Heparin-Bound Transforming Growth Factor-β3 Enhances Neocartilage Formation by Rabbit Mesenchymal Stem Cells

Cell mediated reactions create TGF-β delivery limitations in engineered cartilage

During native cartilage development, endogenous TGF-β activity is tightly regulated by cell-mediated chemical reactions in the extracellular milieu (e.g., matrix and receptor binding), providing spatiotemporal control in a manner that is localized and short acting. These regulatory paradigms appear to be at odds with TGF-β delivery needs in tissue engineering (TE) where administered TGF-β is required to transport long distances or reside in tissues for extended durations. In this study, we perform a novel examination of the influence of cell-mediated reactions on the spatiotemporal distribution of administered TGF-β in cartilage TE applications. Reaction rates of TGF-β binding to cell-deposited ECM and TGF-β internalization by cell receptors are experimentally characterized in bovine chondrocyte-seeded tissue constructs. TGF-β binding to the construct ECM exhibits non-linear Brunauer-Emmett-Teller (BET) adsorption behavior, indicating that as many as seven TGF-β molecules can aggregate at a binding site. Cell-mediated TGF-β internalization rates exhibit a biphasic trend, following a Michaelis-Menten relation (Vmax = 2.4 molecules cell-1 s-1, Km = 1.7 ng mL-1) at low ligand doses (≤130 ng/mL), but exhibit an unanticipated non-saturating power trend at higher doses (≥130 ng/mL). Computational models are developed to illustrate the influence of these reactions on TGF-β spatiotemporal delivery profiles for conventional TGF-β administration platforms. For TGF-β delivery via supplementation in culture medium, these reactions give rise to pronounced steady state TGF-β spatial gradients; TGF-β concentration decays by ∼90 % at a depth of only 500 μm from the media-exposed surface. For TGF-β delivery via heparin-conjugated affinity scaffolds, cell mediated internalization reactions significantly reduce the TGF-β scaffold retention time (160-360-fold reduction) relative to acellular heparin scaffolds. This work establishes the significant limitations that cell-mediated chemical reactions engender for TGF-β delivery and highlights the need for novel delivery platforms that account for these reactions to achieve optimal TGF-β exposure profiles. STATEMENT OF SIGNIFICANCE: During native cartilage development, endogenous TGF-β activity is tightly regulated by cell-mediated chemical reactions in the extracellular milieu (e.g., matrix and receptor binding), providing spatiotemporal control in a manner that is localized and short acting. However, the effect of these reactions on the delivery of exogenous TGF-β to engineered cartilage tissues remains not well understood. In this study, we demonstrate that cell-mediated reactions significantly restrict the delivery of TGF-β to cells in engineered cartilage tissue constructs. For delivery via media supplementation, reactions significantly limit TGF-β penetration into constructs. For delivery via scaffold loading, reactions significantly limit TGF-β residence time in constructs. Overall, these results illustrate the impact of cell-mediated chemical reactions on TGF-β delivery profiles and support the importance of accounting for these reactions when designing TGF-β delivery platforms for promoting cartilage regeneration.

Evaluation of Articular Cartilage Regeneration Properties of Decellularized Cartilage Powder/Modified Hyaluronic Acid Hydrogel Scaffolds

The articular cartilage has poor intrinsic healing potential, hence, imposing a great challenge for articular cartilage regeneration in osteoarthritis. Tissue regeneration by scaffolds and bioactive materials has provided a healing potential for degenerated cartilage. In this study, decellularized cartilage powder (DCP) and hyaluronic acid hydrogel modified by aldehyde groups and methacrylate (AHAMA) were fabricated and evaluated in vitro for efficacy in articular cartilage regeneration. In vitro tests such as cell proliferation, cell viability, and cell migration showed that DCP/AHAMA has negligible cytotoxic effects. Furthermore, it could provide an enhanced microenvironment for infrapatellar fat pad stem cells (IFPSCs). Mechanical property tests of DCP/AHAMA showed suitable adhesive and compressive strength. IFPSCs under three-dimensional (3D) culture in DCP/AMAHA were used to assess their ability to proliferate and differentiate into chondrocytes using normal and chondroinductive media. Results exhibited increased gene expression of COL2 and ACN and decreased COL1 expression. DCP/AHAMA provides a microenvironment that recapitulates the biomechanical properties of the native cartilage, promotes chondrogenic differentiation, blocks hypertrophy, and demonstrates applicability for cartilage tissue engineering and the potential for clinical biomedical applications.

The role of TGF-beta3 in cartilage development and osteoarthritis

Articular cartilage serves as a low-friction, load-bearing tissue without the support with blood vessels, lymphatics and nerves, making its repair a big challenge. Transforming growth factor-beta 3 (TGF-β3), a vital member of the highly conserved TGF-β superfamily, plays a versatile role in cartilage physiology and pathology. TGF-β3 influences the whole life cycle of chondrocytes and mediates a series of cellular responses, including cell survival, proliferation, migration, and differentiation. Since TGF-β3 is involved in maintaining the balance between chondrogenic differentiation and chondrocyte hypertrophy, its regulatory role is especially important to cartilage development. Increased TGF-β3 plays a dual role: in healthy tissues, it can facilitate chondrocyte viability, but in osteoarthritic chondrocytes, it can accelerate the progression of disease. Recently, TGF-β3 has been recognized as a potential therapeutic target for osteoarthritis (OA) owing to its protective effect, which it confers by enhancing the recruitment of autologous mesenchymal stem cells (MSCs) to damaged cartilage. However, the biological mechanism of TGF-β3 action in cartilage development and OA is not well understood. In this review, we systematically summarize recent progress in the research on TGF-β3 in cartilage physiology and pathology, providing up-to-date strategies for cartilage repair and preventive treatment.

Gelatin Methacrylate Hydrogel for Tissue Engineering Applications—A Review on Material Modifications

To recreate or substitute tissue in vivo is a complicated endeavor that requires biomaterials that can mimic the natural tissue environment. Gelatin methacrylate (GelMA) is created through covalent bonding of naturally derived polymer gelatin and methacrylic groups. Due to its biocompatibility, GelMA receives a lot of attention in the tissue engineering research field. Additionally, GelMA has versatile physical properties that allow a broad range of modifications to enhance the interaction between the material and the cells. In this review, we look at recent modifications of GelMA with naturally derived polymers, nanomaterials, and growth factors, focusing on recent developments for vascular tissue engineering and wound healing applications. Compared to polymers and nanoparticles, the modifications that embed growth factors show better mechanical properties and better cell migration, stimulating vascular development and a structure comparable to the natural-extracellular matrix.

In vitro and in vivo evaluation of the wound healing properties and safety assessment of two seaweeds (Sargassum ilicifolium and Ulva lactuca)

Seaweeds have been regarded as a reservoir of biologically active molecules that are important in the pharmaceutical industry. The aim of the present study was to explore the wound healing properties and to assess the safety of the seaweed Sargassum ilicifolium and Ulva lactuca. Enhanced cell proliferation and cell migration activities were observed in L929 cells treated with S. ilicifolium extract compared to U. lactuca extract treated cells and the control group. In-vivo experiments were conducted using five groups (10 in each) of Albino mice (BALB/c). Mice in group I and group II were treated (Orally, 100 mg/kg BW/day) with aqueous extracts of S. ilicifolium and U. lactuca, respectively for 14 days. Treatment group III received a topical application of the aqueous extract of S. ilicifolium (25% w/w) and ointment base (75% w/w) (2 g/kg BW/day, for 14 days). Group IV (Control) received an equal amount of distilled water, orally and mice in group V kept without wounds. The extract from S. ilicifolium showed stronger wound healing properties than the one from Ulva lactuca. Histopathological findings also revealed that the healing process was significantly enhanced in the mice group treated orally with S. ilicifolium aqueous extract. These findings show that S. ilicifolium species possess promising wound healing properties in-vitro and in-vivo.

Strategies to Control or Mimic Growth Factor Activity for Bone, Cartilage, and Osteochondral Tissue Engineering

Growth factors play a critical role in tissue repair and regeneration. However, their clinical success is limited by their low stability, short half-life, and rapid diffusion from the delivery site. Supraphysiological growth factor concentrations are often required to demonstrate efficacy but can lead to adverse reactions, such as inflammatory complications and increased cancer risk. These issues have motivated the development of delivery systems that enable sustained release and controlled presentation of growth factors. This review specifically focuses on bioconjugation strategies to enhance growth factor activity for bone, cartilage, and osteochondral applications. We describe approaches to localize growth factors using noncovalent and covalent methods, bind growth factors via peptides, and mimic growth factor function with mimetic peptide sequences. We also discuss emerging and future directions to control spatiotemporal growth factor delivery to improve functional tissue repair and regeneration.

Aggrecan and COMP Improve Periosteal Chondrogenesis by Delaying Chondrocyte Hypertrophic Maturation

The generation of cartilage from progenitor cells for the purpose of cartilage repair is often hampered by hypertrophic differentiation of the engineered cartilaginous tissue caused by endochondral ossification. Since a healthy cartilage matrix contains high amounts of Aggrecan and COMP, we hypothesized that their supplementation in the biogel used in the generation of subperiosteal cartilage mimics the composition of the cartilage extracellular matrix environment, with beneficial properties for the engineered cartilage. Supplementation of COMP or Aggrecan was studied in vitro during chondrogenic differentiation of rabbit periosteum cells and periosteum-derived chondrocytes. Low melting agarose was supplemented with bovine Aggrecan, human recombinant COMP or vehicle and was injected between the bone and periosteum at the upper medial side of the tibia of New Zealand white rabbits. Generated subperiosteal cartilage tissue was analyzed for weight, GAG and DNA content and ALP activity. Key markers of different phases of endochondral ossification were measured by RT-qPCR. For the in vitro experiments, no significant differences in chondrogenic marker expression were detected following COMP or Aggrecan supplementation, while in vivo favorable chondrogenic marker expression was detected. Gene expression levels of hypertrophic markers as well as ALP activity were significantly decreased in the Aggrecan and COMP supplemented conditions compared to controls. The wet weight and GAG content of the in vivo generated subperiosteal cartilage tissue was not significantly different between groups. Data demonstrate the potential of Aggrecan and COMP to favorably influence the subperiosteal microenvironment for the in vivo generation of cartilage for the optimization of cartilage regenerative approaches.

Ganglioside GM3 Up-Regulate Chondrogenic Differentiation by Transform Growth Factor Receptors

Mesenchymal stem cells, also known as multipotent stromal progenitor cells, can differentiate into cells of mesodermal lineage. Gangliosides are sialic acid-conjugated glycosphingolipids that are believed to regulate cell differentiation and several signaling molecules. These molecules are localized in glycosphingolipid-enriched microdomains on the cell surface and are regulated by glycosphingolipid composition. Transforming growth factor-beta (TGF-β) signaling plays a critical role in chondrogenic differentiation. However, the role of gangliosides in chondrogenesis is not understood. In this study, the relationship between the ganglioside GM3 and TGF-β activation, during chondrogenic differentiation, was investigated using an aggregate culture of human synovial membrane-derived mesenchymal stem cells. We showed that the gangliosides GM3 and GD3 were expressed after the chondrogenic differentiation of hSMSC aggregates. To test whether GM3 affected the chondrogenic differentiation of hSMSC aggregates, we used GM3 treatment during chondrogenic differentiation. The results showed that the group treated with 5 μM GM3 had higher expression of chondrogenic specific markers, increased toluidine blue, and safranin O staining, and increased accumulation of glycosaminoglycans compared with the untreated group. Furthermore, GM3 treatment enhanced TGF-β signaling via SMAD 2/3 during the chondrogenic differentiation of hSMSC aggregates. Taken together, our results suggested that GM3 may be useful in developing therapeutic agents for cell-based articular cartilage regeneration in articular cartilage disease.

Microparticle-mediated sequestration of cell-secreted proteins to modulate chondrocytic differentiation

Protein delivery is often used in tissue engineering applications to control differentiation processes, but is limited by protein instability and cost. An alternative approach is to control the cellular microenvironment through biomaterial-mediated sequestration of cell-secreted proteins important to differentiation. Thus, we utilized heparin-based microparticles to modulate cellular differentiation via protein sequestration in an in vitro model system of endochondral ossification. Heparin and poly(ethylene-glycol) (PEG; a low-binding material control)-based microparticles were incorporated into ATDC5 cell spheroids or incubated with ATDC5 cells in transwell culture. Reduced differentiation was observed in the heparin microparticle group as compared to PEG and no microparticle-containing groups. To determine if observed changes were due to sequestration of cell-secreted protein, the proteins sequestered by heparin microparticles were analyzed using SDS-PAGE and mass spectrometry. It was found that heparin microparticles bound insulin-like growth factor binding proteins (IGFBP)-3 and 5. When incubated with a small-molecule inhibitor of IGFBPs, NBI 31772, a similar delay in differentiation of ATDC5 cells was observed. These results indicate that heparin microparticles modulated chondrocytic differentiation in this system via sequestration of cell-secreted protein, a technique that could be beneficial in the future as a means to control cellular differentiation processes.

STATEMENT OF SIGNIFICANCE

In this work, we present a proof-of-principle set of experiments in which heparin-based microparticles are shown to modulate cellular differentiation through binding of cell-secreted protein. Unlike existing systems that rely on expensive protein with limited half-lives to elicit changes in cellular behavior, this technique focuses on temporal modulation of cell-generated proteins. This technique also provides a biomaterials-based method that can be used to further identify sequestered proteins of interest. Thus, this work indicates that glycosaminoglycan-based biomaterial approaches could be used as substitutes or additions to traditional methods for modulating and identifying the cell-secreted proteins involved in directing cellular behavior.

TGFβ3 recruits endogenous mesenchymal stem cells to initiate bone regeneration

Background

The recruitment of a sufficient number of endogenous mesenchymal stem cells (MSCs) is the first stage of in-situ tissue regeneration. Transforming growth factor beta-3 (TGFβ3) could recruit stem or progenitor cells and endothelial cells to participate in tissue regeneration. However, the mechanism of TGFβ3 recruiting MSCs toward bone regeneration has remained obscure.

Methods

We estimated the promigratory property of TGFβ3 on human bone marrow MSCs (hBMSCs) cocultured with the vascular cells (human umbilical artery smooth muscle cells or human umbilical vein endothelial cells) or not by Transwell assay. After the addition of the inhibitor (SB431542) or Smad3 siRNA, the levels of MCP1 and SDF1 in coculture medium were tested by ELISA kit, and then the migratory signaling pathway of hBMSCs induced by TGFβ3 was investigated by western blot analysis. In vivo, a 2-mm FVB/N mouse femur defect model was used to evaluate chemokine secretion, endogenous cell homing, and bone regeneration induced by scaffolds loading 1 μg TGFβ3 through qPCR, immunofluorescent staining, immunohistochemical analysis, and Micro-CT, compared to the vehicle group.

Results

TGFβ3 (25 ng/ml) directly showed a nearly 40% increase in migrated hBMSCs via the TGFβ signaling pathway, compared to the vehicle treatment. Then, in the coculture system of hBMSCs and vascular cells, TGFβ3 further upregulated nearly 3-fold MCP1 secretion from vascular cells in a Smad3-dependent manner, to indirectly enhance nearly more than 50% of migrated hBMSCs. In vivo, TGFβ3 delivery improved MCP1 expression by nearly 7.9-fold, recruited approximately 2.0-fold CD31⁺ vascular cells and 2.0-fold Sca-1⁺ PDGFR-α⁺ MSCs, and achieved 2.5-fold bone volume fraction (BV/TV) and 2.0-fold bone mineral density, relative to TGFβ3-free delivery.

Conclusions

TGFβ3, as a MSC homing molecule, recruited MSCs to initiate bone formation in the direct-dependent and indirect-dependent mechanisms. This may shed light on the improvement of MSC homing in bone regeneration.

Extracellular Matrix (ECM) Multilayer Membrane as a Sustained Releasing Growth Factor Delivery System for rhTGF-β3 in Articular Cartilage Repair

Recombinant human transforming growth factor beta-3 (rhTGF-β₃) is a key regulator of chondrogenesis in stem cells and cartilage formation. We have developed a novel drug delivery system that continuously releases rhTGF-β₃ using a multilayered extracellular matrix (ECM) membrane. We hypothesize that the sustained release of rhTGF-β₃ could activate stem cells and result in enhanced repair of cartilage defects. The properties and efficacy of the ECM multilayer-based delivery system (EMLDS) are investigated using rhTGF-β₃ as a candidate drug. The bioactivity of the released rhTGF-ß3 was evaluated through chondrogenic differentiation of mesenchymal stem cells (MSCs) using western blot and circular dichroism (CD) analyses in vitro. The cartilage reparability was evaluated through implanting EMLDS with endogenous and exogenous MSC in both in vivo and ex vivo models, respectively. In the results, the sustained release of rhTGF-ß3 was clearly observed over a prolonged period of time in vitro and the released rhTGF-β₃ maintained its structural stability and biological activity. Successful cartilage repair was also demonstrated when rabbit MSCs were treated with rhTGF-β3-loaded EMLDS ((+) rhTGF-β3 EMLDS) in an in vivo model and when rabbit chondrocytes and MSCs were treated in ex vivo models. Therefore, the multilayer ECM membrane could be a useful drug delivery system for cartilage repair.

Light enhanced bone regeneration in an athymic nude mouse implanted with mesenchymal stem cells embedded in PLGA microspheres

BACKGROUND

Biodegradable microspheres fabricated from poly (Lactic-co-glycolic acid) (PLGA) have attracted considerable attention in the bone tissue regeneration field. In this study, rabbit mesenchymal stem cells (rMSCs) adherent to PLGA microspheres were implanted into athymic nude mice and irradiated with 647 nm red light to promote bone formation. It was found that irradiating rMSCs with high levels of red light (647 nm) from an LED (light-emitting diode) increased levels of bone specific markers in rMSCs embedded on PLGA microspheres.

RESULT

These increased expressions were observed by RT-PCR, real time-QPCR, immunohistochemistry (IHC), and von Kossa and Alizarin red S staining. Microsphere matrices coated with rMSCs were injected into athymic nude mice and irradiated with red light for 60 seconds showed significantly greater bone-specific phenotypes after 4 weeks in vivo.

CONCLUSION

The devised PLGA microsphere matrix containing rMSCs and irradiation with red light at 647 nm process shows promise as a means of coating implantable biomedical devices to improve their biocompatibilities and in vivo performances.

Exogenous Heparan Sulfate Enhances the TGF-β3-Induced Chondrogenesis in Human Mesenchymal Stem Cells by Activating TGF-β/Smad Signaling

Heparan sulfate (HS) interacts with growth factors and has been implicated in regulating chondrogenesis. However, the effect of HS on TGF-β-mediated mesenchymal stem cell (MSC) chondrogenesis and molecular mechanisms remains unknown. In this study, we explored the effects of exogenous HS alone and in combination with TGF-β3 on chondrogenic differentiation of human MSCs and possible signal mechanisms. The results indicated that HS alone had no obvious effects on chondrogenic differentiation of human MSCs and TGF-β/Smad2/3 signal pathways. However, the combined TGF-β3/HS treatment resulted in a significant increase in GAG synthesis, cartilage matrix protein secretion, and cartilage-specific gene expression compared to cells treated with TGF-β3 alone. Furthermore, HS inhibited type III TGF-β receptors (TβRIII) expression and increased TGF-β3-mediated ratio of the type II (TβRII) to the type I (TβRI) TGF-β receptors and phosphorylation levels of Smad2/3. The inhibitor of the TGF-β/Smad signal, SB431542, not only completely inhibited HS-stimulated TGF-β3-mediated Smad2/3 phosphorylation but also completely inhibited the effects of HS on TGF-β3-induced chondrogenic differentiation. These results demonstrate exogenous HS enhances TGF-β3-induced chondrogenic differentiation of human MSCs by activating TGF-β/Smad2/3 signaling.

TGF-β1 conjugated chitosan collagen hydrogels induce chondrogenic differentiation of human synovium-derived stem cells

Background

Unlike bone tissue, articular cartilage regeneration has not been very successful and has many challenges ahead. We have previously developed injectable hydrogels using photopolymerizable chitosan (MeGC) that supported growth of chondrocytes. In this study, we demonstrate a biofunctional hydrogel for specific use in cartilage regeneration by conjugating transforming growth factor-β1 (TGF-β1), a well-documented chondrogenic factor, to MeGC hydrogels impregnating type II collagen (Col II), one of the major cartilaginous extracellular matrix (ECM) components.

Results

TGF-β1 was delivered from MeGC hydrogels in a controlled manner with reduced burst release by chemically conjugating the protein to MeGC. The hydrogel system did not compromise viability of encapsulated human synovium-derived mesenchymal stem cells (hSMSCs). Col II impregnation and TGF-β1 delivery significantly enhanced cellular aggregation and deposition of cartilaginous ECM by the encapsulated cells, compared with pure MeGC hydrogels.

Conclusions

This study demonstrates successful engineering of a biofunctional hydrogel with a specific microenvironment tailored to promote chondrogenesis. This hydrogel system can provide promising efficacious therapeutics in the treatment of cartilage defects.

Electronic supplementary material

The online version of this article (doi:10.1186/1754-1611-9-1) contains supplementary material, which is available to authorized users.

Overexpression of TGF-β1 enhances chondrogenic differentiation and proliferation of human synovium-derived stem cells

Transforming growth factor-beta (TGF-β) superfamily proteins play a critical role in proliferation, differentiation, and other functions of mesenchymal stem cells (MSCs). During chondrogenic differentiation of MSCs, TGF-β up-regulates chondrogenic gene expression by enhancing the expression of the transcription factor SRY (sex-determining region Y)-box9 (Sox9). In this study, we investigated the effect of continuous TGF-β1 overexpression in human synovium-derived MSCs (hSD-MSCs) on immunophenotype, differentiation potential, and proliferation rate. hSD-MSCs were transduced with recombinant retroviruses (rRV) encoding TGF-β1. The results revealed that continuous overexpression of TGF-β1 did not affect their phenotype as evidenced by flow cytometry and reverse transcriptase PCR (RT-PCR). In addition, continuous TGF-β1 overexpression strongly enhanced cell proliferation of hSD-MSCs compared to the control groups. Also, induction of chondrogenesis was more effective in rRV-TGFB-transduced hSD-MSCs as shown by RT-PCR for chondrogenic markers, toluidine blue staining and glycosaminoglycan (GAG)/DNA ratio. Our data suggest that overexpression of TGF-β1 positively enhances the proliferation and chondrogenic potential of hSD-MSCs.

Stem Cell-assisted Approaches for Cartilage Tissue Engineering

The regeneration of damaged articular cartilage remains challenging due to its poor intrinsic capacity for repair. Tissue engineering of articular cartilage is believed to overcome the current limitations of surgical treatment by offering functional regeneration in the defect region. Selection of proper cell sources and ECM-based scaffolds, and incorporation of growth factors or mechanical stimuli are of primary importance to successfully produce artificial cartilage for tissue repair. When designing materials for cartilage tissue engineering, biodegradability and biocompatibility are the key factors in selecting material candidates, for either synthetic or natural polymers. The unique environment of cartilage makes it suitable to use a hydrogel with high water content in the cross-linked or thermosensitive (injectable) form. Moreover, design of composite scaffolds from two polymers with complementary physicochemical and biological properties has been explored to provide residing chondrocytes with a combination of the merits that each component contributes.

One-step repair for cartilage defects in a rabbit model: a technique combining the perforated decalcified cortical-cancellous bone matrix scaffold with microfracture

BACKGROUND

Cartilage repair still presents a challenge to clinicians and researchers alike. A more effective, simpler procedure that can produce hyaline-like cartilage is needed for articular cartilage repair.

HYPOTHESIS

A technique combining microfracture with a biomaterial scaffold of perforated decalcified cortical-cancellous bone matrix (DCCBM; composed of cortical and cancellous parts) would create a 1-step procedure for hyaline-like cartilage repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

For the in vitro portion of this study, mesenchymal stem cells (MSCs) were isolated from bone marrow aspirates of New Zealand White rabbits. Scanning electron microscopy (SEM), confocal microscopy, and 1,9-dimethylmethylene blue assay were used to assess the attachment, proliferation, and cartilage matrix production of MSCs grown on a DCCBM scaffold. For the in vivo experiment, full-thickness defects were produced in the articular cartilage of the trochlear groove of 45 New Zealand White rabbits, and the rabbits were then assigned to 1 of 3 treatment groups: perforated DCCBM combined with microfracture (DCCBM+M group), perforated DCCBM alone (DCCBM group), and microfracture alone (M group). Five rabbits in each group were sacrificed at 6, 12, or 24 weeks after the operation, and the repair tissues were analyzed by histological examination, assessment of matrix staining, SEM, and nanoindentation of biomechanical properties.

RESULTS

The DCCBM+M group showed hyaline-like articular cartilage repair, and the repair tissues appeared to have better matrix staining and revealed biomechanical properties close to those of the normal cartilage. Compared with the DCCBM+M group, there was unsatisfactory repair tissues with less matrix staining in the DCCBM group and no matrix staining in the M group, as well as poor integration with normal cartilage and poor biomechanical properties.

CONCLUSION

The DCCBM scaffold is suitable for MSC growth and hyaline-like cartilage repair induction when combined with microfracture.

CLINICAL RELEVANCE

Microfracture combined with a DCCBM scaffold is a promising method that can be performed and adopted into clinical treatment for articular cartilage injuries.

Pharmacological modulation of human mesenchymal stem cell chondrogenesis by a chemically oversulfated polysaccharide of marine origin: potential application to cartilage regenerative medicine

Mesenchymal stem cells (MSCs) are considered as an attractive source of cells for cartilage engineering due to their availability and capacity for expansion and multipotency. Differentiation of MSC into chondrocytes is crucial to successful cartilage regeneration and can be induced by various biological agents, including polysaccharides that participate in many biological processes through interactions with growth factors. Here, we hypothesize that growth factor-induced differentiation of MSC can be increased by chemically oversulfated marine polysaccharides. To test our hypothesis, human adipose tissue-derived MSCs (hATSCs) were cultured in pellets with transforming growth factor (TGF)-β1-supplemented chondrogenic medium containing either the polysaccharide GY785 DR or its oversulfated isoform GY785 DRS. Chondrogenesis was monitored by the measurement of pellet volume, quantification of DNA, collagens, glycosaminoglycans (GAGs), and immunohistological staining. Our data revealed an increase in pellet volume, total collagens, and GAG production with GY785 DRS and chondrogenic medium. The enhanced chondrogenic differentiation of hATSC was further demonstrated by the increased expression of several chondrogenic markers by real-time reverse transcription-polymerase chain reaction. In addition, surface plasmon resonance analyses revealed that TGF-β1 bound GY785 DRS with higher affinity compared to GY785 DR. In association with TGF-β1, GY785 DRS was found to upregulate the phosphorylation of extracellular signal-regulated kinase 1/2, indicating that oversulfated polysaccharide affects the mitogen activated protein kinase signaling activity. These results demonstrate the upregulation of TGF-β1-dependent stem cell chondrogenesis by a chemically oversulfated marine polysaccharide. This polysaccharide of marine origin is easily producible and therefore could be considered a promising additive to drive efficient and reliable MSC chondrogenesis for cartilage tissue engineering.

Chondrogenesis of hMSC in affinity-bound TGF-beta scaffolds

Herein we describe a bio-inspired, affinity binding alginate-sulfate scaffold, designed for the presentation and sustained release of transforming growth factor beta 1 (TGF-β1), and examine its effects on the chondrogenesis of human mesenchymal stem cells (hMSCs). When attached to matrix via affinity interactions with alginate sulfate, TGF-β1 loading was significantly greater and its initial release from the scaffold was attenuated compared to its burst release (>90%) from scaffolds lacking alginate-sulfate. The sustained TGF-β1 release was further supported by the prolonged activation (14 d) of Smad-dependent (Smad2) and Smad-independent (ERK1/2) signaling pathways in the seeded hMSCs. Such presentation of TGF-β1 led to hMSC chondrogenic differentiation; differentiated chondrocytes with deposited collagen type II were seen within three weeks of in vitro hMSC seeding. By contrast, in scaffolds lacking alginate-sulfate, the effect of TGF-β1 was short-term and hMSCs could not reach a similar differentiation degree. When hMSC constructs were subcutaneously implanted in nude mice, chondrocytes with deposited type II collagen and aggrecan typical of the articular cartilage were found in the TGF-β1 affinity-bound constructs. Our results highlight the fundamental importance of appropriate factor presentation to its biological activity, namely - inducing efficient stem cell differentiation.

The use of growth factors and mesenchymal stem cells in orthopaedics

Stem cell therapy is an exciting and upcoming branch of tissue engineering with application in the field of orthopaedics. The most commonly used type of stem cells, mesenchymal stem cells (MSCs), can be easily isolated from bone marrow or synovium and cultured in vitro. Newer techniques using tissue engineering to regenerate musculoskeletal tissue by using biomimetic materials are now being studied. These osteoconductive three dimensional constructs seeded with MSCs are highly porous, biodegradable and biomechanically stable scaffolds which do not evoke an immunogenic host cell response. Research has shown the importance of growth factors in guiding and modulating the differentiation of MSCs in order to obtain the required cell type. Gene-based delivery systems have aided the delivery of sustained quantities of these growth factors. The evidence from growth factor enhanced tissue engineering studies for tissue healing looks very positive. This is a multi-disciplinary approach that integrates molecular, biochemical and clinical techniques with developmental and engineering processes. Initial studies indicate an immense potential for cell based strategies to enhance current orthopaedic approaches in skeletal tissue reconstruction. Ultimately, there is a need for randomised controlled trials on human populations to apply these findings to a clinical setting. Nevertheless, stem cell based tissue engineering in orthopaedics shows a promising future.

Chondrogenesis of human mesenchymal stem cells by local transforming growth factor-beta delivery in a biphasic resorbable carrier

Little is known about the potential of growth factor-augmented biphasic implants composed of a gel and a solid scaffold to enhance chondrogenesis of mesenchymal stem cells (MSCs). We analyzed whether a collagen type I/III carrier and fibrin glue (FG) combined to a biphasic construct support in vitro chondrogenesis of MSCs and allow for local release of bioactive transforming growth factor-beta1 (TGF-beta1). Further, a possible advantage of partial autologous fibrin glue (PAF) over commercial FG was assessed. Collagen carriers seeded with 5 x 10(5) human MSCs with or without FG, PAF, or TGF-beta1-upgraded FG were cultured for 6 weeks in chondrogenic medium with or without TGF-beta1. Pellets with or without FG/PAF served as controls. FG and collagen carriers allowed strong upregulation of COL2A1, AGC, and COL10A1 mRNA, deposition of collagen-type II, and mediated a significantly higher proteoglycan content compared with biomaterial-free pellets. Collagen-carrier groups contained significantly more proteoglycan than FG and PAF pellets, whereas biphasic PAF-carrier constructs were inferior to FG-carrier constructs. Upgrading of biphasic FG-carrier constructs with 50 ng TGF-beta1/construct mediated chondrogenesis as successfully as supply of TGF-beta1 via the medium. In conclusion, the biphasic carrier constructs showed a high biofunctionality by continuous form stability with improved chondrogenesis and long-term local supply of bioactive TGF-beta1 which may be useful to enhance matrix-assisted repair strategies for damaged cartilage.

The role of pharmacologically active microcarriers releasing TGF-beta3 in cartilage formation in vivo by mesenchymal stem cells

Cartilage engineering using mesenchymal stem cells (MSC) will require the use of a scaffold which will act as a support for cell adhesion keeping the cells in the cartilage defect. Optimally, a tissue engineered construct should allow sustained delivery of bioactive factors capable of inducing MSC differentiation into chondrocytes and should be easily injected inside the cartilage lesions to avoid surgical operations. We therefore developed pharmacologically active microcarriers (PAM) made of poly-lactic-co-glycolic acid (PLGA) produced using an oil-in-water (o/w) emulsion method. The microspheres were coated with a biomimetic surface of fibronectin (FN) and engineered to release TGF-beta3 as a chondrogenic differentiation factor. When human MSCs were incubated in vitro with TGF-beta3 releasing FN-coated PAMs in chondrogenic medium, they firmly adhered onto the surface of PAMs rapidly forming cell aggregates. After 3 weeks, strong up-regulation of cartilage-specific markers was observed both at the mRNA and protein level whereas osteogenic or adipogenic genes could not be detected. Importantly, implantation of MSC/TGF-beta3 releasing PAM complexes in SCID mice resulted in the formation of histologically resembling cartilage which stained positive for chondrocyte markers, collagen II and aggrecan. The present study demonstrated that functionalized PLGA-based microparticles can provide an appropriate environment for chondrogenic differentiation of MSCs and should contribute to injectable biomedical device development improving in vivo cartilage engineering.

Chondrogenic differentiation of mesenchymal stem cells embedded in a scaffold by long-term release of TGF-beta 3 complexed with chondroitin sulfate

In this study, mesenchymal stem cells (MSCs) embedded in biodegradable and water-swollen, elastic block copolymer scaffolds were assessed for MSC chondrogenesis. To determine the optimal conditions for chondrogenesis of the embedded rMSCs, transforming growth factor-beta 3 (TGF-beta 3) was physically conjugated with chondroitin sulfate (CS) and mixed into scaffolds, which were subsequently evaluated for the differentiation of transplanted rMSCs. In determination of CS-bound growth factors for chondrogenesis, scaffold mixed with rMSCs and TGF-beta 3 was then tested by growth factor release profiles, confocal laser microscopy, RT-PCR analysis, real time-QPCR, and histology. The results of several different analyses of the transplanted rMSCs embedded in the scaffolds showed that rMSCs coupled with a CS-bound TGF-beta 3 encapsulated scaffold evidenced superior cartilage tissue formation as measured by an assay of specific gene and protein expression. Moreover, the scaffold exhibited more rapid and more distinct morphology of differentiated rMSCs than was observed with other scaffolds, as determined by histology and immunochemical histology analysis. These results indicate that the elastic block copolymer scaffolds combined with a CS-bound TGF-beta 3 should prove very suitable matrix for cell-based cartilage tissue engineering.

Controlling stem cell fate with material design

Advances in our understanding of stem cell interactions with their environment are leading to the development of new materials-based approaches to control stem cell behavior toward cellular culture and tissue regeneration applications. Materials can provide cues based on chemistry, mechanics, structure, and molecule delivery that control stem cell fate decisions and matrix formation. These approaches are helping to advance clinical translation of a range of stem cell types through better expansion techniques and scaffolding for use in tissue engineering approaches for the regeneration of many tissues. With this in mind, this progress report covers basic concepts and recent advances in the use of materials for manipulating stem cells.

Human circulating fibrocytes have the capacity to differentiate osteoblasts and chondrocytes

Fibrocytes are bone marrow-derived cells. Fibrocytes can differentiate into adipocyte- and myofibroblast-like cells. Since fibrocytes can behave like mesenchymal progenitor cells, we hypothesized that fibrocytes have the potential to differentiate into other mesenchymal lineage cells, such as osteoblasts and chondrocytes. In this study, we found that fibrocytes differentiated into osteoblast-like cells when cultured in osteogenic media in a manner similar to osteoblast precursor cells. Under these conditions, fibrocytes and osteoblast precursor cells displayed increased calcium deposition, and increased expression of specific osteogenic genes. In addition, dephosphorylation of cAMP-responsive element binding protein was associated with the increased ratio of receptor activator of the NF-kappaB Ligand/osteoprotegerin gene expression and enhanced gene expression of osterix in these cells under these conditions. Both events are important in promoting osteogenesis. In contrast, fibrocytes and mesenchymal stem cells cultured in chondrogenic media in the presence of transforming growth factor-beta3 were found to differentiate to chondrocyte-like cells. Fibrocytes and mesenchymal stem cells under these conditions were found to express increased levels of aggrecan and type II collagen genes. Transcription factor genes associated with chondrogenesis were also found to be induced in fibrocytes and mesenchymal stem cells under these conditions. In contrast, beta-catenin protein and the core binding factor alpha1 subunit protein transcription factor were decreased in expression under these conditions. These data indicate that human fibrocytes have the capability to differentiate into osteoblast- and chondrocyte-like cells. These findings suggest that such cells could be used in cell-based tissue-regenerative therapy.

TGF-beta3: A potential biological therapy for enhancing chondrogenesis

BACKGROUND

TGF-beta has been proposed to stimulate chondrogenesis through intracellular pathways involving small mothers against decapentaplegic proteins (Smads).

OBJECTIVE

To examine the use of exogenous TGF-beta3 to promote new hyaline cartilage formation.

METHODS

An overview of in vitro and in vivo evidence on the effects of TGF-beta3 on cartilage regeneration.

RESULTS/CONCLUSION

There is robust in vitro evidence suggesting a positive dose- and time-dependent effect of TGF-beta3 on anabolic chondrogenic gene markers such as alpha1-collagen type II and cartilage oligomeric matrix protein in human mesenchymal stem cells. TGF-beta3 cultured with silk elastin-like polymer scaffold carrier exhibits significantly increased glycosaminoglycan and collagen content. In vivo data showed that TGF-beta3 cultured with ovine mesenchymal stem cells in a chitosan scaffold stimulated the growth of hyaline cartilage that was fully integrated into host cartilage tissue of sheep. We highlight the potential for the clinical enhancement of cartilage formation through the use of TGF-beta3 with a suitable dose and scaffold carrier.

Critical factors in the design of growth factor releasing scaffolds for cartilage tissue engineering

BACKGROUND

Trauma or degenerative diseases of the joints are common clinical problems resulting in high morbidity. Although various orthopedic treatments have been developed and evaluated, the low repair capacities of articular cartilage renders functional results unsatisfactory in the long term. Over the last decade, a different approach (tissue engineering) has emerged that aims not only to repair impaired cartilage, but also to fully regenerate it, by combining cells, biomaterials mimicking extracellular matrix (scaffolds) and regulatory signals. The latter is of high importance as growth factors have the potency to induce, support or enhance the growth and differentiation of various cell types towards the chondrogenic lineage. Therefore, the controlled release of different growth factors from scaffolds appears to have great potential to orchestrate tissue repair effectively.

OBJECTIVE

This review aims to highlight considerations and limitations of the design, materials and processing methods available to create scaffolds, in relation to the suitability to incorporate and release growth factors in a safe and defined manner. Furthermore, the current state of the art of signalling molecules release from scaffolds and the impact on cartilage regeneration in vitro and in vivo is reported and critically discussed.

METHODS

The strict aspects of biomaterials, scaffolds and growth factor release from scaffolds for cartilage tissue engineering applications are considered.

CONCLUSION

Engineering defined scaffolds that deliver growth factors in a controlled way is a task seldom attained. If growth factor delivery appears to be beneficial overall, the optimal delivery conditions for cartilage reconstruction should be more thoroughly investigated.