Comparison of human fibroblast ECM-related gene expression on elastic three-dimensional substrates relative to two-dimensional films of the same material

3D-Printed Gelatin Methacrylate Scaffolds with Controlled Architecture and Stiffness Modulate the Fibroblast Phenotype towards Dermal Regeneration

Impaired skin wound healing due to severe injury often leads to dysfunctional scar tissue formation as a result of excessive and persistent myofibroblast activation, characterised by the increased expression of α-smooth muscle actin (αSMA) and extracellular matrix (ECM) proteins. Yet, despite extensive research on impaired wound healing and the advancement in tissue-engineered skin substitutes, scar formation remains a significant clinical challenge. This study aimed to first investigate the effect of methacrylate gelatin (GelMA) biomaterial stiffness on human dermal fibroblast behaviour in order to then design a range of 3D-printed GelMA scaffolds with tuneable structural and mechanical properties and understand whether the introduction of pores and porosity would support fibroblast activity, while inhibiting myofibroblast-related gene and protein expression. Results demonstrated that increasing GelMA stiffness promotes myofibroblast activation through increased fibrosis-related gene and protein expression. However, the introduction of a porous architecture by 3D printing facilitated healthy fibroblast activity, while inhibiting myofibroblast activation. A significant reduction was observed in the gene and protein production of αSMA and the expression of ECM-related proteins, including fibronectin I and collagen III, across the range of porous 3D-printed GelMA scaffolds. These results show that the 3D-printed GelMA scaffolds have the potential to improve dermal skin healing, whilst inhibiting fibrosis and scar formation, therefore potentially offering a new treatment for skin repair.

Chitin-Based Double-Network Hydrogel as Potential Superficial Soft-Tissue-Repairing Materials

Chitin is a biopolymer, which has been proven to be a biomedical material candidate, yet the weak mechanical properties seriously limit their potentials. In this work, a chitin-based double-network (DN) hydrogel has been designed as a potential superficial repairing material. The hydrogel was synthesized through a double-network (DN) strategy composing hybrid regenerated chitin nanofiber (RCN)-poly (ethylene glycol diglycidyl ether) (PEGDE) as the first network and polyacrylamide (PAAm) as the second network. The hybrid RCN-PEGDE/PAAm DN hydrogel was strong and tough, possessing Young's modulus (elasticity) E 0.097 ± 0.020 MPa, fracture stress σ_f 0.449 ± 0.025 MPa, and work of fracture W_f 5.75 ± 0.35 MJ·m^-3. The obtained DN hydrogel was strong enough for surgical requirements in the usage of soft tissue scaffolds. In addition, chitin endowed the DN hydrogel with good bacterial resistance and accelerated fibroblast proliferation, which increased the NIH3T3 cell number by nearly five times within 3 days. Subcutaneous implantation studies showed that the DN hydrogel did not induce inflammation after 4 weeks, suggesting a good biosafety in vivo. These results indicated that the hybrid RCN-PEGDE/PAAm DN hydrogel had great prospect as a rapid soft-tissue-repairing material.

In Vitro Cultures of Adipose-Derived Stem Cells: An Overview of Methods, Molecular Analyses, and Clinical Applications

Adipose-derived stem cells (ASCs) exhibiting mesenchymal stem cell (MSC) characteristics, have been extensively studied in recent years. Because they have been shown to differentiate into lineages such as osteogenic, chondrogenic, neurogenic or myogenic, the focus of most of the current research concerns either their potential to replace bone marrow as a readily available and abundant source of MSCs, or to employ them in regenerative and reconstructive medicine. There is close to consensus regarding the methodology used for ASC isolation and culture, whereas a number of molecular analyses implicates them in potential therapies of a number of pathologies. When it comes to clinical application, there is a range of examples of animal trials and clinical studies employing ASCs, further emphasizing the advancement of studies leading to their more widespread use. Nevertheless, in vitro studies will most likely continue to play a significant role in ASC studies, both providing the molecular knowledge of their ex vivo properties and possibly serving as an important step in purification and application of those cells in a clinical setting. Therefore, it is important to consider current methods of ASC isolation, culture, and processing. Furthermore, molecular analyses and cell surface properties of ASCs are essential for animal studies, clinical studies, and therapeutic applications of the MSC properties.

Biological characterization of surface-treated dental implant materials in contact with mammalian host and bacterial cells: titanium versus zirconia

Early-colonizing oral bacterial adhesion and mammal cell proliferation were similar on surface-treated titanium and zirconia.

Suppression of T24 human bladder cancer cells by ROS from locally delivered hematoporphyrin-containing polyurethane films

Systemic injection of a photosensitizer is a general method in photodynamic therapy, but it has complications due to the unintended systemic distribution and remnants of photosensitizers. This study focused on the possibility of suppressing luminal proliferative cells by excessive reactive oxygen species from locally delivered photosensitizer with biocompatible polyurethane, instead of the systemic injection method. We used human bladder cancer cells, hematoporphyrin as the photosensitizer, and polyurethane film as the photosensitizer-delivering container. The light source was a self-made LED (510 nm, 5 mW cm-2) system. The cancer cells were cultured on different doses of hematoporphyrin-containing polyurethane film and irradiated with LED for 15 minutes and 30 minutes each. After irradiating with LED and incubating for 24 hours, cell viability analysis, cell cycle analysis, apoptosis assay, intracellular and extracellular ROS generation study and western blot were performed. The cancer cell suppression effects of different concentrations of the locally delivered hematoporphyrin with PDT were compared. Apoptosis dominant cancer cell suppressions were shown to be hematoporphyrin dose-dependent. However, after irradiation, intracellular ROS amounts were similar in all the groups having different doses of hematoporphyrin, but these values were definitely higher than those in the control group. Excessive extracellular ROS from the intended, locally delivered photosensitizer for photodynamic treatment application had an inhibitory effect on luminal proliferative cancer cells. This method can be another possibility for PDT application on contactable or attachable lesions.

Nanoscale characteristics of antibacterial cationic polymeric brushes and single bacterium interactions probed by force microscopy

A direct probing technique was applied to PEI brushes to investigate bacteria–PEI brush interactions in a single bacterium resolution.

Breast Cancer Cell Line Aggregate Morphology Does Not Predict Invasive Capacity

To invade and metastasize to distant loci, breast cancer cells must breach the layer of basement membrane surrounding the tumor and then invade through the dense collagen I-rich extracellular environment of breast tissue. Previous studies have shown that breast cancer cell aggregate morphology in basement membrane extract correlated with cell invasive capacity in some contexts. Moreover, cell lines from the same aggregate morphological class exhibited similarities in gene expression patterns. To further assess the capacity of cell and aggregate morphology to predict invasive capacity in physiologically relevant environments, six cell lines with varied cell aggregate morphologies were assessed in a variety of assays including a 3D multicellular invasion assay that recapitulates cell-cell and cell-environment contacts as they exist in vivo in the context of the primary breast tumor. Migratory and invasive capacities as measured through a 2D gap assay and a 3D spheroid invasion assay reveal that breast cancer cell aggregate morphology alone is insufficient to predict migratory speed in 2D or invasive capacity in 3D. Correlations between the 3D spheroid invasion assay and gene expression profiles suggest this assay as an inexpensive functional method to predict breast cancer invasive capacity.

Morphological effects on expression of growth differentiation factor 15 (GDF15), a marker of metastasis

Cancer cells typically demonstrate altered morphology during the various stages of disease progression as well as metastasis. While much is known about how altered cell morphology in cancer is a result of genetic regulation, less is known about how changes in cell morphology affect cell function by influencing gene expression. In this study, we altered cell morphology in different types of cancer cells by disrupting the actin cytoskeleton or by modulating attachment and observed a rapid up-regulation of growth differentiation factor 15 (GDF15), a member of the transforming growth factor-beta (TGF-β) super-family. Strikingly, this up-regulation was sustained as long as the cell morphology remained altered but was reversed upon allowing cell morphology to return to its typical configuration. The potential significance of these findings was examined in vivo using a mouse model: a small number of cancer cells grown in diffusion chambers that altered morphology increased mouse serum GDF15. Taken together, we propose that during the process of metastasis, cancer cells experience changes in cell morphology, resulting in the increased production and secretion of GDF15 into the surrounding environment. This indicates a possible relationship between serum GDF15 levels and circulating tumor cells may exist. Further investigation into the exact nature of this relationship is warranted.

Using vocally inspired mechanical conditioning to enhance the synthesis of a cell-derived biomaterial

The collection of cell-derived extracellular matrix (ECM) to form implantable biomaterials has therapeutic potential. However, a significant challenge to the creation of these biomaterials is the ability to produce an adequate quantity of ECM from cells in culture. Mechanical stimulation has long been viewed as a practical means to enhance cellular matrix production. In this study we explored the influence of vocally inspired mechanical stimulation, a unique combination of high frequency vibration and low frequency strain, on the production of ECM. Using a custom fabricated vocal bioreactor, tracheal fibroblast seeded sacrificial foams were treated for 3 weeks using either isolated cyclic strain, combined cyclic strain and vibration (dual mode), or static conditioning. When compared to static controls, ECM production was significantly increased for samples conditioned with either cyclic strain or dual mode stimulation. The quantity of ECM harvested from sacrificial foams increased from 25 ± 1 mg for statically conditioned control foams, to 34 ± 3 and 52 ± 10 mg for cyclic strain and dual mode conditioned samples respectively. Furthermore, mechanical conditioning significantly increased the elastic modulus of ECM biomaterials collected from sacrificial foams. Static control modulus increased from 40 ± 2 to 63 ± 7 kPa and 92 ± 7 kPa following isolated cyclic strain and dual mode conditioning, respectively. These results indicate that cyclic strain conditioning can be used to accelerate the production of ECM by human tracheal cells during growth in culture, and that the addition of high frequency vibration to the conditioning program further enhances ECM production.

The effects of interactive mechanical and biochemical niche signaling on osteogenic differentiation of adipose-derived stem cells using combinatorial hydrogels

Stem cells reside in a multi-factorial environment containing biochemical and mechanical signals. Changing biochemical signals in most scaffolds often leads to simultaneous changes in mechanical properties, which makes it difficult to elucidate the complex interplay between niche cues. Combinatorial studies on cell-material interactions have emerged as a tool to facilitate analyses of stem cell responses to various niche cues, but most studies to date have been performed on two-dimensional environments. Here we developed three-dimensional combinatorial hydrogels with independent control of biochemical and mechanical properties to facilitate analysis of interactive biochemical and mechanical signaling on adipose-derived stem cell osteogenesis in three dimensions. Our results suggest that scaffold biochemical and mechanical signals synergize only at specific combinations to promote bone differentiation. Leading compositions were identified to have intermediate stiffness (∼55kPa) and low concentration of fibronectin (10μg ml(-1)), which led to an increase in osteocalcin gene expression of over 130-fold. Our results suggest that scaffolds with independently tunable niche cues could provide a powerful tool for conducting mechanistic studies to decipher how complex niche cues regulate stem cell fate in three dimensions, and facilitate rapid identification of optimal niche cues that promote desirable cellular processes or tissue regeneration.

The effect of substrate modulus on the growth and function of matrix-embedded endothelial cells

Endothelial cells (EC) are potent bioregulatory cells, modulating thrombosis, inflammation and control over mural smooth muscle cells and vascular health. The biochemical roles of EC are retained when cells are embedded within three-dimensional (3D) denatured collagen matrices. Though substrate mechanics have long been known to affect cellular morphology and function and 3D-EC systems are increasingly used as therapeutic modalities little is known about the effect of substrate mechanics on EC in these 3D systems. In this work, we examined the effect of isolated changes in modulus on EC growth and morphology, extracellular matrix gene expression, modulation of smooth muscle cell growth, and immunogenicity. EC growth, but not morphology was dependent on scaffold modulus. Increased scaffold modulus reduced secretion of smooth muscle cell growth inhibiting heparan sulfate proteoglycans (HSPGs), but had no effect on secreted growth factors, resulting in a loss of smooth muscle cell growth inhibition by EC on high modulus scaffolds. Expression of ICAM-1, VCAM-1 and induction of CD4(+) T cell proliferation was reduced by increased scaffold modulus, and correlated with changes in integrin α5 expression. Expression of several common ECM proteins by EC on stiffer substrates dropped, including collagen IV(α1), collagen IV(α5), fibronectin, HSPGs (perlecan and biglycan). In contrast, expression of elastin and TIMPs were increased. This work shows even modest changes in substrate modulus can have a significant impact on EC function in three-dimensional systems. The mechanism of these changes is not clear, but the data presented here within suggests a model wherein EC attempt to neutralize changes in environmental force balance by altering ECM and integrin expression, leading to changes in effects on downstream signaling and function.

Using growth factor conditioning to modify the properties of human cell derived extracellular matrix

We have recently reported on a bench-top approach for isolating extracellular matrix (ECM) from pure populations of cells grown in culture using sacrificial, open-celled foams to concentrate and capture the ECM. To increase both the accumulation and the strength of the ECM harvested, cell-seeded polyurethane (PU) foams were cultured in media supplemented with either transforming growth factor β-1 (TGFβ1) or hepatocyte growth factor (HGF). At the end of a 3-week culture period, ECM yield was significantly increased for samples conditioned in supplemented media. Control foams yielded 48 ± 12 mg of material for every gram of PU foam seeded. Yield values increased to 102 ± 21 and 243 ± 25 mg for HGF and TGFβ1-treated samples, respectively. HGF supplementation increased the modulus by 59%, while TGFβ1 treatment increased the elastic modulus by 204%. TGFβ1-stimulated material was organized into a network that was markedly denser than control material, with HGF-stimulated network density intermediate to TGFβ1 and controls. Our study showed that TGFβ1-treated samples were collagen enriched while HGF samples had an increased gylcosaminoglycan concentration. The results demonstrate that growth factor supplementation, particularly with TGFβ1, can significantly alter the biomechanical properties of cell-derived ECM that may be used for therapeutic applications.

Three dimensional neuronal cell cultures more accurately model voltage gated calcium channel functionality in freshly dissected nerve tissue

It has been demonstrated that neuronal cells cultured on traditional flat surfaces may exhibit exaggerated voltage gated calcium channel (VGCC) functionality. To gain a better understanding of this phenomenon, primary neuronal cells harvested from mice superior cervical ganglion (SCG) were cultured on two dimensional (2D) flat surfaces and in three dimensional (3D) synthetic poly-L-lactic acid (PLLA) and polystyrene (PS) polymer scaffolds. These 2D- and 3D-cultured cells were compared to cells in freshly dissected SCG tissues, with respect to intracellular calcium increase in response to high K⁺ depolarization. The calcium increases were identical for 3D-cultured and freshly dissected, but significantly higher for 2D-cultured cells. This finding established the physiological relevance of 3D-cultured cells. To shed light on the mechanism behind the exaggerated 2D-cultured cells’ functionality, transcriptase expression and related membrane protein distributions (caveolin-1) were obtained. Our results support the view that exaggerated VGCC functionality from 2D cultured SCG cells is possibly due to differences in membrane architecture, characterized by uniquely organized caveolar lipid rafts. The practical implication of use of 3D-cultured cells in preclinical drug discovery studies is that such platforms would be more effective in eliminating false positive hits and as such improve the overall yield from screening campaigns.

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.

The isolation of cell derived extracellular matrix constructs using sacrificial open-cell foams

Extracellular matrix derived from human and animal tissues is being used to repair and reconstruct a variety of tissues clinically. The utility of such constructs is limited by the geometry, composition and constitutive properties of the tissue or organ from which the ECM is harvested. To address this limitation, we have developed an approach to isolate extracellular matrix in bulk from populations of living cells grown in culture on three-dimensional substrates. Human biopsy derived fibroblasts were seeded within open-cell foams and cultured in-vitro for periods up to three weeks, after which the synthetic component was removed by incubation in a water miscible solvent. After several wash steps and lyophilization, a white, lacy, multi-molecular construct was isolated. Tandem mass spectroscopy showed that it contained 22 extracellular matrix constituents, including such proteins and proteoglycans as collagen type I and type III, fibronectin, transforming growth factor beta, decorin and biglycan among others. On average 47 mg of construct was isolated for each gram of synthetic substrate initially seeded with cells. The biomaterial harvested from human tracheal fibroblasts had an elastic modulus (250 kPa) and a composition similar to that of human vocal fold tissue, and supported reseeding with human tracheal derived fibroblasts. An important finding was that the approach was useful in isolating ECM from a variety of cell lineages and developmental stages including skin fibroblasts, brain derived astrocytes and mesenchymal stem cells. The results, together with the archival literature, suggest that the approach can be used to produce a range of cell derived constructs with unique physical and chemical attributes for a variety of research and medical applications.

Cervical tissue engineering using silk scaffolds and human cervical cells

Spontaneous preterm birth is a frequent complication of pregnancy and a common cause of morbidity in childhood. Obstetricians suspect abnormalities of the cervix are implicated in a significant number of preterm births. The cervix is composed of fibrous connective tissue and undergoes significant remodeling in preparation for birth. We hypothesized that a tissue engineering strategy could be used to develop three-dimensional cervical-like tissue constructs that would be suitable for investigating cervical remodeling. Cervical cells were isolated from two premenopausal women undergoing hysterectomy for a benign gynecological condition, and the cells were seeded on porous silk scaffolds in the presence or absence of dynamic culture and with 10% or 20% serum. Morphological, biochemical, and mechanical properties were measured during the 8-week culture period. Cervical cells proliferated in three-dimensions and synthesized an extracellular matrix with biochemical constituents and morphology similar to native tissue. Compared to static culture, dynamic culture was associated with significantly increased collagen deposition (p < 0.05), sulfated glycosaminoglycan synthesis (p < 0.05), and mechanical stiffness (p < 0.05). Serum concentration did not affect measured variables. Relevant human tissue-engineered cervical-like constructs constitute a novel model system for a range of fundamental and applied studies related to cervical remodeling.

Synthesis and Characterization of Elastin-Mimetic Hybrid Polymers with Multiblock, Alternating Molecular Architecture and Elastomeric Properties

We are interested in developing elastin-mimetic hybrid polymers (EMHPs) that capture the multiblock molecular architecture of tropoelastin as well as the remarkable elasticity of mature elastin. In this study, multiblock EMHPs containing flexible synthetic segments based on poly(ethylene glycol) (PEG) alternating with alanine-rich, lysine-containing peptides were synthesized by step-growth polymerization using α,ω-azido-PEG and alkyne-terminated AKA(3)KA (K = lysine, A = alanine) peptide, employing orthogonal click chemistry. The resulting EMHPs contain an estimated three to five repeats of PEG and AKA(3)KA and have an average molecular weight of 34 kDa. While the peptide alone exhibited α-helical structures at high pH, the fractional helicity for EMHPs was reduced. Covalent cross-linking of EMHPs with hexamethylene diisocyanate (HMDI) through the lysine residue in the peptide domain afforded an elastomeric hydrogel (xEMHP) with a compressive modulus of 0.12 MPa when hydrated. The mechanical properties of xEMHP are comparable to a commercial polyurethane elastomer (Tecoflex SG80A) under the same conditions. In vitro toxicity studies showed that while the soluble EMHPs inhibited the growth of primary porcine vocal fold fibroblasts (PVFFs) at concentrations ≥0.2 mg/mL, the cross-linked hybrid elastomers did not leach out any toxic reagents and allowed PVFFs to grow and proliferate normally. The hybrid and modular approach provides a new strategy for developing elastomeric scaffolds for tissue engineering.

Effects of fabrication parameters on viscoelastic shear modulus of 2,3-dialdehydecellulose membranes--potential scaffolds for vocal fold lamina propria tissue engineering

Porous 2,3-dialdehydecellulose (2,3-DAC) membranes were investigated for use as a synthetic scaffold for engineering vocal fold-like tissues. Two criteria of this application are (i) the viscoelastic shear properties of the scaffold should be controllable in the range of vocal fold tissues and (ii) scaffolds should remain biomechanically stable to withstand vibrational stresses in a bioreactor. Porous 2,3-DAC membranes were fabricated from methylolcellulose by water-induced cellulose regeneration, with or without sodium chloride leaching, followed by periodate oxidation. They were freeze-dried and ethylene oxide-sterilized. Different degrees of oxidation were obtained on reacting with sodium metaperiodate for different time points. Rheological studies were performed to investigate the effect of freeze-drying, porosity, degree of oxidation, sterilization, and incubation time on elastic and viscous shear moduli, G' and G'', respectively, for frequencies 0.01-10 Hz. Freeze drying increased G' and G'', while increased porosity and degree of oxidation reduced G' and G''. Sterilization had no effect on viscoelasticity. When incubated in Dulbecco's minimum essential medium at 37 degrees C, membranes with 6-7% and 19-20% oxidation disintegrated after 7 and 3 days, respectively, while membranes with 3-4% oxidation showed little viscoelastic change over a period of 42 days. The upper frequency limit of rheologic measurement was a limitation of the study and should be addressed in future investigations.

The role of extracellular matrix in glioma invasion: a cellular Potts model approach

In this work, a cellular Potts model based on the differential adhesion hypothesis is employed to analyze the relative importance of select cell-cell and cell-extracellular matrix (ECM) contacts in glioma invasion. To perform these simulations, three types of cells and two ECM components are included. The inclusion of explicit ECM with an inhomogeneous fibrous component and a homogeneously dispersed afibrous component allows exploration of the importance of relative energies of cell-cell and cell-ECM contacts in a variety of environments relevant to in vitro and in vivo experimental investigations of glioma invasion. Simulations performed here focus chiefly on reproducing findings of in vitro experiments on glioma spheroids embedded in collagen I gels. For a given range and set ordering of energies associated with key cell-cell and cell-ECM interactions, our model qualitatively reproduces the dispersed glioma invasion patterns found for most glioma cell lines embedded as spheroids in collagen I gels of moderate concentration. In our model, we find that invasion is maximized at intermediate collagen concentrations, as occurs experimentally. This effect is seen more strongly in model gels composed of short collagen fibers than in those composed of long fibers, which retain significant connectivity even at low density. Additional simulations in aligned model matrices further elucidate how matrix structure dictates invasive patterns. Finally, simulations that allow invading cells to both dissolve and deposit ECM components demonstrate how Q-Potts models may be elaborated to allow active cell alteration of their surroundings. The model employed here provides a quantitative framework with which to bound the relative values of cell-cell and cell-ECM interactions and investigate how varying the magnitude and type of these interactions, as well as ECM structure, could potentially curtail glioma invasion.

Cell viability viscoelastic measurement in a rheometer used to stress and engineer tissues at low sonic frequencies

Effects of vibration on human vocal fold extracellular matrix composition and the resultant tissue viscoelastic properties are difficult to study in vivo. Therefore, an in vitro bioreactor, simulating the in vivo physiological environment, was explored. A stress-controlled commercial rheometer was used to administer shear vibrations to living tissues at stresses and frequencies corresponding to male phonation, while simultaneously measuring tissue viscoelastic properties. Tissue environment was evaluated and adjustments made in order to sustain cell life for short term experimentation up to 6 h. Cell nutrient medium evaporation, osmolality, pH, and cell viability of cells cultured in three-dimensional synthetic scaffolds were quantified under comparably challenging environments to the rheometer bioreactor for 4 or 6 h. The functionality of the rheometer bioreactor was demonstrated by applying three vibration regimes to cell-seeded three-dimensional substrates for 2 h. Resulting strain was quantified throughout the test period. Rheologic data and cell viability are reported for each condition, and future improvements are discussed.

Hylan B Gel Restores Structure and Function to Laser-Ablated Canine Vocal Folds

Objectives:

We evaluated cross-linked hyaluronic acid (hylan B gel) as a scaffold for tissue regeneration and mucosal wave restoration in carbon dioxide laser–ablated canine vocal folds.

Methods:

Five beagles underwent stroboscopy before ablation of the left vocal fold with a carbon dioxide laser. Four weeks later, stroboscopy was repeated before and after submucosal injection of hylan B gel into the left vocal fold of 4 animals and of saline solution in 1 animal. Stroboscopy was repeated 12 weeks later, and histologic analysis was performed.

Results:

Four weeks after laser ablation, all animals had soft tissue defects and absence of mucosal waves. Hylan B injection restored mucosal waves, and saline injection did not. Twelve weeks after injection, hylan B–injected larynges had tissue regeneration and mucosal waves, and the saline-injected larynx had neither. Histology showed regenerated lamina propria with residual foci of hylan B in the hylan B–injected larynges and dense submucosal scar in the saline-injected animal.

Conclusions:

Submucosal hylan B gel injection in laser-ablated canine vocal folds restored tissue volume and mucosal waves and facilitated functional tissue regeneration over 12 weeks. Hylan B gel may have utility as a soft tissue scaffold for rehabilitation of phonatory function in vocal folds with lamina propria defects.

Variation of cyclic strain parameters regulates development of elastic modulus in fibroblast/substrate constructs

Dynamic mechanical culture systems are a widely studied approach for improving the functional mechanical properties of tissue engineering constructs intended for loading-bearing orthopedic applications such as tendon/ligament reconstruction. The design of effective mechanical stimulation regimes requires a fundamental understanding of the effects of cyclic strain parameters on the resulting construct properties. Toward this end, these studies employed a modular cyclic strain bioreactor system and fibroblast-seeded, porous polyurethane substrates to systematically investigate the effect of varying cyclic strain amplitude, rate, frequency, and daily cycle number on construct mechanical properties. Significant differences were observed in response to variation of all four loading parameters tested. In general, the highest values of elastic modulus within each experimental group were observed at low to intermediate values of the experimental variables tested, corresponding to the low to subphysiological range (2.5% strain amplitude, 25%/s strain rate, 0.1-0.5 Hz frequency, and 7,200-28,800 cycles/day). These studies demonstrate that fibroblasts are sensitive and responsive to multiple characteristics of their mechanical environment, and suggest that systematic optimization of dynamic culture conditions may be useful for the acceleration of construct maturation and mechanical function.

Fabrication of combinatorial polymer scaffold libraries

We have designed a novel combinatorial research platform to help accelerate tissue engineering research. Combinatorial methods combine many samples into a single specimen to enable accelerated experimentation and discovery. The platform for fabricating combinatorial polymer scaffold libraries can be used to rapidly identify scaffold formulations that maximize tissue formation. Many approaches for screening cell-biomaterial interactions utilize a two-dimensional format such as a film or surface to present test substrates to cells. However, cells in vivo exist in a three-dimensional milieu of extracellular matrix and cells in vitro behave more naturally when cultured in a three-dimensional environment than when cultured on a two-dimensional surface. Thus, we have designed a method for fabricating combinatorial biomaterial libraries where the materials are presented to cells in the form of three-dimensional, porous, salt-leached, polymer scaffolds. Many scaffold variations and compositions can be screened in a single experiment so that optimal scaffold formulations for tissue formation can be rapidly identified. In summary, we have developed a platform technology for fabricating combinatorial polymer scaffold libraries that can be used to screen cell response to materials in a three-dimensional, scaffold format.

Effects of Growth Factors on Extracellular Matrix Production by Vocal Fold Fibroblasts in 3-Dimensional Culture

Culturing cells in 3-dimensional (3D) systems is important in tissue engineering and in fundamental studies of cellular mechanisms that are sensitive or specific to the 3D environment. To guide the engineering of artificial vocal fold lamina propria tissue, we developed 3D cultures containing human vocal fold fibroblasts (hVFFs) dispersed in a synthetic peptide hydrogel matrix. Growth factors were added to the culture to examine their influence on extracellular matrix (ECM) synthesis, cell proliferation, and matrix contraction. The hVFF-hydrogel constructs were treated with transforming growth factor-beta 1 (TGF-beta1), basic fibroblast growth factor (bFGF), or hepatocyte growth factor (HGF), and the culture was maintained for 21 days. TGF-beta1 induced matrix contraction and enhanced collagen and sulfated glycosaminoglycan production, bFGF effectively increased cell proliferation, and HGF stimulated synthesis of hyaluronic acid and elastin with less collagen accumulation than other conditions. Of the growth factors tested, HGF appears to be most useful for stimulating essential tissue components for restoring vocal fold pliability. The results also suggest that multiple growth factors might be employed sequentially or in combination to program the makeup of cell-hydrogel constructs for vocal fold tissue repair.

Key Processing Parameters for Microcellular Molded Polystyrene Material

Microcellular injection molding was used as processing method to generate porous samples made of polystyrene material. A promising application for this kind of structures is the use as three dimensional cell culture substrate. The influence of key processing parameters on the morphology of the porous structures was examined. An increase in injection speed and a temperature decrease of the polymer melt decreased pore sizes whereas an increase in the degree of weight reduction increased pore sizes. Polystyrene samples with average pore sizes from 23 to 92 μm were produced.

Cyclic strain increases fibroblast proliferation, matrix accumulation, and elastic modulus of fibroblast-seeded polyurethane constructs

Rapid induction of matrix production and mechanical strengthening is essential to the development of bio-artificial constructs for repair and replacement of load-bearing connective tissues. Toward this end, we describe the development of a mechanical bioreactor and its application to investigate the influence of cyclic strain on fibroblast proliferation, matrix accumulation, and the mechanical properties of fibroblast-seeded polyurethane constructs (FSPC). Human fibroblasts were cultured in 10% serum-containing conditions within three-dimensional, porous elastomeric substrates under static conditions and a model regime of cyclic strain (10% strain, 0.25 Hz, 8 h/day), with and without ascorbic acid supplementation. After one week, the combination of cyclic strain and ascorbic acid resulted in significantly increased construct elastic modulus (>110%) relative to either condition alone. In contrast, cyclic strain alone was sufficient to stimulate significant increases in fibroblast proliferation. Mechanical strengthening of FSPCs was accompanied by increased type I collagen and fibronectin matrix accumulation and distribution, and significantly increased gene expression for type I collagen, TGFbeta-1, and CTGF. These results suggest that strain-induced conditioning in vitro leads to mechanical strengthening of fibroblast/material constructs, most likely resulting from increased collagen matrix deposition, secondary to strain-induced increases in cytokine production.

Cyclic strain modulates tubulogenesis of endothelial cells in a 3D tissue culture model

Angiogenesis is the formation of new blood vessels from preexisting capillaries or venules. It occurs in a mechanically dynamic environment due to blood flow, but the role of hemodynamic forces in angiogenesis remains poorly understood. We have developed a unique in vitro system for the investigation of angiogenesis under cyclic strain. In this system, tubulogenesis of vascular endothelial cells in 3D collagen gels occurs under well-defined cyclic strain, which mimics blood-pressure-induced stretch. Using this system, we demonstrate that cyclic strain results in alignment of endothelial-cord-like structures perpendicular to the principal axis of stretch. Such preferential orientation was the most evident in deep and long cord-like structures. This in vitro system, along with the novel findings of strain-modulated endothelial tube morphology, enables the formation of an experimental basis for understanding the role of cyclic strain in the regulation of angiogenesis.

Osteogenic differentiation is inhibited and angiogenic expression is enhanced in MC3T3-E1 cells cultured on three-dimensional scaffolds

Osteogenic differentiation of osteoprogenitor cells in three-dimensional (3D) in vitro culture remains poorly understood. Using quantitative real-time RT-PCR techniques, we examined mRNA expression of alkaline phosphatase, osteocalcin, and vascular endothelial growth factor (VEGF) in murine preosteoblastic MC3T3-E1 cells cultured for 48 h and 14 days on conventional two-dimensional (2D) poly(l-lactide-co-glycolide) (PLGA) films and 3D PLGA scaffolds. Differences in VEGF secretion and function between 2D and 3D culture systems were examined using Western blots and an in vitro Matrigel-based angiogenesis assay. Expression of both alkaline phosphatase and osteocalcin in cells cultured on 3D scaffolds was significantly downregulated relative to 2D controls in 48 h and 14 day cultures. In contrast, elevated levels of VEGF expression in 3D culture were noted at every time point in short- and long-term culture. VEGF protein secretion in 3D cultures was triple the amount of secretion observed in 2D controls. Conditioned medium from 3D cultures induced an enhanced level of angiogenic activity, as evidenced by increases in branch points observed in in vitro angiogenesis assays. These results collectively indicate that MC3T3-E1 cells commit to osteogenic differentiation at a slower rate when cultured on 3D PLGA scaffolds and that VEGF is preferentially expressed by these cells when they are cultured in three dimensions.

Composite articular cartilage engineered on a chondrocyte-seeded aliphatic polyurethane sponge

To circumvent the reconstructive disadvantages inherent in resorbable polyglycolic acid (PGA)/polylactic acid (PLA) used in cartilage engineering, a nonresorbable, and nonreactive polyurethane sponge (Tecoflex sponge, TS) was studied as both a cell delivery device and as an internal support scaffolding. The in vitro viability and proliferation of porcine articular chondrocytes (PACs) in TS, and the in vivo generation of new articular cartilage and long-term resorption, were examined. The initial cell attachment rate was 40%, and cell density increased more than 5-fold after 12 days of culture in vitro. PAC-loaded TS blocks were implanted into nude mice, became opalescent, and resembled native cartilage at weeks 12 and 24 postimplantation. The mass and volume of newly formed cartilage were not significantly different at week 24 from samples harvested at week 6 or week 12. Safranin O-fast green staining revealed that the specimens from cell-loaded TS groups at week 12 and week 24 consisted of mature cartilage. Collagen typing revealed that type II collagen was present in all groups of tissue-engineered cartilage. In conclusion, the implantation of PAC-TS resulted in composite tissue-engineered articular cartilage with TS as an internal support. Long-term observation (24 weeks) of mass and volume showed no evidence of resorption.

[Cell transplantation for a CSF-fistula. Experience with fibrin glue and fibroblasts]

BACKGROUND

In the present study we investigated the culturing of fibroblasts on fibrin glue embedded suture nets, to analyse the possibility of using these components in a suture application technique for the closure of a CSF-fistula.

RESULTS

Placement of centrally perforated dura pieces on fibrin glue coated surfaces resulted in cellular migration from the dura borders into the defect, resulting in a complete cellular closure of the perforation. Inversion microscopic follow-up during culturing and the Alamar blue-essay found strong growth stimulation for oral mucosa fibroblasts on fibrin glue coated surfaces by insulin and FGF. Three-dimensional fibroblast growth was observed along the suture lines in the presence of fibrin glue.

CONCLUSIONS

Fibrin glue is an attractive extracellular matrix for cellular migration from the dura which is suited to fibroblast culturing in suture nets. Our findings support the idea of achieving closure of cerebrospinal fluid fistulas by suture application of autologous fibroblasts and fibrin/thrombin preparations as a realistic future goal.