Ectopic Cartilage Formation Induced by Mesenchymal Stem Cells on Porous Gelatin-Chondroitin-Hyaluronate Scaffold Containing Microspheres Loaded with TGF-β1

Gelatin Microsphere for Cartilage Tissue Engineering: Current and Future Strategies

The gelatin microsphere (GM) provides an attractive option for tissue engineering due to its versatility, as reported by various studies. This review presents the history, characteristics of, and the multiple approaches to, the production of GM, and in particular, the water in oil emulsification technique. Thereafter, the application of GM as a drug delivery system for cartilage diseases is introduced. The review then focusses on the emerging application of GM as a carrier for cells and biologics, and biologics delivery within a cartilage construct. The influence of GM on chondrocytes in terms of promoting chondrocyte proliferation and chondrogenic differentiation is highlighted. Furthermore, GM seeded with cells has been shown to have a high tendency to form aggregates; hence the concept of using GM seeded with cells as the building block for the formation of a complex tissue construct. Despite the advancement in GM research, some issues must still be addressed, particularly the improvement of GM’s ability to home to defect sites. As such, the strategy of intraarticular injection of GM seeded with antibody-coated cells is proposed. By addressing this in future studies, a better-targeted delivery system, that would result in more effective intervention, can be achieved.

Expansion and Chondrogenic Differentiation of Human Mesenchymal Stem Cells

The potential of human mesenchymal stem cells (hMSC) to differentiate into various types of mesenchymal tissue, such as chondrocytes, makes them a potential cell source in cartilage tissue engineering. Because of the requirement of high cell amounts for the generation of cartilage implants or for the extensive experimental studies to investigate the culture parameters, the initial cells have to be expanded, which leads to high population doubling numbers. It is known that hMSC can differentiate into chondrocytes at least up to the 15th population doubling. To monitor the differentiation status, the protein MIA (melanoma inhibitory activity), which is only synthesized by malignant melanomas and chondrocytes, can be used. In this study the chondrogenic differentiation potential of hMSC beyond the 15th population doubling was investigated using MIA as a chondrocyte marker. A chondrogenic potential of hMSC at higher population doubling numbers may be of interest due to the requirement of less frequent isolations of cells. Therefore hMSC were cultured in a monolayer until the 37th population doubling. Cells of different passages were cultured as pellets for two weeks in transforming growth factor (TGF)-β3 containing differentiation medium. The MIA contents in medium on the last three cultivation days were measured for each case using an MIA-ELISA-kit. A significant difference between MIA content in medium of the pellet and non-stimulated monolayer reference cultures was detectable until the 32nd population doubling. In addition, the hMSC were seeded at lower densities to investigate whether the cells may be expanded faster and with less amount of work due to higher population doubling numbers per passage. The reduced inoculation density led to an increased growth rate. (Int J Artif Organs 2007; 30: 611–8)

Comparison of Chondral Defects Repair with In Vitro and In Vivo Differentiated Mesenchymal Stem Cells

The purpose of this study was to compare chondral defects repair with in vitro and in vivo differentiated mesenchymal stem cells (MSCs). A novel PLGA-gelatin/chondroitin/hyaluronate (PLGA-GCH) hybrid scaffold with transforming growth factor-β1 (TGF-β1)-impregnated microspheres (MS-TGF) was fabricated to mimic the extracellular matrix. MS-TGF showed an initial burst release (22.5%) and a subsequent moderate one that achieved 85.1% on day 21. MSCs seeded on PLGA-GCH/MS-TGF or PLGA-GCH were incubated in vitro and showed that PLGA-GCH/MS-TGF significantly augmented proliferation of MSCs and glycosaminoglycan synthesis compared with PLGA-GCH. Then MSCs seeded on PLGA-GCH/MS-TGF were implanted and differentiated in vivo to repair chondral defect on the right knee of rabbit (in vivo differentiation repair group), while the contralateral defect was repaired with in vitro differentiated MSCs seeded on PLGA-GCH (in vitro differentiation repair group). The histology observation demonstrated that in vivo differentiation repair showed better chondrocyte morphology, integration, and subchondral bone formation compared with in vitro differentiation repair 12 and 24 weeks postoperatively, although there was no significant difference after 6 weeks. The histology grading score comparison also demonstrated the same results. The present study implies that in vivo differentiation induced by PLGA-GCH/MS-TGF and the host microenviroment could keep chondral phenotype and enhance repair. It might serve as another way to induce and expand seed cells in cartilage tissue engineering.

Proteomic analysis of chondromodulin-I-induced differentiation of mesenchymal stem cells into chondrocytes

To identify novel proteins that might help clarify the molecular mechanisms underlying chondromodulin-I (ChM-I) induction of mesenchymal stem cells (MSCs) differentiate into chondrocytes. MSCs are triggered to differentiate into chondrocytes, which are recognized as important factors in cartilage tissue engineering. ChM-I is a glycoprotein that stimulates the growth of chondrocytes and inhibits angiogenesis in vitro. In this study, the proteomic approach was used to evaluate protein changes between undifferentiated MSCs and ChM-I-transfected MSCs. The expression of the protein spots was analyzed using two-dimensional gel electrophoresis. Then, 14 protein spots were identified between MSCs and ChM-I-transfected MSCs. 309 proteins were identified using mass spectrometry (MS). The differentially regulated proteins were categorized and annotated using Protein Analysis Through Evolutionary Relationships (PANTHER) analysis with the aid of the Database for Annotation, Visualization and Integrated Discovery (DAVID) tool. These proteins are included in a variety of metabolic pathways and signal transduction pathways, such as focal adhesion, glycolysis, actin cytoskeleton regulation, and ribosome. These results demonstrate novel information about the molecular mechanism by which ChM-I induce MSCs to differentiate into chondrocytes. These results also provide a solid foundation for the development of tissue-engineered cartilage.

Stem cells display a donor dependent response to escalating levels of growth factor release from extracellular matrix-derived scaffolds

Numerous growth factor delivery systems have been developed for tissue engineering. However, little is known about how the dose of a specific protein will influence tissue regeneration, or how different patients will respond to altered levels of growth factor presentation. The objective of the present study was to assess stem cell chondrogenesis within extracellular-matrix (ECM)-derived scaffolds loaded with escalating levels of transforming growth factor (TGF)-β3. It was also sought to determine if stem cells display a donor-dependent response to different doses of TGF-β3, from low (5 ng) to high (200 ng), released from such scaffolds. It was found that ECM-derived scaffolds possess the capacity to bind and release increasing amounts of TGF-β3, with between 60% and 75% of this growth factor released into the media over the first 12 days of culture. After seeding these scaffolds with human infrapatellar fat pad-derived stem cells (FPSCs), it was found that cartilage-specific ECM accumulation was greatest for the higher levels of growth factor loading. Importantly, soak-loading cartilage ECM-derived scaffolds with high levels of TGF-β3 always resulted in at least comparable levels of chondrogenesis to controls where this growth factor was continuously added to the culture media. Similar results were observed for FPSCs from all donors, although the absolute level of secreted matrix did vary from donor to donor. Therefore, while no single growth factor release profile will be optimal for all patients, the results of this study suggest that the combination of a highly porous cartilage ECM-derived scaffold coupled with appropriate levels of TGF-β3 can consistently drive chondrogenesis of adult stem cells. Copyright © 2016 John Wiley & Sons, Ltd.

Chondrogenic differentiation of ChM-I gene transfected rat bone marrow-derived mesenchymal stem cells on 3-dimensional poly (L-lactic acid) scaffold for cartilage engineering

We have explored the role of Chondromodulin-I (ChM-I) in chondrogenesis of bone marrow-derived mesenchymal stem cells (BMSCs) in 3-dimensional (3D) scaffold for cartilage tissue engineering. BMSCs of Sprague Dawley (SD) rats were cultured on poly-(L-lactic acid) [PLLA] scaffolds with different pore sizes (80-200 μm, 200-450 μm) with or without surface modification by chitosan. Cell viability, proliferation, and morphology were measured using confocal microscope and the CCK-8 method. Untransfected BMSCs, BMSCs expressing pcDNA3.1(+), BMSCs expressing plasmid pcDNA3.1 (+)/ChM-I were cultured on 3D scaffolds in standard growth medium or transforming growth factor-β1 (TGF-β1) supplemented chondrogenic induction medium in vitro for 3 weeks and the expression of collagen type II was determined. Cell-scaffolds constructs were implanted subcutaneously for 3 months in vivo. BMSCs had a higher viability and proliferation in PLLA scaffolds of pore size 200-450 μm than that of 80-200 μm, and surface modification with chitosan did not enhance cell attachment. The ChM-I gene enhanced chondrogenesis and increased collagen type II synthesis. Immunohistochemistry from in vivo study showed enhanced cartilage regeneration in BMSCs expressing pcDNA3.1 (+)/ChM-I on 3D PLLA scaffolds. It also demonstrated that TGF-β1 might promote chondrogenesis of rat BMSCs by synergizing with the ChM-I gene. ChM-I could be beneficial to future applications in cartilage repair.

Transforming growth factor Beta-releasing scaffolds for cartilage tissue engineering

The maintenance of a critical threshold concentration of transforming growth factor beta (TGF-β) for a given period of time is crucial for the onset and maintenance of chondrogenesis. Thus, the development of scaffolds that provide temporal and/or spatial control of TGF-β bioavailability has appeal as a mechanism to induce the chondrogenesis of stem cells in vitro and in vivo for articular cartilage repair. In the past decade, many types of scaffolds have been designed to advance this goal: hydrogels based on polysaccharides, hyaluronic acid, and alginate; protein-based hydrogels such as fibrin, gelatin, and collagens; biopolymeric gels and synthetic polymers; and solid and hybrid composite (hydrogel/solid) scaffolds. In this study, we review the progress in developing strategies to deliver TGF-β from scaffolds with the aim of enhancing chondrogenesis. In the future, such scaffolds could prove critical for tissue engineering cartilage, both in vitro and in vivo.

Natural and Genetically Engineered Proteins for Tissue Engineering

To overcome the limitations of traditionally used autografts, allografts and, to a lesser extent, synthetic materials, there is the need to develop a new generation of scaffolds with adequate mechanical and structural support, control of cell attachment, migration, proliferation and differentiation and with bio-resorbable features. This suite of properties would allow the body to heal itself at the same rate as implant degradation. Genetic engineering offers a route to this level of control of biomaterial systems. The possibility of expressing biological components in nature and to modify or bioengineer them further, offers a path towards multifunctional biomaterial systems. This includes opportunities to generate new protein sequences, new self-assembling peptides or fusions of different bioactive domains or protein motifs. New protein sequences with tunable properties can be generated that can be used as new biomaterials. In this review we address some of the most frequently used proteins for tissue engineering and biomedical applications and describe the techniques most commonly used to functionalize protein-based biomaterials by combining them with bioactive molecules to enhance biological performance. We also highlight the use of genetic engineering, for protein heterologous expression and the synthesis of new protein-based biopolymers, focusing the advantages of these functionalized biopolymers when compared with their counterparts extracted directly from nature and modified by techniques such as physical adsorption or chemical modification.

Isolation, culture, and osteogenic/chondrogenic differentiation of bone marrow-derived mesenchymal stem cells

Musculoskeletal disorders, as non-healing fractures and large bone defects, articular cartilage and subchondral bone injuries, often result in lifelong chronic pain and compromised quality of life. Although generally a natural process, failure of large bone defects to heal such as after complex fractures, resection of tumours, infections, or revisions of joint replacements remains a critical challenge that requires more appropriate solutions as those currently available. In addition, regeneration of chondral and osteochondral defects continues to be a challenge until to date. A profound understanding of the underlying mechanisms of endogenous regeneration is a prerequisite for successful bone and cartilage regeneration. Presently, one of the most promising therapeutic approaches is cell-based tissue engineering which provides a healthy population of cells to the injured site. Use of differentiated cells has severe limitations; an excellent alternative would be the application of adult marrow stromal cells/mesenchymal stem cells (MSC) which possess extensive proliferation potential and proven capability to differentiate along the osteochondral pathway. The process of osteo-/chondrogenesis can be mimicked in vitro by inducing osteo-chondroprogenitor stem cells to undergo osteogenesis and chondrogenesis through exposure of osteo-/chondrogenic favourable microenvironmental, mechanical, and nutritional conditions. This chapter provides comprehensive protocols for the isolation, expansion, and osteo-/chondrogenic differentiation of adult bone marrow-derived MSC.

Cartilage regeneration using adipose-derived stem cells and the controlled-released hybrid microspheres

OBJECTIVE

This study was to evaluate the effect of hybrid microspheres (MS) composed of gelatin transforming growth factor-beta (TGF-beta1)-loaded MS and chitosan MS on the enhancement of differentiation of adipose-derived stem cells (ASCs) into chondrocytes in pellet culture in vitro and the reparative capacity of pellet from ASCs and the hybrid MS-TGF used to repair cartilage defects in vivo.

METHODS

The morphology of the controlled-released MS was observed with scanning electron microscopy (SEM) and mechanical property was also tested in this study. In vitro TGF-beta1 release was evaluated by an enzyme-linked immunosorbent assay. The protein expression of Collagen II was tested by Western blot. In addition, a preliminary study on cartilage regeneration was also performed in vivo.

RESULTS

When chondrogenic differentiation of ASCs in both MS was evaluated, the protein expression of Collagen II became significantly increased for the hybrid MS-TGF, as compared with the gelatin MS-TGF. Mechanical result showed that the hybrid MS was superior to the gelatin MS. Observation of histology in vivo demonstrated that the pellet from ASCs and the hybrid MS-TGF promoted cartilage regeneration in the defects of articular cartilage much better than other groups.

CONCLUSION

Our study demonstrated that the pellet from ASCs and the hybrid MS-TGF can provide an easy and effective way to construct the tissue engineered cartilage in vitro and in vivo.

Cartilage tissue engineering: towards a biomaterial-assisted mesenchymal stem cell therapy

Injuries to articular cartilage are one of the most challenging issues of musculoskeletal medicine due to the poor intrinsic ability of this tissue for repair. Despite progress in orthopaedic surgery, the lack of efficient modalities of treatment for large chondral defects has prompted research on tissue engineering combining chondrogenic cells, scaffold materials and environmental factors. The aim of this review is to focus on the recent advances made in exploiting the potentials of cell therapy for cartilage engineering. These include: 1) defining the best cell candidates between chondrocytes or multipotent progenitor cells, such as multipotent mesenchymal stromal cells (MSC), in terms of readily available sources for isolation, expansion and repair potential; 2) engineering biocompatible and biodegradable natural or artificial matrix scaffolds as cell carriers, chondrogenic factors releasing factories and supports for defect filling, 3) identifying more specific growth factors and the appropriate scheme of application that will promote both chondrogenic differentiation and then maintain the differentiated phenotype overtime and 4) evaluating the optimal combinations that will answer to the functional demand placed upon cartilage tissue replacement in animal models and in clinics. Finally, some of the major obstacles generally encountered in cartilage engineering are discussed as well as future trends to overcome these limiting issues for clinical applications.

Silk fibroin/hyaluronan scaffolds for human mesenchymal stem cell culture in tissue engineering

The design of new bioactive scaffolds mimicking the physiologic environment present during tissue formation is an important frontier in biomaterials research. Herein, we evaluated scaffolds prepared from blends of two biopolymers: silk fibroin and hyaluronan. Our rationale was that such blends would allow the combination of silk fibroin's superior mechanical properties with the biological characteristics of hyaluronan. We prepared scaffolds with porous microstructures by freeze-drying aqueous solutions of silk fibroin and hyaluronan and subsequent incubation in methanol to induce water insolubility of silk fibroin. Hyaluronan acted as an efficient porogenic excipient for the silk fibroin scaffolding process, allowing the formation of microporous structures within the scaffolds under mild processing conditions. Mesenchymal stem cells were seeded on silk fibroin/hyaluronan scaffolds and cultured for three weeks. Histology of the constructs after cell culture showed enhanced cellular ingrowth into silk fibroin/hyaluronan scaffolds as compared to plain silk fibroin scaffolds. In the presence of tissue-inductive stimuli, in vitro stem cell culture on silk fibroin/hyaluronan scaffolds resulted in more efficient tissue formation when measured by glycosaminoglycan and type-I and type-III collagen gene expression, as compared to plain silk fibroin scaffolds. In conclusion, our data encourages further exploration of silk fibroin/hyaluronan scaffolds as biomimetic platform for mesenchymal stem cells in tissue engineering.

Mesenchymal stem cell-based repair of articular cartilage with polyglycolic acid-hydroxyapatite biphasic scaffold

This study investigates the capacity of a composite scaffold composed of polyglycolic acid-hydroxyapatite (PGA-HA) and autologous mesenchymal stem cells (MSCs) to promote repair of osteochondral defects. MSCs from culture-expanded rabbits were seeded onto a PGA and HA scaffold. After a 72-hour co-culture period, the cell-adhered PGA and HA were joined together, forming an MSCs-PGA-HA composite. Full-thickness cartilage defects in the intercondylar fossa of the femur were then implanted with the MSC-PGA-HA composite, the PGA-HA scaffold only, or they were left empty (n=20). Animals were sacrificed 16 or 32 weeks after surgery and the gross appearance of the defects was evaluated. The specimens were examined histologically for morphologic features, and stained immunohistochemically for type 2 collagen. Specimens of the MSCs-PGA-HA composite implantation group demonstrated hyaline cartilage and a complete subchondral bone formation. At 16 weeks post-implantation, significant integration of the newly formed tissue with surrounding normal cartilage and subchondral bone was observed when compared to the two control groups. At 32 weeks, no sign of progressive degeneration of the newly formed tissue was found. A significant difference in histological grading score was found compared with the control groups. The novel MSCs-seeded, PGA-HA biphasic graft facilitated both articular cartilage and subchondral bone regeneration in an animal model and might serve as a new approach for clinical applications.

Smart biomaterials for tissue engineering of cartilage

Biological regeneration using cartilage tissue engineering in which cells are grown on biomaterial scaffolds and then implanted into the cartilage defects could provide new treatment options for articular cartilage defects. This review aims to give an overview of the wide variety of biomaterials that are currently developed as scaffolds for cartilage tissue engineering. Emphasis will be placed on the current development of the materials that are able to direct cell differentiation and metabolism. These so-called "smart" biomaterials are produced by modifying the physical properties of the scaffolds using peptide sequences and most importantly by developing materials that can deliver proteins to enhance tissue regeneration. Besides providing drug delivery systems, the materials respond to environmental stimuli or release their cargo on cellular demand. However, critical issues remain, such as the transferability of basic science insights to clinical products and the applicability of certain data sets to human patients.

The dependence of in vivo stable ectopic chondrogenesis by human mesenchymal stem cells on chondrogenic differentiation in vitro

In vivo niche plays an important role in determining the fate of implanted mesenchymal stem cells (MSCs) by directing committed differentiation. An inappropriate in vivo niche can also alter desired ultimate fate of exogenous MSCs even they are in vitro induced to express a specific phenotype before in vivo implantation. Studies have shown that in vitro chondrogenically differentiated MSCs are apt to lose their phenotype and fail to form stable cartilage in subcutaneous environment. We hypothesized that failure of maintaining the phenotype of induced MSCs in subcutaneous environment is due to the insufficient chondrogenic differentiation in vitro and fully differentiated MSCs can retain their chondrocyte-like phenotype and form stable ectopic cartilage. To test this hypothesis, extended in vitro chondrogenic induction and cartilage formation were carried out before implantation. Human bone marrow stem cells (hBMSCs) were seeded onto polylactic acid coated polyglycolic acid scaffolds. The cell-scaffold constructs were chondrogenically induced from 4 to 12 weeks for in vitro chondrogenesis, and then implanted subcutaneously into nude mice for 12 or 24 weeks. The engineered cartilages were evaluated by gross view, glycosaminoglycan content measurement, and histological staining before and after implantation. Histological examination showed typical cartilage structure formation after 8 weeks of induction in vitro. However, part of the constructs became ossified after implantation when in vitro induction lasted 8 weeks or less time. In contrast, those induced for 12 weeks in vitro could retain their cartilage structure after in vivo implantation. These results indicate that a fully differentiated stage achieved by extended chondrogenic induction in vitro is necessary for hBMSCs to form stable ectopic chondrogenesis in vivo.

Gelatin microspheres containing TGF-beta3 enhance the chondrogenesis of mesenchymal stem cells in modified pellet culture

The study is to investigate the chondrogenesis of a kind of modified cell pellet formed using mesenchymal stem cells (MSCs) and gelatin microspheres containing transforming growth factor beta3 (TGF-beta3). The gelatin microspheres loaded with TGF-beta3 (MS-TGF) were prepared and showed the controlled release of cytokine in a biphasic fashion. Then the mixture of MSCs and MS-TGF was centrifuged to form pellet. The pellet was cultured over 4 weeks to determine the effects of MS-TGF on cartilage matrix production by biochemical analysis, immunohistochemistry staining, and Western blot test. The transcription level of cartilage-related genes was also evaluated by real-time quantitative RT-PCR assay. After 4 weeks of culture, the MSCs were distributed uniformly in the pellet and had good viability. Cells showed faster proliferation and higher DNA content compared to MSCs in a conventional pellet. The production of collagen and glycosaminoglycan also increased significantly. The immunohistochemistry staining and alcian blue staining confirmed the synthesis of cartilage extracellular matrix (ECM). Furthermore, the differentiated MSCs located in lacunae within the metachromatic staining matrix exhibited the typical chondrocyte morphology. The chondrogenic differentiation of MSCs was proved by the expression of collagen II gene in mRNA and protein level. The results indicate that MS-TGF can induce chondrogenic differentiation of MSCs and increase cartilage ECM production, which result in a bigger cartilage pellet. In conclusion, this modified pellet culture can provide an easy and effective way to construct the tissue-engineered cartilage in vitro.