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.

The use of basic fibroblast growth factor to improve vocal function: A systematic review and meta-analysis

OBJECTIVES

This systematic review and meta-analysis examines if intralaryngeal injection of basic fibroblast growth factor 2 (FGF2) can improve voice outcomes in those with vocal disability.

DESIGN

A Systematic review of original human studies reporting voice outcomes following intra-laryngeal injection of basic fibroblast growth factor 2 in those with vocal dysfunction. Databases searched were Medline (1946-July 2022), Embase (1947-July 2022), Cochrane database and Google Scholar.

SETTING

Secondary or tertiary care centres that undertook the management of voice pathology Hospital.

PARTICIPANTS

Inclusion criteria were original human studies reporting voice outcome measurements following intralaryngeal injection of FGF2 to treat vocal fold atrophy, vocal fold scarring, vocal fold sulcus or vocal fold palsy. Articles not written in English, studies that did not include human subjects and studies where voice outcome measures were not recorded before and after FGF2 injection were excluded from the review.

MAIN OUTCOME MEASURES

The primary outcome measure was maximum phonation time. Secondary outcome measures included acoustic analysis, glottic closure, mucosal wave formation, voice handicap index and GRBAS scale.

RESULTS

Fourteen articles were included out of a search of 1023 and one article was included from scanning reference lists. All studies had a single arm design without control groups. Conditions treated were vocal fold atrophy (n = 186), vocal cord paralysis (n = 74), vocal fold fibrosis (n = 74) and vocal fold sulcus (n = 56). A meta-analysis of six articles reporting on the use of FGF2 in patients with vocal fold atrophy showed a significant increase of mean maximum phonation time of 5.2 s (95% CI: 3.4-7.0) at 3-6 months following injection. A significant improvement in maximum phonation time, voice handicap index and glottic closure was found following injection in most studies assessed. No major adverse events were reported following injection.

CONCLUSIONS

To date, intralaryngeal injection of basic FGF2 appears to be safe and it may be able to improve voice outcomes in those with vocal dysfunction, especially vocal fold atrophy. Randomised controlled trials are needed to further evaluate efficacy and support the wider use of this therapy.

The wound healing effect of collagen/adipose-derived stem cells (ADSCs) hydrogel: In vivo study

BACKGROUND

The complex wound healing process involves activating and synchronizing intracellular, intercellular, and extracellular components. Adipose tissue is attracting attention to promote wound healing. Within subcutaneous adipose tissue, stromal vascular cells and their subsets release growth factors and cytokines critical for neovascularization and wound repair.

OBJECTIVES

This study evaluated human placental collagen/adipose-derived stem cells (ADSCs) hydrogel for wound healing in rats.

METHODS

In this study, ADSCs were harvested, cultured, and mixed with placental collagen. Twelve rats were used, and their backs were excised three times each. Group one received collagen/ADSCs, group two collagen, and group three non-filled (control) excisions. The healing processes were assessed by histological analysis, taking photographs, and calculating the percentage of wound contraction in mentioned times.

RESULTS

Histopathological analysis revealed that the content of fibroblasts, follicles of the hair, and angiogenesis in group one was significantly more than in other groups. Group one had a significant result compared with the collagen and control groups. In group one, significant wound healing and wound contraction were observed with 52% and 80% wound contraction at 7 and 14 days, respectively.

CONCLUSION

Collagen/ADSCs can be considered a suitable candidate hydrogel in wound healing with a high potential for enhancing wound repairing.

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.

Human amniotic epithelial cell transplantation improves scar remodeling in a rabbit model of acute vocal fold injury: a pilot study

Objective

To gain insight into the molecular mechanisms underlying the early stages of vocal fold extracellular matrix (ECM) remodeling after a mid-membranous injury resulting from the use of human amniotic epithelial cells (hAEC), as a novel regenerative medicine cell-based therapy.

Methods

Vocal folds of six female, New Zealand White rabbits were bilaterally injured. Three rabbits had immediate bilateral direct injection of 1 × 10⁶ hAEC in 100 µl of saline solution (hAEC) and three with 100 µl of saline solution (controls, CTR). Rabbits were euthanized 6 weeks after injury. Proteomic analyses (in-gel trypsin protein digestion, LC–MS/MS, protein identification using Proteome Discoverer and the Uniprot Oryctolagus cuniculus (Rabbit) proteome) and histological analyses were performed.

Results

hAEC treatment significantly increased the expression of ECM proteins, elastin microfibril interface-located protein 1 (EMILIN-1) and myocilin that are primarily involved in elastogenesis of blood vessels and granulation tissue. A reactome pathway analysis showed increased activity of the anchoring fibril formation by collagen I and laminin, providing mechanical stability and activation of cell signaling pathways regulating cell function. hAEC increased the abundance of keratin 1 indicating accelerated induction of the differentiation programming of the basal epithelial cells and, thereby, improved barrier function. Lastly, upregulation of Rab GDP dissociation inhibitor indicates that hAEC activate the vesicle endocytic and exocytic pathways, supporting the exosome-mediated activation of cell–matrix and cell-to-cell interactions.

Conclusions

This pilot study suggests that injection of hAEC into an injured rabbit vocal fold favorably alters ECM composition creating a microenvironment that accelerates differentiation of regenerated epithelium and promotes stabilization of new blood vessels indicative of accelerated and improved repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02701-w.

Bioprinting of Stem Cells in Multimaterial Scaffolds and Their Applications in Bone Tissue Engineering

Bioprinting stem cells into three-dimensional (3D) scaffolds has emerged as a new avenue for regenerative medicine, bone tissue engineering, and biosensor manufacturing in recent years. Mesenchymal stem cells, such as adipose-derived and bone-marrow-derived stem cells, are capable of multipotent differentiation in a 3D culture. The use of different printing methods results in varying effects on the bioprinted stem cells with the appearance of no general adverse effects. Specifically, extrusion, inkjet, and laser-assisted bioprinting are three methods that impact stem cell viability, proliferation, and differentiation potential. Each printing method confers advantages and disadvantages that directly influence cellular behavior. Additionally, the acquisition of 3D bioprinters has become more prominent with innovative technology and affordability. With accessible technology, custom 3D bioprinters with capabilities to print high-performance bioinks are used for biosensor fabrication. Such 3D printed biosensors are used to control conductivity and electrical transmission in physiological environments. Once printed, the scaffolds containing the aforementioned stem cells have a significant impact on cellular behavior and differentiation. Natural polymer hydrogels and natural composites can impact osteogenic differentiation with some inducing chondrogenesis. Further studies have shown enhanced osteogenesis using cell-laden scaffolds in vivo. Furthermore, selective use of biomaterials can directly influence cell fate and the quantity of osteogenesis. This review evaluates the impact of extrusion, inkjet, and laser-assisted bioprinting on adipose-derived and bone-marrow-derived stem cells along with the effect of incorporating these stem cells into natural and composite biomaterials.

Collagen- and hyaluronic acid-based hydrogels and their biomedical applications

Hydrogels have been widely investigated in biomedical fields due to their similar physical and biochemical properties to the extracellular matrix (ECM). Collagen and hyaluronic acid (HA) are the main components of the ECM in many tissues. As a result, hydrogels prepared from collagen and HA hold inherent advantages in mimicking the structure and function of the native ECM. Numerous studies have focused on the development of collagen and HA hydrogels and their biomedical applications. In this extensive review, we provide a summary and analysis of the sources, features, and modifications of collagen and HA. Specifically, we highlight the fabrication, properties, and potential biomedical applications as well as promising commercialization of hydrogels based on these two natural polymers.

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.

Feasibility of First Injection of Autologous Adipose Tissue-Derived Stromal Vascular Fraction in Human Scarred Vocal Folds: A Nonrandomized Controlled Trial

Importance

Patients with scarred vocal folds, whether congenitally or after phonosurgery, often exhibit dysphonia that negatively affects daily life and is difficult to treat. The autologous adipose tissue-derived stromal vascular fraction (ADSVF) is a readily accessible source of cells with angiogenic, anti-inflammatory, immunomodulatory, and regenerative properties.

Objective

To evaluate the feasibility and tolerability of local injections of autologous ADSVF in patients with scarred vocal folds.

Design, Setting, and Participants

CELLCORDES (Innovative Treatment for Scarred Vocal Cords by Local Injection of Autologous Stromal Vascular Fraction) is a prospective, open-label, single-arm, single-center, nonrandomized controlled trial with a 12-month follow-up and patient enrollment from April 1, 2016, to June 30, 2017. Eight patients with severe dysphonia attributable to vocal fold scarring associated with a congenital malformation or resulting from microsurgical sequelae (voice handicap index score >60 of 120) completed the study. Data analysis was performed from September 1, 2018, to January 1, 2019.

Interventions

Injection of ADSVF into 1 or 2 vocal folds.

Main Outcomes and Measures

The primary outcomes were feasibility and the number and severity of adverse events associated with ADSVF-based therapy. The secondary outcomes were changes in vocal assessment, videolaryngostroboscopy, self-evaluation of dysphonia, and quality of life at 1, 6, and 12 months after cell therapy.

Results

Seven women and 1 man (mean [SD] age, 44.6 [10.4] years) were enrolled in this study. Adverse events associated with liposuction and ADSVF injection occurred; most of them resolved spontaneously. One patient received minor treatment to drain local bruising, and another experienced a minor contour defect at the liposuction site. At 12 months, the voice handicap index score was improved in all patients, with a mean (SD) improvement from baseline of 40.1 (21.5) points. Seven patients (88%) were considered to be responders, defined as improvement by 18 points or more in the voice handicap index score (the minimum clinically important difference).

Conclusions and Relevance

The findings suggest that autologous ADSVF injection in scarred vocal folds is feasible and tolerable. The findings require confirmation in a randomized clinical trial with a larger population.

Trial Registration

ClinicalTrials.gov Identifier: NCT02622464.

Polymeric Microspheres Containing Human Vocal Fold Fibroblasts for Vocal Fold Regeneration

OBJECTIVE

Most acellular injectable biomaterials for vocal fold (VF) wound treatment have limited regenerative potential due to their fast enzymatic degradation and limited recruitment of native cells postinjection. The injection of cells as therapeutic treatment often results in apoptosis due to stresses within the needle and the immune response of the host. Degradable microspheres may improve treatment effectiveness by increasing cell residence time, shielding cells during injection, and offering early protection against the immune system response. The objective of the present study was to investigate the potential of human VF fibroblasts encapsulated in polymeric microspheres as an injectable therapeutic treatment in vitro.

METHODS

Alginate, alginate-poly-L-lysine, and alginate-chitosan microspheres were fabricated using electrospraying and characterized in terms of biocompatibility, swelling, and mechanical properties as well as cytokine production.

RESULTS

Alginate microspheres were found to have the most desirable properties for VF regeneration. They were resistant to mechanical challenges. They were found to have a stiffness similar to that reported for native VF-lamina propria. They were found to be biocompatible and increased the proliferation of fibroblasts. Human VF fibroblasts encapsulated in alginate microspheres induced the production of interleukin (IL)-8 and IL-4 at 24 hours.

CONCLUSION

The alginate microspheres fabricated in this study were found to offer potential advantages, as cell delivery tool. This study highlights the importance of combining biomaterials and cells to expedite the wound-healing process through cytokine production. Future work is aimed to further analysis of the wound-healing properties the microspheres.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:1828-1834, 2021.

Hyaluronic acid containing scaffolds ameliorate stem cell function for tissue repair and regeneration

Recent evidence based studies have proposed hyaluronic acid (HA) as an emerging biopolymer for various tissue engineering application. Meanwhile, stem cells (SCs) have also gained immense popularity for their tissue regenerative capacity. Thus, combining HA and stem cells for tissue engineering application have shown to foster tissue repair and regeneration process. HA possesses the ability to interact with SCs via cellular surface receptors along with the capacity to elicit the process of differentiation. The influence of HA on stem cells has been widely investigated in cartilage and bone repair but their properties of reducing inflammation has also been explored in various other tissue repair processes. In this review, we have provided an insight to the effect of crosslinked and non-crosslinked HA on various stem cells. Further, HA based scaffolds combined with stem cells have shown to have a synergistic effect in the regeneration capacity. Also, various chemically modified HA and biomolecules conjugated HA as a suitable carrier or matrix for stem cells delivery and the effect of HA in fine tuning the stem cells function is discussed.

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.

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.

Injection Laryngoplasty Using Autologous Fat Enriched with Adipose-Derived Regenerative Stem Cells: A Safe Therapeutic Option for the Functional Reconstruction of the Glottal Gap after Unilateral Vocal Fold Paralysis

Background

Paralysis of one vocal fold leads to glottal gap and vocal fold insufficiency that has significant impact upon a patient's quality of life. Fillers have been tested to perform intracordal injections, but they do not provide perdurable results. Early data suggest that enriching fat grafts with adipose-derived regenerative cells (ADRCs) promote angiogenesis and modulate the immune response, improving graft survival. The aim of this study is to propose ADRC-enriched adipose tissue grafts as effective filler for the paralyzed vocal fold to use it for functional reconstruction of the glottal gap.

Method

This is the first phase I-IIA clinical trial (phase I/IIA clinical trial, unicentric, randomized, controlled, and two parallel groups), to evaluate the safety of a new therapy with ADRC-enriched fat grafting (ADRC: group I) for laryngoplasty after unilateral vocal fold paralysis. Control group patients received centrifuged autologous fat (CAF: group II) grafts. Overall mean age is 52.49 ± 16.60 years. Group I (ADRC): 7 patients (3 males and 4 females), 52.28 ± 20.95 year. Group II (CAF): 7 patients (3 males and 4 females), 52.71 ± 12.59 year.

Results

VHI-10 test showed that preoperative mean score was 24.21 ± 8.28. Postoperative mean score was 6.71 ± 6.75. Preoperative result in group I was 21.14 ± 3.58 and postoperative result was 3.14 ± 3.53. Preoperative result for group II was 27.29 ± 10.66. Postoperative score in group II was 10.29 ± 7.52. Wilcoxon and the Student t-tests showed that the patient's self-perception of posttreatment improvement is larger when ADRCs are used. Comparing pre- and posttreatment voice quality analysis, group I showed a p = 0.053. Group II showed a p = 0.007. There would be no significant differentiation between pre- and posttreatment results. This is true for group II and limited for group I.

Conclusions

This prospective trial demonstrates the safety and efficacy of the treatment of glottal gap defects utilizing ADRC-enriched fat grafts. This trial is registered with NCT02904824.

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.

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.

Macrophage Response to Allogeneic Adipose Tissue-Derived Stromal Cells in Hyaluronan-Based Hydrogel in a Porcine Vocal Fold Injury Model

OBJECTIVE

Adipose tissue-derived stromal cells (ASC) embedded in hyaluronan scaffold is a beneficial prophylactic treatment for vocal fold (VF) surgical scar. Here, we investigated the macrophage inflammatory response to allogeneic ASC-constructs and identified changes in lamina propria extracellular matrix.

METHOD

Pig ASC were characterized and transfected with GFP+ lentivirus. Thirty-three pigs underwent VF biopsies, and after 3 days, gel alone, gel+pASC, placebo, or pASC alone was injected into wound bed. Animals were sacrificed 3, 7, or 26 days post-injection. Flow cytometry; qPCR for NF-α, TGFβ, IL-10, IL-4, IFNγ, IL-12, FGF2, Col1A1, and HGF; and immunohistochemistry for collagen, elastin, HA, and fibronectin were performed to characterize macrophage phenotype, quantify cytokine transcription, analyze extracellular matrix remodeling, and track GFP+ cells.

RESULTS

No significant differences were found in SWC3+/SWC9+ phenotype or mRNA expression between cells+gel, gel, or placebo. The ASC alone exhibited significantly greater collagen, gel alone resulted in significantly less hyaluronan, and gel+pASC significantly more fibronectin (all P < .05). The pASC-GFP+ were detected 26 days post-injection.

CONCLUSIONS

The ASC-constructs were biocompatible; they did not influence the macrophage inflammatory response or provoke increases in collagen expression. Long-term engraftment was confirmed.

Cogels of Hyaluronic Acid and Acellular Matrix for Cultivation of Adipose-Derived Stem Cells: Potential Application for Vocal Fold Tissue Engineering

Stem cells based tissue engineering has been one of the potential promising therapies in the research on the repair of tissue diseases including the vocal fold. Decellularized extracellular matrix (DCM) as a promising scaffold has be used widely in tissue engineering; however, it remained to be an important issue in vocal fold regeneration. Here, we applied the hydrogels (hyaluronic acid [HA], HA-collagen [HA-Col], and HA-DCM) to determine the effects of hydrogel on the growth and differentiation of human adipose-derived stem cells (hADSCs) into superficial lamina propria fibroblasts. hADSCs were isolated and characterized by fluorescence-activated cell sorting. The results indicated that HA-DCM hydrogel enhanced cell proliferation and prolonged cell morphology significantly compared to HA and HA-Col hydrogel. Importantly, the differentiation of hADSCs into fibroblasts was also promoted by cogels of HA-Col and HA-DCM significantly. The differentiation of hADSCs towards superficial lamina propria fibroblasts was accelerated by the secretion of HGF, IL-8, and VEGF, the decorin and elastin expression, and the synthesis of chondroitin sulfate significantly. Therefore, the cogel of HA-DCM hydrogel was shown to be outstanding in apparent stimulation of hADSCs proliferation and differentiation to vocal fold fibroblasts through secretion of important growth factors and synthesis of extracellular matrix.

An in vitro scaffold-free epithelial-fibroblast coculture model for the larynx

OBJECTIVES/HYPOTHESIS

Physiologically relevant, well-characterized in vitro vocal fold coculture models are needed to test the effects of various challenges and therapeutics on vocal fold physiology. We characterize a healthy state coculture model, created by using bronchial/tracheal epithelial cells and immortalized vocal fold fibroblasts. We also demonstrate that this model can be induced into a fibroplastic state to overexpress stress fibers using TGFβ1.

STUDY DESIGN

In vitro.

METHODS

Cell metabolic activity of immortalized human vocal fold fibroblasts incubated in different medium combinations was confirmed with an MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide) assay. Fibroblasts were grown to confluence, and primary bronchial/tracheal epithelial cells suspended in coculture medium were seeded directly over the base layer of the fibroblasts. Cells were treated with transforming growth factor β1 (TGFβ1) to induce myofibroblast formation. Cell shape and position were confirmed by live cell tracking, fibrosis was confirmed by probing for α smooth muscle actin (αSMA), and phenotype was confirmed by immunostaining for vimentin and E-cadherin.

RESULTS

Fibroblasts retain metabolic activity in coculture epithelial medium. Live cell imaging revealed a layer of epithelial cells atop fibroblasts. αSMA expression was enhanced in TGFβ1-treated cells, confirming that both cell types maintained a healthy phenotype in coculture, and can be induced into overexpressing stress fibers. Vimentin and E-cadherin immunostaining show that cells retain phenotype in coculture.

CONCLUSIONS

These data lay effective groundwork for a functional coculture model that retains the reproducibility necessary to serve as a viable diagnostic and therapeutic screening platform.

LEVEL OF EVIDENCE

NA Laryngoscope, 127:E185-E192, 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.

Adipose stromal cells improve healing of vocal fold scar: Morphological and functional evidences

OBJECTIVES/HYPOTHESIS

Adipose derived stromal cells (ASCs) are abundant and easy to prepare. Such cells may be useful for treating severe vocal disturbance caused by acute vocal fold scars.

STUDY DESIGN

Prospective animal experiments with controls.

METHODS

Twenty New-Zealand white rabbits were used in the present study. We evaluated vocal fold healing, with or without injection of autologous ASCs, after acute scarring. A defined lesion was created and the ASCs were immediately injected. Vocal fold regeneration was evaluated histomorphometrically and via viscoelastic analysis using an electrodynamic shaker.

RESULTS

Six weeks after ASC injection, vocal folds exhibited significantly less inflammation than control folds (P < 0.005). In addition, hypertrophy of the lamina propria and fibrosis were significantly reduced upon ASC injection (P < 0.02). The decrease in viscoelastic parameters was less important in the ASC injected group compared to the noninjected group (P = 0.08).

CONCLUSION

Injection of autologous ASCs improved vocal fold healing in our preclinical model. Further studies are needed, but this method may be useful in humans.

LEVEL OF EVIDENCE

NA. Laryngoscope, 126:E278-E285, 2016.

Tissue-Engineered Vocal Fold Mucosa Implantation in Rabbits

OBJECTIVE

To assess phonatory function and wound healing of a tissue-engineered vocal fold mucosa (TE-VFM) in rabbits. An "artificial" vocal fold would be valuable for reconstructing refractory scars and resection defects, particularly one that uses readily available autologous cells and scaffold. This work implants a candidate TE-VFM after resecting native epithelium and lamina propria in rabbits.

STUDY DESIGN

Prospective animal study.

SETTING

Research laboratory.

SUBJECTS AND METHODS

Rabbit adipose-derived stem cells were isolated and cultured in three-dimensional fibrin scaffolds to form TE-VFM. Eight rabbits underwent laryngofissure, unilateral European Laryngologic Society type 2 cordectomy, and immediate reconstruction with TE-VFM. After 4 weeks, larynges were excised, phonated, and examined by histology.

RESULTS

Uniform TE-VFM implants were created, with rabbit mesenchymal cells populated throughout fibrin hydrogels. Rabbits recovered uneventfully after implantation. Phonation was achieved in all, with mucosal waves evident at the implant site. Histology after 4 weeks showed resorbed fibrin matrix, continuous epithelium, and mildly increased collagen relative to contralateral unoperated vocal folds. Elastic fiber appearance was highly variable. Inflammatory cell infiltrate was limited to animals receiving sex-mismatched implants.

CONCLUSION

TE-VFMs were successfully implanted into 8 rabbits, with minor evidence of scar formation and immune reaction. Vibration was preserved 4 weeks after resecting and reconstructing the complete vocal fold cover layer. Further studies will investigate the mechanism and durability of improvement. TE-VFM with autologous cells is a promising new approach for vocal fold reconstruction.

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.

Comparison of ASCs and BMSCs combined with atelocollagen for vocal fold scar regeneration

OBJECTIVES/HYPOTHESIS

Vocal fold scar remains a therapeutic challenge. Mesenchymal stromal cells (MSCs) are promising tools for regenerative medicine. Nevertheless, few in vivo studies have directly compared various sources of MSCs. The aim of this study was to investigate the therapeutic potential of adipose-derived stromal cells (ASCs) in comparison with bone marrow-derived stromal cells (BMSCs) for vocal fold regeneration.

STUDY DESIGN

Prospective animal experiments with controls.

METHODS

Two months after stripping of the lamina propria, 18 beagles were divided into four implantation groups: atelocollagen alone (collagen group), atelocollagen with BMSCs (BMSC-collagen), atelocollagen with ASCs (ASC-collagen), or a sham-treated group. One or 6 months after implantation, vibratory and histological examinations were performed.

RESULTS

Mucosal vibration was significantly improved in both of the MSC-implanted groups compared with the sham-treated group, whereas only the ASC-collagen group showed a significantly smaller glottal gap than the collagen group. Moreover, in the ASC-collagen group, a significant reduction of collagen density was observed compared to the sham-treated group, and there was a trend for better restoration of hyaluronic acid (HA). Implanted MSCs were detected 1 month postimplantation; however, none survived 6 months postimplantation.

CONCLUSIONS

Although implantation of an atelocollagen sponge and ASCs into vocal fold scars induced vibratory recovery comparable to that of BMSCs, ASCs might have more potential in terms of restoration of HA and suppression of excessive collagen deposition.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:1143-1150, 2016.

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

Three-dimensional differentiation of adipose-derived mesenchymal stem cells into insulin-producing cells

The aim of this study is to evaluate the collagen/hyaluronic acid (Col/HA) scaffold effect on the differentiation of insulin-producing cells (IPCs) from adipose-derived mesenchymal stem cells (ASCs). In this experimental study, ASCs were cultured and seeded in a Col/HA scaffold (3D culture) and then treated with induction media. After induction, the presence of IPCs was evaluated using gene expression (PDX-1, GLUT-2 and insulin) analysis and immunocytochemistry, while functional maturity was determined by measuring insulin release in response to low- and high-glucose media. The induced IPCs were morphologically similar to pancreatic islet-like cells. Expression of the islet-associated genes PDX-1, GLUT-2 and insulin genes in 3D-cultured cells was markedly higher than the 2D-cultured cells exposure differentiation media. Compared to the 2D culture of ASCs-derived IPCs, the insulin release from 3D ASCs-derived IPCs showed a nearly 4-fold (p < 0.05) increase when exposed to a high glucose (25 mmol) medium. The percentage of insulin-positive cells in the 3D experimental group showed an approximately 4-fold increase compared to the 2D experimental culture cells. The results of this study demonstrated that the COL/HA scaffold can enhance the differentiation of IPCs from rat ASCs.

Adipose-derived stem cells versus bone marrow-derived stem cells for vocal fold regeneration

OBJECTIVES/HYPOTHESIS

Vocal fold scarring presents therapeutic challenges. Recently, cell therapy with mesenchymal stromal cells has become a promising approach. The aim of this study was to compare the therapeutic potential of adipose-derived stem cells (ASC) with bone marrow-derived stem cells (BMSC) for vocal fold regeneration.

STUDY DESIGN

Prospective animal experiments with controls.

METHODS

The vocal folds of Sprague-Dawley rats were unilaterally injured. Two months after injury, rats were treated with a local injection of ASC (ASC group), BMSC (BMSC group), or saline (sham-treated group). The GFP-labeled ASC and BMSC were extracted from CAG-EGFP rats. Larynges were harvested for histological and immunohistochemical examinations 1 and 3 months posttransplantation and for quantitative real-time polymerase chain reaction (PCR) 1 month posttransplantation.

RESULTS

After 1 month, no surviving cells from the transplant were detected. Histological examination showed significantly increased hyaluronic acid (HA) and decreased dense collagen deposition in both ASC and BMSC groups compared to shams 1 and 3 months after treatment. Real-time PCR revealed that hyaluronan synthase 1 (Has1) and Has2 were upregulated in only the ASC group compared with the sham-treated group. Fibroblast growth factor 2 (basic) (Fgf2), hepatocyte growth factor (Hgf) and Has3 were upregulated in both cell transplantation groups. ASC seemed to upregulate Hgf more than did BMSC.

CONCLUSIONS

The regenerative effects of ASC and BMSC transplantation were found to be similar for the restoration. It is suggested that ASC might have more potential because of better recovery of HA, a superior antifibrotic effect, and the upregulation of Hgf.

LEVEL OF EVIDENCE

N/A.

Strategies for directing the structure and function of three-dimensional collagen biomaterials across length scales

Collagen type I is a widely used natural biomaterial that has found utility in a variety of biological and medical applications. Its well-characterized structure and role as an extracellular matrix protein make it a highly relevant material for controlling cell function and mimicking tissue properties. Collagen type I is abundant in a number of tissues, and can be isolated as a purified protein. This review focuses on hydrogel biomaterials made by reconstituting collagen type I from a solubilized form, with an emphasis on in vitro studies in which collagen structure can be controlled. The hierarchical structure of collagen from the nanoscale to the macroscale is described, with an emphasis on how structure is related to function across scales. Methods of reconstituting collagen into hydrogel materials are presented, including molding of macroscopic constructs, creation of microscale modules and electrospinning of nanoscale fibers. The modification of collagen biomaterials to achieve the desired structures and functions is also addressed, with particular emphasis on mechanical control of collagen structure, creation of collagen composite materials and crosslinking of collagenous matrices. Biomaterials scientists have made remarkable progress in rationally designing collagen-based biomaterials and in applying them both to the study of biology and for therapeutic benefit. This broad review illustrates recent examples of techniques used to control collagen structure and thereby to direct its biological and mechanical functions.

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.

A reporter assay for the next generation of biomaterials: porous-wall hollow glass microspheres

OBJECTIVES/HYPOTHESIS

The primary objective was to design a reporter assay to measure molecular release kinetics from a new porous-wall hollow glass microsphere biomaterial with great potential in regenerative medicine and drug delivery. Second, future avenues for research will be discussed specifically in regard to potential clinical uses in laryngology.

STUDY DESIGN

Basic science data report.

METHODS

We developed an assay using fluorescent nanocrystals or quantum dots (Qdot 605) as a reporter. A Nuance FX multispectral imaging system was used to detect fluorescence in aqueous phase. Spectral output of known concentrations of aqueous Qdot 605 was measured by the Nuance system to create a standard curve.

RESULTS

These data were plotted and fit to a curve. Qdot 605 emission demonstrates excellent correlation with concentration in a log-log relationship [R(2) = 0.99649, median error = 9.9%], indicating that the Qdot 605 assay is reliable and should be explored regarding its ability to evaluate the drug-eluting properties of this material.

CONCLUSIONS

We have derived a method to measure Qdot concentration using fluorescent microscopy, which will facilitate future research on this exciting new biomaterial. This material has great potential for use in head and neck surgery. Specific avenues within laryngology to be investigated include laryngeal and tracheal reconstruction, vocal fold healing, and nerve regeneration. Furthermore, we believe this is the first documented use of the Nuance system to determine aqueous molecular concentrations.

LEVEL OF EVIDENCE

NA.

Hyaluronic acid hydrogels for vocal fold wound healing

The unique vibrational properties inherent to the human vocal fold have a significant detrimental impact on wound healing and scar formation. Hydrogels have taken prominence as a tissue engineered strategy to restore normal vocal structure and function as cellularity is low. The frequent vibrational and shear forces applied to, and present in this connective tissue make mechanical properties of such hydrogels a priority in this active area of research. Hyaluronic acid has been chemically modified in a variety of ways to address cell function while maintaining desirable tissue mechanical properties. These various modifications have had mixed results when injected in vivo typically resulting in better biomechanical function but not necessarily with a concomitant decrease in tissue fibrosis. Recent work has focused on seeding mesenchymal progenitor cells within 3D architecture of crosslinked hydrogels. The data from these studies demonstrate that this approach has a positive effect on cells in both early and late wound healing, but little work has been done regarding the biomechanical effects of these treatments. This paper provides an overview of the various hyaluronic acid derivatives, their crosslinking agents, and their effect when implanted into the vocal folds of various animal models.