Effect of local environment, fibrin, and basic fibroblast growth factor incorporation on a canine autologous model of bioengineered cartilage tissue

Ethanol treatment of nanoPGA/PCL composite scaffolds enhances human chondrocyte development in the cellular microenvironment of tissue-engineered auricle constructs

A major obstacle for tissue engineering ear-shaped cartilage is poorly developed tissue comprising cell-scaffold constructs. To address this issue, bioresorbable scaffolds of poly-ε-caprolactone (PCL) and polyglycolic acid nanofibers (nanoPGA) were evaluated using an ethanol treatment step before auricular chondrocyte scaffold seeding, an approach considered to enhance scaffold hydrophilicity and cartilage regeneration. Auricular chondrocytes were isolated from canine ears and human surgical samples discarded during otoplasty, including microtia reconstruction. Canine chondrocytes were seeded onto PCL and nanoPGA sheets either with or without ethanol treatment to examine cellular adhesion in vitro. Human chondrocytes were seeded onto three-dimensional bioresorbable composite scaffolds (PCL with surface coverage of nanoPGA) either with or without ethanol treatment and then implanted into athymic mice for 10 and 20 weeks. On construct retrieval, scanning electron microscopy showed canine auricular chondrocytes seeded onto ethanol-treated scaffolds in vitro developed extended cell processes contacting scaffold surfaces, a result suggesting cell-scaffold adhesion and a favorable microenvironment compared to the same cells with limited processes over untreated scaffolds. Adhesion of canine chondrocytes was statistically significantly greater (p ≤ 0.05) for ethanol-treated compared to untreated scaffold sheets. After implantation for 10 weeks, constructs of human auricular chondrocytes seeded onto ethanol-treated scaffolds were covered with glossy cartilage while constructs consisting of the same cells seeded onto untreated scaffolds revealed sparse connective tissue and cartilage regeneration. Following 10 weeks of implantation, RT-qPCR analyses of chondrocytes grown on ethanol-treated scaffolds showed greater expression levels for several cartilage-related genes compared to cells developed on untreated scaffolds with statistically significantly increased SRY-box transcription factor 5 (SOX5) and decreased interleukin-1α (inflammation-related) expression levels (p ≤ 0.05). Ethanol treatment of scaffolds led to increased cartilage production for 20- compared to 10-week constructs. While hydrophilicity of scaffolds was not assessed directly in the present findings, a possible factor supporting the summary data is that hydrophilicity may be enhanced for ethanol-treated nanoPGA/PCL scaffolds, an effect leading to improvement of chondrocyte adhesion, the cellular microenvironment and cartilage regeneration in tissue-engineered auricle constructs.

State of the art of clinical applications of Tissue Engineering in 2021

Tissue engineering (TE) was introduced almost 30 years ago as a potential technique for regenerating human tissues. However, despite promising laboratory findings, the complexity of the human body, scientific hurdles, and lack of persistent long-term funding still hamper its translation towards clinical applications. In this report, we compile an inventory of clinically applied TE medical products relevant to surgery. A review of the literature, including articles published within the period from 1991 to 2020, was performed according to the PRISMA protocol, using databanks PubMed, Cochrane Library, Web of Science, and Clinicaltrials.gov. We identified 1039 full-length articles as eligible; due to the scarcity of clinical, randomised, controlled trials and case studies, we extended our search towards a broad surgical spectrum. Forty papers involved clinical TE studies. Amongst these, 7 were related to TE protocols for cartilage applied in the reconstruction of nose, ear, and trachea. Nine papers reported TE protocols for articular cartilage, 9 for urological purposes, 7 described TE strategies for cardiovascular aims, and 8 for dermal applications. However, only two clinical studies reported on three-dimensional (3D) and functional long-lasting TE constructs. The concept of generating 3D TE constructs and organs based on autologous molecules and cells is intriguing and promising. The first translational tissue-engineered products and techniques have been clinically implemented. However, despite the 30 years of research and development in this field, TE is still in its clinical infancy. Multiple experimental, ethical, budgetary, and regulatory difficulties hinder its rapid translation. Nevertheless, the first clinical applications show great promise and indicate that the translation towards clinical medical implementation has finally started.

Proliferation medium in three-dimensional culture of auricular chondrocytes promotes effective cartilage regeneration in vivo

Introduction

Cartilage regeneration have been attracted attentions because of the poor ability of cartilage tissues to regenerate. Three-dimensional (3D) culture of chondrocytes is considered to be advantageous for cartilage regeneration. Although it is plausible that maturation of the constructs before transplantation positively affects the chondrogenesis, matured constructs after cultures for longer periods do not necessarily result in effective cartilage regeneration. In this study, we compared different types of culture media including growth factors which are clinically available. We prepared differentiation medium containing insulin-like growth factor-1 (IGF-1), proliferation medium containing fibroblast growth factor-2 (FGF-2) and insulin, and combination of them, and compared their efficacies on chondrogenesis when used in 3D culture of engineered cartilage constructs.

Methods

Cartilage constructs were fabricated by auricular chondrocytes and atelocollagen, and they were 3D-cultured with four types of media: control medium, differentiation medium, proliferation medium, and combination medium. After 3 weeks of culture, the constructs were analyzed for cell number, gene and protein expressions and mechanical properties. The constructs were also transplanted into nude mice. After 8 weeks, the degree of cartilage regeneration was evaluated. Constructs manufactured with canine auricular chondrocytes were subjected to autologous transplantation into beagles and examined for cartilage regeneration.

Results

During 3D culture, remarkably high gene expression of type II collagen was detected in the construct cultured with the differentiation medium whereas cell apoptosis were suppressed in the proliferation medium. When transplanted into nude mice, the constructs 3D-cultured in the proliferation medium produced abundant cartilage matrices. In autologous implantation model, the construct cultured in the proliferation medium again showed better chondrogenesis than those in other media.

Conclusions

The present study indicates that 3D culture with the proliferation medium maintains the cell viability to potentiate the subsequent cartilage regeneration. Here, we propose that not only differentiation but also high cell viability accompanied by proliferation factors should be taken into account to improve cartilage regeneration.

A fibrin-coated pericardial extracellular matrix prevented heart adhesion in a rat model

As most surgical treatments pose a risk of tissue adhesion, methods to prevent adhesion are needed across various surgical fields. In this study, we investigated the use of a decellularized pericardium with fibrin glue to prevent rat heart adhesion. Porcine pericardia were decellularized by a high-hydrostatic pressure method. Cells adhered to the resulting pericardial extracellular matrix (ECM) during an in vitro cell-seeding test, but fibrin-coated pericardial ECM showed reduced cell adhesion. In a rat surgical model of heart adhesion, the fibrin-coated pericardial ECM did not adhere to the heart and mesothelial cell adhesion was observed on the ECM surface. Notably, the anti-adhesion effect of fibrin-coated pericardial ECM was observed 4 weeks after surgery. These results support the utility of fibrin-coated pericardial ECM as an adhesion prevention material for cardiovascular surgery. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1088-1094, 2019.

Prolonged in vitro precultivation alleviates post-implantation inflammation and promotes stable subcutaneous cartilage formation in a goat model

Synthetic biodegradable scaffolds such as polylactic acid coated polyglycolic acid (PLA-PGA) are especially suitable for engineering shaped cartilage such as auricle, but they induce a serious inflammatory reaction particularly in the immunologically aggressive subcutaneous site, leading to resorption of the engineered autologous cartilage. Our previous study in a rabbit model has demonstrated 2 weeks of in vitro precultivation could significantly alleviate the post-implantation inflammation induced by PLA-PGA engineered cartilaginous grafts, but reproduction of this result failed in a preclinical goat model. The aims of the current study were to investigate whether prolonged in vitro precultivation could form a mature cartilaginous graft to resist the acute host response and promote stable subcutaneous cartilage formation in a preclinical goat model. Goat chondrocytes were seeded onto PLA-PGA scaffolds, in vitro precultivated for 2, 4, 8, and 12 weeks, and then implanted subcutaneously in autologous goats for 1 and 8 weeks. The in vitro engineered cartilage (vitro-EC) was examined histologically (hematoxylin and eosin, safranin-O, collagen II). The 1 week explants were examined histologically and stained for CD3, CD68, collagen I, and apoptosis. The 8 week explants were evaluated by histology, wet weight, volume, glycosaminoglycan (GAG) quantification and Young's modulus. With prolonged in vitro time, the quality of vitro-EC improved and the amount of scaffold residue decreased; more pronounced cartilage formation with fewer immune cells (CD3 and CD68 positive), apoptotic cells, and less collagen I expression were observed in explants that had been in vitro precultivated for a longer period. The subcutaneously regenerated neocartilage became more mature after prolonged implantation. These results suggested that prolonged in vitro precultivation allowed formation of a mature cartilaginous graft to resist the acute host response and promoted stable subcutaneous cartilage formation in autologous goats. These findings may provide useful reference for engineering auricle, trachea, nose, and eyelid shaped cartilage, for example.

Ear-Shaped Stable Auricular Cartilage Engineered from Extensively Expanded Chondrocytes in an Immunocompetent Experimental Animal Model

Advancement of engineered ear in clinical practice is limited by several challenges. The complex, largely unsupported, three-dimensional auricular neocartilage structure is difficult to maintain. Neocartilage formation is challenging in an immunocompetent host due to active inflammatory and immunological responses. The large number of autologous chondrogenic cells required for engineering an adult human-sized ear presents an additional challenge because primary chondrocytes rapidly dedifferentiate during in vitro culture. The objective of this study was to engineer a stable, human ear-shaped cartilage in an immunocompetent animal model using expanded chondrocytes. The impact of basic fibroblast growth factor (bFGF) supplementation on achieving clinically relevant expansion of primary sheep chondrocytes by in vitro culture was determined. Chondrocytes expanded in standard medium were either combined with cryopreserved, primary passage 0 chondrocytes at the time of scaffold seeding or used alone as control. Disk and human ear-shaped scaffolds were made from porous collagen; ear scaffolds had an embedded, supporting titanium wire framework. Autologous chondrocyte-seeded scaffolds were implanted subcutaneously in sheep after 2 weeks of in vitro incubation. The quality of the resulting neocartilage and its stability and retention of the original ear size and shape were evaluated at 6, 12, and 20 weeks postimplantation. Neocartilage produced from chondrocytes that were expanded in the presence of bFGF was superior, and its quality improved with increased implantation time. In addition to characteristic morphological cartilage features, its glycosaminoglycan content was high and marked elastin fiber formation was present. The overall shape of engineered ears was preserved at 20 weeks postimplantation, and the dimensional changes did not exceed 10%. The wire frame within the engineered ear was able to withstand mechanical forces during wound healing and neocartilage maturation and prevented shrinkage and distortion. This is the first demonstration of a stable, ear-shaped elastic cartilage engineered from auricular chondrocytes that underwent clinical-scale expansion in an immunocompetent animal over an extended period of time.

Optimal amount of basic fibroblast growth factor in gelatin sponges incorporating β-tricalcium phosphate with chondrocytes

BACKGROUND

A gelatin sponge with slowly releasing basic fibroblast growth factor (b-FGF) enhances chondrogenesis. This study investigated the optimal amount of b-FGF in gelatin sponges to fabricate engineered cartilage.

MATERIALS AND METHODS

b-FGF (0, 10, 100, 500, 1000, and 2000 μg/cm(3))-impregnated gelatin sponges incorporating β-tricalcium phosphate (β-TCP) were produced. Chondrocytes were isolated from the auricular cartilage of C57B6J mice and expanded. The expanded auricular chondrocytes (10×10(6) cells/cm(3)) were seeded onto the gelatin sponges, which served as scaffolds. The construct assembly was implanted in the subcutaneous space of mice through a syngeneic fashion. Thereafter, constructs were retrieved at 2, 4, or 6 weeks.

RESULTS

(1) Morphology: The size of implanted constructs was larger than the size of the scaffold with 500, 1000, and 2000 μg/cm(3) b-FGF-impregnated gelatin sponges incorporating β-TCP at 4 and 6 weeks after implantation. (2) The weight of the constructs increased roughly proportional to the increase in volume of the b-FGF-impregnated scaffold at 2, 4, and 6 weeks after implantation, except in the 2000 μg/cm(3) b-FGF-impregnated constructs group. (3) Histological examination: Extracellular matrix in the center of the constructs was observed in gelatin sponges impregnated with more than 100 μg/cm(3) b-FGF at 4 weeks after implantation. The areas of cells with an abundant extracellular matrix were positive for cartilage-specific marker type 2 collagen in the constructs. (4) Protein assay: Glycosaminoglycan and collagen type 2 expression were significantly increased at 4 and 6 weeks on implantation of gelatin sponges impregnated with more than 100 μg/cm(3) b-FGF. At 6 weeks after implantation, the ratio of type 2 collagen to type 1 collagen in constructs impregnated with 100 μg/cm(3) or more b-FGF was higher than that in mice auricular cartilage.

CONCLUSION

Gelatin sponges impregnated with more than 100 μg/cm(3) b-FGF incorporating β-TCP with chondrocytes (10×10(6) cells/cm(3)) can fabricate engineered cartilage at 4 weeks after implantation.

Evaluation of nanofiber-based polyglycolic acid scaffolds for improved chondrocyte retention and in vivo bioengineered cartilage regeneration

BACKGROUND

In conventional studies on the regeneration of auricle-shaped cartilage in autogenous models using large animals, there were problems with the cartilage regeneration induction capacity and long-term retention of geometric shape. In this study, the authors sought to improve on outcome in these regards: a nonwoven fabric of polyglycolic acid was developed through nanotechnology, and the effect of nanofiber diameter on in vitro cell-seeding efficiency and the in vivo response after implantation in an autogenous large-animal model were evaluated.

METHODS

Canine chondrocytes were isolated and seeded onto polyglycolic acid fabric ranging from 0.5 to 20 μm in average diameter. Cell seeding efficiency was highest for mid-range polyglycolic acid fibers (average diameter, 0.8, 3.0, and 7.0 μm). Flat and auricle-shaped scaffolds were constructed using polypropylene structural support, sandwiching a nonwoven polyglycolic acid fabric that contained autogenous chondrocytes together with basic fibroblast growth factor-laden particles and an exterior fibrin sealant. Scaffolds were then implanted autogenously and evaluated at 5 and 20 weeks.

RESULTS

Biomechanical strength was optimal for polyglycolic acid fiber diameters of 0.8 to 3.0 μm. Optimal cell maintenance and neocartilage response were seen with polyglycolic acid fiber diameters in the same mid-range for nanofiber constructs.

CONCLUSION

These findings demonstrate the potential for nanoscale modulation of auricle-shaped cartilage regeneration in a large-animal model.

Similar in vitro effects and pulp regeneration in ectopic tooth transplantation by basic fibroblast growth factor and granulocyte-colony stimulating factor

OBJECTIVES

Granulocyte-colony stimulating factor (G-CSF) has been shown to have combinatorial trophic effects with dental pulp stem cells for pulp regeneration. The aim of this investigation is to examine the effects of basic fibroblast growth factor (bFGF) in vitro and in vivo compared with those of G-CSF and to assess the potential utility of bFGF as an alternative to G-CSF for pulp regeneration.

MATERIALS AND METHODS

Five different types of cells were examined in the in vitro effects of bFGF on cell migration, proliferation, anti-apoptosis, neurite outgrowth, angiogenesis, and odontogenesis compared with those of G-CSF. The in vivo regenerative potential of pulp tissue including vasculogenesis and odontoblastic differentiation was also compared using an ectopic tooth transplantation model.

RESULTS

Basic fibroblast growth factor was similar to G-CSF in high migration, proliferation and anti-apoptotic effects and angiogenic and neurite outgrowth stimulatory activities in vitro. There was no significant difference between bFGF and G-CSF in the regenerative potential in vivo.

CONCLUSIONS

The potential utility of bFGF for pulp regeneration is demonstrated as a homing/migration factor similar to the influence of G-CSF.

Successful creation of tissue-engineered autologous auricular cartilage in an immunocompetent large animal model

Tissue-engineered cartilage has historically been an attractive alternative treatment option for auricular reconstruction. However, the ability to reliably generate autologous auricular neocartilage in an immunocompetent preclinical model should first be established. The objectives of this study were to demonstrate engineered autologous auricular cartilage in the immunologically aggressive subcutaneous environment of an immunocompetent animal model, and to determine the impact of in vitro culture duration of chondrocyte-seeded constructs on the quality of neocartilage maturation in vivo. Auricular cartilage was harvested from eight adult sheep; chondrocytes were isolated, expanded in vitro, and seeded onto fibrous collagen scaffolds. Constructs were cultured in vitro for 2, 6, and 12 weeks, and then implanted autologously in sheep and in control nude mice for 6 and 12 weeks. Explanted tissue was stained with hematoxylin and eosin, safranin O, toluidine blue, collagen type II, and elastin. DNA and glycosaminoglycans (GAGs) were quantified. The quality of cartilage engineered in sheep decreased with prolonged in vitro culture time. Superior cartilage formation was demonstrated after 2 weeks of in vitro culture; the neocartilage quality improved with increased implantation time. In nude mice, neocartilage resembled native sheep auricular cartilage regardless of the in vitro culture length, with the exception of elastin expression. The DNA quantification was similar in all engineered and native cartilage (p>0.1). All cartilage engineered in sheep had significantly less GAG than native cartilage (p<0.02); significantly more GAG was observed with increased implantation time (p<0.02). In mice, the GAG content was similar to that of native cartilage and became significantly higher with increased in vitro or in vivo durations (p<0.02). Autologous auricular cartilage was successfully engineered in the subcutaneous environment of an ovine model using expanded chondrocytes seeded on a fibrous collagen scaffold after a 2-week in vitro culture period.

Usefulness of polyglycolic acid-polypropylene composite scaffolds for three-dimensional cartilage regeneration in a large-animal autograft model

BACKGROUND

Approaches to auricular reconstruction have shown improved outcome when a basic fibroblast growth factor (bFGF) slow-release system and fibrin spraying are combined with biodegradable polymers. More complex, three-dimensional structures, such as those that replicate the human auricle, are often lost because of biodegradation of the synthetic scaffold.

METHODS

To improve the mechanical strength of regenerated cartilage, the authors grafted canine autologous chondrocytes after seeding onto scaffolds made of a complex of polyglycolic acid and polypropylene, incorporating a slow-release bFGF system with a fibrin spray coating.

RESULTS

Five weeks after grafting, thicker cartilage with increased bending stress was obtained with the slow-release bFGF. In a three-polyglycolic acid-layer construct sandwiched around polypropylene, simulating a three-dimensional auricular structure, greater cartilage regeneration and angiogenesis were found around the implant. Sox5-positive cells were identified, indicative of maturation of neocartilage with chondroblast proliferation.

CONCLUSION

These results support the usefulness of combining absorbable and nonabsorbable materials (polyglycolic acid and polypropylene) in composite scaffolds for autologous cartilage regeneration in a large-animal autograft model.