Beta-1 integrin expression by human nasal chondrocytes in microcarrier spinner culture

Avocado/Soybean Unsaponifiables, Glucosamine and Chondroitin Sulfate Combination Inhibits Proinflammatory COX-2 Expression and Prostaglandin E2 Production in Tendon-Derived Cells

Tendinopathy, a common disorder in man and horses, is characterized by pain, dysfunction, and tendon degeneration. Inflammation plays a key role in the pathogenesis of tendinopathy. Tendon cells produce proinflammatory molecules that induce pain and tissue deterioration. Currently used nonsteroidal anti-inflammatory drugs are palliative but have been associated with adverse side effects prompting the search for safe, alternative compounds. This study determined whether tendon-derived cells' expression of proinflammatory cyclooxygenase (COX)-2 and production of prostaglandin E2 (PGE2) could be attenuated by the combination of avocado/soybean unsaponifiables (ASU), glucosamine (GLU), and chondroitin sulfate (CS). ASU, GLU, and CS have been used in the management of osteoarthritis-associated joint inflammation. Tenocytes in monolayer and microcarrier spinner cultures were incubated with media alone, or with the combination of ASU (8.3 μg/mL), GLU (11 μg/mL), and CS (20 μg/mL). Cultures were next incubated with media alone, or stimulated with interleukin-1β (IL-1β; 10 ng/mL) for 1 h to measure COX-2 gene expression, or for 24 h to measure PGE2 production, respectively. Tenocyte phenotype was analyzed by phase-contrast microscopy, immunocytochemistry, and Western blotting. Tendon-derived cells proliferated and produced extracellular matrix component type I collagen in monolayer and microcarrier spinner cultures. IL-1β-induced COX-2 gene expression and PGE2 production were significantly reduced by the combination of (ASU+GLU+CS). The suppression of IL-1β-induced inflammatory response suggests that (ASU+GLU+CS) may help attenuate deleterious inflammation in tendons.

Anti-Inflammatory Effect of Carprofen Is Enhanced by Avocado/Soybean Unsaponifiables, Glucosamine and Chondroitin Sulfate Combination in Chondrocyte Microcarrier Spinner Culture

OBJECTIVE

Osteoarthritis is a painful, chronic joint disease affecting man and animals with no known curative therapies. Palliative nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used but they cause adverse side effects prompting the search for safer alternatives. To address this need, we evaluated the anti-inflammatory activity of avocado/soybean unsaponifiables (ASU), glucosamine (GLU), and chondroitin sulfate (CS) with or without the NSAID carprofen.

DESIGN

Canine chondrocytes were propagated in microcarrier spinner culture and incubated with (1) control medium, (2) ASU (8.3 µg/mL) + GLU (11 µg/mL) + CS (20 µg/mL) combination for 24 hours; and/or carprofen (40 ng/mL). Cultures were next incubated with control medium alone or IL-1β (10 ng/mL) for another 24 hours. Production of PGE2, IL-6, IL-8, and MCP-1 (also known as CCL-2) were measured by ELISA.

RESULTS

Chondrocytes proliferated in microcarrier spinner culture and produced type II collagen and aggrecan. Stimulation with IL-1β induced significant increases in PGE2, IL-6, IL-8, and MCP-1 production. The increases in production were suppressed by carprofen as well as [ASU+GLU+CS]. The combination of carprofen and [ASU+GLU+CS] reduced PGE2 production significantly more than either preparation alone. The inhibitory effect of carprofen on IL-6, IL-8, and MCP-1 production was significantly less than that of [ASU+GLU+CS], whereas the combination did not reduce the production of these molecules significantly more than [ASU+GLU+CS] alone.

CONCLUSIONS

The potentiating effect of [ASU+GLU+CS] on low-dose carprofen was identified in chondrocyte microcarrier spinner cultures. Our results suggest that the combination of low-dose NSAIDs like carprofen with [ASU+GLU+CS] could offer a safe, effective management for joint pain.

Propagation of Human Nasal Chondrocytes in Microcarrier Spinner Culture

Objective

The aim of this study was to test the effectiveness of nasal septal chondrocytes, propagated in microcarrier spinner culture, as an alternative tissue source of chondrocytic cells for cartilage grafts for head and neck surgery and for articular cartilage repair.

Methods

We harvested chondrocytes from 159 patients, ranging in age from 15 to 80 years and undergoing repair of a deviated nasal septum, and propagated the cells in a microcarrier spinner culture system. The nasal chondrocytes proliferated and produced extracellular matrix components similar to that produced by articular chondrocytes.

Results

In microcarrier spinner culture on collagen beads, chondrocyte numbers increased up to 14-fold in 2 weeks. After a month, the microcarriers seeded with nasal chondrocytes began to aggregate, producing a dense cartilage-like material. The newly synthesized extracellular matrix was rich in high molecular weight proteoglycans, and the chondrocytes expressed type II collagen and aggrecan but not type I collagen.

Conclusion

These studies support the feasibility of engineering cartilage tissue using chondrocytes harvested from the nasal septum. Injectable and solid formulations based on this technology are being evaluated for applications in craniomaxillofacial reconstructive surgery and for plastic and orthopedic surgery practices.

Evaluation of β1-integrin expression on chondrogenically differentiating human adipose-derived stem cells using atomic force microscopy

The expression of β1-integrin on human adipose-derived stem cells, differentiating toward a chondrogenic lineage, is hypothesized to decrease when cells are grown under in vivo-like environments due to sufficient extracellular matrix (ECM) buildup in the engineered tissues. The opposite is true when cells are grown in static cultures such as in pellet or micromass. To probe β1-integrin distribution on cellular surfaces, atomic force microscopy cantilevers modified with anti-β1-integrin antibodies were used. Specific antibody-antigen adhesion forces were identified and indicated the locations of β1-integrins on cells. ECM properties were assessed by estimating the Young's modulus of the matrix. Specific single antibody-antigen interactions averaged 78 ± 10 pN with multiple bindings occurring at approximate multiples of 78 pN. The author's results show that upregulated β1-integrin expression coincided with a less robust ECM as assessed by mechanical properties of tissues. In micromass and pellet cultures, transforming growth factor β3(TGF-β3) elicited a decrease in Young's modulus by 3.7- and 4.4-fold while eliciting an increase in β1-integrin count by 1.1- and 1.3-fold, respectively. β1-integrin counts on cells grown in the presence of TGF-β3 with oscillating hydrostatic pressure decreased by a 1.1-fold while the Young's modulus increased by a 1.9-fold. Collectively, our results suggest that cells in insufficiently robust ECM express more integrin perhaps to facilitate cell-ECM adhesion and compensate for a looser less robust ECM.

A combinatorial variation in surface chemistry and pore size of three-dimensional porous poly(ε-caprolactone) scaffolds modulates the behaviors of mesenchymal stem cells

Biomaterial properties play significant roles in controlling cellular behaviors. The objective of the present study was to investigate how pore size and surface chemistry of three-dimensional (3D) porous scaffolds regulate the fate of mesenchymal stem cells (MSCs) in vitro in combination. First, on poly(ε-caprolactone) (PCL) films, the hydrolytic treatment was found to stimulate the adhesion, spreading and proliferation of human MSCs (hMSCs) in comparison with pristine films, while the aminolysis showed mixed effects. Then, 3D porous PCL scaffolds with varying pore sizes (100-200μm, 200-300μm and 300-450μm) were fabricated and subjected to either hydrolysis or aminolysis. It was found that a pore size of 200-300μm with hydrolysis in 3D scaffolds was the most favorable condition for growth of hMSCs. Importantly, while a pore size of 200-300μm with hydrolysis for 1h supported the best osteogenic differentiation of hMSCs, the chondrogenic differentiation was greatest in scaffolds with a pore size of 300-450μm and treated with aminolysis for 1h. Taken together, these results suggest that surface chemistry and pore size of 3D porous scaffolds may potentially have a synergistic impact on the behaviors of MSCs.

Integrin-β1 regulates chondrocyte proliferation and apoptosis through the upregulation of GIT1 expression

Chondrocytes play a critical role in the repair process of osteoarthritis, which is also known as degenerative arthritis. Integrins, as the key family of cell surface receptors, are responsible for the regulation of chondrocyte proliferation, differentiation, survival and apoptosis through the recruitment and activation of downstream adaptor proteins. Moreover, G-protein-coupled receptor kinase interacting protein-1 (GIT1) exerts its effects on cell proliferation and migration through interaction with various cytokines. It has been previously suggested that GIT1 acts as a vital protein downstream of the integrin-mediated pathway. In the present study, we investigated the effects of integrin-β1 on cell proliferation and apoptosis, as well as the underlying mechanisms in chondrocytes in vitro. Following transfection with a vector expressing integrin-β1, our results revealed that the overexpression of integrin-β1 enhanced GIT1 expression, whereas the knockdown of integrin-β1 by siRNA suppressed GIT1 expression. However, no significant effect was observed on integrin-β1 expression following the enforced overexpression of GIT1, which suggests that GIT1 is localized downstream of integrin-β1. In other words, integrin-β1 regulates the expression of GIT1. Furthermore, this study demonstrated that integrin-β1 and GIT1 increased the expression levels of aggrecan and type II collagen, thus promoting chondrocyte proliferation; however, they inhibited chondrocyte apoptosis. Taken together, our data demonstrate that integrin-β1 plays a vital role in chondrocyte proliferation, differentiation and apoptosis. GIT1 exerts effects similar to those of integrin-β1 and is a downstream target of integrin-β1.

Novel injectable porous poly(γ-benzyl-l-glutamate) microspheres for cartilage tissue engineering: preparation and evaluation

A novel injectable synthetic polypeptide of a poly(γ-benzyl-l-glutamate) macroporous microcarrier was developed for cartilage tissue engineering.

Dynamic culturing of cartilage tissue: the significance of hydrostatic pressure

Human articular cartilage functions under a wide range of mechanical loads in synovial joints, where hydrostatic pressure (HP) is the prevalent actuating force. We hypothesized that the formation of engineered cartilage can be augmented by applying such physiologic stimuli to chondrogenic cells or stem cells, cultured in hydrogels, using custom-designed HP bioreactors. To test this hypothesis, we investigated the effects of distinct HP regimens on cartilage formation in vitro by either human nasal chondrocytes (HNCs) or human adipose stem cells (hASCs) encapsulated in gellan gum (GG) hydrogels. To this end, we varied the frequency of low HP, by applying pulsatile hydrostatic pressure or a steady hydrostatic pressure load to HNC-GG constructs over a period of 3 weeks, and evaluated their effects on cartilage tissue-engineering outcomes. HNCs (10×10(6) cells/mL) were encapsulated in GG hydrogels (1.5%) and cultured in a chondrogenic medium under three regimens for 3 weeks: (1) 0.4 MPa Pulsatile HP; (2) 0.4 MPa Steady HP; and (3) Static. Subsequently, we applied the pulsatile regimen to hASC-GG constructs and varied the amplitude of loading, by generating both low (0.4 MPa) and physiologic (5 MPa) HP levels. hASCs (10×10(6) cells/mL) were encapsulated in GG hydrogels (1.5%) and cultured in a chondrogenic medium under three regimens for 4 weeks: (1) 0.4 MPa Pulsatile HP; (2) 5 MPa Pulsatile HP; and (3) Static. In the HNC study, the best tissue development was achieved by the pulsatile HP regimen, whereas in the hASC study, greater chondrogenic differentiation and matrix deposition were obtained for physiologic loading, as evidenced by gene expression of aggrecan, collagen type II, and sox-9; metachromatic staining of cartilage extracellular matrix; and immunolocalization of collagens. We thus propose that both HNCs and hASCs detect and respond to physical forces, thus resembling joint loading, by enhancing cartilage tissue development in a frequency- and amplitude-dependant manner.

Novel measurements of mammary stem cells in human umbilical cord blood as prospective predictors of breast cancer susceptibility in later life

BACKGROUND

The size of the breast stem-cell pool could underlie the intrauterine roots of breast cancer. We studied whether breast stem cells exist in umbilical cord blood and if they correlate with hematopoietic stem-cell measurements that have been positively associated with perinatal risk factors for breast cancer.

SUBJECTS AND METHODS

We isolated mononuclear cells from umbilical cord blood of 170 singleton full-term pregnancies and determined, by reverse transcription polymerase chain reaction, the presence of genes of putative breast epithelial stem-cell/progenitor markers [including epithelial cell adhesion molecule (EpCAM), CD49f (α6-integrin), CD117 (c-kit receptor), CD24, and CD29 (β1-integrin)]. By immunocytochemistry, we colocalized protein expressions of EpCAM+CD49f+, CD49f+CD24+, and CD24+CD29+. We correlated concentrations of putative breast stem-cell/progenitor subpopulations, quantified by flow cytometry, with concentrations of hematopoietic stem cells.

RESULTS

Mammary stem-cell phenotypes were identified in umbilical cord blood. The measured EpCAM+ subpopulation was positively correlated with concentrations of CD34+ and CD34+CD38- hematopoietic stem cells (both P=0.006). Additionally, EpCAM+CD49f+ and CD49f+CD24+ subpopulations were positively correlated to the CD34+ cells (P=0.03 and 0.008, respectively).

CONCLUSION

The positive association between measurable breast and hematopoietic stem cells in human umbilical cord blood suggests plausible mechanisms for a prenatal influence on breast cancer risk.

Derivation, characterization and expansion of fetal chondrocytes on different microcarriers

Fetal chondrocytes (FCs) have recently been identified as an alternative cell source for cartilage tissue engineering applications because of their partially chondrogenically differentiated phenotype and developmental plasticity. In this study, chondrocytes derived from fetal bovine cartilage were characterized and then cultured on commercially available Cytodex-1 and Biosilon microcarriers and thermosensitive poly(hydroxyethylmethacrylate)-poly(N-isopropylacrylamide) (PHEMA-PNIPAAm) beads produced by us. Growth kinetics of FCs were estimated by means of specific growth rate and metabolic activity assay. Cell detachment from thermosensitive microcarriers was induced by cold treatment at 4 °C for 20 min or enzymatic treatment was applied for the detachment of cells from Cytodex-1 and Biosilon. Although attachment efficiency and proliferation of FCs on PHEMA-PNIPAAm beads were lower than that of commercial Cytodex-1 and Biosilon microcarriers, these beads also supported growth of FCs. Detached cells from thermosensitive beads by cold induction exhibited a normal proliferative activity. Our results indicated that Cytodex-1 microcarrier was the most suitable material for the production of FCs in high capacity, however, 'thermosensitive microcarrier model' could be considered as an attractive solution to the process scale up for cartilage tissue engineering by improving surface characteristics of PHEMA-PNIPAAm beads.

Adult human articular chondrocytes in a microcarrier-based culture system: expansion and redifferentiation

Expanding human chondrocytes in vitro while maintaining their ability to form cartilage remains a key challenge in cartilage tissue engineering. One promising approach to address this is to use microcarriers as substrates for chondrocyte expansion. While microcarriers have shown beneficial effects for expansion of animal and ectopic human chondrocytes, their utility has not been determined for freshly isolated adult human articular chondrocytes. Thus, we investigated the proliferation and subsequent chondrogenic differentiation of these clinically relevant cells on porous gelatin microcarriers and compared them to those expanded using traditional monolayers. Chondrocytes attached to microcarriers within 2 days and remained viable over 4 weeks of culture in spinner flasks. Cells on microcarriers exhibited a spread morphology and initially proliferated faster than cells in monolayer culture, however, with prolonged expansion they were less proliferative. Cells expanded for 1 month and enzymatically released from microcarriers formed cartilaginous tissue in micromass pellet cultures, which was similar to tissue formed by monolayer-expanded cells. Cells left attached to microcarriers did not exhibit chondrogenic capacity. Culture conditions, such as microcarrier material, oxygen tension, and mechanical stimulation require further investigation to facilitate the efficient expansion of clinically relevant human articular chondrocytes that maintain chondrogenic potential for cartilage regeneration applications. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:539-546, 2011.

Expression of putative stem cell genes Musashi-1 and beta1-integrin in human colorectal adenomas and adenocarcinomas

BACKGROUND AND AIMS

Recent studies revealed that Musashi-1and beta1-integrin were putative stem cell genes. Overexpressions of Musashi-1 and beta1-integrin have been reported in some tumor tissues and cell lines. This study was to detect expressions of the two genes in colorectal adenomas and carcinomas and to analyze the correlation between Musashi-1 and beta1-integrin.

METHODS

Musashi-1 and beta1-integrin immunoreactivity was studied immunohistochemically in tissue microarray-based samples containing 69 colorectal adenocarcinomas, eight normal mucosa, and eight adenomas, and their messenger RNA (mRNA) expression level was detected by RT-PCR in resected specimens including the three types of tissue.

RESULTS

A percentage of 66.7% (46/69) and 59.2% (41/69) of colorectal adenocarcinomas were immunoreactive with Musashi-1 and beta1-integrin, respectively. The expressions of Musashi-1 and beta1-integrin protein were significantly higher in tissue samples of stage III than those of stage I-II (P = 0.0252; P = 0.0018, respectively). beta1-integrin expression was higher in group of adenocarcinomas than that of adenomas (P = 0.0276). Musashi-1 expression was closely correlated with beta1-integrin (rs = 0.631, P = 0.0001). Significant differences of Musashi-1 and beta1-integrin mRNA expression levels were found between the normal colorectal mucosa, adenoma, and adenocarcinoma tissues (P = 0.01; P = 0.03, respectively).

CONCLUSIONS

Musashi-1 and beta1-integrin may be involved in human colorectal tumor carcinogenesis and progression. Our observations also indicate the need for further investigations to test in vivo whether cells with these markers have stem cell properties.

Nasal chondrocytes and fibrin sealant for cartilage tissue engineering

Hybrid constructs associating a biodegradable matrix and autologous chondrocytes hold promise for the treatment of articular cartilage defects. In this context, our objective was to investigate the potential use of nasal chondrocytes associated with a fibrin sealant for the treatment of articular cartilage defects. The phenotype of primary nasal chondrocytes (NC) from human (HNC) and rabbit (RNC) origin were characterized by RT-PCR. The ability of constructs associating fibrin sealant and NC to form a cartilaginous tissue in vivo was investigated, firstly in a subcutaneous site in nude mice and secondly in an articular cartilage defect in rabbit. HNC express type II collagen and aggrecan, the two major hallmarks of a chondrocytic phenotype. Furthermore, when injected subcutaneously into nude mice within a fibrin sealant, these chondrocytes were able to form a cartilage-like tissue. Our data indicate that RNC also express type II collagen and aggrecan and maintained their phenotype in three-dimensional culture within a fibrin sealant. Moreover, treatment of rabbit articular cartilage defects with autologous RNC embedded in a fibrin sealant led to the formation of a hyalin-like repair tissue. The use of fibrin sealant containing hybrid autologous NC therefore appears as a promising approach for cell-based therapy of articular cartilage.

Cartilage tissue engineering and bioreactor systems for the cultivation and stimulation of chondrocytes

Damage to and degeneration of articular cartilage is a major health issue in industrialized nations. Articular cartilage has a particularly limited capacity for auto regeneration. At present, there is no established therapy for a sufficiently reliable and durable replacement of damaged articular cartilage. In this, as well as in other areas of regenerative medicine, tissue engineering methods are considered to be a promising therapeutic component. Nevertheless, there remain obstacles to the establishment of tissue-engineered cartilage as a part of the routine therapy for cartilage defects. One necessary aspect of potential tissue engineering-based therapies for cartilage damage that requires both elucidation and progress toward practical solutions is the reliable, cost effective cultivation of suitable tissue. Bioreactors and associated methods and equipment are the tools with which it is hoped that such a supply of tissue-engineered cartilage can be provided. The fact that in vivo adaptive physical stimulation influences chondrocyte function by affecting mechanotransduction leads to the development of specifically designed bioreactor devices that transmit forces like shear, hydrostatic pressure, compression, and combinations thereof to articular and artificial cartilage in vitro. This review summarizes the basic knowledge of chondrocyte biology and cartilage dynamics together with the exploration of the various biophysical principles of cause and effect that have been integrated into bioreactor systems for the cultivation and stimulation of chondrocytes.

Development of porous collagen beads for chondrocyte culture

A method for the preparation of bioresorbable collagen beads with an open porous structure is presented. These beads were prepared from collagen-alginate composite beads by removal of the alginate component. These collagen beads were suitable for rapid proliferation of chondrocytes in a dynamic, spinner culture system. Histology and immuno-histology showed that biochemical markers of chondrocytes are present during this cell proliferation, indicating that there was control of phenotype and that cell de-differentiation had not occurred. Unlike other 3-D scaffolds that have been used, the cells were amplified from very low cell densities and were able to proliferate freely without loss of phenotype.

Microcarriers in the engineering of cartilage and bone

A major problem in tissue engineering is the availability of a sufficient number of cells with the appropriate phenotype for delivery to damaged or diseased cartilage and bone; the challenge is to amplify cell numbers and maintain the appropriate phenotype for tissue repair and restoration of function. The microcarrier bioreactor culture system offers an attractive method for cell amplification and enhancement of phenotype expression. Besides serving as substrates for the propagation of anchorage-dependent cells, microcarriers can also be used to deliver the expanded undifferentiated or differentiated cells to the site of the defect. The present article provides an overview of the microcarrier culture system, its utility as an in vitro research tool and its potential applications in tissue engineering, particularly in the repair of cartilage and bone.

Effects of mixing intensity on cell seeding and proliferation in three-dimensional fibrous matrices

Nonwoven fibrous matrices have been widely used in cell and tissue cultures because their three-dimensional (3-D) structures with large surface areas and pore spaces can support high-density cell growth. Although cell adherence and growth on 2-D surfaces have been thoroughly investigated, very little is known for cells cultured in 3-D matrices. The effects of mixing intensity on cell seeding, adherence, and growth in fibrous matrices were thus investigated. Chinese Hamster Ovary and osteosarcoma cells were inoculated into nonwoven polyethylene terephthalate matrices by dynamic and static seeding methods, of which the former was found to be superior in seeding efficiency and cell distribution in the matrices. Dynamic seeding increased seeding efficiency from approximately 40% to more than 90%. When higher mixing intensities were applied, both cell attachment and detachment rates increased. Cell attachment was transport limited, as indicated by the increased attachment rate with increasing the mass transfer coefficient of the cells. Meanwhile, cell detachment from the 3-D matrix can be described by the Bell model. The effects of matrix pore size on cell adherence and proliferation were also investigated. In general, the smaller pore size is favorable to cell attachment and proliferation. Further analysis revealed that the interaction between mixing intensity and pore size played a vital role in hydrodynamic damage to cells, which was found to be significant when the Kolomogorov eddy size was smaller than the matrix pores. Increasing mixing intensity also increased oxygen transfer, decreased the lactate yield from glucose, and improved cell growth.

Encapsulation of Osteoblast Seeded Microcarriers into Injectable, Photopolymerizable Three-Dimensional Scaffolds Based ond,l-Lactide and ε-Caprolactone

UMR-106 seeded microcarriers were encapsulated into in situ, photopolymerizable three-dimensional scaffolds based on d,l-lactide and epsilon-caprolactone. UMR-106 and rat bone marrow cells proliferated and differentiated well on the microcarriers. The microcarriers were completely colonized after 14 days in culture. The viscous polymer paste allowed to mix the UMR-106 seeded microcarriers and gelatin (porosigen) properly. After the photopolymerization process, microcarriers and gelatin were evenly distributed throughout the scaffold. Gelatin was leached out within 7 h, and a porous scaffold was obtained. The microcarriers remained in the scaffold even after 7 days which demonstrates that they were well entrapped in the polymer. Increasing the amount of entrapped microcarriers (20-50%) leads to scaffolds with a reduced cross-linking. Hence, the microcarriers leached out. The encapsulated UMR-106 cells did not show pyknotic nuclei which demonstrates that the photopolymerization and handling the viscous polymer/gelatin/microcarrier paste is not detrimental for the cells.

Cyclic strain stimulates proliferative capacity, alpha2 and alpha5 integrin, gene marker expression by human articular chondrocytes propagated on flexible silicone membranes

Chondrocytes comprise less than 10% of cartilage tissue but are responsible for sensing and responding to mechanical stimuli imposed on the joint. However, the effect of mechanical signals at the cellular level is not yet fully defined. The purpose of this study was to test the hypothesis that mechanical stimulation in the form of cyclic strain modulates proliferative capacity and integrin expression of chondrocytes from osteoarthritic knee joints. Chondrocytes isolated from articular cartilage during total knee arthroplasty were propagated on flexible silicone membranes. The cells were subjected to cyclic strain for 24 h using a computer-controlled vacuum device, with replicate samples maintained under static conditions. Our results demonstrated increase in proliferative capacity of the cells subjected to cyclic strain compared with cells maintained under static conditions. The flexed cells also exhibited upregulation of the chondrocytic gene markers type II collagen and aggrecan. In addition, cyclic strain resulted in increased expression of the alpha2 and alpha5 integrin subunits, as well as an increased expression of vimentin. There was also intracellular reconfiguration of the enzyme protein kinase C. Our findings suggest that these molecules may play a role in the signal transduction pathway, eliciting cellular response to mechanical stimulation.

Expansion of human nasal chondrocytes on macroporous microcarriers enhances redifferentiation

Articular cartilage has a limited capacity for self-repair. To overcome this problem, it is expected that functional cartilage replacements can be created from expanded chondrocytes seeded in biodegradable scaffolds. Expansion of chondrocytes in two-dimensional culture systems often results in dedifferentiation. This investigation focuses on the post-expansion phenotype of human nasal chondrocytes expanded on macroporous gelatin CultiSpher G microcarriers. Redifferentiation was evaluated in vitro via pellet cultures in three different culture media. Furthermore, the chondrogenic potential of expanded cells seeded in polyethylene glycol terephthalate/ polybuthylene terephthalate (PEGT/PBT) scaffolds, cultured for 14 days in vitro, and subsequently implanted subcutaneously in nude mice, was assessed. Chondrocytes remained viable during microcarrier culture and yielded doubling times (1.07+/-0.14 days) comparable to T-flask expansion (1.20+/-0.36 days). Safranin-O staining from pellet culture in different media demonstrated that production of GAG per cell was enhanced by microcarrier expansion. Chondrocyte-polymer constructs with cells expanded on microcarriers contained significantly more proteoglycans after subcutaneous implantation (288.5+/-29.2 microg) than those with T-flask-expanded cells (164.0+/-28.7 microg). Total collagen content was similar between the two groups. This study suggests that macroporous gelatin microcarriers are effective matrices for nasal chondrocyte expansion, while maintaining the ability of chondrocyte differentiation. Although the exact mechanism by which chondrocyte redifferentiation is induced through microcarrier expansion has not yet been elucidated, this technique shows promise for cartilage tissue engineering approaches.

Thermally reversible polymer gel for chondrocyte culture

We have evaluated a biomaterial to serve as a scaffold for the propagation and amplification of chondrocytes that promotes the original cellular phenotype of these cells. The goal of the present study was to investigate the use of thermally reversible polymer gels poly(NiPAAm-co-AAc), as a biocompatible supporting scaffold for the propagation of chondrocytic cells. The polymer gels at temperatures above its lower critical solution temperature whereas liquefying at temperatures below its lower critical solution temperature of 34.5 degrees C. Hence, the polymer, in its gelled form, has the ability to hold cells in situ, forming a matrix similar to the natural cellular environment or the extracellular matrix that comprises cartilage. We tested the hypothesis that the polymer gel promotes cell viability and function. Human osteoblast-like cells, nasal chondrocytes, and articular chondrocytes (1 x 10(5)/150 microL) were resuspended in enriched Dulbecco's minimal essential media and were plated onto control (without gel) and gel containing 24-well plates. The plates were reincubated at 37 degrees C, 5% CO(2) for the time point of interest. Additional media was added to the plates and exchanged as needed. After cell culture, cells were retrieved, enumerated, and cell viability was determined. Other aliquots of the cells were stained for morphological analysis whereas expression of chondrocyte markers including collagen type II and aggrecan were determined using reverse transcriptase-polymerase chain reaction. The polymer gel was not cytotoxic because the cell number retrieved from three-dimensional culture gel was found to be one to two times higher than that retrieved from monolayer culture. Chondrocytes propagated in the thermo-reversible polymers expressed enhanced or maintained expression of collagen type II and aggrecan. Collagen type I expression was decreased or unaltered. The N-isopropylacrylamide and acrylic acid copolymer gel has potential use as a cell culture substrate and as a cell delivery vehicle.

COLLAGEN MICROCARRIER SPINNER CULTURE PROMOTES OSTEOBLAST PROLIFERATION AND SYNTHESIS OF MATRIX PROTEINS

In vitro propagation of osteoblasts in three-dimensional culture has been explored as a means of cell line expansion and tissue engineering purposes. Studies investigating optimal culture conditions are being conducted to produce bone-like material. This study demonstrates the use of collagen microcarrier beads as a substrate for three-dimensional cell culture. We have earlier reported that microcarriers consisting of cross-linked type I collagen support chondrocyte proliferation and synthesis of extracellular matrix. In this study, we investigated the use of collagen microcarriers to propagate human trabecular bone-derived osteoblasts. Aggregation of cell-seeded microcarriers and production of extracellular matrix-like material were observed after 5 d in culture. Expression of extracellular matrix proteins osteocalcin, osteopontin, and type I collagen was confirmed by messenger ribonucleic acid analysis, radioimmunoassay, and Western blot analysis. The efficient recovery of viable cells was achieved by collagenase digestion of the cell-seeded microcarriers. The collagen microcarrier spinner culture system provides an efficient method to amplify large numbers of healthy functional cells that can be subsequently used for further in vitro or transplantation studies.