanding research questions, as well as future directions within the field.

EXPERT OPINION

The complex immune interaction between the transplant and host in vivo is only beginning to be untangled. Recent progress in our understanding of stem cell biology, decellularization techniques, biomaterials and transplantation immunobiology offers the prospect of transplanting airways without the need for lifelong immunosuppression. In addition, progress in airway revascularization, reinnervation and ever-increasingly sophisticated bioreactor design is opening up new avenues for the construction of a tissue-engineered larynx. Finally, 3D printing is a novel technique with the potential to render microscopic control over how cells are incorporated and grown onto the tissue-engineered airway.

Fibroblast-like cells differentiated from adipose-derived mesenchymal stem cells for vocal fold wound healing

Tissue engineering has revealed the potential to regenerate injured vocal folds, and identification of the most suitable seed cells has remained a hot topic of research. The aim of this study was to implant fibroblast-like cells differentiated from adipose-derived mesenchymal stem cells (ADSCs) in a canine acute vocal fold wound model. We then sought to characterize changes in the extracellular matrix (ECM) proteins of vocal fold lamina propria. For this purpose, ADSCs were induced to differentiate into fibroblasts under the regulation of connective tissue growth factor in vitro. Cell surface proteins were identified by immunofluorescence staining. Thirty vocal folds of 17 canines were injured by localized resection and injected with fibroblast-like cells (differentiated ADSCs, dADSCs), ADSCs or vocal fold fibroblasts (VFFs). The morphology of vocal folds was observed, and the characteristics of ECM protein components (collagen, elastin, hyaluronic acid, decorin and fibronectin) were evaluated by immunofluorescence staining from 15 days to 6 months following implantation. The results showed that in vitro, the dADSCs showed morphology and cell surface protein expression similar to those of VFFs. After implantation in vivo, the surfaces of the recipient vocal folds became almost smooth in the dADSCs and ADSCs groups at 6 months but remained slightly concave and stiff in the VFFs group. The elastin fluorescence intensity increased significantly and was maintained at a high level in the dADSCs group. The collagen fluorescence intensity increased slightly in the dADSCs and ADSCs groups, whereas it demonstrated a more irregular arrangement in the VFFs group. The fluorescence intensity of hyaluronic acid, decorin and fibronectin was similar between the three implanted groups. These results indicated that dADSCs may confer an advantage for vocal fold wound healing. Furthermore, dADSCs have the ability to secrete ECM components in vivo, particularly elastin, which may be beneficial for vocal fold vibration recovery.

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.

Vocal fold scars: current concepts and future directions. Consensus report of the Phonosurgery Committee of the European Laryngological Society

Scarring of the vocal folds leads to a deterioration of the highly complex micro-structure with consecutively impaired vibratory pattern and glottic insufficiency. The resulting dysphonia is predominantly characterized by a reduced vocal capacity. Despite the considerable progress in understanding of the underlying pathophysiology, the treatment of scarred vocal folds is still an unresolved chapter in laryngology and phonosurgery. Essential for a successful treatment is an individual, multi-dimensional concept that comprises the whole armamentarium of surgical and non-surgical (i.p. voice therapy) modalities. An ideal approach would be to soften the scar, because the reduced pliability and consequently the increased vibratory rigidity impede the easiness of vibration. The chosen phonosurgical method is determined by the main clinical feature: Medialization techniques for the treatment of glottic gap, or epithelium freeing techniques for improvement of vibration characteristics often combined with injection augmentation or implantation. In severe cases, buccal mucosa grafting can be an option. New developments, include treatment with anxiolytic lasers, laser technology with ultrafine excision/ablation properties avoiding coagulation (Picosecond infrared laser, PIRL), or techniques of tissue engineering. However, despite the promising results by in vitro experiments, animal studies and first clinical trials, the step into clinical routine application has yet to be taken.

Regenerative phonosurgical treatments for vocal fold scar and sulcus with basic fibroblast growth factor

OBJECTIVES/HYPOTHESIS

Vocal fold scar and sulcus are still challenges. Basic fibroblast growth factor (bFGF) has proven to be effective to resolve scar tissue in animal models. This study reports the efficacy of regenerative treatments using bFGF on vocal fold scar and sulcus in human cases.

STUDY DESIGN

Retrospective chart review.

METHODS

Fifteen cases (7 scar; 8 sulcus) were treated by either local injection of bFGF (n = 6) or regenerative surgery using bFGF (n = 9). Injection regimen was to locally apply 10 micrograms of bFGF in 0.5 mL saline into each vocal fold under topical anesthesia repeatedly (4 times with intervals of 1 week between each injection). The regenerative surgical procedure consisted of the dissection of scar tissue and the implant of gelatin sponge with bFGF. Follow-up periods ranged from 6 months to 24 months.

RESULTS

Maximum Phonation Time (MPT); Voice Handicap Index (VHI)-10; and Grade, Roughness, Breathiness, Asthenia, Strain (GRBAS) scale were assessed in both groups. The injection group showed significant improvement on VHI-10 and GRBAS. The regenerative surgery group showed significant improvement in all parameters. Jitter and shimmer were evaluated in the surgery group, and the results indicated improvement in six and five cases of nine cases, respectively. No major adverse effects were observed in both treatment groups.

CONCLUSIONS

Regenerative treatments using bFGF has shown to be effective for improvement of vocal function in scar and sulcus.

[Vocal fold scars: pathogenesis, diagnosis, therapy]

Scarring of the vocal folds leads to a deterioration of the highly complex microstructure with consecutively impaired vibratory pattern and glottic insufficiency. The resulting dysphonia is predominantly characterized by a reduced vocal capacity. Despite considerable progress in the understanding of the underlying pathophysiology, treatment of scarred vocal folds is still an unresolved chapter in laryngology and phonosurgery. Decisive for successful treatment is an individual, multidimensional concept that comprises the whole armamentarium of surgical and nonsurgical (e.g. voice therapy) modalities. The chosen phonosurgical method is determined by the main clinical feature: medialization techniques for treatment of glottic insufficiency, or epithelium-freeing techniques for improvement of vibration characteristics often combined with injection augmentation or implantation. In severe cases, buccal mucosa grafting can be an option. New developments include treatment with angiolytic lasers [pulse dye laser, PDL; potassium titanyl phosphate (KTP) laser], or techniques of tissue engineering. However, despite promising results with in vitro experiments, animal studies and first clinical trials, application in clinical routine has not yet been achieved.

Effect of vocal fold injury location on vibratory parameters in excised canine larynges

OBJECTIVE

To investigate the effect of vocal fold injury location on vibratory amplitude and lateral phase difference.

STUDY DESIGN

Repeated measures with each excised canine larynx serving as own control.

SETTING

Basic science study conducted in university laboratory.

METHODS

Vocal fold vibration of excised canine larynges was recorded with a high-speed camera before and after inducing vocal fold injury at 1 of 5 locations: anterior, middle, posterior, medial, or superior. Medial and superior injuries were created within the middle third of the vocal fold. Five larynges were used for each of the 5 injury locations. Kymography was performed at the midpoint of the vocal folds for each video. Pre- and postinjury vibratory amplitude and lateral phase difference were compared for each location.

RESULTS

The anterior and medial injuries produced consistent decreases in vibratory amplitude. Middle and posterior injuries might slightly decrease amplitude. Superior injuries seemed to have no effect on amplitude. Anterior and medial injuries induced phase asymmetry between the right and left vocal folds. Middle injuries appeared to affect phase difference slightly, whereas posterior and superior injuries had no effect.

CONCLUSION

Injury to the anterior or medial portions of the vocal fold may be most likely to cause abnormal vocal fold vibration. Using caution in these locations during phonosurgery may favor superior postoperative vocal outcomes.

Regenerative medicine of the larynx. Where are we today? A review

Tissue engineering is a multidimensional process combining cells, scaffold matrices, and chemical signals to produce a structure similar to a target tissue. These techniques have opened a completely new field in diagnosis and therapy in numerous fields, including that of laryngology. Laryngeal tissue engineering has emerged in the last decade, although clinical applications are rare. The reasons therefore are numerous including ethical reasons, as well as the extremely complex anatomical structure of the vocal fold. The search for new treatment options has also enlarged our knowledge about the microphysiology and micropathophysiology of the vocal fold. To date, only specific growth factors are in clinical use for treatment of vocal fold atrophy. Big advances have been made in creating state-of-the-art scaffolds with various techniques including biomaterials as well as fully synthetic polymers. These scaffolds are supposed to provide an optimal environment for residual or implanted cells. Several in vitro settings showed practicability of these scaffolds, also in studying effects of growth factors. Cell therapy is a powerful tool in regenerative medicine but bears the uncertainty of possible malignant transformation. The aim of this review was to give a comprehensive overview about current knowledge in the field of laryngeal tissue engineering and regenerative medicine, including restoration of both vocal folds and laryngeal cartilage, and furthermore to elucidate further trends in this fascinating field.

Therapeutic potential of gel-based injectables for vocal fold regeneration

Vocal folds are anatomically and biomechanically unique, thus complicating the design and implementation of tissue engineering strategies for repair and regeneration. Integration of an enhanced understanding of tissue biomechanics, wound healing dynamics and innovative gel-based therapeutics has generated enthusiasm for the notion that an efficacious treatment for vocal fold scarring could be clinically attainable within several years. Fibroblast phenotype and gene expression are mediated by the three-dimensional mechanical and chemical microenvironment at an injury site. Thus, therapeutic approaches need to coordinate spatial and temporal aspects of the wound healing response in an injured vocal tissue to achieve an optimal clinical outcome. Successful gel-based injectables for vocal fold scarring will require a keen understanding of how the native inflammatory response sets into motion the later extracellular matrix remodeling, which in turn will determine the ultimate biomechanical properties of the tissue. We present an overview of the challenges associated with this translation as well as the proposed gel-based injectable solutions.

Injection of human mesenchymal stem cells improves healing of vocal folds after scar excision--a xenograft analysis

OBJECTIVES

Using a xenograft model the aim was to analyze if injection of human mesenchymal stem cells (hMSC) into the rabbit vocal fold (VF), after excision of an established scar, can improve the functional healing of the VF.

STUDY DESIGN

Prospective design with an experimental xenograft model.

METHODS

The VFs of 12 New Zealand rabbits were injured by a bilateral localized resection. After 9 weeks the scar after the resection was excised and hMSC were injected into the VFs. After another 10 weeks 10 VFs were dissected and stained for histology. Lamina propria thickness and relative content of collagen type I were measured. Viscoelasticity of 14 VFs at phonatory frequencies was quantified by a simple-shear rheometer. The hMSC survival was determined using a human DNA specific reference probe, that is, FISH analysis.

RESULTS

The viscoelastic measurements, that is, dynamic viscosity and elastic shear modulus for the hMSC-treated VFs, were found to be similar to those of normal controls and were significantly lower than those of untreated controls (P < .05). A significant reduction in lamina propria thickness was also shown for the hMSC treated VFs compared with the untreated VFs (P < .05). This histologic finding corresponded with the viscoelastic results. No hMSC survived 10 weeks after the injection.

CONCLUSIONS

Human mesenchymal stem cells injected into the rabbit VF following the excision of a chronic scar, were found to enhance the functional healing of the VF with reduced lamina propria thickness and restored viscoelastic shear properties.

Characterization of vocal fold scar formation, prophylaxis, and treatment using animal models

PURPOSE OF REVIEW

To review recent literature on animal models used to study the pathogenesis, detection, prevention, and treatment of vocal fold scarring. Animal work is critical to studying vocal fold scarring because it is the only way to conduct systematic research on the biomechanical properties of the layered structure of the vocal fold lamina propria, and therefore develop reliable prevention and treatment strategies for this complex clinical problem.

RECENT FINDINGS

During the period of review, critical anatomic, physiologic, and wound healing characteristics, which may serve as the bases for selection of a certain species to help answer a specific question, have been described in mouse, rat, rabbit, ferret, and canine models. A number of different strategies for prophylaxis and chronic scar treatment in animals show promise for clinical application. The pathways of scar formation and methods for quantifying treatment-induced change have become better defined.

SUMMARY

Recent animal vocal fold scarring studies have enriched and confirmed earlier work indicating that restoring pliability to the scarred vocal fold mucosa is challenging but achievable. Differences between animal models and differences in outcome measurements across studies necessitate considering each study individually to obtain guidance for future research. With increased standardization of measurement techniques it may be possible to make more inter-study comparisons.

Prospective multi-arm evaluation of surgical treatments for vocal fold scar and pathologic sulcus vocalis

OBJECTIVES/HYPOTHESIS

The purpose of this study was to compare the clinical effectiveness of type I thyroplasty, injection laryngoplasty, and graft implantation for the treatment of vocal fold scar and pathologic sulcus vocalis.

STUDY DESIGN

Prospective, multi-arm, quasi-experimental research design.

METHODS

Twenty-eight patients with newly diagnosed vocal fold scar and/or pathologic sulcus vocalis were assigned to one of three treatment modalities: type I thyroplasty (n = 9), injection laryngoplasty (n = 9), and graft implantation (n = 10). Psychosocial, auditory-perceptual, acoustic, aerodynamic, and videostroboscopic data were collected pretreatment and at 1, 6, 12, and 18 months posttreatment.

RESULTS

Type I thyroplasty and graft implantation both resulted in reduced voice handicap with no concomitant improvement in auditory-perceptual, acoustic, aerodynamic, or vocal fold physiologic performance. Injection laryngoplasty resulted in no improvement on any vocal function index. Patients who underwent graft implantation exhibited the slowest improvement trajectory across the 18-month follow-up period.

CONCLUSIONS

A persistent challenge in this area is that no single treatment modality is successful for the majority of patients, and there is no evidence-based decision algorithm for matching a given treatment to a given patient. Progress therefore requires the identification and categorization of predictive clinical features that can drive evidence-based treatment assignment.

Adipose-Derived Mesenchymal Stem Cells in Collagen—Hyaluronic Acid Gel Composite Scaffolds for Vocal Fold Regeneration

Objectives:

We sought to characterize the changes in the extracellular matrix (ECM) of the lamina propria following the implantation of autologous adipose-derived mesenchymal stem cells (ADSCs) in composite scaffolds in a rabbit vocal fold wound model.

Methods:

The ADSCs were co-cultured with collagen or hyaluronic acid gel. Each vocal fold was injured by localized resection and injected with ADSC complexes, ADSCs, or scaffolds or left untreated. From 15 days to 12 months, the vocal fold shape and the characteristics of the ECM components were analyzed.

Results:

With implantation of the ADSC complexes, the collagen content was significantly increased and had a disorderly distribution at 3 months. Subsequently, it began to decrease and reached close to normal by 12 months. The hyaluronic acid content was increased at 40 days, but it was reduced to normal levels and was limited to the superficial and middle layers of the lamina propria over the following 12 months. Fibronectin continued to be scattered in the lamina propria, at peak levels at 40 days, and then decreased over the following 12 months to reach near-normal levels. At 12 months, the vocal folds had a normal surface.

Conclusions:

ADSC complexes can play a facilitatory role in vocal fold regeneration, regulating the generation and orderly distribution of ECM.