Novel isolation and biochemical characterization of immortalized fibroblasts for tissue engineering vocal fold lamina propria

Tissue engineering for treatment of vocal fold scar

PURPOSE OF REVIEW

Creating a neovocal fold or lamina propria by tissue engineering is a potential scheme for treating severe vocal fold scar. Although still investigational, multiple approaches have recently been described in tissue culture or animal models.

RECENT FINDINGS

Proposed cell types for vocal fold application have been native vocal fold fibroblasts, autologous fibroblasts from nonlaryngeal tissues, and adult-derived stem cells. Scaffolds of interest include decellularized matrix, biological polymers, and synthetic or chemically modified biopolymers. Chemical, mechanical, and spatial signals have been applied, such as hepatocyte growth factor, cyclic stretch, and air interface. Cells, matrix, and signals are combined in an effort to replicate normal vocal fold tissue as closely as possible. Each of these components of vocal fold tissue engineering is discussed here.

SUMMARY

Multiple tissue engineering approaches hold promise for reproducing functional vocal fold tissue. Scar prevention techniques have been the most successful. Modifying existing scar is more difficult and may necessitate complete scar excision and replacement with a three-dimensional neotissue. Functional assessment in vivo is essential to the ongoing evaluation of techniques.

The effect of mesenchymal stromal cell-hyaluronic acid hydrogel constructs on immunophenotype of macrophages

During the past several years, multipotent mesenchymal stromal cells (MSCs) have rapidly moved from in vitro and animal studies into clinical trials as a therapeutic modality potentially applicable to a wide range of disorders. It has been proposed that ex vivo culture-expanded MSCs exert their tissue regeneration potential through their immunomodulatory and anti-inflammatory properties, and paracrine effects more than their ability to differentiate into multiple tissue lineages. Since extracellular matrix (ECM) deposition and tissue support is also one of many physiological roles of MSCs, there is increasing interest in their potential use for tissue engineering, particularly in combination with ECM-based scaffolds such as hyaluronic acid (HA). We investigated the effect of MSCs on immunophenotype of macrophages in the presence of an HA-hydrogel scaffold using a unique 3D coculture system. MSCs were encapsulated in the hydrogel and peripheral blood CD14+ monocyte-derived macrophages plated in direct contact with the MSC-gel construct. To determine the immunophenotype of macrophages, we looked at the expression of cell surface markers CD14, CD16, CD206, and human leukocyte antigen (HLA)-DR by flow cytometry. MSCs and macrophages cultured on the HA-hydrogel remained viable and were able to be recovered from the construct. There was a significant difference in the immunophenotype observed between monocyte-derived macrophages cultured on the HA scaffold compared to tissue culture polystyrene. Macrophages cultured on gels with MSCs expressed lower CD16 and HLA-DR with higher expression of CD206, indicating the least inflammatory profile overall, compatible with the immunophenotype of alternatively activated macrophages. Development of macrophages, with this immunophenotype, upon interaction with the MSC-hydrogel constructs may play a potentially significant role in tissue repair when using a cellular-biomaterial therapeutic approach.

Controlling the adhesion and differentiation of mesenchymal stem cells using hyaluronic acid-based, doubly crosslinked networks

We have created hyaluronic acid (HA)-based, cell-adhesive hydrogels that direct the initial attachment and the subsequent differentiation of human mesenchymal stem cells (MSCs) into pre-osteoblasts without osteogenic supplements. HA-based hydrogel particles (HGPs) with an average diameter of 5-6 μm containing an estimated 2.2 wt% gelatin (gHGPs) were synthesized by covalent immobilization of gelatin to HA HGPs prepared via an inverse emulsion polymerization technique. Separately, a photocrosslinkable HA macromer (HAGMA) was synthesized by chemical modification of HA with glycidyl methacrylate (GMA). Doubly crosslinked networks (DXNs) were engineered by embedding gHGPs in a secondary network established by HAGMA at a particle concentration of 2.5 wt%. The resultant composite gels, designated as HA-gHGP, have an average compressive modulus of 21 kPa, and are non-toxic to the cultured MSCs. MSCs readily attached to these gels, exhibiting an early stage of stress fiber assembly 3 h post seeding. By day 7, stellate-shaped cells with extended filopodia were found on HA-gHGP gels. Moreover, cells had migrated deep into the matrix, forming a three dimensional, branched and interconnected cell community. Conversely, MSCs on the control gels lacking gelatin moieties formed isolated spheroids with rounded cell morphology. After 28 days of culture on HA-gHGP, Type I collagen production and mineral deposition were detected in the absence of osteogenic supplements, suggesting induction of osteogenic differentiation. In contrast, cells on the control gels expressed markers for adipogenesis. Overall, the HA-gHGP composite matrix has great promise for directing the osteogenic differentiation of MSCs by providing an adaptable environment through the spatial presentation of cell-adhesive modules.

Role of tumor necrosis factor-alpha in wound repair in human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Tumor necrosis factor-alpha (TNF-alpha) is an inflammatory cytokine and apoptotic molecule that appears to be a mediator in inflammation and fibrosis. The objective of this investigation was to examine the effects of TNF-alpha on 3D Carbylan-GSX in vitro cultured human vocal fold fibroblasts (hVFFs), to provide insight into the mechanism responsible for the improved vocal fold wound healing that has been previous reported with Carbylan-GSX treatment.

STUDY DESIGN

In vitro cell culture.

METHODS

hVFF were cultured in 3D Carbylan-GSX and on polystyrene with different dosages of TNF-alpha (0, 0.1, 1, 10, and 100 ng/mL) with and without 10% fetal bovine serum (FBS). hVFF response to TNF-alpha was characterized by morphology, proliferation rates, and gene transcript levels for matrix metalloproteinase 1 (MMP1), matrix metalloproteinase 2 (MMP2), tissue inhibitor of metalloproteinase 3 (TIMP3), collagen I, collagen III, fibronectin, and TNF-alpha receptor.

RESULTS

In 3D Carbylan-GSX, TNF-alpha inhibited hVFF proliferation in a dose-dependent manner. TNF-alpha (0.1-100 ng/mL) was shown to significantly downregulate TIMP3 and extracellular matrix-related mRNA transcript levels for collagen III and fibronectin and to upregulate MMP1 and MMP2 expression, resulting in increased MMP/TIMP3 ratios. TNF-alpha receptor expression was significantly upregulated in Carbylan-GSX compared to control polystyrene. Responses were more marked in 10% FBS culture.

CONCLUSIONS

After vocal fold injury, locally injected Carbylan-GSX can enhance the role of TNF-alpha in remodeling the lamina propria layer of the vocal fold, accelerating wound healing. Carbylan-GSX has potential as a new therapeutic approach that may lead to better treatment of vocal fold wound healing.

Biocompatibility of a synthetic extracellular matrix on immortalized vocal fold fibroblasts in 3-D culture

In order to promote wound repair and induce tissue regeneration, an engineered hyaluronan (HA) hydrogel - Carbylan GSX, which contains di(thiopropionyl) bishydrazide-modified hyaluronic acid, di(thiopropionyl) bishydrazide-modified gelatin and polyethylene glycol diacrylate - has been developed for extracellular matrix (ECM) defects of the superficial and middle layers of the lamina propria. The purpose of this study was to evaluate the biocompatibility of Carbylan GSX in a previously established immortalized human vocal fold fibroblast (hVFF) cell line prior to human clinical trials. Immortalized hVFF proliferation, viability, apoptosis and transcript analysis for both ECM constituents and inflammatory markers were measured for two-dimensional and three-dimensional (3-D) culture conditions. There were no significant differences in morphology, cell marker protein expression, proliferation, viability and apoptosis of hVFF cultured with Carbylan GSX compared to Matrigel, a commercial 3-D control, after 1 week. Gene expression levels for fibromodulin, transforming growth factor-beta1 and tumor necrosis factor-alpha were similar between Carbylan GSX and Matrigel. Fibronectin, hyaluronidase 1 and cyclooxygenase II expression levels were induced by Carbylan GSX, whereas interleukins 6 and 8, Col I and hyaluronic acid synthase 3 expression levels were decreased by Carbylan GSX. This investigation demonstrates that Carbylan GSX may serve as a natural biomaterial for tissue-engineering of human vocal folds.

Effects of matrix composition, microstructure, and viscoelasticity on the behaviors of vocal fold fibroblasts cultured in three-dimensional hydrogel networks

Vocal fold diseases and disorders are difficult to treat surgically or therapeutically. Tissue engineering offers an alternative strategy for the restoration of functional vocal folds. As a first step toward vocal fold tissue engineering, we investigated the responses of primary vocal fold fibroblasts (PVFFs) to two types of collagen and hyaluronic acid (HA)-based hydrogels that are compositionally similar, but structurally variable and mechanically different. Type A hydrogels were composed of mature collagen fibers reinforced by oxidized HA, whereas type B hydrogels contained immature collagen fibrils interpenetrated in an amorphous, covalently cross-linked HA matrix. PVFFs encapsulated in either matrix adopted a fibroblastic morphology and expressed genes related to important extracellular matrix proteins. DNA analysis indicated a linear growth profile for cells encapsulated in type B gels from day 0 to 21, in contrast to an initial dormant, nonproliferative period from day 0 to 3 experienced by cells in type A gels. At the end of the culture, similar DNA content was detected in both types of constructs. A reduction in collagen content was observed for both types of constructs after 28 days of culture, with type A constructs generally retaining higher amounts of collagen than type B constructs. The HA content in the constructs decreased steadily throughout the culture, with type A constructs consistently exhibiting less HA than type B constructs. Using the torsional wave analysis, we found that the elastic moduli for type A constructs decreased sharply during the first week of culture, followed by 2 weeks of matrix stabilization without significant changes in matrix stiffness. Conversely, the elastic modulus for type B constructs increased moderately over time. It is postulated that PVFFs residing in gels alter the matrix organization, chemical compositions, and viscoelasticity through cell-mediated remodeling processes.

Tissue regeneration of the vocal fold using bone marrow mesenchymal stem cells and synthetic extracellular matrix injections in rats

OBJECTIVES/HYPOTHESIS

To determine the effectiveness of bone marrow mesenchymal stem cell (BM-MSC) transplantation in isolation or within a synthetic extracellular matrix (sECM) for tissue regeneration of the scarred vocal fold lamina propria.

METHODS

In vitro stability and compatibility of mouse BM-MSC embedded in sECM was assessed by flow cytometry detection of BM-MSC marker expression and proliferation. Eighteen rats were subjected to vocal fold injury bilaterally, followed by 1 month post-treatment with unilateral injections of saline or sECM hydrogel (Extracel; Glycosan BioSystems, Inc., Salt Lake City, UT), green fluorescence protein (GFP)-mouse BM-MSC, or BM-MSC suspended in sECM. Outcomes measured 1 month after treatment included procollagen-III, fibronectin, hyaluronan synthase-III (HAS3), hyaluronidase (HYAL3), smooth muscle actin (SMA), and transforming growth factor-beta 1(TGF-beta1) mRNA expression. The persistence of GFP BM-MSC, proliferation, apoptosis, and myofibroblast differentiation was assessed by immunofluorescence.

RESULTS

BM-MSC grown in vitro within sECM express Sca-1, are positive for hyaluronan receptor CD44, and continue to proliferate. In the in vivo study, groups injected with BM-MSC had detectable GFP-labeled BM-MSC remaining and showed proliferation and low apoptotic or myofibroblast markers compared to the contralateral side. Embedded BM-MSC in the sECM group exhibited increased levels of procollagen III, fibronectin, and TGF-beta1. BM-MSC within sECM downregulated the expression of SMA compared to BM-MSC alone and exhibited upregulation of HYAL3 and no change in HAS3 compared to saline.

CONCLUSIONS

Treatment of vocal fold scarring with BM-MSC injected in a sECM displayed the most favorable outcomes in ECM production, hyaluronan metabolism, myofibroblast differentiation, and production of TGF-beta1. Furthermore, the combined treatment had no detectable cytotoxicity and preserved local cell proliferation.

Characterization of mesenchymal stem cells from human vocal fold fibroblasts

OBJECTIVES/HYPOTHESIS

Mesenchymal stem cells (MSCs) originally isolated from bone marrow (BM), are fibroblast-looking cells that are now assumed to be present in the stromal component of many tissues. MSCs are characterized by a certain set of criteria, including their growth culture characteristics, a combination of cell surface markers, and the ability to differentiate along multiple mesenchymal tissue lineages. We hypothesized that human vocal fold fibroblasts (hVFF) isolated from the lamina propria meet the criteria established to define MSCs and are functionally similar to MSCs derived from BM and adipose tissue.

STUDY DESIGN

In vitro study.

METHODS

hVFF were previously derived from human vocal fold tissues. MSCs were derived from adipose tissue (AT), and BM of healthy donors based on their attachment to culture dishes and their morphology and expanded in culture. Cells were analyzed for standard cell surface markers identified on BM-derived MSCs and the ability to differentiate into cells of mesenchymal lineage (i.e., fat, bone, and cartilage). We investigated the immunophenotype of these cells before and after interferon-gamma (INF-gamma) stimulation.

RESULTS

hVFF displayed cell surface markers and multipotent differentiation capacity characteristic of MSCs. Furthermore, these cells exhibited similar patterns of expression of human leukocyte antigen and costimulatory molecules, after stimulation with INF-gamma compared to MSCs derived from BM and AT.

CONCLUSIONS

Based on our findings, hVFF derived from lamina propria have the same cell surface markers, immunophenotypic characteristics, and differentiation potential as BM- and AT-derived MSCs. We propose that vocal fold fibroblasts are MSCs resident in the vocal fold lamina propria.