TGF-beta3: A potential biological therapy for enhancing chondrogenesis

Signalling by Transforming Growth Factor Beta Isoforms in Wound Healing and Tissue Regeneration

Transforming growth factor beta (TGFβ) signalling is essential for wound healing, including both non-specific scar formation and tissue-specific regeneration. Specific TGFβ isoforms and downstream mediators of canonical and non-canonical signalling play different roles in each of these processes. Here we review the role of TGFβ signalling during tissue repair, with a particular focus on the prototypic isoforms TGFβ1, TGFβ2, and TGFβ3. We begin by introducing TGFβ signalling and then discuss the role of these growth factors and their key downstream signalling mediators in determining the balance between scar formation and tissue regeneration. Next we discuss examples of the pleiotropic roles of TGFβ ligands during cutaneous wound healing and blastema-mediated regeneration, and how inhibition of the canonical signalling pathway (using small molecule inhibitors) blocks regeneration. Finally, we review various TGFβ-targeting therapeutic strategies that hold promise for enhancing tissue repair.

Biologic Treatments for Sports Injuries II Think Tank-Current Concepts, Future Research, and Barriers to Advancement, Part 3: Articular Cartilage

Focal chondral defects of the articular surface are a common occurrence in the field of orthopaedics. These isolated cartilage injuries, if not repaired surgically with restoration of articular congruency, may have a high rate of progression to posttraumatic osteoarthritis, resulting in significant morbidity and loss of function in the young, active patient. Both isolated and global joint disease are a difficult entity to treat in the clinical setting given the high amount of stress on weightbearing joints and the limited healing potential of native articular cartilage. Recently, clinical interest has focused on the use of biologically active compounds and surgical techniques to regenerate native cartilage to the articular surface, with the goal of restoring normal joint health and overall function. This article presents a review of the current biologic therapies, as discussed at the 2015 American Orthopaedic Society for Sports Medicine (AOSSM) Biologics Think Tank, that are used in the treatment of focal cartilage deficiencies. For each of these emerging therapies, the theories for application, the present clinical evidence, and specific areas for future research are explored, with focus on the barriers currently faced by clinicians in advancing the success of these therapies in the clinical setting.

Chondrogenic effect of cell-based scaffold of self-assembling peptides/PLGA-PLL loading the hTGFβ3 plasmid DNA

With the application of tissue engineering to tissue regeneration, additional new complexes have been made in response to the challenge of cartilage-injury repair. This study was performed to construct a rat precartilaginous stem cells-based scaffold of self-assembling peptides RADA16-I/PLGA-PLL (poly-L-lysine coated PLGA) as extracellular matrix loading the NLS-TAT as a peptide-based carrier for a plasmid DNA containing hTGFβ3. After composites were cultured for 1, 2, 3 and 4 weeks, respectively, the results showed that the levels of chondrogenic-related gene expression were higher in the experimental group with and hTGFβ3 gene by reverse transcription-polymerase chain reaction, and with higher histochemical and immunohistochemical expression. hTGFβ3 protein expression had increased at 4 weeks based on western blot analysis. The results of this study show that a complex may be a suitable scaffold for cartilage repair and offer a strategy for tissue regeneration through the use of tissue engineering.

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.

Cartilage tissue engineering: recent advances and perspectives from gene regulation/therapy

Diseases in articular cartilages affect millions of people. Despite the relatively simple biochemical and cellular composition of articular cartilages, the self-repair ability of cartilage is limited. Successful cartilage tissue engineering requires intricately coordinated interactions between matrerials, cells, biological factors, and phycial/mechanical factors, and still faces a multitude of challenges. This article presents an overview of the cartilage biology, current treatments, recent advances in the materials, biological factors, and cells used in cartilage tissue engineering/regeneration, with strong emphasis on the perspectives of gene regulation (e.g., microRNA) and gene therapy.

The effects of 1α, 25-dihydroxyvitamin D3 and transforming growth factor-β3 on bone development in an ex vivo organotypic culture system of embryonic chick femora

Transforming growth factor-beta3 (TGF-β3) and 1α,25-dihydroxyvitamin D₃ (1α,25 (OH) ₂D₃) are essential factors in chondrogenesis and osteogenesis respectively. These factors also play a fundamental role in the developmental processes and the maintenance of skeletal integrity, but their respective direct effects on these processes are not fully understood. Using an organotypic bone rudiment culture system the current study has examined the direct roles the osteotropic factors 1α,25 (OH)₂D₃ and TGF-β3 exert on the development and modulation of the three dimensional structure of the embryonic femur. Isolated embryonic chick femurs (E11) were organotypically cultured for 10 days in basal media, or basal media supplemented with either 1α,25 (OH) ₂D₃ (25 nM) or TGF-β3 (5 ng/mL & 15 ng/mL). Analyses of the femurs were undertaken using micro-computed tomography (μCT), histology and immunohistochemistry. 1α,25 (OH)2D3 supplemented cultures enhanced osteogenesis directly in the developing femurs with elevated levels of osteogenic markers such as type 1 collagen. In marked contrast organotypic femur cultures supplemented with TGF-β3 (5 ng/mL & 15 ng/mL) demonstrated enhanced chondrogenesis with a reduction in osteogenesis. These studies demonstrate the efficacy of the ex vivo organotypic embryonic femur culture employed to elucidate the direct roles of these molecules, 1α,25 (OH) ₂D₃ and TGF-β3 on the structural development of embryonic bone within a three dimensional framework. We conclude that 1α,25(OH)₂D and TGF-β3 modify directly the various cell populations in bone rudiment organotypic cultures effecting tissue metabolism resulting in significant changes in embryonic bone growth and modulation. Understanding the roles of osteotropic agents in the process of skeletal development is integral to developing new strategies for the recapitulation of bone tissue in later life.

Chondrodysplasias and TGFβ signaling

Human chondrodysplasias are a group of conditions that affect the cartilage. This review is focused on the involvement of transforming growth factor-β signaling in a group of chondrodysplasias, entitled acromelic dysplasia, characterized by short stature, short hands and restricted joint mobility.

Comparison of growth factor adsorbed scaffold and conventional scaffold with growth factor supplemented media for primary human articular chondrocyte 3D culture

Background

Cartilage tissue engineering offers new strategies in repairing damaged cartilage. Scaffolds have been used for the in vitro and in vivo procedures for this application, which demonstrates the compatible biological and physical properties that mimic natural tissues. Several types of scaffolds were used and had different effects on cell functions. The study was designed to develop a functional gelatin scaffold by adsorption of hyaluronan (HA) and the transforming growth factor β3 (TGF-β3) in a commercially available gelatin scaffold.

Results

The biological properties of human articular chondrocytes were investigated during a 21-day cultivation embedded in either HA + TGF-β3 adsorbed scaffolds or the conventional supplemented method. The rising of proliferation of chondrocytes embedded in adsorbed scaffolds was observed at day 17 and 21 of cultivation (1.27 and 1.28 fold, respectively). The chondrogenic gene expression of the chondrocytes embedded in HA + TGF-β3 adsorbed scaffolds significantly increased: SOX-9 (1.65 fold), ACAN (7.65 fold) and COL2A1 (1.83 fold). Remarkably, over the 21 days of cultivation, HA + TGF-β3 adsorbed scaffolds promoted the extracellular matrix molecules production with higher accumulation of HA (1.2 fold), collagen (1.42 fold) and uronic acid (1.41 fold). Moreover, the cell population and extracellular matrix production, which were examined by a histological analysis and a scanning electron microscope, were correlated with the biochemical analysis.

Conclusion

A small amount of HA and TGF-β3 initially adsorbed in the scaffolds (70 μg and 10 ng, respectively) was consumed over the 21-day cultivation. The HA + TGF-β3 adsorbed gelatin scaffold is effective and more suitable than the conventional supplemented method for the in vitro assessment of human chondrocyte 3D culture.

Evaluation of skeletal tissue repair, part 1: assessment of novel growth-factor-releasing hydrogels in an ex vivo chick femur defect model

Current clinical treatments for skeletal conditions resulting in large-scale bone loss include autograft or allograft, both of which have limited effectiveness. In seeking to address bone regeneration, several tissue engineering strategies have come to the fore, including the development of growth factor releasing technologies and appropriate animal models to evaluate repair. Ex vivo models represent a promising alternative to simple in vitro systems or complex, ethically challenging in vivo models. We have developed an ex vivo culture system of whole embryonic chick femora, adapted in this study as a critical size defect model to investigate the effects of novel bone extracellular matrix (bECM) hydrogel scaffolds containing spatio-temporal growth factor-releasing microparticles and skeletal stem cells on bone regeneration, to develop a viable alternative treatment for skeletal degeneration. Alginate/bECM hydrogels combined with poly (d,l-lactic-co-glycolic acid) (PDLLGA)/triblock copolymer (10-30% PDLLGA-PEG-PDLLGA) microparticles releasing VEGF, TGF-β3 or BMP-2 were placed, with human adult Stro-1+ bone marrow stromal cells, into 2mm central segmental defects in embryonic chick femurs. Alginate/bECM hydrogels loaded with HSA/VEGF or HSA/TGF-β3 demonstrated a cartilage-like phenotype, with minimal collagen I deposition, comparable to HSA-only control hydrogels. The addition of BMP-2 releasing microparticles resulted in enhanced structured bone matrix formation, evidenced by increased Sirius red-stained matrix and collagen expression within hydrogels. This study demonstrates delivery of bioactive growth factors from a novel alginate/bECM hydrogel to augment skeletal tissue formation and the use of an organotypic chick femur defect culture system as a high-throughput test model for scaffold/cell/growth factor therapies for regenerative medicine.

Initial boost release of transforming growth factor-β3 and chondrogenesis by freeze-dried bioactive polymer scaffolds

In cartilage regeneration, bio-activated implants are used in stem and progenitor cell-based microfracture cartilage repair procedures. Our aim was to analyze the chondrogenic potential of freeze-dried resorbable polymer-based polyglycolic acid (PGA) scaffolds bio-activated with transforming growth factor-β3 (TGFB3) on human subchondral mesenchymal progenitor cells known from microfracture. Progenitor cells derived from femur heads were cultured in the presence of freeze-dried TGFB3 in high-density pellet culture and in freeze-dried TGFB3-PGA scaffolds for chondrogenic differentiation. Progenitor cell cultures in PGA scaffolds as well as pellet cultures with and without continuous application of TGFB3 served as controls. Release studies showed that freeze-dried TGFB3-PGA scaffolds facilitate a rapid, initial boost-like release of 71.5% of TGFB3 in the first 10 h. Gene expression analysis and histology showed induction of typical chondrogenic markers like type II collagen and formation of cartilaginous tissue in TGFB3-PGA scaffolds seeded with subchondral progenitor cells and in pellet cultures stimulated with freeze-dried TGFB3. Chondrogenic differentiation in freeze-dried TGFB3-PGA scaffolds was comparable to cultures receiving TGFB3 continuously, while non-stimulated controls did not show chondrogenesis during prolonged culture for 14 days. These results suggest that bio-activated, freeze-dried TGFB3-PGA scaffolds have chondrogenic potential and are a promising tool for stem cell-mediated cartilage regeneration.

Recent research on the growth plate: Mechanisms for growth plate injury repair and potential cell-based therapies for regeneration

Injuries to the growth plate cartilage often lead to bony repair, resulting in bone growth defects such as limb length discrepancy and angulation deformity in children. Currently utilised corrective surgeries are highly invasive and limited in their effectiveness, and there are no known biological therapies to induce cartilage regeneration and prevent the undesirable bony repair. In the last 2 decades, studies have investigated the cellular and molecular events that lead to bony repair at the injured growth plate including the identification of the four phases of injury repair responses (inflammatory, fibrogenic, osteogenic and remodelling), the important role of inflammatory cytokine tumour necrosis factor alpha in regulating downstream repair responses, the role of chemotactic and mitogenic platelet-derived growth factor in the fibrogenic response, the involvement and roles of bone morphogenic protein and Wnt/B-catenin signalling pathways, as well as vascular endothelial growth factor-based angiogenesis during the osteogenic response. These new findings could potentially lead to identification of new targets for developing a future biological therapy. In addition, recent advances in cartilage tissue engineering highlight the promising potential for utilising multipotent mesenchymal stem cells (MSCs) for inducing regeneration of injured growth plate cartilage. This review aims to summarise current understanding of the mechanisms for growth plate injury repair and discuss some progress, potential and challenges of MSC-based therapies to induce growth plate cartilage regeneration in combination with chemotactic and chondrogenic growth factors and supporting scaffolds.

Chondrogenic differentiation of marrow clots after microfracture with BMSC-derived ECM scaffold in vitro

Repairing articular cartilage by combining microfracture and various scaffolds has been extensively performed in in vivo animal models. We previously described a novel extracellular matrix (ECM) scaffold for cartilage tissue engineering. The aim of this study was to investigate the effect of a bone marrow-derived mesenchymal stem cells-derived ECM (BMSC-dECM) scaffold on the chondrogenic differentiation of marrow clots following microfracture in vitro. In this study, we manufactured the BMSC-dECM scaffold using a freeze-drying method. To obtain the marrow clots, a full-thickness cartilage defect was established and microholes were created in the trochlear groove of New Zealand white rabbits. The samples were divided and cultured in vitro for 1, 2, 4, and 8 weeks. The samples included a culture of the marrow clot alone (Group 1), a culture of the marrow clot with transforming growth factor-beta 3 (TGF-β3) (Group 2), a culture of the composite of the BMSC-dECM scaffold and the marrow clot alone (Group 3), and a culture of the composite with TGF-β3 (Group 4). A smooth and glossy surface was observed in Group 2 and Group 4 over time, but the surface for Group 4 was larger from week 1 onward. Compressive strength gradually increased in Groups 2 and 4, and greater increases were observed in Group 4 during the 8-week culture period. Enhanced cartilage-like matrix deposition of glycosaminoglycan (GAG) and type II collagen were confirmed by Safranin O and immunohistochemistry staining, respectively, in Groups 2 and 4. The GAG and collagen contents also gradually increased over time in Groups 2 and 4; the increase was greater in Group 4. In addition, real-time-polymerase chain reaction demonstrated that the expression of chondrogenic genes, such as COL2, ACAN, and SOX9, was gradually upregulated in Groups 2 and 4. However, greater increases in the expression of these cartilage-like genes were observed in Group 4 from week 4 onward. Our results suggest that the BMSC-dECM scaffold may favor the chondrogenesis of marrow clots following microfracture in vitro. In conclusion, these tissue engineering-like constructs could be potential candidates for cartilage repair.

Chondrogenic effect of precartilaginous stem cells following NLS-TAT cell penetrating peptide-assisted transfection of eukaryotic hTGFβ3

Cell penetrating peptides (CPPs) are a series of promising carriers for delivering exogenous DNA to living cells. Among them, the combination of the human immunodeficiency virus TAT protein (TAT) with the SV40 large T protein nuclear localization signal (NLS) to form NLS-TAT performs well. In the present study, we took advantage of this new carrier to deliver transforming growth factor-beta 3 (TGFβ3) genes. TGFβ3 was expressed by the pEGFP-N1 vector following transfection of rat precartilaginous stem cells (PSCs), which promoted hTGFβ3 protein self-expression. At 24, 48, 72, and 120 h after transfection, the expression levels of hTGFβ3 were found to be elevated as compared with the control. The expression of hTGFβ3 was found to mediate the chondrogenic effect of PSCs. Thus, we determined the expression of the chondrogenesis-related genes type II collagen, Sox 9, and aggrecan in PSCs at 24, 48, 72, and 120 h after transfection. We found that their transcription and translation was augmented, which indicated a trend of active chondrogenesis in the PSCs. Our results demonstrated that NLS-TAT had the ability to deliver exogenous DNA into rat PSCs and could be actively expressed. This process successfully promoted PSC chondrogenesis. Additionally, PSC, may represent a new type of stem cells, and thus show great potential in regenerative repair following cartilage injury.

Bioactive factors in platelet-rich plasma obtained by apheresis

INTRODUCTION

The use of platelet-rich plasma (PRP) in regenerative approaches in cartilage repair is becoming more common. Information about PRP composition and its content of putative bioactive chondrogenic growth factors (GF) that may support cartilage regeneration is scarce.

METHODS

GF composition of a pool of 6 PRP preparations was determined using Protein Antibody Membrane Arrays covering 507 GF, signaling molecules, and receptors. To verify the chondrogenic GF variability in PRP, Growth Factor Antibody Membrane Arrays covering 26 GF were applied to 6 individual PRP preparations. Selected GF involved in chondrogenic differentiation were quantified by Enzyme-Linked Immunosorbent Assay (ELISA).

RESULTS

417 out of 507 possible detectable proteins were present in the PRP pool, including 76 GF. Quantification of selected chondrogenic GF by ELISA showed an average of 0.31 ng/ml bone morphogenetic protein-2, 0.50 ng/ml connective tissue growth factor, 0.76 ng/ml fibroblast growth factor-2, and 0.59 ng/ml transforming growth factor-β3.

CONCLUSION

PRP as a therapeutic option in regenerative cartilage repair strategies is a powerful tool for the local application of chondrogenic GF to the site of injury. Chondrogenic GF are present in PRP and may support cartilage repair by inducing cell differentiation and cartilage matrix formation.

Chondrogenic differentiation of mesenchymal stem cells in a hydrogel system based on an enzymatically crosslinked tyramine derivative of hyaluronan

Hyaluronan-based tissue substitutes are promising materials in cartilage reconstruction surgery. Herein, the chondrogenesis of human mesenchymal stem cells (MSC) in a hydrogel based on a tyramine derivative of hyaluronan crosslinked by hydrogen peroxidase (HA-TA) was evaluated. Human MSC seeded in the scaffold were incubated in standard chondrogenic medium and medium enriched with bone morphogenetic protein-6 (BMP6). Cell viability, the gene expression of selected markers (collagen type II, aggrecan, SOX9, collagen type X, and osteopontin), and the histological characteristics were examined during three weeks of in vitro cultivation. The tissue reaction of both unseeded and MSC seeded HA-TA scaffolds were tested in vivo after subcutaneous application in rats for 12 weeks. The data showed that cells resisted the process of crosslinking and remained viable for the whole time while exhibiting changes in cell organization. Human MSC cultivated in HA-TA hydrogel expressed genes of both chondrogenic and osteogenic differentiation and the addition of BMP6 revealed a tendency to potentiate both processes. Histological analysis of HA-TA in vivo implants did not reveal a chronic inflammatory reaction. In both cases, in vivo HA-TA implants were continuously degraded and MSC-seeded hydrogels tended to form clusters similar to in vitro samples. In conclusion, MSC chondrogenic differentiation may proceed in a HA-TA scaffold that is biocompatible. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3523-3530, 2014.

Enhanced tissue regeneration potential of juvenile articular cartilage

BACKGROUND

Articular cartilage undergoes substantial age-related changes in molecular composition, matrix structure, and mechanical properties. These age-related differences between juvenile and adult cartilage manifest themselves as markedly distinct potentials for tissue repair and regeneration.

PURPOSE

To compare the biological properties and tissue regeneration capabilities of juvenile and adult bovine articular cartilage.

STUDY DESIGN

Controlled laboratory study.

METHODS

Articular cartilage harvested from juvenile (age, 4 months) and adult (age, 6-8 years) bovine femoral condyles was cultured for 4 weeks to monitor chondrocyte migration, glycosaminoglycan content conservation, and new tissue formation. The cartilage cell density and proliferative activity were also compared. Additionally, the effects of age-related changes on cartilage gene expression were analyzed using the Affymetrix GeneChip array.

RESULTS

Compared with adult cartilage, juvenile bovine cartilage demonstrated a significantly greater cell density, higher cell proliferation rate, increased cell outgrowth, elevated glycosaminoglycan content, and enhanced matrix metallopeptidase 2 activity. During 4 weeks in culture, only juvenile cartilage was able to generate new cartilaginous tissues, which exhibited pronounced labeling for proteoglycan and type II collagen but not type I collagen. With over 19,000 genes analyzed, distinctive gene expression profiles were identified. The genes mostly involved in cartilage growth and expansion, such as COL2A1, COL9A1, MMP2, MMP14, and TGFB3, were upregulated in juvenile cartilage, whereas the genes primarily responsible for structural integrity, such as COMP, FN1, TIMP2, TIMP3, and BMP2, were upregulated in adult cartilage.

CONCLUSION

As the first comprehensive comparison between juvenile and adult bovine articular cartilage at the tissue, cellular, and molecular levels, the results strongly suggest that juvenile cartilage possesses superior chondrogenic activity and enhanced regenerative potential over its adult counterpart. Additionally, the differential gene expression profiles of juvenile and adult cartilage suggest possible mechanisms underlying cartilage age-related changes in their regeneration capabilities, structural components, and biological properties.

CLINICAL RELEVANCE

The results of this comparative study between juvenile and adult bovine articular cartilage suggest an enhanced regenerative potential of juvenile cartilage tissue in the restoration of damaged articular cartilage.

Transplantation of autologous endothelial progenitor cells in porous PLGA scaffolds create a microenvironment for the regeneration of hyaline cartilage in rabbits

OBJECTIVE

Repairing articular cartilage is clinically challenging. We investigated a simple, effective and clinically feasible cell-based therapeutic approach using a poly(lactide-co-glycolide) (PLGA) scaffold seeded with autologous endothelial progenitor cells (EPC) to repair a full-thickness osteochondral defect in rabbits using a one-step surgery.

METHODS

EPC obtained by purifying a small amount of peripheral blood from rabbits were seeded into a highly porous, biocompatible PLGA scaffold, namely, EPC-PLGA, and implanted into the osteochondral defect in the medial femoral condyle. Twenty two rabbits were randomized into one of three groups: the empty defect group (ED), the PLGA-only group or the EPC-PLGA group. The defect sites were evaluated 4 and 12 weeks after implantation.

RESULTS

At the end of testing, only the EPC-PLGA group showed the development of new cartilage tissue with a smooth, transparent and integrated articular surface. Moreover, histological analysis showed obvious differences in cartilage regeneration. At week 4, the EPC-PLGA group showed considerably higher TGF-β2 and TGF-β3 expression, a greater amount of synthesized glycosaminoglycan (GAG) content, and a higher degree of osteochondral angiogenesis in repaired tissues. At week 12, the EPC-PLGA group showed enhanced hyaline cartilage regeneration with a normal columnar chondrocyte arrangement, higher SOX9 expression, and greater GAG and collagen type II (COLII) content. Moreover, the EPC-PLGA group showed organized osteochondral integration, the formation of vessel-rich tubercular bone and significantly higher bone volume per tissue volume and trabecular thickness (Tb.Th).

CONCLUSION

The present EPC-PLGA cell delivery system generates a suitable in situ microenvironment for osteochondral regeneration without the supplement of exogenous growth factors.

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.

Operative treatment of osteochondral lesions of the talus

➤ Osteochondral lesions of the talus are common injuries in recreational and professional athletes, with up to 50% of acute ankle sprains and fractures developing some form of chondral injury. Surgical treatment paradigms aim to restore the articular surface with a repair tissue similar to native cartilage and to provide long-term symptomatic relief.➤ Arthroscopic bone-marrow stimulation techniques, such as microfracture and drilling, perforate the subchondral plate with multiple openings to recruit mesenchymal stem cells from the underlying bone marrow to stimulate the differentiation of fibrocartilaginous repair tissue in the defect site. The ability of fibrocartilage to withstand mechanical loading and protect the subchondral bone over time is a concern.➤ Autologous osteochondral transplantation techniques replace the defect with a tubular unit of viable hyaline cartilage and bone from a donor site in the ipsilateral knee. In rare cases, a graft can also be harvested from the ipsilateral talus or contralateral knee. The limitations of donor site morbidity and the potential need for an osteotomy about the ankle should be considered. Some anterior or far posterior talar lesions can be accessed without arthrotomy or with a plafondplasty.➤ Osteochondral allograft transplantation allows an osteochondral lesion with a large surface area to be replaced with a single unit of viable articular cartilage and subchondral bone from a donor that is matched to size, shape, and surface curvature. The best available evidence suggests that this procedure should be limited to large-volume cystic lesions or salvage procedures.➤ Autologous chondrocyte implantation techniques require a two-stage procedure, the first for chondrocyte harvest and the second for implantation in a periosteum-covered or matrix-induced form after in vivo culture expansion. Theoretically, the transplantation of chondrocyte-like cells into the defect will result in hyaline-like repair tissue.

Chondrogenesis of periodontal ligament stem cells by transforming growth factor-β3 and bone morphogenetic protein-6 in a normal healthy impacted third molar

The periodontal ligament-derived mesenchymal stem cell is regarded as a source of adult stem cells due to its multipotency. However, the proof of chondrogenic potential of the cells is scarce. Therefore, we investigated the chondrogenic differentiation capacity of periodontal ligament derived mesenchymal stem cells induced by transforming growth factor (TGF)-β3 and bone morphogenetic protein (BMP)-6. After isolation of periodontal ligament stem cells (PDLSCs) from human periodontal ligament, the cells were cultured in Dulbecco's modified Eagle's medium (DMEM) with 20% fetal bovine serum (FBS). A mechanical force initiated chondrogenic differentiation of the cells. For chondrogenic differentiation, 10 µg·L⁻¹ TGF-β3 or 100 µg∙L⁻¹ BMP-6 and the combination treating group for synergistic effect of the growth factors. We analyzed the PDLSCs by fluorescence-activated cell sorting and chondrogenesis were evaluated by glycosaminoglycans assay, histology, immunohistochemistry and genetic analysis. PDLSCs showed mesenchymal stem cell properties proved by FACS analysis. Glycosaminoglycans contents were increased 217% by TGF-β3 and 220% by BMP-6. The synergetic effect of TGF-β3 and BMP-6 were shown up to 281% compared to control. The combination treatment increased Sox9, aggrecan and collagen II expression compared with not only controls, but also TGF-β3 or BMP-6 single treatment dramatically. The histological analysis also indicated the chondrogenic differentiation of PDLSCs in our conditions. The results of the present study demonstrate the potential of the dental stem cell as a valuable cell source for chondrogenesis, which may be applicable for regeneration of cartilage and bone fracture in the field of cell therapy.

MicroRNA-181b regulates articular chondrocytes differentiation and cartilage integrity

MicroRNAs are endogenous gene regulators that have been implicated in various developmental and pathological processes. However, the precise identities and functions of the miRNAs involved in cartilage development are not yet well understood. Here, we report that miR-181b regulates chondrocyte differentiation and maintains cartilage integrity, and is thus a potent therapeutic target. MiR-181b was significantly down-regulated during chondrogenic differentiation of TGF-β3-stimulated limb mesenchymal cells, but it was significantly up-regulated in osteoarthritic chondrocytes isolated from the cartilage of osteoarthritis patients. The use of a mimic or an inhibitor to alter miR-181b levels in chondroblasts and articular chondrocytes showed that attenuation of miR-181b reduced MMP-13 expression while inducing type II collagen expression. Furthermore, over-expression of anti-miR-181b significantly reduced the cartilage destruction caused by DMM surgery in mice. In sum, our data suggest that miR-181b is a negative regulator of cartilage development, and that inhibition of miR-181b could be an effective therapeutic strategy for cartilage-related disease.

Prognostic significance of the containment and location of osteochondral lesions of the talus: independent adverse outcomes associated with uncontained lesions of the talar shoulder

BACKGROUND

Uncontained osteochondral lesions of the talar shoulder are associated with an increased risk of clinical failure in patients treated with current cylindrical osteochondral autograft techniques. Whether the same holds true in patients undergoing arthroscopic treatment is unknown.

PURPOSE

To determine the relative prognostic significance of the containment (shoulder vs nonshoulder type) and location (medial vs lateral) of an osteochondral lesion of the talus (OLT).

HYPOTHESIS

Arthroscopic treatment may not be ideal for uncontained lesions of the talar shoulder due to a lack of structural support.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Arthroscopic treatment for OLT was performed on the ankles of 399 patients between 2001 and 2009. Analyses were performed by grouping the patients according to type of containment (shoulder, n = 181; nonshoulder, n = 218), location (medial, n = 274; lateral, n = 125), and both type of containment and location (medial shoulder, n = 129; medial nonshoulder, n = 145; lateral shoulder, n = 52; lateral nonshoulder, n = 73). To evaluate the role of containment and location independently of OLT size, patients were grouped according to quartile of defect size, and outcomes were analyzed within each group.

RESULTS

Patients with shoulder-type OLT had a substantially worse clinical outcome than did those with nonshoulder-type OLT, even after adjustment for OLT size (P < .05). However, there was no significant difference in clinical outcome between patients with medial OLT and those with lateral OLT, and the clinical failure rates of the 2 groups were similar (P > .05). A Cox proportional hazards regression model demonstrated that OLT containment, but not location, exerted an independent prognostic effect.

CONCLUSION

Patients with uncontained OLT of the talar shoulder experienced a more complicated clinical outcome than did those with contained, nonshoulder-type OLT even after adjustment for OLT size and regardless of location.

Cartilage development and degeneration: a Wnt Wnt situation

The Wnt signaling pathway plays a crucial role in the development and homeostasis of a variety of adult tissues and, as such, is emerging as an important therapeutic target for numerous diseases. Factors involved in the Wnt pathway are expressed throughout limb development and chondrogenesis and have been shown to be critical in joint homeostasis and endochondral ossification. Therefore, in this review, we discuss Wnt regulation of chondrogenic differentiation, hypertrophy and cartilage function. Moreover, we detail the role of the Wnt signaling pathway in cartilage degeneration and its potential to act as a target for therapy in osteoarthritis.

Chitosan, hyaluronan and chondroitin sulfate in tissue engineering for cartilage regeneration: a review

Injection of hyaluronan into osteoarthritic joints restores the viscoelasticity, augments the flow of joint fluid, normalizes endogenous hyaluronan synthesis, and improves joint function. Chitosan easily forms polyelectrolyte complexes with hyaluronan and chondroitin sulfate. Synergy of chitosan with hyaluronan develops enhanced performances in regenerating hyaline cartilage, typical results being structural integrity of the hyaline-like neocartilage, and reconstitution of the subchondral bone, with positive cartilage staining for collagen-II and GAG in the treated sites. Chitosan qualifies for the preparation of scaffolds intended for the regeneration of cartilage: it yields mesoporous cryogels; it provides a friendly environment for chondrocytes to propagate, produce typical ECM, and assume the convenient phenotype; it is a good carrier for growth factors; it inactivates metalloproteinases thus preventing collagen degradation; it is suitable for the induction of the chondrogenic differentiation of mesenchymal stem cells; it is a potent means for hemostasis and platelet delivery.

Dynamic compression of rabbit adipose-derived stem cells transfected with insulin-like growth factor 1 in chitosan/gelatin scaffolds induces chondrogenesis and matrix biosynthesis

Articular cartilage is routinely subjected to mechanical forces and growth factors. Adipose-derived stem cells (ASCs) are multi-potent adult stem cells and capable of chondrogenesis. In the present study, we investigated the comparative and interactive effects of dynamic compression and insulin-like growth factor-I (IGF-I) on the chondrogenesis of rabbit ASCs in chitosan/gelatin scaffolds. Rabbit ASCs with or without a plasmid overexpressing of human IGF-1 were cultured in chitosan/gelatin scaffolds for 2 days, then subjected to cyclic compression with 5% strain and 1 Hz for 4 h per day for seven consecutive days. Dynamic compression induced chondrogenesis of rabbit ASCs by activating calcium signaling pathways and up-regulating the expression of Sox-9. Dynamic compression plus IGF-1 overexpression up-regulated expression of chondrocyte-specific extracellular matrix genes including type II collagen, Sox-9, and aggrecan with no effect on type X collagen expression. Furthermore, dynamic compression and IGF-1 expression promoted cellular proliferation and the deposition of proteoglycan and collagen. Intracellular calcium ion concentration and peak currents of Ca(2+) ion channels were consistent with chondrocytes. The tissue-engineered cartilage from this process had excellent mechanical properties. When applied together, the effects achieved by the two stimuli (dynamic compression and IGF-1) were greater than those achieved by either stimulus alone. Our results suggest that dynamic compression combined with IGF-1 overexpression might benefit articular cartilage tissue engineering in cartilage regeneration.

Preclinical studies on mesenchymal stem cell-based therapy for growth plate cartilage injury repair

In the last two decades, there has been a strong interest in searching for biological treatments for regeneration of injured growth plate cartilage and prevention of its bony repair. Various means have been tried, including implantation of chondrocytes, mesenchymal stem cell (MSC), together with exogenous growth factor and scaffolds, and gene therapy. However, with the lack of success with chondrocytes, more research has focussed on MSC-based treatments. In addition to circumvent limitations with MSC-based treatments (including cell harvest-associated morbidity, difficulties/time/cost involved in MSC isolation and ex vivo expansion, and potential disease transmission), mobilising endogenous MSCs to the growth plate injury site and enhancing in situ regeneration mechanisms would represent an alternative attractive approach. Further studies are required to investigate the potential particularly in large animal models or clinical setting of the ex vivo MSC approach and the feasibility of the endogenous MSC in situ approach in growth plate regeneration.

Biological responses to spider silk-antibiotic fusion protein

The development of a new generation of multifunctional biomaterials is a continual goal for the field of materials science. The in vivo functional behaviour of a new fusion protein that combines the mechanical properties of spider silk with the antimicrobial properties of hepcidin was addressed in this study. This new chimeric protein, termed 6mer + hepcidin, fuses spider dragline consensus sequences (6mer) and the antimicrobial peptide hepcidin, as we have recently described, with retention of bactericidal activity and low cytotoxicity. In the present study, mouse subcutaneous implants were studied to access the in vivo biological response to 6mer + hepcidin, which were compared with controls of silk alone (6mer), polylactic-glycolic acid (PLGA) films and empty defects. Along with visual observations, flow cytometry and histology analyses were used to determine the number and type of inflammatory cells at the implantation site. The results show a mild to low inflammatory reaction to the implanted materials and no apparent differences between the 6mer + hepcidin films and the other experimental controls, demonstrating that the new fusion protein has good in vivo biocompatibility, while maintaining antibiotic function.

Tuning the differentiation of periosteum-derived cartilage using biochemical and mechanical stimulations

OBJECTIVE

In this study, we aim at tuning the differentiation of periosteum in an organ culture model towards cartilage, rich in collagen type II, using combinations of biochemical and mechanical stimuli. We hypothesize that addition of TGF-β will stimulate chondrogenesis, whereas sliding indentation will enhance collagen synthesis.

DESIGN

Periosteum was dissected from the tibiotarsus of 15-day-old chick embryos. Explants were embedded in between two agarose layers, and cultured without stimulation (control), with biochemical stimulation (10 ng/ml TGF-β1), with mechanical stimulation (sliding indentation), or both biochemical and mechanical stimulations. Sliding indentation was introduced as a method to induce tensile tissue strain. Analysis included quantification of DNA, collagen and GAG content, conventional histology, and immunohistochemistry for collagen type I and II at 1 or 2 weeks of culture.

RESULTS

Embedding the periosteal explants in between agarose layers induced cartilage formation, confirmed by synthesis of sGAG and collagen type II. Addition of TGF-β1 to the culture medium did not further enhance this chondrogenic response. Applying sliding indentation only to the periosteum in between agarose layers enhanced the production of collagen type I, leading to the formation of fibrous tissue without any evidence of cartilage formation. However, when stimulated by both TGF-β1 and sliding indentation, collagen production was still enhanced, but now collagen type II, while sGAG was found to be similar to TGF-β1 or unloaded samples.

CONCLUSIONS

The type of tissue produced by periosteal explants can be tuned by combining mechanical stimulation and soluble factors. TGF-β1 stimulated a chondrocyte phenotype and sliding indentation stimulated collagen synthesis. Such a combination may be valuable for improvement of the quality of tissue-engineered cartilage.

Osteoinduction: translating preclinical promise into clinical reality

This review, the second in a series of three editorials, focuses on the problems of translating basic scientific research on induction of bone into reliable clinical applications.

A Review of Arthroscopic Bone Marrow Stimulation Techniques of the Talus: The Good, the Bad, and the Causes for Concern

Osteochondral lesions of the talus are common injuries following acute and chronic ankle sprains. Numerous surgical treatment strategies have been employed for treating these lesions; arthroscopic bone marrow stimulation is recognized as the first-line technique to provide fibrocartilage infill of the defect site. While the short- and medium-term outcomes of this technique are good, the long-term outcomes are not yet known. An increasing number of studies, however, show a cause for concern in employing this technique, including declining outcome scores over time. The current authors have therefore developed a treatment strategy based on previously established guidelines in addition to morphological cartilage-sensitive fast spin echo techniques and quantitative T2 mapping magnetic resonance imaging (MRI). Accordingly, the authors advocate arthroscopic bone marrow stimulation in lesion sizes up to 8 mm in diameter and osteochondral autograft transplant (OATS) in lesion sizes greater than 8 mm in diameter. In the absence of long-term studies, confining the use of arthroscopic bone marrow stimulation to smaller lesions may support prolonged joint life by decreasing the rate at which the fibrocartilage ultimately degenerates over time. Employing the OATS procedure in larger lesions has the advantage of replacing "like with like." The current review examines the role of arthroscopic bone marrow stimulation techniques of the talus.

New molecular targets for the treatment of osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disorder characterized by destruction of the articular cartilage, subchondral bone alterations and synovitis. Current treatments are focused on symptomatic relief but they lack efficacy to control the progression of this disease which is a leading cause of disability. Therefore, the development of effective disease-modifying drugs is urgently needed. Different initiatives are in progress to define the molecular mechanisms involved in the initiation and progression of OA. These studies support the therapeutic potential of pathways relevant in joint metabolism such as Wnt/beta-catenin, discoidin domain receptor 2 or proteinase-activated receptor 2. The dysregulation in cartilage catabolism and subchondral bone remodeling could be improved by selective inhibitors of matrix metalloproteinases, aggrecanases and other proteases. Another approach would favor the activity of anabolic processes by using growth factors or regulatory molecules. Recent studies have also revealed the role of oxidative stress and synovitis in the progression of this disease, supporting the development of a number of inhibitory strategies. Novel targets in OA are represented by genes involved in OA pathophysiology discovered using gene network, epigenetic and microRNA approaches. Further insights into the molecular mechanisms involved in OA initiation and progression may lead to the development of new therapies able to control joint destruction and repair.