Synergistic Effects of FGF-2 with Insulin or IGF-I on the Proliferation of Human Auricular Chondrocytes

Synergistic effect of FGF-2 and TGF-β1 on the mineralization of human umbilical cord perivascular cells

OBJECTIVE

Human umbilical cord perivascular cells (HUCPVCs) are derived from the human umbilical cord perivascular tissue and are expected to replace mesenchymal stromal cells in the future. We investigated the synergistic effects of fibroblast growth factor 2 (FGF-2) and transforming growth factor-beta 1 (TGF-β1) on HUCPVC mineralization.

DESIGN

We prepared HUCPVCs with (FGF(+)HUCPVCs) or without FGF-2 (FGF(-)HUCPVCs) in the presence of activated vitamin D3, a bone morphogenic protein inhibitor, and TGF-β1. We examined the cell proliferative capacity, expression of various hard tissue-forming cell gene markers, and mineralization induction ability and identified the crystalline phases of the mineralized nodules.

RESULTS

FGF(+)HUCPVCs exhibited higher intracellular alkaline phosphatase (ALP) gene expression and ALP activity, and their cell proliferation rate was higher than that of FGF(-)HUCPVCs. The expression levels of osteoblast marker genes increased in FGF(+)HUCPVCs, whereas those of elastic fiber and muscle cell markers increased in FGF(-)HUCPVCs. The expression of genes related to matrix vesicle-mediated mineralization was increased in FGF(+)HUCPVCs. While FGF(-)HUCPVCs displayed myofibroblast-like properties and could not induce mineralization, FGF(+)HUCPVCs demonstrated the ability to produce mineralized nodules. The resulting mineralized nodules consisted of hydroxyapatite as the major phase and minor amounts of octacalcium phosphate. The mineralized nodules exhibited the morphological characteristics of bone hydroxyapatite, composed of fibrous hydroxyapatite nanorods and polycrystalline sheets.

CONCLUSION

We found that FGF-2 synergizes with TGF-β1 and is a key factor in the differentiation of HUCPVCs into osteoblast-like cells. Thus, HUCPVCs can potentially serve as a new stem cell source for future bone regeneration and dental treatments.

Strategies to Convert Cells into Hyaline Cartilage: Magic Spells for Adult Stem Cells

Damaged hyaline cartilage gradually decreases joint function and growing pain significantly reduces the quality of a patient’s life. The clinically approved procedure of autologous chondrocyte implantation (ACI) for treating knee cartilage lesions has several limits, including the absence of healthy articular cartilage tissues for cell isolation and difficulties related to the chondrocyte expansion in vitro. Today, various ACI modifications are being developed using autologous chondrocytes from alternative sources, such as the auricles, nose and ribs. Adult stem cells from different tissues are also of great interest due to their less traumatic material extraction and their innate abilities of active proliferation and chondrogenic differentiation. According to the different adult stem cell types and their origin, various strategies have been proposed for stem cell expansion and initiation of their chondrogenic differentiation. The current review presents the diversity in developing applied techniques based on autologous adult stem cell differentiation to hyaline cartilage tissue and targeted to articular cartilage damage therapy.

Cartilage Regeneration Characteristics of Human and Goat Auricular Chondrocytes

Although cartilage regeneration technology has achieved clinical breakthroughs, whether auricular chondrocytes (AUCs) represent optimal seed cells to achieve stable cartilage regeneration is not clear. In this study, we systematically explore biological behaviors of human- and goat-derived AUCs during in vitro expansion as well as cartilage regeneration in vitro and in vivo. To eliminate material interference, a cell sheet model was used to evaluate the feasibility of dedifferentiated AUCs to re-differentiate and regenerate cartilage in vitro and in vivo. We found that the dedifferentiated AUCs could re-differentiate and regenerate cartilage sheets under the chondrogenic medium system, and the generated chondrocyte sheets gradually matured with increased in vitro culture time (2, 4, and 8 weeks). After the implantation of cartilage sheets with different in vitro culture times in nude mice, optimal neocartilage was formed in the group with 2 weeks in vitro cultivation. After in vivo implantation, ossification only occurred in the group with goat-regenerated cartilage sheet of 8 weeks in vitro cultivation. These results, which were confirmed in human and goat AUCs, suggest that AUCs are ideal seed cells for the clinical translation of cartilage regeneration under the appropriate culture system and culture condition.

Bioinformatics analysis of candidate genes involved in ethanol-induced microtia pathogenesis based on a human genome database: GeneCards

OBJECTIVE

Ethanol used by women during pregnancy increases the risk for microtia in the foetus. Traditionally, laboratory experiments and Mouse Genome Informatics (MGI) have been used to explore microtia pathogenesis. The aim of this study was to screen and verify hub genes involved in ethanol-induced microtia and to explore the potential molecular mechanisms.

METHODS

Overlapping genes related to ethanol and microtia were acquired from the GeneCards database and filtered by confidence score. These genes were further analysed via bioinformatics. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis results were visualized with the clusterProfiler R package. A protein-protein interaction (PPI) network was constructed based on data from the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database.

RESULTS

Overall, 41 genes related to both ethanol and microtia were identified. The genes most relevant to ethanol-induced microtia pathogenesis included FGFR-2, FGFR-3, FGF-8, TP53, IGF1, SHH, CTNNB1, and PAX6, among others. Most genes were strongly enriched for tissue and organ development in GO analysis. Additionally, many genes were enriched in the Ras, FoxO, MAPK, and PI3K-Akt signalling pathways in KEGG analysis.

CONCLUSIONS

Bioinformatics analysis was conducted on genes currently known to be related to ethanol-induced microtia pathogenesis. We propose that mechanisms involving FGF-family genes, TP53, IGF1 and SHH contribute significantly to ethanol-induced microtia and the accompanying malformation of other structures.

Controlling the Phenotype of Macrophages Promotes Maturation of Tissue-Engineered Cartilage

Tissue reactions after transplantation can affect the maturation and prognosis of the transplanted engineered tissue in regenerative medicine. Since macrophages are broadly subdivided into two major phenotypes, inflammatory (M1) and anti-inflammatory/wound healing (M2), in this study, we examined the properties of macrophages in transplantation of tissue-engineered cartilage, to clarify their effects on cartilage maturation. Human chondrocytes were embedded in a poly-L-lactic acid scaffold, which was transplanted subcutaneously on the back in athymic mice. When the constructs were analyzed by real-time polymerase chain reaction, interleukin 1 expression was detectable at 4 days, and it reached a peak at 7 days. Interleukin 6 expression was increased at 7 to 11 days, suggesting that M1 macrophages were abundant around this time. On the other hand, expression of markers for M2 macrophages occurred rather later, with Fizz and Ym1 expression peaking at around 11 to 14 days, possibly indicating that polarization of macrophages in tissue-engineered cartilage could shift from M1 to M2 around 11 days after transplantation. When cultured by using the conditioned medium of M2 macrophages, chondrocytes showed significantly increased expression of type 2 collagen, suggesting that M2 macrophages could enhance the maturation of tissue-engineered cartilage. Also, by partially depleting macrophages with clodronate liposomes in the initial period, during which M1 macrophages were dominant, more cartilage matrix accumulated in transplanted constructs at 2 weeks. It was suggested that polarization of macrophages shifted from M1 to M2 in the transplantation of tissue-engineered cartilage, and controlling the polarization could be advantageous for the maturation of transplanted engineered tissues. Impact statement In transplantation of engineered tissues, it is imperative for immune reactions to proceed in a proper and timely manner. In this study, we transplanted tissue-engineered cartilage consisting of a biodegradable polymer scaffold and chondrocytes, and examined the properties of macrophages. It was shown that the polarization of macrophages shifted from inflammatory (M1) to anti-inflammatory/wound healing (M2) around 11 days after transplantation. Partial suppression of macrophages at the early stage of transplantation, which were mainly M1 macrophages, promoted more accumulation of cartilage matrix. This study indicates a possible approach to facilitate cartilage maturation by intervening in the polarity of macrophages.

Glial Fibrillary Acidic Protein as Biomarker Indicates Purity and Property of Auricular Chondrocytes

Instead of the silicone implants previously used for repair and reconstruction of the auricle and nose lost due to accidents and disease, a new treatment method using tissue-engineered cartilage has been attracting attention. The quality of cultured cells is important in this method because it affects treatment outcomes. However, a marker of chondrocytes, particularly auricular chondrocytes, has not yet been established. The objective of this study was to establish an optimal marker to evaluate the quality of cultured auricular chondrocytes as a cell source of regenerative cartilage tissue. Gene expression levels were comprehensively compared using the microarray method between human undifferentiated and dedifferentiated auricular chondrocytes to investigate a candidate quality control index with an expression level that is high in differentiated cells, but markedly decreases in dedifferentiated cells. We identified glial fibrillary acidic protein (GFAP) as a marker that decreased with serial passages in auricular chondrocytes. GFAP was not detected in articular chondrocytes, costal chondrocytes, or fibroblasts, which need to be distinguished from auricular chondrocytes in cell cultures. GFAP mRNA expression was observed in cultured auricular chondrocytes, and GFAP protein levels were also measured in the cell lysates and culture supernatants of these cells. However, GFAP levels detected from mRNA and protein in cell lysates were significantly decreased by increases in the incubation period. In contrast, the amount of protein in the cell supernatant was not affected by the incubation period. Furthermore, the protein level of GFAP in the supernatants of cultured cells correlated with the in vitro and in vivo production of the cartilage matrix by these cells. The productivity of the cartilage matrix in cultured auricular chondrocytes may be predicted by measuring GFAP protein levels in the culture supernatants of these cells. Thus, GFAP is regarded as a marker of the purity and properties of cultured auricular chondrocytes.

Influence of Damage-Associated Molecular Patterns from Chondrocytes in Tissue-Engineered Cartilage

To obtain stable outcomes in regenerative medicine, the quality of cells for transplantation is of great importance. Cellular stress potentially results in the release of damage-associated molecular patterns (DAMPs) and activates immunological responses, affecting the outcome of transplanted tissue. In this study, we intentionally prepared necrotic chondrocytes that would gradually die and release DAMPs and investigated how the maturation of tissue-engineered cartilage was affected. Necrotic chondrocytes were prepared by a conventional heat-treatment method, by which their viability started to decrease after 24 h. When tissue-engineered cartilage containing necrotic chondrocytes was subcutaneously transplanted into C57BL/6J mice, accumulation of cartilage matrix was decreased compared to the control. Meanwhile, immunohistochemical staining demonstrated that localization of macrophages and neutrophils was more apparent in the constructs of necrotic chondrocytes, suggesting that DAMPs from necrotic chondrocytes could prompt migration of more immune cells. Two-dimensional electrophoresis and mass spectrometry identified prelamin as a significant biomolecule released from necrotic chondrocytes. Also, when prelamin was added to a culture of RAW264, Inos and Il1b were increased in accordance with the content of added prelamin. It was suggested that DAMPs from dying chondrocytes could induce inflammatory properties in surrounding macrophages, impairing the maturation of tissue-engineered cartilage. In conclusion, maturation of tissue-engineered cartilage was hampered when less viable chondrocytes releasing DAMPs were included. Impact statement In regenerative medicine, the quality of cells is of great importance to secure clinical safety. During culture, damage of cells could occur, if not critical enough to cause immediate cell death, but still inducing a less viable status. Damage-associated molecular patterns (DAMPs) are released from necrotic cells, but their influence in regenerative medicine has yet to be clarified. In this study, we elucidated how DAMPs from chondrocytes could affect the maturation of tissue-engineered cartilage. Also, possible DAMPs from necrotic chondrocytes were comprehensively analyzed, and prelamin was identified as a significant molecule, which may serve for detecting the existence of necrotic chondrocytes.

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.

Implant-type tissue-engineered cartilage derived from human auricular chondrocyte may maintain cartilaginous property even under osteoinductive condition

INTRODUCTION

There is a growing need for chondrocyte implantation for reconstructing cartilage defect. However, ossification of the implanted cartilage is a challenging problem. Implant-type tissue-engineered cartilage from human auricular chondrocytes is a three-dimensional implant type cartilage using PLLA as a scaffold for chondrocytes. Although there is a study which evaluated the ossification of this cartilage in subcutaneous area, there is no study which clarify the possibility of ossification in osteoinductive surroundings. The purpose of this study was to elucidate the possibility of the ossification of implant-type tissue-engineered cartilage using human auricular chondrocyte in an osteoinductive environment.

METHODS

Human chondrocytes were harvested from ear cartilage. After dispersion by enzyme digestion, they were put into either a poly-L-lactic acid (PLLA) or poly lactic-co-glycolic acid (PLGA) scaffold, with collagen gel. Implant-type tissue-engineered cartilage was interposed between pieces of human iliac bone harvested from the same donor and implanted subcutaneously in nude rats. Scaffold without chondrocytes was used as a control. After 1, 3, and 6 months, ossification and cartilage formation were evaluated by X-ray, hematoxylin-eosin (HE) stain and toluidine blue (TB) stain.

RESULTS

There was no ossification of implant-type cartilage using human chondrocytes, even under osteoinductive conditions. HE staining showed that perichondrium formed around the constructs and chondrocytes were observed 6months after the implantation. TB staining showed metachromasia in every sample, with the area of metachromasia increasing over time, suggesting maturation of the cartilage.

CONCLUSIONS

In conclusion, adjacent iliac bone had no apparent effect on the maturation of cartilage in implant-type tissue-engineered cartilage. Cartilage retention and maturation even in the presence of iliac bone could have been due to a scarcity of mesenchymal stem cells in the bone and surrounding area.

Three-dimensional changes of noses after transplantation of implant-type tissue-engineered cartilage for secondary correction of cleft lip-nose patients

INTRODUCTION

We have developed an implant-type tissue-engineered cartilage using a poly-l-lactide scaffold. In a clinical study, it was inserted into subcutaneous areas of nasal dorsum in three patients, to correct cleft lip-nose deformity. The aim of this study was to helping evaluation on the efficacy of the regenerative cartilage.

METHODS

3D data of nasal shapes were compared between before and after surgery in computed tomography (CT) images. Morphological and qualitative changes of transplants in the body were also evaluated on MRI, for one year.

RESULTS

The 3D data from CT images showed effective augmentation (>2 mm) of nasal dorsum in almost whole length, observed on the medial line of faces. It was maintained by 1 year post-surgery in all patients, while affected curves of nasal dorsum was not detected throughout the observation period. In magnetic resonance imaging (MRI), the images of transplanted cartilage had been observed until 1 year post-surgery. Those images were seemingly not straight when viewed from the longitudinal plain, and may have shown gentle adaptation to the surrounding nasal bones and alar cartilage tissues.

CONCLUSION

Those findings suggested the potential efficacy of this cartilage on improvement of cleft lip-nose deformity. A clinical trial is now being performed for industrialization.

The effect of temporal manipulation of transforming growth factor beta 3 and fibroblast growth factor 2 on the derivation of proliferative chondrocytes from mensenchymal stem cells-A study monitored by quantitative reverse transcription polymerase chain reaction and molecular beacon based nanosensors

Proliferative chondrocytes are critical to realize regeneration of damaged epiphyseal growth plate. However, acquiring autologous replacement cells involves highly invasive procedures and often results in limited cell quantity. Mesenchymal stem cells (MSCs) are a potential source of chondrogenic cells for the treatment of cartilage disorders and injuries. The temporal effect of transforming growth factor beta 3 (TGFβ3) and fibroblast growth factor 2 (FGF2) on the derivation of proliferative chondrocytes from MSCs in three-dimensional agarose was investigated by manipulating the duration of TGFβ3 and FGF2 treatment. The differentiation process was monitored by quantitative reverse transcription polymerase chain reaction (qRT-PCR) as well as nanosensors containing two molecular beacons that target critical biomarkers for proliferative chondrocytes (i.e., collagen type-II messenger ribonucleic acid [mRNA] and Ki67 mRNA). The molecular beacon-based nanosensors were found to be comparable to qRT-PCR in measuring mRNA expression and thus providing a noninvasive mean to screen and monitor culture samples. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 895-904, 2018.

Effects of insulin-like growth factor 1 and basic fibroblast growth factor on the morphology and proliferation of chondrocytes embedded in Matrigel in a microfluidic platform

An integrated microfluidic device was utilized in the present study to investigate the morphology and proliferation of rabbit articular chondrocytes embedded in Matrigel in the presence of insulin-like growth factor 1 (IGF-1) and/or basic fibroblast growth factor (bFGF). The microfluidic device was composed of two parallel channels and a central perfusion-based three-dimensional cell culture module. The rabbit chondrocytes were cultured for 2 weeks at series of concentration gradients of IGF-1 and/or bFGF, which were generated through a diffusion process. At the end of the experiment, the morphology and quantity of cells were measured. Since high expression of collagen II is essential to the function of hyaline cartilage, immunofluorescent images of collagen II expression prior to and after the experiments were gathered for each group. The mean fluorescence intensity ratio (MIR) of collagen II in each group was calculated. The MIRs of collagen II in chondrocytes treated with IGF-1 ranged from 0.6-0.81, those in the cells treated with bFGF ranged from 0.47-0.52, and those in cells treated with a combination of IGF-1 and bFGF ranged from 0.63-0.83. Chondrocyte aggregations were observed in the group treated with 75-100 ng/ml IGF-1 (3.46-fold proliferation ratio). Similarly, a 3.83-fold proliferation ratio was identified in chondrocytes treated with 2.5-5.0 ng/ml bFGF. The group treated with 50-75 ng/ml IGF-1 and 2.5-5.0 ng/ml bFGF exhibited the optimum increase in proliferation (4.83-fold proliferation ratio). The microfluidic device used in the present study can be easily adapted to investigate other growth factors at any concentration gradient. In addition, parallel experiments can be performed simultaneously with a small quantity of cells, making it an attractive platform for the high-throughput screening of cell culture parameters. This platform will aid in the optimization of culture conditions for the in vitro expansion of chondrocytes while maintaining their in vivo morphology, which will improve autologous chondrocyte implantation capabilities for the treatment of cartilage injury.

Roles of macrophage migration inhibitory factor in cartilage tissue engineering

To obtain stable outcomes in regenerative medicine, understanding and controlling immunological responses in transplanted tissues are of great importance. In our previous study, auricular chondrocytes in tissue-engineered cartilage transplanted in mice were shown to express immunological factors, including macrophage migration inhibitory factor (MIF). Since MIF exerts pleiotropic functions, in this study, we examined the roles of MIF in cartilage regenerative medicine. We made tissue-engineered cartilage consisting of auricular chondrocytes of C57BL/6J mouse, atellocollagen gel and a PLLA scaffold, and transplanted the construct subcutaneously in a syngeneic manner. Localization of MIF was prominent in cartilage areas of tissue-engineered cartilage at 2 weeks after transplantation, though it became less apparent by 8 weeks. Co-culture with RAW264 significantly increased the expression of MIF in chondrocytes, suggesting that the transplanted chondrocytes in tissue-engineered cartilage could enhance the expression of MIF by stimulation of surrounding macrophages. When MIF was added in the culture of chondrocytes, the expression of type II collagen was increased, indicating that MIF could promote the maturation of chondrocytes. Meanwhile, toluidine blue staining of constructs containing wild type (Mif+/+) chondrocytes showed increased metachromasia compared to MIF-knockout (Mif-/-) constructs at 2 weeks. However, this tendency was reversed by 8 weeks, suggesting that the initial increase in cartilage maturation in Mif+/+ constructs deteriorated by 8 weeks. Since the Mif+/+ constructs included more iNOS-positive inflammatory macrophages at 2 weeks, MIF might induce an M1 macrophage-polarized environment, which may eventually worsen the maturation of tissue-engineered cartilage in the long term.

The effect of local delivery of adiponectin from biodegradable microsphere-scaffold composites on new bone formation in adiponectin knockout mice

Adiponectin (APN) is the most abundant adipocyte-secreted adipokine; it regulates energy homeostasis and exerts well-characterized insulin-sensitizing properties. Previous studies have verified that globular adiponectin (gAPN) is also involved in bone metabolism, although observations have been controversial. The purpose of the current study is to use an APN-knockout (APN-KO) mouse model to evaluate the local delivery of gAPN to new bone formation. Using chitosan microspheres (CMs), we found that following an initial burst at 1 week, the release behavior of gAPN from the scaffold was sustained in a linear manner for the first 4 weeks, followed by a slower, more stable release from week 5 onwards. Interestingly, PLGA/β-TCP/CM-loaded gAPN scaffolds implanted in APN-KO mice increased bone formation and mineralization, and enhanced osteogenic marker expression 28 days post-implantation. gAPN also promoted preosteoblast (MC3T3-E1) cellular proliferation in vitro. In MC3T3-E1 cells, adaptor protein-containing pleckstrin homology domain, phosphotyrosine domain, leucine zipper motif (APPL1) and phosphoinositide 3-kinase (PI3K) expression was upregulated in a time-dependent manner upon gAPN treatment, while APPL1 small interfering RNA (siRNA) pre-treatment reversed this enhanced expression. In conclusion, modified bone graft substitutes loaded with gAPN increase bone formation and mineralization in part by promoting osteoblast proliferation via the APPL1/PI3K pathway.

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.

Conjugated polyelectrolyte materials for promoting progenitor cell growth without serum

The discovery of new active biomaterials for promoting progenitor cell growth and differentiation in serum-free medium is still proving more challenging for the clinical treatments of degenerative diseases. In this work, a conjugated polyelectrolyte, polythiophene derivative (PMNT), was discovered to significantly drive the cell cycle progression from G₁ to S and G₂ phases and thus efficiently promote the cell growth without the need of serum. Furthermore, the fluorescent characteristic of PMNT makes it simultaneously able to trace its cellular uptake and localization by cell imaging. cDNA microarray study shows that PMNT can greatly regulate genes related to cell growth or differentiation. To the best of our knowledge, this is the first example of cell growth or differentiation promotion by polyelectrolyte material without the need of serum, thereby providing an important demonstration of degenerative biomaterial discovery through polymer design.

Tailoring adipose stem cell trophic factor production with differentiation medium components to regenerate chondral defects

Recent endeavors to use stem cells as trophic factor production sources have the potential to translate into viable therapies for damaged or diseased musculoskeletal tissues. Adipose stem cells (ASCs) can be differentiated into chondrocytes using the chondrogenic medium (CM), but it is unknown if this approach can optimize ASC growth factor secretion for cartilage regeneration by increasing the chondrogenic factor production, while decreasing angiogenic and hypertrophic factor production. The objective of this study was to determine the effects the CM and its components have on growth factor production from ASCs to promote cartilage regeneration. ASCs isolated from male Sprague-Dawley rats and cultured in monolayer or alginate microbeads were treated with either the growth medium (GM) or the CM for 5 days. In subsequent studies, ASC monolayers were treated with either the GM supplemented with different combinations of 50 μg/mL ascorbic acid-2-phosphate (AA2P), 100 nM dexamethasone (Dex), 10 ng/mL transforming growth factor (TGF)-β1, and 100 ng/mL bone morphogenetic protein (BMP)-6 or with the CM excluding different combinations of AA2P, Dex, TGF-β1, and BMP-6. mRNA levels and growth factor production were quantified at 8 and 24 h after the last media change, respectively. The CM increased chondrogenic factor secretion (TGF-β2, TGF-β3, and insulin-like growth factor [IGF]-I) and decreased angiogenic factor production (the vascular endothelial growth factor [VEGF]-A, the fibroblast growth factor [FGF]-2). Microencapsulation in the GM increased production of the chondrogenic (IGF-I, TGF-β2) and angiogenic (VEGF-A) factors. AA2P increased secretion of chondrogenic factors (IGF-I, TGF-β2), and decreased angiogenic factor (VEGF-A) secretion, in addition to decreasing mRNA levels for factors associated with chondrocyte hypertrophy (FGF-18). Dex increased mRNA levels for hypertrophic factors (BMP-2, FGF-18) and decreased angiogenic factor secretion (VEGF-A). TGF-β1 increased angiogenic factor production (FGF-2, VEGF-A) and decreased chondrogenic factor mRNA levels (IGF-I, PTHrP). BMP-6 increased hypertrophic mRNA levels (FGF-18) and chondrogenic factor production (TGF-β2). When ASC microbeads preconditioned with the CM were implanted in a focal cartilage defect and immobilized within an RGD-conjugated hydrogel, tissue infiltration from the edges of the defect and perichondrium was observed. These results show that differentiation media components have distinct effects on ASC's production of angiogenic, chondrogenic, and hypertrophic factors and that AA2P may be the most beneficial CM component for preconditioning ASCs to stimulate cartilage regeneration.

In vitro and in vivo evaluation of zinc-modified ca-si-based ceramic coating for bone implants

The host response to calcium silicate ceramic coatings is not always favorable because of their high dissolution rates, leading to high pH within the surrounding physiological environment. Recently, a zinc-incorporated calcium silicate-based ceramic Ca2ZnSi2O7 coating, developed on a Ti-6Al-4V substrate using plasma-spray technology, was found to exhibit improved chemical stability and biocompatibility. This study aimed to investigate and compare the in vitro response of osteoblastic MC3T3-E1 cells cultured on Ca2ZnSi2O7 coating, CaSiO3 coating, and uncoated Ti-6Al-4V titanium control at cellular and molecular level. Our results showed Ca2ZnSi2O7 coating enhanced MC3T3-E1 cell attachment, proliferation, and differentiation compared to CaSiO3 coating and control. In addition, Ca2ZnSi2O7 coating increased mRNA levels of osteoblast-related genes (alkaline phosphatase, procollagen α1(I), osteocalcin), insulin-like growth factor-I (IGF-I), and transforming growth factor-β1 (TGF-β1). The in vivo osteoconductive properties of Ca2ZnSi2O7 coating, compared to CaSiO3 coating and control, was investigated using a rabbit femur defect model. Histological and histomorphometrical analysis demonstrated new bone formation in direct contact with the Ca2ZnSi2O7 coating surface in absence of fibrous tissue and higher bone-implant contact rate (BIC) in the Ca2ZnSi2O7 coating group, indicating better biocompatibility and faster osseointegration than CaSiO3 coated and control implants. These results indicate Ca2ZnSi2O7 coated implants have applications in bone tissue regeneration, since they are biocompatible and able to osseointegrate with host bone.

Application of floating cells for improved harvest in human chondrocyte culture

Cell culture medium, which must be discarded during medium change, may contain many cells that do not attach to culture plates. In the present study, we focused on these floating cells and attempted to determine their usefulness for cartilage regeneration. We counted the number of floating cells discarded during medium change and compared the proliferation and differentiation between floating cells and their adherent counterparts. Chondrocyte monolayer culture at a density of 5 × 103 cells/cm(2) produced viable floating cells at a rate of 2.7-3.2 × 10(3) cells/cm(2) per primary culture. When only the floating cells from one dish were harvested and replated in another dish, the number of cells was 2.8 × 10(4) cells/cm(2) (approximately half confluency) on culture day 7. The number of cells was half of that obtained by culturing only adherent cells (5 × 10(4) cells/cm(2)). The floating and adherent cells showed similar proliferation and differentiation properties. The recovery of floating cells from the culture medium could provide an approximately 1.5-fold increase in cell number over conventional monolayer culture. Thus, the collection of floating cells may be regarded as a simple, easy, and reliable method to increase the cell harvest for chondrocytes.

Early Stage Foreign Body Reaction against Biodegradable Polymer Scaffolds Affects Tissue Regeneration during the Autologous Transplantation of Tissue-Engineered Cartilage in the Canine Model

To overcome the weak points of the present cartilage regenerative medicine, we applied a porous scaffold for the production of tissue-engineered cartilage with a greater firmness and a 3D structure. We combined the porous scaffolds with atelocollagen to retain the cells within the porous body. We conducted canine autologous chondrocyte transplants using biodegradable poly-l-lactic acid (PLLA) or poly-dl-lactic- co-glycolic acid (PLGA) polymer scaffolds, and morphologically and biochemically evaluated the time course changes of the transplants. The histological findings showed that the tissue-engineered constructs using PLLA contained abundant cartilage 1, 2, and 6 months after transplantation. However, the PLGA constructs did not possess cartilage and could not maintain their shapes. Biochemical measurement of the proteoglycan and type II collagen also supported the superiority of PLLA. The biodegradation of PLGA progressed much faster than that of PLLA, and the PLGA had almost disappeared by 2 months. The degraded products of PLGA may evoke a more severe tissue reaction at this early stage of transplantation than PLLA. The PLLA scaffolds were suitable for cartilage tissue engineering under immunocompetent conditions, because of the retarded degradation properties and the decrease in the severe tissue reactions during the early stage of transplantation.

Cartilage-characteristic matrix reconstruction by sequential addition of soluble factors during expansion of human articular chondrocytes and their cultivation in collagen sponges

OBJECTIVE

Articular cartilage has a poor capacity for spontaneous repair. Tissue engineering approaches using biomaterials and chondrocytes offer hope for treatments. Our goal was to test whether collagen sponges could be used as scaffolds for reconstruction of cartilage with human articular chondrocytes. We investigated the effects on the nature and abundance of cartilage matrix produced of sequential addition of chosen soluble factors during cell amplification on plastic and cultivation in collagen scaffolds.

DESIGN

Isolated human articular chondrocytes were amplified for two passages with or without a cocktail of fibroblast growth factor (FGF)-2 and insulin (FI). The cells were then cultured in collagen sponges with or without a cocktail of bone morphogenetic protein (BMP)-2, insulin, and triiodothyronine (BIT). The constructs were cultivated for 36 days in vitro or for another 6-week period in a nude mouse-based contained-defect organ culture model. Gene expression was analyzed using polymerase chain reaction, and protein production was analyzed using Western-blotting and immunohistochemistry.

RESULTS

Dedifferentiation of chondrocytes occurred during cell expansion on plastic, and FI stimulated this dedifferentiation. We found that addition of BIT could trigger chondrocyte redifferentiation and cartilage-characteristic matrix production in the collagen sponges. The presence of FI during cell expansion increased the chondrocyte responsiveness to BIT.

The development of a serum-free medium utilizing the interaction between growth factors and biomaterials

To promote clinical application of cartilage tissue engineering, we should establish a serum-free chondrocyte growth medium. The serum-free medium would increase the cell numbers by more than 20-fold within one week, which proliferation ability almost matches that of serum-based one. For that, we examined the combinations of growth factors and the methods to enhance their effects by making use of the interaction with biomaterials. From various growth factors that are contained within the serum, we made the cocktail of FGF-2 (100 ng/mL), insulin (5 μg/mL), EGF (10 pg/mL), PDGF (625 pg/mL) and TGF-β (5 pg/mL), which increased the chondrocyte numbers by approximately 3-fold for 7 days. Moreover, we used the biomaterials including albumin and hyaluronan as the carrier of those factors. By direct mixing of those factors with biomaterials before the administration to the medium, the medium containing those mixture showed the chondrocyte growth of approximately a 25-fold increase by day 10. In this medium, the FGF-2 or insulin concentration hardly decreased, and rather enhanced the activation of ERK. Due to the optimal usage of biomaterials, this serum-free medium will realize a constant harvest of chondrocytes and could contribute to the safety and quality in regenerative medicine.

Tissue responses against tissue-engineered cartilage consisting of chondrocytes encapsulated within non-absorbable hydrogel

To disclose the influence of foreign body responses raised against a non-absorbable hydrogel consisting of tissue-engineered cartilage, we embedded human/canine chondrocytes within agarose and transplanted them into subcutaneous pockets in nude mice and donor beagles. One month after transplantation, cartilage formation was observed in the experiments using human chondrocytes in nude mice. No significant invasion of blood cells was noted in the areas where the cartilage was newly formed. Around the tissue-engineered cartilage, agarose fragments, a dense fibrous connective tissue and many macrophages were observed. On the other hand, no cartilage tissue was detected in the autologous transplantation of canine chondrocytes. Few surviving chondrocytes were observed in the agarose and no accumulation of blood cells was observed in the inner parts of the transplants. Localizations of IgG and complements were noted in areas of agarose, and also in the devitalized cells embedded within the agarose. Even if we had inhibited the proximity of the blood cells to the transplanted cells, the survival of the cells could not be secured. We suggest that these cytotoxic mechanisms seem to be associated not only with macrophages but also with soluble factors, including antibodies and complements.

Differences in cartilage-forming capacity of expanded human chondrocytes from ear and nose and their gene expression profiles

The aim of this study was to evaluate the potential of culture-expanded human auricular and nasoseptal chondrocytes as cell source for regeneration of stable cartilage and to analyze the differences in gene expression profile of expanded chondrocytes from these specific locations. Auricular chondrocytes in monolayer proliferated less and more slowly (two passages took 26.7 ± 2.1 days and were reached in 4.37 ± 0.30 population doublings) than nasoseptal chondrocytes (19.3 ± 2.5 days; 5.45 ± 0.20 population doublings). However, auricular chondrocytes produced larger pellets with more cartilage-like matrix than nasoseptal chondrocytes (2.2 ± 0.71 vs. 1.7 ± 0.13 mm in diameter after 35 days of culture). Although the matrix formed by auricular and nasoseptal chondrocytes contained collagen X, it did not mineralize in an in vitro model or after in vivo subcutaneous implantation. A DNA microarray study on expanded auricular and nasoseptal chondrocytes from the same donors revealed 1,090 differentially expressed genes. No difference was observed in the expression of known markers of chondrogenic capacity (e.g., collagen II, FGFR3, BMP2, and ALK1). The most striking differences were that the auricular chondrocytes had a higher expression of anabolic growth factors BMP5 and IGF1, while matrix-degrading enzymes MMP13 and ADAMTS5 were higher expressed in nasoseptal chondrocytes. This might offer a possible explanation for the observed higher matrix production by auricular chondrocytes. Moreover, chondrocytes isolated from auricular or nasoseptal cartilage had specific gene expression profiles even after expansion. These differently expressed genes were not restricted to known characterization of donor site subtype (e.g., elastic), but were also related to developmental processes.

Utility of NucleoCounter for the chondrocyte count in the collagenase digest of human native cartilage

In cartilage tissue engineering, viable cell numbers should be correctly counted in the collagenase digest of the biopsied cartilage. However, this is a difficult task due to the presence of matrix debris, cell ghosts and their aggregates. To search for the correct cell counting method in this situation, we evaluated the utility of an automatic cell counting device, the NucleoCounter, and compared it with conventional staining using the LIVE/DEAD® kit. We first measured the cell numbers of a standard chondrocyte sample by the NucleoCounter, which showed a high accuracy (R(2) = 0.9999) and reproducibility (%CV: 2.00-8.66). We then calculated the cell numbers and viability in some collagenase digests of native cartilage using either the NucleoCounter or LIVE/DEAD® kit, revealing that the total cell numbers, viable ones and viability were highly correlated between them (R(2) = 0.9601, 0.9638 and 0.917, respectively). However, both the intrapersonal and interpersonal variabilities in the NucleoCounter was significantly decreased to about 1/20-1/5, compared to that of the LIVE/DEAD® kit. The NucleoCounter was regarded as a useful tool for simple, rapid, and highly reproducible cell counts, which may not only provide constant experimental data in a certain laboratory, but also contribute to the high reproducibility of the clinical results of cartilage tissue engineering among multiple institutions.

The application of atelocollagen gel in combination with porous scaffolds for cartilage tissue engineering and its suitable conditions

For improving the quality of tissue-engineered cartilage, we examined the in vivo usefulness of porous bodies as scaffolds combined with an atelocollagen hydrogel, and investigated the suitable conditions for atelocollagen and seeding cells within the engineered tissues. We made tissue-engineered constructs using a collagen sponge (CS) or porous poly(L-lactide) (PLLA) with human chondrocytes and 1% hydrogel, the concentration of which maximized the accumulation of cartilage matrices. The CS was soft with a Young's modulus of less than 1 MPa, whereas the porous PLLA was very rigid with a Young's modulus of 10 MPa. Although the constructs with the CS shrank to 50% in size after a 2-month subcutaneous transplantation in nude mice, the PLLA constructs maintained their original sizes. Both of the porous scaffolds contained some cartilage regeneration in the presence of the chondrocytes and hydrogel, but the PLLA counterpart significantly accumulated abundant matrices in vivo. Regarding the conditions of the chondrocytes, the cartilage regeneration was improved in inverse proportion to the passage numbers among passages 3-8, and was linear with the cell densities (10(6) to 10(8) cells/mL). Thus, the rigid porous scaffold can maintain the size of the tissue-engineered cartilage and realize fair cartilage regeneration in vivo when combined with 1% atelocollagen and some conditioned chondrocytes.

Involvement of fibroblast growth factor 18 in dedifferentiation of cultured human chondrocytes

OBJECTIVE

Chondrocytes inevitably decrease production of cartilaginous matrices during long-term cultures with repeated passaging; this is termed dedifferentiation. To learn more concerning prevention of dedifferentiation, we have focused here on the fibroblast growth factor (FGF) family that influences chondrocyte proliferation or differentiation.

MATERIALS AND METHODS

We have compared gene expression between differentiated cells in passage 3 (P3) and dedifferentiated ones in P8 of human cultured chondrocytes. We also performed ligand administration of the responsive factor or its gene silencing, using small interfering RNA (siRNA).

RESULTS

FGFs 1, 5, 10, 13 and 18 were higher at P8 compared to P3, while FGFs 9 and 14 were lower. Especially, FGF18 showed a 10-fold increase by P8. Ligand administration of FGF18 in the P3 cells, or its gene silencing using siRNA in the P8 cells, revealed dose-dependent increase and decrease respectively in type II collagen/type I collagen ratio. Exogenous FGF18 also upregulated expression of transforming growth factor beta (TGF-beta), the anabolic factor of chondrocytes, in P3 chondrocytes, but P8 cells maintained a low level of TGF-beta expression, suggesting a decrease in responsiveness of TGF-beta to FGF18 stimulation in the dedifferentiated chondrocytes.

CONCLUSION

FGF18 seems to play a role in maintenance of chondrocyte properties, although its expression was rather high in dedifferentiated chondrocytes. Upregulation of FGF18 in dedifferentiated chondrocytes implied that it may be a marker of dedifferentiation.

Enhanced meniscal repair by overexpression of hIGF-1 in a full-thickness model

The importance of the menisci to the well-being of the normal knee is well-documented. However, there is no ideal repair or reconstructive approach for damaged menisci. Gene therapy provides one promising alternative strategy, especially when combined with injectable tissue engineering to achieve minimally invasive clinical application. We asked whether the introduction of human insulin-like growth factor 1 (hIGF-1) gene could improve the repair of full-thickness meniscal defects. We created full-thickness meniscal defects in the "white area" of the anterior horn in 48 goats. Bone marrow stromal cells with the transfection of hIGF-1 gene and injectable calcium alginate gel were mixed together to repair the defects; three control groups included cells without transfection, gel without cells, and defects left empty. After 4, 8, and 16 weeks, the animals were euthanized and the excised defects were examined by macroscopic assessment, histological analysis, electron microscopy, proteoglycan determination, and MRI. Sixteen weeks after surgery the repaired meniscal defects were filled with white tissue similar to that in normal meniscal fibrocartilage. The repair tissue was composed of cells embedded within matrix that filled the spaces of the fibers. The proteoglycan content in the gene-enhanced tissue engineering group was higher than those in the control groups, and less than that in the normal meniscus. The results suggest full-thickness meniscal defects in regions without blood supply can be reconstructed with hIGF-1-enhanced injectable tissue engineering.

Treating human meniscal fibrochondrocytes with hIGF-1 gene by liposome

The menisci are intraarticular fibrocartilaginous structures essential to the normal function of the knee that lack the ability to self-repair. Human meniscal fibrochondrocytes may respond to beneficial genes like human insulin growth factor-1 (hIGF-1) and the meniscal cell may be a feasible donor for gene therapy. To explore this possibility, we amplified the hIGF-1 gene sequence in full length and cloned it into a bicistronic plasmid. This gene was then transfected into cultured human meniscal fibrochondrocytes by the liposome FuGene 6. Green fluorescence was expressed in part of the cells 6 hours after transfection and increased gradually, with a peak concentration of the hIGF-1 in the supernatants to 22.68 ng/mL 56 hours after transfection. Phenotypes of some cells changed and the proliferation accelerated after transfection. Flow cytometry analysis demonstrated upregulation of cell numbers in the G2 and S stages after hIGF-1 gene introduction. We conclude the hIGF-1 gene can be transfected into the human meniscal cell efficiently by liposome and it causes accelerated proliferation and differentiation. Within 10 days after transfection, the cytokine appears to be secreted into supernatants with the bioactivity and promotes the proliferation of the NIH 3T3 cell line.

Blocking of tumor necrosis factor activity promotes natural repair of osteochondral defects in rabbit knee

BACKGROUND AND PURPOSE

Osteochondral defects have a limited capacity for repair. We therefore investigated the effects of tumor necrosis factor (TNF) signal blockade by etanercept (human recombinant soluble TNF receptor) on the repair of osteochondral defects in rabbit knees.

MATERIAL AND METHODS

Osteochondral defects (5 mm in diameter) were created in the femoral patellar groove in rabbits. Soon after the procedure, a first subcutaneous injection of etanercept was performed. This single injection or, alternatively, 4 injections in total (twice a week for 2 weeks) were given. Each of these 2 groups was divided further into 3 subgroups: a low-dose group (0.05 microg/kg), an intermediate-dose group (0.4 microg/kg), and a high-dose group (1.6 microg /kg) with 19 rabbits in each. As a control, 19 rabbits were injected with water alone. The rabbits in each subgroup were killed 4 weeks (6 rabbits), 8 weeks (6 rabbits), or 24 weeks (7 rabbits) after surgery and repair was assessed histologically.

RESULTS

Histological examination revealed that the natural process of repair of the osteochondral defects was promoted by 4 subcutaneous injections of intermediate-dose etanercept and by 1 or 4 injections of high-dose etanercept at the various time points examined postoperatively (4, 8, and 24 weeks). Western blot showed that rabbit TNFalpha had a high affinity for etanercept.

INTERPRETATION

Blocking of TNF by etanercept enabled repair of osteochondral defects in rabbit knee. Anti-TNF therapy could be a strategy for the use of tissue engineering for bone and cartilage repair.

A serum free approach towards the conservation of chondrogenic phenotype during in vitro cell expansion

OBJECTIVE

Functionally viable chondrocytes in sufficient quantity is crucial for the success of matrix associated autologous chondrocyte implantation. This is difficult with conventional methods as chondrocytes dedifferentiate during 2D expansion with the loss of their chondrogenic phenotype. Moreover, established protocols are dependent on the use of serum which is not without its drawbacks. This study sought to address the issue by evaluating the feasibility of serum free, growth factors supplemented chondrocyte media with extracellular matrix (ECM) coatings.

DESIGN

Passage 2 human chondrocytes were cultured in serum supplemented media or serum free media with collagen I or fibronectin coatings. Cell attachment and proliferation were assessed in these conditions. The cells were redifferentiated via pellet cultures for 7 and 14 days before being subjected to histological and gene expression analysis.

RESULTS

The serum-free, growth factor cocktail supplemented with ECM coating improved long-term chondrocyte proliferation with enhanced basal Sox 9 expression. Upon induction, the redifferentiated chondrocytes expressed aggrecan and collagen II especially so for the cells plated on collagen coated surfaces. The chondrocytic phenotype was better conserved under the serum free conditions but the loss of the hyaline cartilage characteristics was not completely halted given the expression of collagen I. These essential cartilage markers were, however, reduced or absented for cells expanded with serum. Moreover, serum cultures displayed a higher tendency of undergoing hypertrophy given the stronger collagen X gene expression.

CONCLUSION

The advocated technique promoted cell expansion with respect to conventional serum supplemented cultures while reducing the loss of the chondrogenic phenotype. This demonstrates the feasibility and potential of the novel concomitant use of serum free media and ECM coatings in the expansion of chondrocytes for cartilage regenerative applications.

Determination of Viability of Human Cartilage Allografts by a Rapid and Quantitative Method Not Requiring Cartilage Digestion

Fresh osteochondral allograft transplantation is increasingly used for the treatment of cartilage pathologies of the knee. It is believed that transplantation success depends on the presence of viable chondrocytes in the graft, but methods to evaluate graft viability require the isolation of chondrocytes by enzymatic digestion of the cartilage and/or the use of radioactive precursors. We have adapted the well-known cell viability assay based on the reduction of tetrazolium derivatives to evaluate cartilage viability. We took advantage from the histological properties of cartilage tissue and the fact that some tetrazolium derivatives (e.g., WST-1, XTT) give soluble reduction products that can permeate the hyaline cartilage matrix. We have validated this assay in human cartilage explants from arthrotomy interventions and deceased donors, measuring the reduced product in the explant supernatant. Using this method we have compared the performance of several culture media in cartilage viability. From those tested, DMEM supplemented with fetal bovine serum results in higher viability of the cartilage and the explants remain viable at least 15 days in culture at 37°C. Cartilage cells continued expressing chondrocyte-specific genes, suggesting the maintenance of chondrogenic phenotype. The described method offers a quantitative and convenient method to measure the viability of human cartilage grafts.

Comparative effects of bone morphogenetic proteins and Sox9 overexpression on matrix accumulation by bovine anulus fibrosus cells: implications for anular repair

STUDY DESIGN

An in vitro biologic study comparing the effects of a series of bone morphogenetic proteins (BMPs) and Sox9 on the extracellular matrix accumulation by bovine anulus fibrosus (AF) cells.

OBJECTIVE

To compare the effects of adenoviral-mediated overexpression of various BMPs and Sox9 on extracellular matrix accumulation by AF cells in vitro.

SUMMARY OF BACKGROUND DATA

Repair of the disrupted AF, which is perceived to be a potential therapy to diminish nucleus pulposus (NP) herniation, may also offer a treatment strategy for severe symptomatic degenerative disc disease. To date, no systematic comparison of a large group of growth factors in the AF has been published. In this study, we compared the effects of the adenoviral-mediated overexpression of 12 BMPs and Sox9 on extracellular matrix production by AF cells.

METHODS

Adult monolayer-cultured bovine AF cells were transduced with adenoviral vectors containing human BMP and green fluorescence protein (GFP) genes (AdBMPs), or Sox9 and GFP genes (AdSox9), or GFP gene alone (AdGFP, as negative control). Proteoglycan and collagen accumulation, and cell proliferation were measured for each of the treatment groups 6 days after viral transduction.

RESULTS

AF cells transduced with BMP-2, -3, -5, -7, -8, -12, -13, -14, and -15, and Sox9 accumulated significantly more collagen than AF cells transduced with AdGFP (control). AF cells transduced with AdBMP-2, -4, -7, -10, -12, and -13, and AdSox9 accumulated significantly more proteoglycans than AF cells transduced with AdGFP.

CONCLUSION

We have demonstrated the relative effectiveness of 12 different BMPs and Sox9 on the stimulation of proteoglycan and/or collagen accumulation by AF cells. This study is the first to compare the relative effectiveness of various BMPs and Sox9 on extracellular matrix accumulation by AF. This information should prove useful to those seeking to develop a strategy for repair of the AF in humans.

Optimal Combination of Soluble Factors for Tissue Engineering of Permanent Cartilage from Cultured Human Chondrocytes

Since permanent cartilage has poor self-regenerative capacity, its regeneration from autologous human chondrocytes using a tissue engineering technique may greatly benefit the treatment of various skeletal disorders. However, the conventional autologous chondrocyte implantation is insufficient both in quantity and in quality due to two major limitations: dedifferentiation during a long term culture for multiplication and hypertrophic differentiation by stimulation for the redifferentiation. To overcome the limitations, this study attempted to determine the optimal combination in primary human chondrocyte cultures under a serum-free condition, from among 12 putative chondrocyte regulators. From the exhaustive 2(12) = 4,096 combinations, 256 were selected by fractional factorial design, and bone morphogenetic protein-2 and insulin (BI) were statistically determined to be the most effective combination causing redifferentiation of the dedifferentiated cells after repeated passaging. We further found that the addition of triiodothyronine (T3) prevented the BI-induced hypertrophic differentiation of redifferentiated chondrocytes via the suppression of Akt signaling. The implant formed by the human chondrocytes cultured in atelocollagen and poly(l-latic acid) scaffold under the BI + T3 stimulation consisted of sufficient hyaline cartilage with mechanical properties comparable with native cartilage after transplantation in nude mice, indicating that BI + T3 is the optimal combination to regenerate a clinically practical permanent cartilage from autologous chondrocytes.

Three-Dimensional Microenvironments Retain Chondrocyte Phenotypes During Proliferation Culture

Although autologous chondrocyte implantation has already been in clinical use, chondrocyte dedifferentiation is problematic during proliferation culture. We attempted a three-dimensional (3D) collagen gel culture under chondrocyte proliferation with repeated passaging to prevent the chondrocytes dedifferentiation. Human auricular chondrocytes were cultured in 3D or conventional monolayer conditions, which reached a 1000-fold increase in cell numbers at passages 3 and 4, respectively. During multiplication, the chondrocytes in 3D culture showed greater suppression of collagen type I (COL1) and preservation of collagen type II (COL2) than those in monolayer. Tissue-engineered cartilage made of 3D cells also abundantly accumulated COL2 or proteoglycan and possessed favorable mechanical properties. The advantage of 3D cells may result from the similarity of microenvironments in cell-to-matrix adhesion or cell-to-cell contacts with that of native cartilage. The up-regulation of integrins and down-regulation of cadherins in the 3D cells mimicked the expression pattern of native cartilage, rather than that of monolayer cells. The silencing of integrin beta1 and Ob-cadherin expression by small interfering ribonucleic acid in the cultured chondrocytes led to the promotion of dedifferentiation and redifferentiation, respectively, indicating that the 3D collagen gel culture provided sufficient cell preparation and reduced chondrocyte dedifferentiation, which is regarded as a feasible strategy in autologous chondrocyte implantation.

Collagen scaffolds for nonviral IGF-1 gene delivery in articular cartilage tissue engineering

This study investigated the use of a type II collagen-glycosaminoglycan (CG) scaffold as a nonviral gene delivery vehicle for facilitating gene transfer to seeded adult articular chondrocytes to produce an elevated, prolonged and local expression of insulin-like growth factor (IGF)-1 for enhancing cartilage regeneration. Gene-supplemented CG (GSCG) scaffolds were synthesized by two methods: (1) soaking a pre-cross-linked CG scaffold in a plasmid solution followed by a freeze-drying process, and (2) chemically cross-linking the plasmid DNA to the scaffold. Two different plasmid solutions were also compared: (1) naked plasmid IGF-1 alone, and (2) plasmid IGF-1 with a lipid transfection reagent. Plasmid release studies revealed that cross-linking the plasmid to the CG scaffold prevented passive bolus release of plasmid and resulted in vector release controlled by scaffold degradation. In chondrocyte-seeded GSCG scaffolds, prolonged and elevated IGF-1 expression was enhanced by using the cross-linking method of plasmid incorporation along with the addition of the transfection reagent. The sustained level of IGF-1 overexpression resulted in significantly higher amounts of tissue formation, chondrocyte-like cells, GAG accumulation, and type II collagen production, compared to control scaffolds. These findings demonstrate that CG scaffolds can serve as nonviral gene delivery vehicles of microgram amounts of IGF-1 plasmid (<10 microg per scaffold) to provide a locally sustained therapeutic level of overexpressed IGF-1, resulting in enhanced cartilage formation.