Human chondrocytes proliferate and produce matrix components in microcarrier suspension culture

Novel cell spheroid culture method using Medaka dried fish powder

Highly biocompatible microcarriers are culture materials designed to enhance the efficiency of cell spheroid culture. Typically, collagen or specially processed plastic materials serve as these microcarriers. In the context of cultured-cell-based food production, however, both collagen and plastic materials present challenges regarding their cost-effectiveness and edibility. A notable issue with collagen, especially when derived from fish scales, is its low denaturation temperature, making it unsuitable for use with mammalian cells unless cross-linked. To address this issue, our research pivoted towards utilizing dried fish, a rich source of proteins including collagen. For this study, Medaka fish were selected. The fish were dried, ground into fine particles, and then impregnated with ethanol to create dried fish powder (DFP). Its efficacy was then evaluated as a microcarrier in spheroid cultures. The results revealed that DFP supports the adhesion and proliferation of various cell types, including human epidermal cells, human malignant melanoma cells, mouse fibroblasts, mouse endothelial cells and fish fibroblasts. Furthermore, Western blot analysis was used to verify the expression of mitogen-activated protein kinase-related proteins in both human epidermal cells and mouse fibroblasts cultured with DFP. This fish-derived powdered microcarrier offers a cost-effective production method requiring only a few steps. Its affordability and high performance as a carrier position it as a potentially revolutionary material for use in biological research and food production science.

Scalable and high-throughput production of an injectable platelet-rich plasma (PRP)/cell-laden microcarrier/hydrogel composite system for hair follicle tissue engineering

BACKGROUND

Tissue engineering of hair follicles (HFs) has enormous potential for hair loss treatment. However, certain challenges remain, including weakening of the dermal papilla cell (DPC) viability, proliferation, and HF inducibility, as well as the associated inefficient and tedious preparation process required to generate extracellular matrix (ECM)-mimicking substrates for biomolecules or cells. Herein, we utilized gelatin methacryloyl (GelMA) and chitosan hydrogels to prepare scalable, monodispersed, and diameter-controllable interpenetrating network GelMA/chitosan-microcarriers (IGMs) loaded with platelet-rich plasma (PRP) and seeded with DPCs, on a high-throughput microfluidic chip.

RESULTS

The ECM-mimicking hydrogels used for IGMs exhibited surface nano-topography and high porosity. Mass production of IGMs with distinct and precise diameters was achieved by adjusting the oil and aqueous phase flow rate ratio. Moreover, IGMs exhibited appropriate swelling and sustained growth factor release to facilitate a relatively long hair growth phase. DPCs seeded on PRP-loaded IGMs exhibited good viability (> 90%), adhesion, spreading, and proliferative properties (1.2-fold greater than control group). Importantly, PRP-loaded IGMs presented a higher hair inducibility of DPCs in vitro compared to the control and IGMs group (p < 0.05). Furthermore, DPC/PRP-laden IGMs were effectively mixed with epidermal cell (EPC)-laden GelMA to form a PRP-loaded DPC/EPC co-cultured hydrogel system (DECHS), which was subcutaneously injected into the hypodermis of nude mice. The PRP-loaded DECHS generated significantly more HFs (~ 35 per site) and novel vessels (~ 12 per site) than the other groups (p < 0.05 for each).

CONCLUSION

Taken together, these results illustrate that, based on high-throughput microfluidics, we obtained scalable and controllable production of ECM-mimicking IGMs and DECHS, which simulate an effective micro- and macro-environment to promote DPC bioactivity and hair regeneration, thus representing a potential new strategy for HF tissue engineering.

Selective Proliferation of Highly Functional Adipose-Derived Stem Cells in Microgravity Culture with Stirred Microspheres

Therapeutic effects of adult stem-cell transplantations are limited by poor cell-retention in target organs, and a reduced potential for optimal cell differentiation compared to embryonic stem cells. However, contemporary studies have indicated heterogeneity within adult stem-cell pools, and a novel culturing technique may address these limitations by selecting those for cell proliferation which are highly functional. Here, we report the preservation of stemness in human adipose-derived stem cells (hASCs) by using microgravity conditions combined with microspheres in a stirred suspension. The cells were bound to microspheres (100-300 μm) and cultured using a wave-stirring shaker. One-week cultures using polystyrene and collagen microspheres increased the proportions of SSEA-3(+) hASCs 4.4- and 4.3-fold (2.7- and 2.9-fold increases in their numbers), respectively, compared to normal culture conditions. These cultured hASCs expressed higher levels of pluripotent markers (OCT4, SOX2, NANOG, MYC, and KLF), and had improved abilities for proliferation, colony formation, network formation, and multiple-mesenchymal differentiation. We believe that this novel culturing method may further enhance regenerative therapies using hASCs.

3D Culture of MSCs on a Gelatin Microsphere in a Dynamic Culture System Enhances Chondrogenesis

Recent advancement in cartilage tissue engineering has explored the potential of 3D culture to mimic the in vivo environment of human cartilaginous tissue. Three-dimensional culture using microspheres was described to play a role in driving the differentiation of mesenchymal stem cells to chondrocyte lineage. However, factors such as mechanical agitation on cell chondrogenesis during culture on the microspheres has yet to be elucidated. In this study, we compared the 2D and 3D culture of bone-marrow-derived mesenchymal stem cells (BMSCs) on gelatin microspheres (GMs) in terms of MSC stemness properties, immune-phenotype, multilineage differentiation properties, and proliferation rate. Then, to study the effect of mechanical agitation on chondrogenic differentiation in 3D culture, we cultured BMSCs on GM (BMSCs-GM) in either static or dynamic bioreactor system with two different mediums, i.e., F12: DMEM (1:1) + 10% FBS (FD) and chondrogenic induction medium (CIM). Our results show that BMSCs attached to the GM surface and remained viable in 3D culture. BMSCs-GM proliferated faster and displayed higher stemness properties than BMSCs on a tissue culture plate (BMSCs-TCP). GMs also enhanced the efficiency of in-vitro chondrogenesis of BMSCs, especially in a dynamic culture with higher cell proliferation, RNA expression, and protein expression compared to that in a static culture. To conclude, our results indicate that the 3D culture of BMSCs on gelatin microsphere was superior to 2D culture on a standard tissue culture plate. Furthermore, culturing BMSCs on GM in dynamic culture conditions enhanced their chondrogenic differentiation.

Bioprocess Technologies that Preserve the Quality of iPSCs

Large-scale production of induced pluripotent stem cells (iPSCs) is essential for the treatment of a variety of clinical indications. However, culturing enough iPSCs for clinical applications is problematic due to their sensitive pluripotent state and dependence on a supporting matrix. Developing stem cell bioprocessing strategies that are scalable and meet clinical needs requires incorporating methods that measure and monitor intrinsic markers of cell differentiation state, developmental status, and viability in real time. In addition, proper cell culture modalities that nurture the growth of high-quality stem cells in suspension are critical for industrial scale-up. In this review, we present an overview of cell culture media, suspension modalities, and monitoring techniques that preserve the quality and pluripotency of iPSCs during initiation, expansion, and manufacturing.

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.

Biomimetic polyetheretherketone microcarriers with specific surface topography and self-secreted extracellular matrix for large-scale cell expansion

Reusable microcarriers with appropriate surface topography, mechanical properties, as well as biological modification through decellularization facilitating repeated cell culture are crucial for tissue engineering applications. Herein, we report the preparation of topological polyetheretherketone (PEEK) microcarriers via gas-driven and solvent exchange method followed by hydrothermal treatment at high temperature and pressure. After hydrothermal treated for 8 h, the resulting topological PEEK microcarriers exhibit walnut-like surface topography and good sphericity as well as uniform size distribution of 350.24 ± 19.44 µm. And the average width between ravine-patterned surface of PEEK microcarriers is 780 ± 290 nm. After repeated steam sterilization by autoclaving for three times, topological PEEK microcarriers show nearly identical results compared with previous ones indicating strong tolerance to high temperature and pressure. This is a unique advantage for large-scale cell expansion and clinical applications. Moreover, PEEK microcarriers with special topography possess higher protein adsorption efficiency. In addition, the reutilization and biofunctionalization with repeated decellularization of topological PEEK microcarriers show highly beneficial for cell adhesion and proliferation. Therefore, our study is of great importance for new generation microcarriers with micro-and nano-scale surface feature for a broad application prospect in tissue engineering.

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.

Expansion in microcarrier-spinner cultures improves the chondrogenic potential of human early mesenchymal stromal cells

BACKGROUND AIMS

Cartilage tissue engineering with human mesenchymal stromal cells (hMSC) is promising for allogeneic cell therapy. To achieve large-scale hMSC propagation, scalable microcarrier-based cultures are preferred over conventional static cultures on tissue culture plastic. Yet it remains unclear how microcarrier cultures affect hMSC chondrogenic potential, and how this potential is distinguished from that of tissue culture plastic. Hence, our study aims to compare the chondrogenic potential of human early MSC (heMSC) between microcarrier-spinner and tissue culture plastic cultures.

METHODS

heMSC expanded on either collagen-coated Cytodex 3 microcarriers in spinner cultures or tissue culture plastic were harvested for chondrogenic pellet differentiation with empirically determined chondrogenic inducer bone morphogenetic protein 2 (BMP2). Pellet diameter, DNA content, glycosaminoglycan (GAG) and collagen II production, histological staining and gene expression of chondrogenic markers including SOX9, S100β, MMP13 and ALPL, were investigated and compared in both conditions.

RESULTS

BMP2 was the most effective chondrogenic inducer for heMSC. Chondrogenic pellets generated from microcarrier cultures developed larger pellet diameters, and produced more DNA, GAG and collagen II per pellet with greater GAG/DNA and collagen II/DNA ratios compared with that of tissue culture plastic. Moreover, they induced higher expression of chondrogenic genes (e.g., S100β) but not of hypertrophic genes (e.g., MMP13 and ALPL). A similar trend showing enhanced chondrogenic potential was achieved with another microcarrier type, suggesting that the mechanism is due to the agitated nature of microcarrier cultures.

CONCLUSIONS

This is the first study demonstrating that scalable microcarrier-spinner cultures enhance the chondrogenic potential of heMSC, supporting their use for large-scale cell expansion in cartilage cell therapy.

Novel Technique for Suspension Culture of Autologous Chondrocytes Improves Cell Proliferation and Tissue Architecture

We have developed a new and simple method of chondrocyte suspension culture using a spinner bottle with rotation of the matrices. We compared the characteristics of chondrocytes cultured by this method with those grown in standard monolayer cultures. We also determined the optimal nutritional medium for suspension cultures. Periosteum explants seeded with chondrocytes were grown in monolayer and suspension cultures under three conditions: in medium with no additive (control), with 10% fetal bovine serum (FBS), or with 10% autologous serum (AS). After culturing, the explants were harvested, processed for histology, and stained with hematoxylin-eosin or TUNEL, or immunostained for type I, II, and III collagen, and Ki-67 antigen. In monolayer cultures, the attachment of the chondrocytes to the periosteum was weak and the superficial layer consisted of fibrotic tissue and few nucleated cells. Collagen type II staining was strong, but types I and III were weak. Among the suspension cultures the AS group produced the thickest layer of chondrocytes with the fewest apoptotic cells. The superficial layer of cartilage in these cultures stained positive for type I and III collagen and Ki-67 antigen. Among the suspension cultures, total chondroitin and chondroitin-4 sulfate (C-4S) concentration was highest in the AS group, while prostaglandin E2 (PGE2) was highest in the FBS group. In summary, our new method of suspension culture of periosteal explants using rotational matrices combined with AS nutritional media was the most effective method for maintaining the bond between the chondrocyte layer and periosteum, as well as the production of type I and III collagen in the superficial layer.

Porous microcarrier-enabled three-dimensional culture of chondrocytes for cartilage engineering: A feasibility study

Cartilage repair is substantially intractable due to poor self-healing ability. Porous microspheres can be a fascinating three-dimensional matrix for cell culture and injectable carrier in cartilage engineering. In this study, we assessed the feasible use of porous biopolymer microspheres for chondrocyte carriers. When seeded onto the blended biopolymer microspheres and followed by a dynamic spinner flask culture, the chondrocytes showed robust growth behaviors during the culture period. The gene expressions of SOX9, type II collagen, and aggrecan were significantly upregulated after 2-week of culture. Furthermore, immunolocalization of type II collagen and secretion of glycosaminolglycan became prominent. The results suggest the feasible usefulness of the porous microspheres as the cell culture matrix and the subsequent delivery into cartilage defects.

Nanostructured injectable cell microcarriers for tissue regeneration

Biodegradable polymer microspheres have emerged as cell carriers for the regeneration and repair of irregularly shaped tissue defects due to their injectability, controllable biodegradability and capacity for drug incorporation and release. Notably, recent advances in nanotechnology allowed the manipulation of the physical and chemical properties of the microspheres at the nanoscale, creating nanostructured microspheres mimicking the composition and/or structure of natural extracellular matrix. These nanostructured microspheres, including nanocomposite microspheres and nanofibrous microspheres, have been employed as cell carriers for tissue regeneration. They enhance cell attachment and proliferation, promote positive cell-carrier interactions and facilitate stem cell differentiation for target tissue regeneration. This review highlights the recent advances in nanostructured microspheres that are employed as injectable, biomimetic and cell-instructive cell carriers.

Cell confluency analysis on microcarriers by micro-flow imaging

The productivity of cell culture-derived vaccines grown in anchorage-dependent animal cells is limited by bioreactor surface area. One way to increase the available surface area is by growing cells as monolayers on small spheres called microcarriers, which are approximately 100-250 μm in diameter. In order for microcarrier-based cell culture to be a success, it is important to understand the kinetics of cell growth on the microcarriers. Micro-flow imaging (MFI) is a simple and powerful technique that captures images and analyzes samples as they are drawn through a precision flow cell. In addition to providing size distribution and defect frequency data to compare microcarrier lots, MFI was used to generate hundreds of images to determine cell coverage and confluency on microcarriers. Same-day manual classification of these images provided upstream cell culture teams with actionable data that informed in-process decision making (e.g. time of infection). Additionally, an automated cell coverage algorithm was developed to increase the speed and throughput of the analyses.

Development of a 3D cell printed structure as an alternative to autologs cartilage for auricular reconstruction

Surgical technique using autologs cartilage is considered as the best treatment for cartilage tissue reconstruction, although the burdens of donor site morbidity and surgical complications still remain. The purpose of this study is to apply three-dimensional (3D) cell printing to fabricate a tissue-engineered graft, and evaluate its effects on cartilage reconstruction. A multihead tissue/organ building system is used to print cell-printed scaffold (CPS), then assessed the effect of the CPS on cartilage regeneration in a rabbit ear. The cell viability and functionality of chondrocytes were significantly higher in CPS than in cell-seeded scaffold (CSS) and cell-seeded hybrid scaffold (CSHS) in vitro. CPS was then implanted into a rabbit ear that had an 8 mm-diameter cartilage defect; at 3 months after implantation the CPS had fostered complete cartilage regeneration whereas CSS and autologs cartilage (AC) fostered only incomplete healing. This result demonstrates that cell printing technology can provide an appropriate environment in which encapsulated chondrocytes can survive and differentiate into cartilage tissue in vivo. Moreover, the effects of CPS on cartilage regeneration were even better than those of AC. Therefore, we confirmed the feasibility of CPS as an alternative to AC for auricular reconstruction. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1016-1028, 2017.

Past, present, and future of microcarrier-based tissue engineering

The top issue in tissue engineering is how to obtain more seed cells quickly and to preserve their characteristic morphology during in vitro expansion culture of cells. Microcarriers can help to amplify cell numbers and maintain the appropriate phenotype for tissue repair and restoration of function. In addition, microtissue with cell microcarriers can be used to repair diseased tissues or organs. This review introduces the materials used for, and classification of, microcarriers and the improvements in, and potential applications of, microtissues with cell microcarriers in tissue engineering.

Cell mediated gene therapy: A guide for doctors in the clinic

The recent approval of gene therapy products in Europe and Asia and the upsurge of gene therapy products in clinical trials signal the rebound of this technology not only for many orphan diseases but also for non-life threatening diseases. Following the success of induced pluripotent stem (iPS) cells in research, other modified ex vivo gene therapies are also knocking on the door of the clinic. Historically, gene therapy has experienced many ups and downs and still faces many challenges. During the past 10 years, many new ideas have been tried, and the goal of making this technology a more effective treatment modality through greater safety and control is coming within reach. The first clinical trial of iPS cells has begun, and cell mediated gene therapy products have reached phase III in some countries. The potential for tumorigenicity and immunogenicity are still concerns with these products, so physicians should understand the biological aspects of engineered cells in the clinic. In this review article, we attempted to provide a summary update of the current state of knowledge regarding this technology: that is, we reviewed products that have finished clinical trials, are still in clinical trials and/or are at the research stage. We also focused on the challenges, future directions, and strategies for making this technology available in the clinic. In addition, the available measures for making gene therapy products safer are within the scope of this article. It is also important to understand the manufacturing process for gene therapy products, because cell characteristics can change during the cell expansion process. When physicians use gene therapy products in the clinic, they should be aware of the viability, temperature sensitivity and stability of these cells because biologic products are different from chemical products. Although we may not be able to answer all possible questions and concerns, we believe that this is the right time for physicians to increase their interest in and understanding of this evolving technology.

Dynamic cell culture on calcium phosphate microcarriers for bone tissue engineering applications

Developing appropriate cell culturing techniques to populate scaffolds has become a great challenge in tissue engineering. This work describes the use of spinner flask dynamic cell cultures to populate hydroxyapatite microcarriers for bone tissue engineering. The microcarriers were obtained through the emulsion of a self-setting aqueous α-tricalcium phosphate slurry in oil. After setting, hydroxyapatite microcarriers were obtained. The incorporation of gelatin in the liquid phase of the α-tricalcium phosphate slurry allowed obtaining hybrid gelatin/hydroxyapatite-microcarriers. Initial cell attachment on the microcarriers was strongly influenced by the speed of the dynamic culture, achieving higher attachment at low speed (40 r/min) as compared to high speed (80 r/min). Under moderate culture speeds (40 r/min), the number of cells present in the culture as well as the number of microcarrier-containing cells considerably increased after 3 days, particularly in the gelatin-containing microcarriers. At longer culture times in dynamic culture, hydroxyapatite-containing microcarriers formed aggregates containing viable and extracellular matrix proteins, with a significantly higher number of cells compared to static cultures.

Isolation and ex vivo expansion of synovial mesenchymal stromal cells for cartilage repair

BACKGROUND AIMS

Hyaline articular cartilage is a highly specialized tissue that offers a low-friction and wear-resistant interface for weight-bearing surface articulation in diarthrodial joints, but it lacks vascularity. It displays an inherent inability to heal when injured in a skeletally mature individual. Joint-preserving treatment procedures such as mosaicplasty, débridement, perichondrium transplantation and autologous chondrocyte implantation have shown variable results, and the average long-term result is sub-standard. Because of these limitations of the treatment methods and lack of intrinsic repair capacity of mature cartilage tissue, an alternative treatment approach is needed, and synovial mesenchymal stromal cells (SMSCs) represent an attractive therapeutic alternative because of their ex vivo proliferation capacity, multipotency and ability to undergo chondrogenesis.

METHODS

SMSCs were isolated from tissues obtained by arthroscopy using two types of biopsies. Ex vivo cell expansion was accomplished under static and dynamic culture followed by characterization of cells according to the International Society for Cellular Therapy guidelines. Kinetic growth models and metabolite analysis were used for understanding the growth profile of these cells.

RESULTS

For the first time, SMSCs were expanded in stirred bioreactors and achieved higher cell density in a shorter period of time compared with static culture or with other mesenchymal stromal cell sources.

CONCLUSIONS

In this study we were able to achieve (8.8 ± 0.2) × 10(5) cells within <2 weeks in dynamic culture under complete xeno-free conditions. Our results also provided evidence that after dynamic culture these cells had an up-regulation of chondrogenic genes, which can be a potential factor for articular cartilage regeneration in clinical settings.

Microcarrier culture for efficient expansion and osteogenic differentiation of human fetal mesenchymal stem cells

Stirred microcarrier (MC) culture has been suggested as the method of choice for supplying large volumes of mesenchymal stem cells (MSCs) for bone tissue engineering. In this study, we show that in addition to the improvement in cell expansion capacity, MSCs propagated and harvested from MC culture also demonstrate higher osteogenic potency when differentiated in vivo or in vitro in three-dimensional (3D) scaffold cultures as compared with traditional monolayer (MNL) cultures. Cytodex 3 microcarrier-expanded human fetal MSC (hfMSC) cultures (MC-hfMSCs) achieved 12- to 16-fold expansion efficiency (6×10⁵–8×10⁵ cells/mL) compared to 4- to 6-fold (1.2×10⁵–1.8×10⁵ cells/mL) achieved by traditional MNL-expanded hfMSC culture (MNL-hfMSCs; p<0.05). Both MC-hfMSCs and MNL-hfMSCs maintained similar colony-forming capacity, doubling times, and immunophenotype postexpansion. However, when differentiated under in vitro two-dimensional (2D) osteogenic conditions, MC-hfMSCs exhibited a 45-fold reduction in alkaline phosphatase level and a 37.5% decrease in calcium deposition compared with MNL-hfMSCs (p<0.05). Surprisingly, when MC-hfMSCs and MNL-hfMSCs were seeded on 3D macroporous scaffold culture or subcutaneously implanted into nonobese diabetic/severe combined immunodeficient mice, MC-hfMSCs deposited 63.5% (p<0.05) more calcium and formed 47.2% (p<0.05) more bone volume, respectively. These results suggest that the mode of hfMSC growth in the expansion phase affects the osteogenic potential of hfMSCs differently in various differentiation platforms. In conclusion, MC cultures are advantageous over MNL cultures in bone tissue engineering because MC-hfMSCs have improved cell expansion capacity and exhibit higher osteogenic potential than MNL-hfMSCs when seeded in vitro into 3D scaffolds or implanted in vivo.

High-density cell systems incorporating polymer microspheres as microenvironmental regulators in engineered cartilage tissues

To address the significant clinical need for tissue-engineered therapies for the repair and regeneration of articular cartilage, many systems have recently been developed using bioactive polymer microspheres as regulators of the chondrogenic microenvironment within high-density cell cultures. In this review, we highlight various densely cellular systems utilizing polymer microspheres as three-dimensional (3D) structural elements within developing engineered cartilage tissue, carriers for cell expansion and delivery, vehicles for spatiotemporally controlled growth factor delivery, and directors of cell behavior via regulation of cell-biomaterial interactions. The diverse systems described herein represent a shift from the more traditional tissue engineering approach of combining cells and growth factors within a biomaterial scaffold, to the design of modular systems that rely on the assembly of cells and bioactive polymer microspheres as building blocks to guide the creation of articular cartilage. Cell-based assembly of 3D microsphere-incorporated structures represents a promising avenue for the future of tissue engineering.

The effect of ultrasound stimulation on the cytoskeletal organization of chondrocytes seeded in three-dimensional matrices

The impact of low-intensity diffuse ultrasound (LIDUS) stimulation on the cytoskeletal organization of chondrocytes seeded in three-dimensional (3D) scaffolds was evaluated. Chondrocytes seeded on 3D chitosan matrices were exposed to LIDUS at 5.0 MHz (approx. 15 kPa, 51 s, 4 applications/day) in order to study the organization of actin, tubulin and vimentin. The results showed that actin presented a punctate cytosolic distribution and tubulin presented a quasiparallel organization of microtubules, whereas vimentin distribution was unaffected. Chondrocytes seeded on 3D scaffolds responded to US stimulation by the disruption of actin stress fibers and were sensitive to the presence of Rho-activated kinase (ROCK) inhibitor (Y27632). The gene expression of ROCK-I, a key element in the formation of stress fibers and mDia1, was significantly upregulated under the application of US. We conclude that the results of both the cytoskeletal analyses and gene expression support the argument that the presence of punctate actin upon US stimulation was accompanied by the upregulation of the RhoA/ROCK pathway.

Quantification of Changes in Morphology, Mechanotransduction, and Gene Expression in Bovine Articular Chondrocytes in Response to 2-Dimensional Culture Indicates the Existence of a Novel Phenotype

OBJECTIVE

Matrix-induced autologous chondrocyte implantation (ACI) offers a potential solution for cartilage repair but is currently hindered by loss of the chondrocyte differentiated phenotype. To further our understanding of the mechanism of dedifferentiation, changes in the phenotype in relation to mechanotransduction were recorded in response to monolayer culture.

METHODS

Bovine cartilage explants were excised and chondrocytes cultured for 9 days (P1), 14 days (P2), and 21 (P3) days. Changes in morphology and regulatory volume increase (RVI; a mechanotransduction response) were determined by the expression of key genes by RT-PCR and confocal microscopy, respectively.

RESULTS

A loss of a differentiated phenotype was observed in P1 with a reduction in sphericity and an overall increase in cell volume from 474.7 ± 32.1 µm(3) to 725.2 ± 35.6 µm(3). Furthermore, the effect of 2-dimensional (2-D) culture-induced dedifferentiation on mechanotransduction was investigated, whereby RVI and Gd(3+)-sensitive REV5901-induced calcium rise were only observed in 2-D cultured chondrocytes. A significant up-regulation of types I and II collagens and Sox9 was observed in P1 chondrocytes and no further significant change in type I collagen but a return to baseline levels of type II collagen and Sox9 upon further culture.

CONCLUSION

These data indicated the presence of an intermediate, mesodifferentiated phenotype and highlight the importance of mechanotransduction as a marker of the chondrocytic cell type.

Preparation and evaluation of the electrospun chitosan/PEO fibers for potential applications in cartilage tissue engineering

Fibrous materials have morphological similarities to natural cartilage extracellular matrix and have been considered as candidate for bone tissue engineering scaffolds. In this study, we have evaluated a novel electrospun chitosan mat composed of oriented sub-micron fibers for its tensile property and biocompatibility with chondrocytes (cell attachment, proliferation and viability). Scanning electronic microscope images showed the fibers in the electrospun chitosan mats were indeed aligned and there was a slight cross-linking between the parent fibers. The electrospun mats have significantly higher elastic modulus (2.25 MPa) than the cast films (1.19 MPa). Viability of cells on the electrospun mat was 69% of the cells on tissue-culture polystyrene (TCP control) after three days in culture, which was slightly higher than that on the cast films (63% of the TCP control). Cells on the electrospun mat grew slowly the first week but the growth rate increased after that. By day 10, cell number on the electrospun mat was almost 82% that of TCP control, which was higher than that of cast films (56% of TCP). The electrospun chitosan mats have a higher Young's modulus (P < 0.01) than cast films and provide good chondrocyte biocompatibility. The electrospun chitosan mats, thus, have the potential to be further processed into three-dimensional scaffolds for cartilage tissue repair.

The use of multidimensional image-based analysis to accurately monitor cell growth in 3D bioreactor culture

The transition from traditional culture methods towards bioreactor based bioprocessing to produce cells in commercially viable quantities for cell therapy applications requires the development of robust methods to ensure the quality of the cells produced. Standard methods for measuring cell quality parameters such as viability provide only limited information making process monitoring and optimisation difficult. Here we describe a 3D image-based approach to develop cell distribution maps which can be used to simultaneously measure the number, confluency and morphology of cells attached to microcarriers in a stirred tank bioreactor. The accuracy of the cell distribution measurements is validated using in silico modelling of synthetic image datasets and is shown to have an accuracy >90%. Using the cell distribution mapping process and principal component analysis we show how cell growth can be quantitatively monitored over a 13 day bioreactor culture period and how changes to manufacture processes such as initial cell seeding density can significantly influence cell morphology and the rate at which cells are produced. Taken together, these results demonstrate how image-based analysis can be incorporated in cell quality control processes facilitating the transition towards bioreactor based manufacture for clinical grade cells.

Cell expansion of human articular chondrocytes on macroporous gelatine scaffolds-impact of microcarrier selection on cell proliferation

This study investigates human chondrocyte expansion on four macroporous gelatine microcarriers (CultiSpher) differing with respect to two manufacturing processes-the amount of emulsifier used during initial preparation and the gelatine cross-linking medium. Monolayer-expanded articular chondrocytes from three donors were seeded onto the microcarriers and cultured in spinner flask systems for a total of 15 days. Samples were extracted every other day to monitor cell viability and establish cell counts, which were analysed using analysis of variance and piecewise linear regression. Chondrocyte densities increased according to a linear pattern for all microcarriers, indicating an ongoing, though limited, cell proliferation. A strong chondrocyte donor effect was seen during the initial expansion phase. The final cell yield differed significantly between the microcarriers and our results indicate that manufacturing differences affected chondrocyte densities at this point. Remaining cells stained positive for chondrogenic markers SOX-9 and S-100 but extracellular matrix formation was modest to undetectable. In conclusion, the four gelatine microcarriers supported chondrocyte adhesion and proliferation over a two week period. The best yield was observed for microcarriers produced with low emulsifier content and cross-linked in water and acetone. These results add to the identification of optimal biomaterial parameters for specific cellular processes and populations.

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.

Effects of oxygen and culture system on in vitro propagation and redifferentiation of osteoarthritic human articular chondrocytes

Regenerative medicine-based approaches for the repair of damaged cartilage rely on the ability to propagate cells while promoting their chondrogenic potential. Thus, conditions for cell expansion should be optimized through careful environmental control. Appropriate oxygen tension and cell expansion substrates and controllable bioreactor systems are probably critical for expansion and subsequent tissue formation during chondrogenic differentiation. We therefore evaluated the effects of oxygen and microcarrier culture on the expansion and subsequent differentiation of human osteoarthritic chondrocytes. Freshly isolated chondrocytes were expanded on tissue culture plastic or CultiSpher-G microcarriers under hypoxic or normoxic conditions (5% or 20% oxygen partial pressure, respectively) followed by cell phenotype analysis with flow cytometry. Cells were redifferentiated in micromass pellet cultures over 4 weeks, under either hypoxia or normoxia. Chondrocytes cultured on tissue culture plastic proliferated faster, expressed higher levels of cell surface markers CD44 and CD105 and demonstrated stronger staining for proteoglycans and collagen type II in pellet cultures compared with microcarrier-cultivated cells. Pellet wet weight, glycosaminoglycan content and expression of chondrogenic genes were significantly increased in cells differentiated under hypoxia. Hypoxia-inducible factor-3α mRNA was up-regulated in these cultures in response to low oxygen tension. These data confirm the beneficial influence of reduced oxygen on ex vivo chondrogenesis. However, hypoxia during cell expansion and microcarrier bioreactor culture does not enhance intrinsic chondrogenic potential. Further improvements in cell culture conditions are therefore required before chondrocytes from osteoarthritic and aged patients can become a useful cell source for cartilage regeneration.

Effect of fiber diameter on the spreading, proliferation and differentiation of chondrocytes on electrospun chitosan matrices

Tissue-engineered neocartilage with appropriate biomechanical properties holds promise not only for graft applications but also as a model system for controlled studies of chondrogenesis. Our objective in the present research study is to better understand the impact of fiber diameter on the cellular activity of chondrocytes cultured on nanofibrous matrices. By using the electrospinning process, fibrous scaffolds with fiber diameters ranging from 300 nm to 1 μm were prepared and the physicomechanical properties of the scaffolds were characterized. Bovine articular chondrocytes were then seeded and maintained on the scaffolds for 7 and 14 days in culture. An upregulation in the gene expression of collagen II was noted with decreasing fiber diameters. For cells that were cultured on scaffolds with a mean fiber diameter of 300 nm, a 2-fold higher ratio of collagen II/collagen I was noted when compared to cells cultured on sponge-like scaffolds prepared by freeze drying and lyophilization. Integrin (α(5), αv, β(1)) gene expression was also observed to be influenced by matrix morphology. Our combined results suggest that matrix geometry can regulate and promote the retention of the chondrocyte genotype.

Expansion and preservation of multipotentiality of rabbit bone-marrow derived mesenchymal stem cells in dextran-based microcarrier spin culture

The use of mesenchymal stem cells (MSCs) in tissue repair and regeneration despite their multipotentiality has been limited by their cell source quantity and decelerating proliferative yield efficiency. A study was thus undertaken to determine the feasibility of using microcarrier beads in spinner flask cultures for MSCs expansion and compared to that of conventional monolayer cultures and static microcarrier cultures. Isolation and characterization of bone marrow derived MSCs were conducted from six adult New Zealand white rabbits. Analysis of cell morphology on microcarriers and culture plates at different time points (D0, D3, D10, D14) during cell culture were performed using scanning electron microscopy and bright field microscopy. Cell proliferation rates and cell number were measured over a period of 14 days, respectively followed by post-expansion characterization. MTT proliferation assay demonstrated a 3.20 fold increase in cell proliferation rates in MSCs cultured on microcarriers in spinner flask as compared to monolayer cultures (p < 0.05). Cell counts at day 14 were higher in those seeded on stirred microcarrier cultures (6.24 ± 0.0420 cells/ml) × 10(5) as compared to monolayer cultures (0.22 ± 0.004 cells/ml) × 10(5) and static microcarrier cultures (0.20 ± 0.002 cells/ml) × 10(5). Scanning electron microscopy demonstrated an increase in cell colonization of the cells on the microcarriers in stirred cultures. Bead-expanded MSCs were successfully differentiated into osteogenic and chondrogenic lineages. This system offers an improved and efficient alternative for culturing MSCs with preservation to their phenotype and multipotentiality.

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.

Functional Cells Cultured on Microcarriers for Use in Regenerative Medicine Research

Microcarriers have been successfully used for many years for growing anchorage-dependent cells and as a means of delivering cells for tissue repair. When cultured on microcarriers, the number of anchorage-dependent cells, including primary cells, can easily be scaled up and controlled to generate the quantities of cells necessary for therapeutic applications. Recently, stem cell technology has been recognized as a powerful tool in regenerative medicine, but adequate numbers of stem cells that retain their differentiation potential are still difficult to obtain. For anchorage-dependent stem cells, however, microcarrier-based suspension culture using various types of microcarriers has proven to be a good alternative for effective ex vivo expansion. In this article, we review studies reporting the expansion, differentiation, or transplantation of functional anchorage-dependent cells that were expanded with the microcarrier culture system. Thus, the implementation of technological advances in biodegradable microcarriers, the bead-to-bead transfer process, and appropriate stem cell media may soon foster the ability to produce the numbers of stem cells necessary for cell-based therapies and/or tissue engineering.

Dynamic three-dimensional culture methods enhance mesenchymal stem cell properties and increase therapeutic potential

Mesenchymal stem cells (MSCs) are capable of self-renewal and differentiation along the osteogenic, chondrogenic, and adipogenic lineages and have potential applications in a range of therapies. MSCs can be cultured as monolayers on tissue culture plastic, but there are indications that they lose cell-specific properties with time in vitro and so poorly reflect in vivo MSC behavior. We developed dynamic three-dimensional (3D) techniques for in vitro MSC culture using spinner flasks and a rotating wall vessel bioreactor. We characterized the two methods for dynamic 3D MSC culture and compared the properties of these cultures with monolayer MSCs. Our results showed that under optimal conditions, MSCs form compact cellular spheroids and remain viable in dynamic 3D culture. We demonstrated altered cell size and surface antigen expression together with enhanced osteogenic and adipogenic differentiation potential in MSCs from dynamic 3D conditions. By microarray analysis of monolayer and spinner flask MSCs, we identified many differences in gene expression, including those confirming widespread changes to the cellular architecture and extracellular matrix. The upregulation of interleukin 24 in dynamic 3D cultures was shown to selectively impair the viability of prostate cancer cells cultured in medium conditioned by dynamic 3D MSCs. Overall, this work suggests a novel therapeutic application for dynamic 3D MSCs and demonstrates that these methods are a viable alternative to monolayer techniques and may prove beneficial for retaining MSC properties in vitro.

Biodegradable and injectable cure-on-demand polyurethane scaffolds for regeneration of articular cartilage

This paper describes the synthesis and characterization of an injectable methacrylate functionalized urethane-based photopolymerizable prepolymer to form biodegradable hydrogels. The tetramethacrylate prepolymer was based on the reaction between two synthesized compounds, diisocyanato poly(ethylene glycol) and monohydroxy dimethacrylate poly(epsilon-caprolactone) triol. The final prepolymer was hydrated with phosphate-buffered saline (pH 7.4) to yield a biocompatible hydrogel containing up to 86% water. The methacrylate functionalized prepolymer was polymerized using blue light (450 nm) with an initiator, camphorquinone and a photosensitizer, N,N-dimethylaminoethyl methacrylate. The polymer was stable in vitro in culture media over the 28 days tested (1.9% mass loss); in the presence of lipase, around 56% mass loss occurred over the 28 days in vitro. Very little degradation occurred in vivo in rats over the same time period. The polymer was well tolerated with very little capsule formation and a moderate host tissue response. Human chondrocytes, seeded onto Cultispher-S beads, were viable in the tetramethacrylate prepolymer and remained viable during and after polymerization. Chondrocyte-bead-polymer constructs were maintained in static and spinner culture for 8 weeks. During this time, cells remained viable, proliferated and migrated from the beads through the polymer towards the edge of the polymer. New extracellular matrix (ECM) was visualized with Masson's trichrome (collagen) and Alcian blue (glycosaminoglycan) staining. Further, the composition of the ECM was typical for articular cartilage with prominent collagen type II and type VI and moderate keratin sulphate, particularly for tissue constructs cultured under dynamic conditions.

Preparation of resorbable collagen-based beads for direct use in tissue engineering and cell therapy applications

For tissue engineering and cell therapy applications, expansion of cells such as chondrocytes on beads in spinner culture can provide advantages compared with monolayer culture. The use of resorbable beads that can be included as an integral part of the construct provides the advantage of minimizing the extent of cell handling and eliminating a final trypsin treatment to detach cells from the bead. In this study, we have made various types of beads based on native collagen and denatured collagen (gelatin). The beads have been stabilized by different extents of glutaraldehyde cross-linking, and characterized by a combination of chemical analysis, thermal stability, and microscopy. In vitro examination in the presence and absence of chondrocytes showed that stability increased with the extent of crosslinking and could also be influenced by the manner of fabrication. On the basis of the in vitro stability studies, gelatin beads of a defined stability were shown to resorb over time in subcutaneous implants in nude mice compared with more stable demineralized bone particle (DMB) carriers. These data indicate that for direct use in tissue engineering or cell therapy applications, where resorbable beads can be used for cell expansion and then direct delivery of cells, it is possible to design suitable carrier beads with a range of stabilities that match the implant requirements.

Chondrocytes cultured in stirred suspension with serum-free medium containing pluronic-68 aggregate and proliferate while maintaining their differentiated phenotype

The study of chondrocyte biology requires culture conditions that maintain cell phenotype. Phenotype is rapidly lost in monolayer but is maintained in 3-dimensional scaffolds, which however, experience limited cell proliferation and limited mass transport. In this study, we cultured chondrocytes in aggregates in stirred spinner flask suspension cultures to control aggregate size and promote mass transport. A previously optimized serum-free medium, containing the following growth factors (GFs), epidermal growth factor, platelet-derived growth factor-BB, and basic fibroblast growth factor, all at 2 ng/mL, was used as a control medium. In addition, two modified media were tested: one containing Pluronic F-68 (PF-68) and the other containing PF-68 with 10 times greater GF concentration (20 ng/mL, medium PF-68/10 x GF). Chondrocytes formed limited-size aggregates within 24 h and exhibited high viability (>95%), and cell concentration doubled in 7 days in the presence of PF-68. Low or no collagen I expression was found for any of the three media, whereas collagen II accumulated between cells, as revealed by a dense immunostaining. Integrin alpha10, a marker of differentiated chondrocytes and chondrogenic cells, was also found to be highly expressed. Aggregates resulting from spinner culture were found to be relevant in vitro models and their use for cartilage repair to be also conceivable.