Enhanced repair of articular cartilage defects in vivo by transplanted chondrocytes overexpressing insulin-like growth factor I (IGF-I)

Intraarticular injection of heparin-binding insulin-like growth factor 1 sustains delivery of insulin-like growth factor 1 to cartilage through binding to chondroitin sulfate

OBJECTIVE

Insulin-like growth factor 1 (IGF-1) stimulates cartilage repair but is not a practical therapy due to its short half-life. We have previously modified IGF-1 by adding a heparin-binding domain and have shown that this fusion protein (HB-IGF-1) stimulates sustained proteoglycan synthesis in cartilage. This study was undertaken to examine the mechanism by which HB-IGF-1 is retained in cartilage and to test whether HB-IGF-1 provides sustained growth factor delivery to cartilage in vivo and to human cartilage explants.

METHODS

Retention of HB-IGF-1 and IGF-1 was analyzed by Western blotting. The necessity of heparan sulfate (HS) or chondroitin sulfate (CS) glycosaminoglycans (GAGs) for binding was tested using enzymatic removal and cells with genetic deficiency of HS. Binding affinities of HB-IGF-1 and IGF-1 proteins for isolated GAGs were examined by surface plasmon resonance and enzyme-linked immunosorbent assay.

RESULTS

In cartilage explants, chondroitinase treatment decreased binding of HB-IGF-1, whereas heparitinase had no effect. Furthermore, HS was not necessary for HB-IGF-1 retention on cell monolayers. Binding assays showed that HB-IGF-1 bound both CS and HS, whereas IGF-1 did not bind either. After intraarticular injection in rat knees, HB-IGF-1 was retained in articular and meniscal cartilage, but not in tendon, consistent with enhanced delivery to CS-rich cartilage. Finally, HB-IGF-1 was retained in human cartilage explants but IGF-1 was not.

CONCLUSION

Our findings indicate that after intraarticular injection in rats, HB-IGF-1 is specifically retained in cartilage through its high abundance of CS. Modification of growth factors with heparin-binding domains may be a new strategy for sustained and specific local delivery to cartilage.

The promotion of cartilage defect repair using adenovirus mediated Sox9 gene transfer of rabbit bone marrow mesenchymal stem cells

Although Sox9 is essential for chondrogenic differentiation and matrix production, its application in cartilage tissue engineering has been rarely reported. In this study, the chondrogenic effect of Sox9 on bone marrow mesenchymal stem cells (BMSCs) in vitro and its application in articular cartilage repair in vivo were evaluated. Rabbit BMSCs were transduced with adenoviral vector containing Sox9. Toluidine blue, safranin O staining and real-time PCR were performed to check chondrogenic differentiation. The results showed that Sox9 could induce chondrogenesis of BMSCs both in monolayer and on PGA scaffold effectively. The rabbit model with full-thickness cartilage defects was established and then repaired by PGA scaffold and rabbit BMSCs with or without Sox9 transduction. HE, safranin O staining and immunohistochemistry were used to assess the repair of defects by the complex. Better repair, including more newly-formed cartilage tissue and hyaline cartilage-specific extracellular matrix and greater expression of several chondrogenesis marker genes were observed in PGA scaffold and BMSCs with Sox9 transduction, compared to that without transduction. Our findings defined the important role of Sox9 in the repair of cartilage defects in vivo and provided evidence that Sox9 had the potential and advantage in the application of tissue engineering.

The effect of microRNA-21 on proliferation and matrix synthesis of chondrocytes embedded in atelocollagen gel

The objective of this study was to investigate the effect of microRNA-21 (miR-21) on the proliferation and matrix synthesis of chondrocytes embedded in atelocollagen gel. Articular cartilage was harvested aseptically from the knee and hip joints of rats. In the experimental group, double-stranded miR-21 was transfected into the chondrocytes, and in the control group, scrambled siRNA was used. After that, chondrocytes were cultured in atelocollagen gel for 3 weeks. At 1, 2, and 3 weeks after transfection, the cell numbers were counted, and the expression levels of Col2a1 and aggrecan were measured by real-time PCR. Histological analysis by toluidine blue staining was performed at 3 weeks. The cell number in the experimental group rapidly increased compared to the control group. The expression levels of Col2a1 and aggrecan in the experimental group were higher than in the control. Histological analysis revealed that many more cells with a metachromatic stain were present in the experimental group than in the control. This study demonstrated that miR-21 promotes high proliferation and matrix synthesis of chondrocytes embedded in atelocollagen gel.

Acceleration of articular cartilage repair by combined gene transfer of human insulin-like growth factor I and fibroblast growth factor-2 in vivo

INTRODUCTION

Improving the biochemical and structural qualities of the new tissue that fills deep osteochondral defects is critical to enhance articular cartilage repair. We developed a novel molecular therapy to increase articular cartilage repair based on a combined strategy to stimulate chondrogenesis by co-transfection of the human insulin-like growth factor I (IGF-I) and fibroblast growth factor 2 (FGF-2) in a xenogenic transplantation model.

MATERIALS AND METHODS

NIH 3T3 cells were transfected with expression plasmid vectors containing a cDNA for the E. coli lacZ gene (lacZ implants), the human IGF-I gene (IGF-I implants) or both the human IGF-I and FGF-2 genes (IGF-I/FGF-2 implants). The expression patterns of the transgenes were monitored in vitro for 21 days. LacZ, IGF-I and IGF-I/FGF-2 implants were transplanted into osteochondral defects in the trochlear groove of rabbits. At 3 weeks, the quality of articular cartilage repair was evaluated qualitatively and quantitatively.

RESULTS

Both IGF-I and IGF-I/FGF-2 implants secreted increased levels of the corresponding recombinant proteins in vitro. In vivo, transplantation of the co-transfected IGF-I/FGF-2 implants increased the DNA content of the repair tissue, accelerated the formation of the subchondral bone and improved articular cartilage repair in a magnitude that was larger than with IGF-I alone or when compared to lacZ implants.

CONCLUSION

These results suggest that gene delivery of a combination of IGF-I and FGF-2 to cartilage defects may be more beneficial than application of IGF-I alone.

The effect of insulin-loaded chitosan particle-aggregated scaffolds in chondrogenic differentiation

Osteochondral defect repair requires a tissue engineering approach that aims at mimicking the physiological properties and structure of two different tissues (cartilage and bone) using a scaffold-cell construct. One ideal approach would be to engineer in vitro a hybrid material using a single-cell source. For that purpose, the scaffold should be able to provide the adequate biochemical cues to promote the selective but simultaneous differentiation of both tissues. In this work, attention was paid primarily to the chondrogenic differentiation by focusing on the development of polymeric systems that provide biomolecules release to induce chondrogenic differentiation. For that, different formulations of insulin-loaded chitosan particle-aggregated scaffolds were developed as a potential model system for cartilage and osteochondral tissue engineering applications using insulin as a potent bioactive substance known to induce chondrogenic differentiation. The insulin encapsulation efficiency was shown to be high with values of 70.37 +/- 0.8%, 84.26 +/- 1.76%, and 87.23 +/- 1.58% for loadings of 0.05%, 0.5%, and 5%, respectively. The in vitro release profiles were assessed in physiological conditions mimicking the cell culture procedures and quantified by Micro-BCA protein assay. Different release profiles were obtained that showed to be dependent on the initial insulin-loading percentage. Further, the effect on prechondrogenic ATDC5 cells was investigated for periods up to 4 weeks by studying the influence of these release systems on cell morphology, DNA and glycosaminoglycan content, histology, and gene expression of collagen types I and II, Sox-9, and aggrecan assessed by real-time polymerase chain reaction. When compared with control conditions (unloaded scaffolds cultured with the standard chondrogenic-inducing medium), insulin-loaded scaffolds upregulated the Sox-9 and aggrecan expression after 4 weeks of culture. From the overall results, it is reasonable to conclude that the developed loaded scaffolds when seeded with ATDC5 can provide biochemical cues for chondrogenic differentiation. Among the tested formulations, the higher insulin-loaded system (5%) was the most effective in promoting chondrogenic differentiation.

Chondrogenesis of synovium-derived mesenchymal stem cells in gene-transferred co-culture system

A co-culture strategy has been developed in this study wherein rabbit synovial mesenchymal stem cells (SMSCs) are co-cultured with growth factor (GF) transfected articular chondrocytes. Toward this end, both SMSCs and early passage rabbit articular chondrocytes that had been adenovirally transduced with transforming growth factor-beta 3 (TGF-beta3) gene were separately encapsulated in alginate beads and co-cultured in the same pool of chondrogenic medium. The chondrocytes act as transfected companion cells (TCCs) providing GF supply to induce chondrogenic differentiation of SMSCs that play the role of therapeutic progenitor cells (TPCs). Against the same TCC based TGF-beta3 release profile, the co-culture was started at different time points (Day 0, Day 10 and Day 20) but made to last for identical periods of exposure (30 days) so that the exposure conditions could be optimized in terms of initiation and duration. Transfection of TCCs prevents the stem cell based TPCs from undergoing the invasive procedure. It also prevents unpredictable complications in the TPCs caused by long-term constitutive over-expression of a GF. The adenovirally transfected TCCs exhibit a transient GF expression which results in a timely termination of GF supply to the TPCs. The TCC-sourced transgenic TGF-beta3 successfully induced chondrogenesis in the TPCs. Real-time PCR results show enhanced expression of cartilage markers and immuno/histochemical staining for Glycosaminoglycans (GAG) and Collagen II also shows abundant extracellular matrix (ECM) production and chondrogenic morphogenesis in the co-cultured TPCs. These results confirm the efficacy of directing stem cell differentiation towards chondrogenesis and cartilage tissue formation by co-culturing them with GF transfected chondrocytes.

Advances in Tissue Engineering Techniques for Articular Cartilage Repair

The limited repair potential of human articular cartilage contributes to development of debilitating osteoarthritis and remains a great clinical challenge. This has led to evolution of cartilage treatment strategies from palliative to either reconstructive or reparative methods in an attempt to delay or "bridge the gap" to joint replacement. Further development of tissue engineering-based cartilage repair methods have been pursued to provide a more functional biological tissue. Currently, tissue engineering of articular cartilage has three cornerstones; a cell population capable of proliferation and differentiation into mature chondrocytes, a scaffold that can host these cells, provide a suitable environment for cellular functioning and serve as a sustained-release delivery vehicle of chondrogenic growth factors and thirdly, signaling molecules and growth factors that stimulate the cellular response and the production of a hyaline extracellular matrix (ECM). The aim of this review is to summarize advances in each of these three fields of tissue engineering with specific relevance to surgical techniques and technical notes.

The basic science of the subchondral bone

In the past decades, considerable efforts have been made to propose experimental and clinical treatments for articular cartilage defects. Yet, the problem of cartilage defects extending deep in the underlying subchondral bone has not received adequate attention. A profound understanding of the basic anatomic aspects of this particular site, together with the pathophysiology of diseases affecting the subchondral bone is the key to develop targeted and effective therapeutic strategies to treat osteochondral defects. The subchondral bone consists of the subchondral bone plate and the subarticular spongiosa. It is separated by the cement line from the calcified zone of the articular cartilage. A variable anatomy is characteristic for the subchondral region, reflected in differences in thickness, density, and composition of the subchondral bone plate, contour of the tidemark and cement line, and the number and types of channels penetrating into the calcified cartilage. This review aims at providing insights into the anatomy, morphology, and pathology of the subchondral bone. Individual diseases affecting the subchondral bone, such as traumatic osteochondral defects, osteochondritis dissecans, osteonecrosis, and osteoarthritis are also discussed. A better knowledge of the basic science of the subchondral region, together with additional investigations in animal models and patients may translate into improved therapies for articular cartilage defects that arise from or extend into the subchondral bone.

IGF-1 and BMP-2 induces differentiation of adipose-derived mesenchymal stem cells into chondrocytes-like cells

Articular cartilage defects are common, causing significant morbidities. Tissue engineering using pluripotent stem cells is a new promising modality for cartilage repair. In the current study, we investigated the chondrogenesis of rabbit adipose-derived stem cells (ADSCs). We isolated rabbit ADSCs and transfected these cells with constructs encoding human insulin growth like factor 1 (IGF-1) and bone morphogenic protein 2 (BMP-2). We examined the growth and morphology of these transfected cells and their production of type II collagen and MMP-3. We found that IGF-1 and BMP-2 drove the chondrogenesis of ADSCs, which showed mature chondrocyte-like cells and formed cartilage nodules. These cells also produced type II collagen with a reduced production of MMP-3. Our findings suggested that human ADSCs could differentiate into chondrocyte-like cells driven by IGF-1 and BMP-2 and held promises as an abundant and ready source of stem cells for cartilage repair and regeneration.

IGFBP-5 Metabolism Is Disrupted in the Rat Medial Meniscal Tear Model of Osteoarthritis

Insulin-like growth factor binding protein 5 (IGFBP-5) has been proposed to promote cartilage anabolism through insulin-like growth factor (IGF-1) signaling. A proteolytic activity towards IGFBP-5 has been detected in synovial fluids from human osteoarthritic (OA) joints. The purpose of this study was to determine if protease activity towards IGFBP-5 is present in the rat medial meniscal tear (MMT) model of OA and whether inhibition of this activity would alter disease progression. Sprague-Dawley rats were subject to MMT surgery. Synovial fluid lavages were assessed for the presence of IGFBP-5 proteolytic activity. Treatment animals received intra-articular injections of vehicle or protease inhibitor peptide PB-145. Cartilage lesions were monitored by India ink staining followed by macroscopic measurement of lesion width and depth. The MMT surgery induced a proteolytic activity towards IGFPB-5 that was detectable in joint fluid. This activity was stimulated by calcium and was sensitive to serine protease inhibitors as well as peptide PB-145. Significantly, intra-articular administration of PB-145 after surgery protected cartilage from lesion development. PB-145 treatment also resulted in an increase in cartilage turnover as evidenced by increases in serum levels of procollagen type II C-propeptide (CPII) as well as synovial fluid lavage levels of collagen type II neoepitope (TIINE). IGFBP-5 metabolism is disrupted in the rat MMT model of OA, potentially contributing to cartilage degradation. Inhibition of IGFBP-5 proteolysis protected cartilage from lesion development and enhanced cartilage turnover. These data are consistent with IGFBP-5 playing a positive role in anabolic IGF signaling in cartilage.

Effects of Low Concentrated BMP-7 Administered by co-Cultivation or Plasmid Transfection on Human Osteoarthritic Chondrocytes

Introduction

While BMP-7 has proven to be one of the most potent growth factors in cartilage tissue engineering, protein concentration and route of administration remain a matter of debate. Here we investigated the effects of a low concentration of BMP-7 on human osteoarthritic chondrocytes administered by protein co-cultivation and plasmid transfection.

Methods

Freshly released (P0) or in vitro propagated chondrocytes (P2) were cultivated in a collagen type-I gel for 3 weeks in vitro or in nude mice. Seeded chondrocytes were treated with 50 ng/mL BMP-7 directly added to the medium or were subject to transient BMP-7 plasmid transfection prior to gel cultivation. Untreated specimens served as a control. After recovery, samples were investigated by histological and immunohistochemical staining and real-time PCR.

Results

In vitro, collagen type-II protein production was enhanced, and it was stored mainly pericellularly. Collagen type-II and aggrecan gene expression were enhanced in both treatment groups. After nude mouse cultivation, col-II protein production was further enhanced, but specimens of the BMP-7 transfection group revealed a clustering of col-II positive cells. Gene expression was strongly up-regulated, chondrocyte number was increased and the differentiated phenotype prevailed. In general, freshly released chondrocytes (P0) proved to be superior to chondrocytes pre-amplified in vitro (P2).

Conclusions

Both BMP-7 co-cultivation and plasmid transfection of human osteoarthritic chondrocytes led to improved cartilage repair tissue. Nevertheless, the col-II distribution following BMP-7 co-cultivation was homogeneous, while samples produced by transient transfection revealed a col-II clustering.

Effect of transfection strategy on growth factor overexpression by articular chondrocytes

Articular cartilage damage remains an unsolved problem in orthopaedics. Insulin-like growth factor I (IGF-I) and fibroblast growth factor-2 (FGF-2) are anabolic and mitogenic for articular chondrocytes, and are candidates for the application of gene therapy to articular cartilage repair. We tested the hypothesis that the production of IGF-I and FGF-2 can be augmented by modulating vector designs and delivery methods used for gene transfer to articular chondrocytes. We developed a novel adeno-associated virus (AAV)-based plasmid (pAAV) to overexpress IGF-I and FGF-2 cDNAs in adult bovine articular chondrocytes. We found that the pAAV-based vectors generated significantly more growth factor than pcDNA vectors carrying the same cDNAs. Chondrocytes cotransfected with both IGF-I and FGF-2 cDNAs in two separate pAAV plasmids produced significantly more IGF-I and FGF-2 than cells transfected by a single pAAV plasmid carrying both cDNAs in a dicistronic cassette. These data indicate that pAAV vectors are more effective than pcDNA vectors for transfer of IGF-I and FGF-2 genes to articular chondrocytes. They further suggest that cotransfection may be an effective strategy for multiple gene transfer to these cells. These findings may be important in applying growth factor gene transfer to cell-based articular cartilage gene therapy.

Ex vivo serotype-specific transduction of equine joint tissue by self-complementary adeno-associated viral vectors

Cell transplantation for the treatment of joint disease is an important clinical tool. Genetic modification of cells before transplantation has shown enhanced healing. Ex vivo genetic modification of joint tissue cells with various adeno-associated virus (AAV) serotypes has not been investigated. The transduction efficiencies of self-complementary AAV serotypes (1-6 and 8) were determined in joint tissue containing chondrocytes and synoviocytes isolated from equine models. When comparing scAAV serotypes for efficient transduction ex vivo, in chondrocytes versus synoviocytes, serotypes 6 and 2, and serotypes 3 and 2, respectively, appeared superior for gene expression. Unlike adenoviral vectors, no upregulation of inflammatory markers, such as matrix metalloproteinases and aggrecanase, was seen on treatment of joint tissue with AAV vectors ex vivo. Our findings also corroborate that ex vivo transduction of joint tissue can result in high transgene protein levels over time, and transplantation modalities might be feasible using AAV vectors in the treatment of joint-related diseases.

Baculovirus-mediated growth factor expression in dedifferentiated chondrocytes accelerates redifferentiation: effects of combinational transduction

Transduction of partially dedifferentiated rabbit chondrocytes with a baculovirus (Bac-CB) expressing bone morphogenetic protein-2 (BMP-2) reverses dedifferentiation and enhances matrix production. Hereby we examined whether transduction with Bac-CB in combination with another baculovirus expressing transforming growth factor-beta1 (TGF-beta1) or insulin-like growth factor-1 (IGF-1) synergistically augmented chondrogenic differentiation. Passage 3 rabbit articular chondrocytes were transduced by different baculovirus combinations: single transduction with Bac-CB, cotransduction with Bac-CB and Bac-CT (expressing TGF-beta1), cotransduction with Bac-CB and Bac-CI (expressing IGF-1), and transduction with Bac-CB followed by repeated transduction with Bac-CT, Bac-CI, or Bac-CB 5 days later. Transduced cells were encapsulated into alginate beads for culture. Among these strategies, only cotransduction with Bac-CB and Bac-CT led to improved redifferentiation when compared with Bac-CB single transduction, as evidenced by the enhanced expression of aggrecan and collagen IIB (Col IIB), suppressed expression of Col I and Col X, emergence of chondrocyte-specific lacunae, and elevated deposition of matrix molecules. The cotransduction also accelerated the expression of Sox9, Col IIB, and aggrecan. In summary, baculovirus-mediated coexpression of TGF-beta1 and BMP-2 synergistically accelerates the chondrocyte redifferentiation process and improves the maintenance of chondrocyte phenotype and accumulation of cartilage-specific matrix molecules.

Enhanced in vitro chondrogenesis of primary mesenchymal stem cells by combined gene transfer

Because articular cartilage has a poor regeneration capacity, numerous cell-based approaches to therapy are currently being explored. The present study involved the use of gene transfer as a means to provide sustained delivery of chondrogenic proteins to primary mesenchymal stem cells (MSCs). In previous work, we found that adenoviral-mediated gene transfer of transforming growth factor-beta1 (TGF-beta1) and bone morphogenetic protein 2 (BMP-2), but not insulin-like growth factor 1 (IGF-1), could be used to induce chondrogenic differentiation of MSCs in an aggregate culture system. In the present study, we examined the effects on chondrogenesis of these transgenes when delivered in combination. Cultures of bone marrow-derived MSCs were infected with 2.5 x 10(2) or 2.5 x 10(3) viral particles/cell of each adenoviral vector individually, or in combination, seeded into aggregates, and cultured for 3 weeks in a defined serum-free medium. Levels of transgene product in the medium were initially high, approximately 100 ng/mL TGF-beta1, 120 ng/mL BMP-2, and 80 ng/mL IGF-1 at day 3, and declined thereafter. We found that co-expression of IGF-1 and TGF-beta1, BMP-2, or both at low doses resulted in larger aggregates, higher levels of glycosaminoglycan synthesis, stronger staining for proteoglycans and collagen type II and X, and greater expression of cartilage-specific marker genes than with either transgene alone. Gene-induced chondrogenesis of MSCs using multiple genes that act synergistically may enable the administration of reduced viral doses in vivo and could be of considerable benefit for the development of cell-based therapies for cartilage repair.

A localizable, biological-based system for the delivery of bioactive IGF-1 utilizing microencapsulated genetically modified human fibroblasts

Insulin-like growth factor 1 (IGF-1) is a potent mitogen and differentiation factor with particular relevance to orthopedic tissue engineering. A biologically based Ca2+-alginate microcapsule vehicle, utilizing genetically modified primary normal human fibroblasts (NHFs), was developed and characterized for localized synthesis and delivery of human IGF-1 (hIGF-1). Normal human fibroblasts were transfected to overexpress the hIGF-1 gene, leading to cells that expressed 4 ng of hIGF-1 per 10(6) cells per 24 hours. Encapsulation within alginate led to a six-fold enhancement in the generation and release of hIGF-1 to 22 ng of hIGF-1 per 10(6) cells per 24 hours. Release was constitutive, predictable, and exhibited highly repeatable first-order kinetics with no initial burst. Released growth factor was biologically active and exhibited a proliferative effect comparable to commercially available recombinant hIGF-1. The magnitude of hIGF-1 release met the requirements of orthopedic tissue generation, and this approach is considered an attractive alternative to other proposed methods of growth factor delivery.

Proteoglycan production is required in initial stages of new cartilage matrix formation but inhibits integrative cartilage repair

The optimal stimulus to repair or regenerate cartilage is not known. We therefore modulated collagen deposition, collagen crosslinking and GAG deposition simultaneously during cartilage matrix production and integrative repair, creating more insight into their role in cartilage repair processes. Insulin-like growth factor 1 (IGF-1; increases proteoglycan and collagen synthesis), beta-aminopropionitrile (BAPN; a reversible inhibitor of collagen crosslinking) and para-nitrophenyl-beta-D-xyloside (PNPX; interferes with proteoglycan production) were used. Bovine articular chondrocytes were cultured in alginate beads for 3 weeks with or without IGF-1, BAPN or PNPX alone and in all possible combinations, followed by 3 weeks in control medium. DNA content, GAG and collagen deposition and collagen crosslinks were determined. Cartilage constructs were cultured under the same conditions and histologically analysed for integration of two opposing cartilage matrices. In alginate cultures, inhibition of collagen crosslinking with BAPN, in combination with promotion of matrix synthesis using IGF1, was most beneficial for matrix deposition. Addition of PNPX was always detrimental for matrix deposition. For integration of opposing cartilage constructs, the combination of BAPN, IGF1 and temporary prevention of proteoglycan formation with PNPX was most beneficial. When a new matrix is produced, proteoglycans are important to retain collagen in the matrix. When two already formed cartilage matrices have to integrate, a temporary absence of proteoglycans and temporary inhibition of collagen crosslinking might be more beneficial in combination with stimulation of collagen production, e.g. by IGF1. Therefore, the choice of soluble factors to promote cartilage regeneration depends on the type of therapy that will be used.

Articular cartilage tissue engineering

Articular cartilage repair remains a challenge to surgeons and basic scientists. The field of tissue engineering allows the simultaneous use of material scaffolds, cells and signalling molecules to attempt to modulate the regenerative tissue. This review summarises the research that has been undertaken to date using this approach, with a particular emphasis on those techniques that have been introduced into clinical practice, via in vitro and preclinical studies.

Complement 1s is the serine protease that cleaves IGFBP-5 in human osteoarthritic joint fluid

Insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBPs) are trophic factors for cartilage and have been shown to be chondroprotective in animal models of osteoarthritis (OA). IGFBP-5 is degraded in joint fluid and inhibition of IGFBP-5 degradation has been shown to enhance the trophic effects of IGF-I.

OBJECTIVE

To determine the identity of IGFBP-5 protease activity in human OA joint fluid.

METHOD

OA joint fluid was purified and the purified material was analyzed by IGFBP-5 zymography.

RESULTS

Both crude joint fluid and purified material contained a single band of proteolytic activity that cleaved IGFBP-5. Immunoblotting of joint fluid for complement 1s (C1s) showed a band that had the same Mr estimate, e.g., 88 kDa. In gel tryptic digestion and subsequent peptide analysis by LC-MS/MS showed that the band contained human C1s. A panel of protease inhibitors was tested for their ability to inhibit IGFBP-5 cleavage by the purified protease. Three serine protease inhibitors, FUT175 and CP-143217 and CB-349547 had IC50's between 1 and 6 microM. Two other serine protease inhibitors had intermediate activity (e.g., IC50's 20-40 microM) and MMP inhibitors had no detectible activity at concentrations up to 300 microM.

CONCLUSION

Human OA fluid contains a serine protease that cleaves IGFBP-5. Zymography, immunoblotting and LC-MS/MS analysis indicate that C1s is the protease that accounts for this activity.

Orthopedic gene therapy in 2008

Orthopedic disorders, although rarely fatal, are the leading cause of morbidity and impose a huge socioeconomic burden. Their prevalence will increase dramatically as populations age and gain weight. Many orthopedic conditions are difficult to treat by conventional means; however, they are good candidates for gene therapy. Clinical trials have already been initiated for arthritis and the aseptic loosening of prosthetic joints, and the development of bone-healing applications is at an advanced, preclinical stage. Other potential uses include the treatment of Mendelian diseases and orthopedic tumors, as well as the repair and regeneration of cartilage, ligaments, and tendons. Many of these goals should be achievable with existing technologies. The main barriers to clinical application are funding and regulatory issues, which in turn reflect major safety concerns and the opinion, in some quarters, that gene therapy should not be applied to nonlethal, nongenetic diseases. For some indications, advances in nongenetic treatments have also diminished enthusiasm. Nevertheless, the preclinical and early clinical data are impressive and provide considerable optimism that gene therapy will provide straightforward, effective solutions to the clinical management of several common debilitating disorders that are otherwise difficult and expensive to treat.

Growth factor regulation of growth factors in articular chondrocytes

Several lines of evidence indicate that polypeptide growth factors are important in articular cartilage homeostasis and repair. It is not yet clear how these growth factors are regulated. We tested the hypothesis that the growth factors responsible for regulating cartilage are themselves regulated by growth factors. We delivered insulin-like growth factor I (IGF-I), fibroblast growth factor-2 (FGF-2), and/or transforming growth factor-beta1 (TGF-beta1) to adult bovine articular chondrocytes in primary culture and measured the resulting changes in IGF-I, FGF-2, and TGF-beta1 gene expression and protein production. These growth factors differentially regulated their own and each others gene expression and protein production. In concert, they regulated each other in an interactive fashion. Their interactions ranged from inhibitory to synergistic. The time course of the regulatory effects differed among the individual growth factors and combinations. Growth factor-induced changes in growth factor protein production by articular chondrocytes generally corresponded to the changes in gene expression patterns. These studies suggest that interactions among IGF-I, FGF-2, and TGF-beta1 substantially modulate their regulatory functions. The results may help guide the application of growth factors to articular cartilage repair.

Current status of gene therapy for rheumatoid arthritis

Gene therapy offers great possibilities for treating rheumatoid arthritis (RA). Traditional surgical and pharmaceutical methods of treating RA have met with limited therapeutic success and have failed to produce a cure, but the past several years have seen extensive progress toward development of a gene therapy for arthritis. Numerous vectors and therapeutic genes have been investigated in animal models of arthritis, and the potential of gene therapy to treat or manage RA has been demonstrated in several clinical studies. Gene therapy offers the possibility of overcoming many of the limitations of current biologic therapies by providing long-term, high-level localized expression of therapeutic genes, potentially in as little as a single dose. In this review, we explore the advances in gene therapy for RA and summarize the recent preclinical and clinical data. In addition, we provide an overview of vectors and targets for RA gene therapy.

The repair of osteochondral defects using baculovirus-mediated gene transfer with de-differentiated chondrocytes in bioreactor culture

Baculovirus has emerged as a promising gene delivery vector. Hereby de-differentiated rabbit chondrocytes were transduced ex vivo with a recombinant baculovirus expressing BMP-2 (Bac-CB), seeded to scaffolds and cultured statically for 1 day (Bac-w0 group) or in a rotating-shaft bioreactor (RSB) for 1 week (Bac-w1 group) or 3 weeks (Bac-w3 group). Mock-transduced constructs were cultured statically for 1 day to serve as the control (Mock-w0 group). We unraveled that Bac-CB transduction and increasing culture time in the RSB yielded more mature cartilaginous constructs in vitro. Eight weeks after implanting into the rabbit osteochondral defects, Mock-w0 constructs failed to repair the lesion while Bac-w0 constructs resulted in augmented, yet incomplete, repair. Bac-w1 constructs yielded neocartilage layers rich in glycosaminoglycans and collagen II, but the integration between the graft and host cartilages was not complete. In contrast, Bac-w3 constructs led to the regeneration of hyaline cartilages as characterized by cartilage-like appearance, improved integration, chondrocytes clustered in lacunae, smooth and homogeneous matrix rich in collagen II and glycosaminoglycans but deficient in collagen I. In conclusion, combining baculovirus-modified de-differentiated chondrocytes and RSB culture creates constructs that repair osteochondral defects, and in vitro culture time dictates the construct maturation and subsequent in vivo repair.

Stimulation of ankle cartilage: other emerging technologies (cellular, electricomagnetic, etc.)

Advances in understanding age-related changes in articular cartilage, joint homeostasis, the natural healing process after cartilage injury, and improved standards for evaluation of a joint surface made the ultimate goal of cartilage repair a possibility. New strategies for enhancement of articular cartilages' limited healing potential and biologic regeneration include advances in tissue engineering and the use of electromagnetic fields. This article reviews developments in basic science and clinical research made with these emerging technologies concerning treatment of articular cartilage defects and treatment of osteoarthritis of the ankle.

Mesenchymal stromal cells genetically engineered to overexpress IGF-I enhance cell-based gene therapy of renal failure-induced anemia

We previously demonstrated that erythropoietin (EPO)-secreting mesenchymal stromal cells (MSC) can be used for the long-term correction of renal failure-induced anemia. The present study provides evidence that coimplantation of insulin-like growth factor I (IGF-I)-overexpressing MSC (MSC-IGF) improves MSC-based gene therapy of anemia by providing paracrine support to EPO-secreting MSC (MSC-EPO) within a subcutaneous implant. IGF-I receptor RNA expression in murine MSC was demonstrated by RT-PCR. Functional protein expression was confirmed by immunoblots and MSC responsiveness to IGF-I stimulation in vitro. IGF-I was also shown to improve MSC survival following staurosporin-induced apoptosis in vitro. A cohort of C57Bl/6 mice was rendered anemic by right kidney electrocoagulation and left nephrectomy. MSC-EPO were subsequently admixed in a bovine collagen matrix and implanted, in combination with MSC-IGF or MSC null, by subcutaneous injection in renal failure mice. In mice receiving MSC-EPO coimplanted with MSC-IGF, hematocrit elevation was greater and enhanced compared with control mice; heart function was also improved. MSC-IGF coimplantation, therefore, represents a promising new strategy for enhancing MSC survival within implanted matrices and for improving cell-based gene therapy of renal anemia.

Concepts in gene therapy for cartilage repair

Once articular cartilage is injured, it has a very limited capacity for self repair. Although current surgical therapeutic procedures for cartilage repair are clinically useful, they cannot restore a normal articular surface. Current research offers a growing number of bioactive reagents, including proteins and nucleic acids, that may be used to augment various aspects of the repair process. As these agents are difficult to administer effectively, gene-transfer approaches are being developed to provide their sustained synthesis at sites of repair. To augment regeneration of articular cartilage, therapeutic genes can be delivered to the synovium or directly to the cartilage lesion. Gene delivery to the cells of the synovial lining is generally considered more suitable for chondroprotective approaches, based on the expression of anti-inflammatory mediators. Gene transfer targeted at cartilage defects can be achieved by either direct vector administration to cells located at or surrounding the defects, or by transplantation of genetically modified chondrogenic cells into the defect. Several studies have shown that exogenous cDNAs encoding growth factors can be delivered locally to sites of cartilage damage, where they are expressed at therapeutically relevant levels. Furthermore, data is beginning to emerge indicating that efficient delivery and expression of these genes is capable of influencing a repair response toward the synthesis of a more hyaline cartilage repair tissue in vivo. This review presents the current status of gene therapy for cartilage healing and highlights some of the remaining challenges.

IGF-1 gene therapy to protect articular cartilage in a rat model of joint damage

INTRODUCTION

An adeno-associated virus (AAV) derived vector in gene transfer model that induces IGF-1 expression could repair articular cartilage.

MATERIALS AND METHODS

Male Wistar rats, 150 and 200 g, and 7 weeks old, were used. Effectiveness of constructed vectors was assayed inoculating them in rat knees of control and damaged animals either mechanically or by collagen-induced arthritis. Inoculation was intra-articular with 50 microL of recombinant AAV-Luciferase (1.25 x 10(8) particles). The rats were killed after 1, 2, 4 and 8 weeks. IGF-I activity was analyzed by injecting 50 microL of recombinant AAV (1.25 x 10(8) particles) in animals with damaged knees. Final analysis was performed after 8 weeks.

RESULTS

The activity of AAV vectors in vitro shows the presence of mRNA coding to IGF-I in cells infected with AAV-IGF and not in control cells without viral vectors and an increase in secreted IGF-I protein in culture medium. In vivo, AAV derived vectors induced protein expression in cartilage 2 months after inoculation. In the animals killed after 1 and 2 weeks, no significant increase in the reaction of luciferase was observed (P > 0.05). In the group of animals with no injury an increase was observed at 4 weeks, which was more marked and significant after 8 weeks (P = 0.029). The same behavior occurred in the animals with induced arthritis and in the mechanical injury group. In the levels of expression after 8 weeks, no significant differences were found between the two groups of injured animals and the group of healthy animals infected with the virus. The joints of the animals that were subjected to injuries in the cartilage and inoculated with AAV-IGF-I presented a similar appearance to those animals inoculated with saline solution.

CONCLUSION

Autoimmune and mechanical lesions did not show improvement in the state of its cartilage after the treatment. The use of AAV vectors capable of inducing the expression of IGF-I in vitro is therefore not sufficient to protect the cartilage from the serious damage.

Major biological obstacles for persistent cell-based regeneration of articular cartilage

Hyaline articular cartilage, the load-bearing tissue of the joint, has very limited repair and regeneration capacities. The lack of efficient treatment modalities for large chondral defects has motivated attempts to engineer cartilage constructs in vitro by combining cells, scaffold materials and environmental factors, including growth factors, signaling molecules, and physical influences. Despite promising experimental approaches, however, none of the current cartilage repair strategies has generated long lasting hyaline cartilage replacement tissue that meets the functional demands placed upon this tissue in vivo. The reasons for this are diverse and can ultimately result in matrix degradation, differentiation or integration insufficiencies, or loss of the transplanted cells and tissues. This article aims to systematically review the different causes that lead to these impairments, including the lack of appropriate differentiation factors, hypertrophy, senescence, apoptosis, necrosis, inflammation, and mechanical stress. The current conceptual basis of the major biological obstacles for persistent cell-based regeneration of articular cartilage is discussed, as well as future trends to overcome these limitations.

Engineering cartilage tissue

Cartilage tissue engineering is emerging as a technique for the regeneration of cartilage tissue damaged due to disease or trauma. Since cartilage lacks regenerative capabilities, it is essential to develop approaches that deliver the appropriate cells, biomaterials, and signaling factors to the defect site. The objective of this review is to discuss the approaches that have been taken in this area, with an emphasis on various cell sources, including chondrocytes, fibroblasts, and stem cells. Additionally, biomaterials and their interaction with cells and the importance of signaling factors on cellular behavior and cartilage formation will be addressed. Ultimately, the goal of investigators working on cartilage regeneration is to develop a system that promotes the production of cartilage tissue that mimics native tissue properties, accelerates restoration of tissue function, and is clinically translatable. Although this is an ambitious goal, significant progress and important advances have been made in recent years.

Plasmid size influences chitosan nanoparticle mediated gene transfer to chondrocytes

The objective of the present study was to prepare chitosan nanoparticles incorporating a relatively large plasmid encoding for osteogenic protein (OP)-1 and to determine the ability of these nanoparticles to transfect adult canine articular chondrocytes in vitro. The positive charge of chitosan acted to condense the relatively large negatively-charged OP-1 plasmid such that it could be incorporated into nanoparticles. Incorporation of the plasmid into the chitosan nanoparticles did not affect the structural integrity of the plasmid as demonstrated by gel electrophoresis. The morphology and size of the nanoparticles were found to vary with the chitosan:plasmid weight ratio. Nanoparticles formulated with a chitosan:plasmid ratio of 10:1 were of uniformly small size (less than 250 nm) and spherical shape. These nanoparticles had a positive charge of about 20 mV. FITC-labeled chitosan nanoparticles were found in virtually all of the cells after 24 h of incubation with the nanoparticles, and confocal microscopy revealed FITC-related fluorescence in the nucleus of the chondrocytes. Although transfection of the chondrocytes was demonstrated by the fluorescence of cells treated with chitosan nanoparticles containing the plasmid for the enhanced green fluorescence protein, cells transfected with nanoparticles incorporating the larger OP-1 plasmid did not show OP-1 expression measured by ELISA for up to 2 weeks in culture. These results indicate that although a large plasmid can be successfully incorporated within chitosan nanoparticles, the size of the plasmid incorporated within the nanoparticles may still significantly affect gene transfer to cells.

Delivery of plasmid IGF-1 to chondrocytes via cationized gelatin nanoparticles

The objective of the present study was to investigate the use of gelatin and cationized-gelatin nanoparticles for the nonviral delivery of the plasmid DNA encoding for insulin-like growth factor (IGF)-1 to adult canine articular chondrocytes in vitro; plasmid for enhanced green fluorescence protein (EGFP) was used as a marker gene. The spherical cationized gelatin nanoparticles were on average 172 nm in diameter, compared with the often ellipsoid-shaped unmodified (noncationized) gelatin particles that generally appeared to be 10 mum to greater than 20 mum in length. The zeta potential of the positively charged cationized gelatin nanoparticles containing the plasmid was around 20 mV compared with about 2 mV for the unmodified gelatin particles. There was no noticeable fluorescence from the cells treated with the nanoparticles prepared with the original (noncationized) gelatin particles containing the pEGFP. In contrast, numerous cells in the group transfected with the cationized gelatin-pEGFP nanoparticles were found to fluoresce demonstrating the transfection of the cells. There was five-fold elevation in the amount of IGF-1 produced by the cells treated with the cationized gelatin nanoparticles containing the IGF-1 plasmid compared with the unmodified (noncationized) gelatin particles. There was a clear effect of varying the weight ratio of plasmid IGF-1 in the cationized gelatin nanoparticles on the IGF-1 in the medium of cells exposed to the nanoparticles for 5 h. A peak in the amount of released IGF-1 was detected at a gelatin:IGF-1 weight ratio of 250:1.

Comparison of glucosamine sulfate and a polyherbal supplement for the relief of osteoarthritis of the knee: a randomized controlled trial [ISRCTN25438351]

Background

The efficacy and safety of a dietary supplement derived from South American botanicals was compared to glucosamine sulfate in osteoarthritis subjects in a Mumbai-based multi-center, randomized, double-blind study.

Methods

Subjects (n = 95) were screened and randomized to receive glucosamine sulfate (n = 47, 1500 mg/day) or reparagen (n = 48, 1800 mg/day), a polyherbal consisting of 300 mg of vincaria (Uncaria guianensis) and 1500 mg of RNI 249 (Lepidium meyenii) administered orally, twice daily. Primary efficacy variable was response rate based on a 20% improvement in WOMAC pain scores. Additional outcomes were WOMAC scores for pain, stiffness and function, visual analog score (VAS) for pain, with assessments at 1, 2, 4, 6 and 8 weeks. Tolerability, investigator and subject global assessments and rescue medication consumption (paracetamol) were measured together with safety assessments including vital signs and laboratory based assays.

Results

Subject randomization was effective: age, gender and disease status distribution was similar in both groups. The response rates (20% reduction in WOMAC pain) were substantial for both glucosamine (89%) and reparagen (94%) and supported by investigator and subject assessments. Using related criteria response rates to reparagen were favorable when compared to glucosamine. Compared to baseline both treatments showed significant benefits in WOMAC and VAS outcomes within one week (P < 0.05), with a similar, progressive improvement over the course of the 8 week treatment protocol (45–62% reduction in WOMAC or VAS scores). Tolerability was excellent, no serious adverse events were noted and safety parameters were unchanged. Rescue medication use was significantly lower in the reparagen group (p < 0.01) at each assessment period. Serum IGF-1 levels were unaltered by treatments.

Conclusion

Both reparagen and glucosamine sulfate produced substantial improvements in pain, stiffness and function in subjects with osteoarthritis. Response rates were high and the safety profile was excellent, with significantly less rescue medication use with reparagen. Reparagen represents a new natural productive alternative in the management of joint health.

Trial registration

Current Controlled Trials ISRCTN25438351.

Genetic engineering for skeletal regenerative medicine

The clinical challenges of skeletal regenerative medicine have motivated significant advances in cellular and tissue engineering in recent years. In particular, advances in molecular biology have provided the tools necessary for the design of gene-based strategies for skeletal tissue repair. Consequently, genetic engineering has emerged as a promising method to address the need for sustained and robust cellular differentiation and extracellular matrix production. As a result, gene therapy has been established as a conventional approach to enhance cellular activities for skeletal tissue repair. Recent literature clearly demonstrates that genetic engineering is a principal factor in constructing effective methods for tissue engineering approaches to bone, cartilage, and connective tissue regeneration. This review highlights this literature, including advances in the development of efficacious gene carriers, novel cell sources, successful delivery strategies, and optimal target genes. The current status of the field and the challenges impeding the clinical realization of these approaches are also discussed.

Analysis of novel nonviral gene transfer systems for gene delivery to cells of the musculoskeletal system

The aim of the present study was to evaluate the efficacy of novel nonviral gene delivery systems in cells of musculoskeletal origin. Primary cultures of lapine skeletal muscle cells, lapine articular chondrocytes, human cells from fibrous dysplasia and cell lines established from human osteosarcoma (SAOS-2), chondrosarcoma (CS-1), murine skeletal myoblasts (L8) and fibroblasts (NIH 3T3) were transfected with the P. pyralis luc or the E. coli lacZ genes using Nanofectin 1 and 2, Superfect, JetPEI, GeneJammer, Effectene, TransPass D2, FuGENE 6, Lipofectamine 2000, Dreamfect, Metafectene, Escort III, and calcium phosphate. Maximal transfection efficiency in lapine skeletal muscle cells was of 60.8 +/- 21.2% using Dreamfect, 38.9 +/- 5.0% in articular chondrocytes using Gene Jammer, 5.2 +/- 8.0% in human cells from fibrous dysplasia using Lipofectamine 2000, 12.7 +/- 16.2% in SAOS-2 cells using FuGENE 6, 29.9 +/- 3.5% in CS-1 cells using Lipofectamine 2000, 70.7 +/- 8.6% in L8 cells using FuGENE 6, and 48.9 +/- 13.0% in NIH 3T3 cells using Metafectene. When the cells were transfected with a human IGF-I gene, significant amounts of the IGF-I protein were secreted. These results indicate that relatively high levels of transfection can be achieved using novel nonviral gene transfer methods.

Chondroprotective effects of a proanthocyanidin rich Amazonian genonutrient reflects direct inhibition of matrix metalloproteinases and upregulation of IGF-1 production by human chondrocytes

Background

The Amazonian medicinal plant Sangre de grado (Croton palanostigma) has traditional applications for the treatment of wound healing and inflammation. We sought to characterize two extracts (progrado and zangrado) in terms of safety and oligomeric proanthocyanidin chain length. Additionally progrado was evaluated for antioxidant activity and possible chondroprotective actions.

Methods

Acute oral safety and toxicity was tested in rats according under OECD protocol number 420. The profile of proanthocyanidin oligomers was determined by HPLC and progrado's antioxidant activity quantified by the ORAC, NORAC and HORAC assays. Human cartilage explants, obtained from surgical specimens, were used to assess chondroproteciton with activity related to direct inhibitory effects on human matrix metalloproteinase (MMP, gelatinolytic) activity using synovial fluid and chondrocytes activated with IL-1β (10 ng/ml). Additionally, progrado (2–10 μg/ml) was tested for its ability to maintain optimal IGF-1 transcription and translation in cartilage explants and cultured chondrocytes.

Results

Both progrado and zangrado at doses up to 2000 mg/kg (po) displayed no evidence of toxicity. Oligomeric proanthocyanidin content was high for both progrado (158 mg/kg) and zangrado (124 mg/kg), with zangrado almost entirely composed of short oligomers (<6 mer), whereas the majority of oligomers in progrado exceeded 10 mers. Progrado was a remarkably potent antioxidant in the standardized tests ORAC, NORAC and HORAC. Progrado was exceptionally effective in reducing both basal and IL-1β induced glycosaminoglycan release from human cartilage explants at concentrations that also directly blocked the gelatinolytic activity of MMP-2 and MMP-9. Progrado prevented IL-1β induced suppression of IGF-1 production from human cartilage explants as well as stimulating basal IGF-1 production (P < 0.05). Comparable changes in IGF-1 gene expression were noted in cultured human chondrocytes.

Conclusion

Progrado has a promising safety profile, significant chondroprotective and antioxidant actions, directly inhibits MMP activity and promotes the production of the cartilage repair factor, IGF-1. This suggests that progrado may offer therapeutic benefits in joint health, wound healing and inflammation.

Gene therapy for articular cartilage repair

Articular cartilage serves as the gliding surface of joints. It is susceptible to damage from trauma and from degenerative diseases. Restoration of damaged articular cartilage may be achievable through the use of cell-regulatory molecules that augment the reparative activities of the cells, inhibit the cells' degradative activities, or both. A variety of such molecules have been identified. These include insulin-like growth factor I, fibroblast growth factor 2, bone morphogenetic proteins 2, 4, and 7, and interleukin-1 receptor antagonist. It is now possible to transfer the genes encoding such molecules into articular cartilage and synovial lining cells. Although preliminary, data from in-vitro and in-vivo studies suggest that gene therapy can deliver such potentially therapeutic agents to protect existing cartilage and to build new cartilage.

Gene transfer strategies in tissue engineering

Aiming for regeneration of severed or lost parts of the body, the combined application of gene therapy and tissue engineering has received much attention by regenerative medicine. Techniques of molecular biology can enhance the regenerative potential of a biomaterial by co-delivery of therapeutic genes, and several different strategies have been used to achieve that goal. Possibilities for application are many-fold and have been investigated to regenerate tissues such as skin, cartilage, bone, nerve, liver, pancreas and blood vessels. This review discusses advantages and problems encountered with the different gene delivery strategies as far as they relate to tissue engineering, analyses the positive aspects of polymeric gene delivery from matrices and discusses advances and future challenges of gene transfer strategies in selected tissues.

Alginate Encapsulation Impacts the Insulin-like Growth Factor-I System of Monolayer-Expanded Equine Articular Chondrocytes and Cell Response to Interleukin-1β

Alginate hydrogel culture has been shown to reestablish chondrocytic phenotype following monolayer expansion; however, previous studies have not adequately addressed how culture conditions affect the signaling systems responsible for chondrocyte metabolic activity. Here we investigate whether chondrocyte culture history influences the insulin-like growth factor-I (IGF-I) signaling system and its regulation by interleukin-1 (IL-1). Articular chondrocytes (ACs) from equine stifle joints were expanded by serial passage and were either encapsulated in alginate beads or maintained in monolayer culture for 10 days. Alginate-derived cells (ADCs) and monolayer-derived cells (MDCs) were then plated at high density, stimulated with IL-1beta (1 and 10 ng/mL) or IGF-I (50 ng/mL) for 48 h, and assayed for levels of type I IGF receptor (IGF-IR), IGF binding proteins (IGFBPs), and endogenously secreted IGF-I. Intermediate alginate culture yielded relatively low IGF-IR levels that increased in response to IL-1beta, whereas higher receptor levels on MDCs were reduced by cytokine. MDCs also secreted substantially more IGFBP-2, the predominant binding protein in conditioned media (CM), though IL-1beta suppressed levels for both cell populations. Concentrations of autocrine/paracrine IGF-I paralleled IGFBP-2 secretion. Disparate basal levels of IGF-IR and IGFBP-2, but not IGF-I, were attributed to relative transcript expression. Systemic differences coincided with varied effects of IL-1beta and IGF-I on cell growth and type I collagen expression. We conclude that culture strategy impacts the IGF-I signaling system of ACs, potentially altering their capacity to mediate cartilage repair. Consideration of hormonal regulators may be an essential element to improve chondrocyte culture protocols used in tissue engineering applications.

Genetic modification of chondrocytes with insulin-like growth factor-1 enhances cartilage healing in an equine model

Gene therapy with insulin-like growth factor-1 (IGF-1) increases matrix production and enhances chondrocyte proliferation and survival in vitro. The purpose of this study was to determine whether arthroscopically-grafted chondrocytes genetically modified by an adenovirus vector encoding equine IGF-1 (AdIGF-1) would have a beneficial effect on cartilage healing in an equine femoropatellar joint model.

A total of 16 horses underwent arthroscopic repair of a single 15 mm cartilage defect in each femoropatellar joint. One joint received 2 × 107 AdIGF-1 modified chondrocytes and the contralateral joint received 2 × 107 naive (unmodified) chondrocytes. Repairs were analysed at four weeks, nine weeks and eight months after surgery. Morphological and histological appearance, IGF-1 and collagen type II gene expression (polymerase chain reaction, in situ hybridisation and immunohistochemistry), collagen type II content (cyanogen bromide and sodium dodecyl sulphate-polyacrylamide gel electrophoresis), proteoglycan content (dimethylmethylene blue assay), and gene expression for collagen type I, matrix metalloproteinase (MMP)-1, MMP-3, MMP-13, aggrecanase-1, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and TIMP-3 were evaluated.

Genetic modification of chondrocytes significantly increased IGF-1 mRNA and ligand production in repair tissue for up to nine weeks following transplantation. The gross and histological appearance of IGF-1 modified repair tissue was improved over control defects. Gross filling of defects was significantly improved at four weeks, and a more hyaline-like tissue covered the lesions at eight months. Histological outcome at four and nine weeks post-transplantation revealed greater tissue filling of defects transplanted with genetically modified chondrocytes, whereas repair tissue in control defects was thin and irregular and more fibrous. Collagen type II expression in IGF-1 gene-transduced defects was increased 100-fold at four weeks and correlated with increased collagen type II immunoreaction up to eight months.

Genetic modification of chondrocytes with AdIGF-1 prior to transplantation improved early (four to nine weeks), and to a lesser degree long-term, cartilage healing in the equine model.

The equine model of cartilage healing closely resembles human clinical cartilage repair. The results of this study suggest that cartilage healing can be enhanced through genetic modification of chondrocytes prior to transplantation.

Tissue-Engineering zur Knorpelreparatur verbessert durch Gentransfer

Cartilage tissue engineering is the creation of functional substitutes of native articular cartilage in bioreactors by attaching chondrogenic cells to polymer scaffolds. One limitation of tissue engineering is the delivery of regulatory signals to cells according to specific temporal and spatial patterns. Using gene transfer techniques, polypeptide growth factor genes such as the human insulin-like growth factor I (IGF-I) gene can be transferred into chondrocytes. When these modified cells are used for cartilage tissue engineering, the resulting cartilaginous constructs have improved structural and functional characteristics compared to constructs based on nonmodified cells. The combination of cartilage tissue engineering with overexpression of potential therapeutic genes using gene transfer technologies provides a basis for the development of novel molecular therapies for the repair of cartilage defects.

Collagen scaffolds for nonviral IGF-1 gene delivery in articular cartilage tissue engineering

This study investigated the use of a type II collagen-glycosaminoglycan (CG) scaffold as a nonviral gene delivery vehicle for facilitating gene transfer to seeded adult articular chondrocytes to produce an elevated, prolonged and local expression of insulin-like growth factor (IGF)-1 for enhancing cartilage regeneration. Gene-supplemented CG (GSCG) scaffolds were synthesized by two methods: (1) soaking a pre-cross-linked CG scaffold in a plasmid solution followed by a freeze-drying process, and (2) chemically cross-linking the plasmid DNA to the scaffold. Two different plasmid solutions were also compared: (1) naked plasmid IGF-1 alone, and (2) plasmid IGF-1 with a lipid transfection reagent. Plasmid release studies revealed that cross-linking the plasmid to the CG scaffold prevented passive bolus release of plasmid and resulted in vector release controlled by scaffold degradation. In chondrocyte-seeded GSCG scaffolds, prolonged and elevated IGF-1 expression was enhanced by using the cross-linking method of plasmid incorporation along with the addition of the transfection reagent. The sustained level of IGF-1 overexpression resulted in significantly higher amounts of tissue formation, chondrocyte-like cells, GAG accumulation, and type II collagen production, compared to control scaffolds. These findings demonstrate that CG scaffolds can serve as nonviral gene delivery vehicles of microgram amounts of IGF-1 plasmid (<10 microg per scaffold) to provide a locally sustained therapeutic level of overexpressed IGF-1, resulting in enhanced cartilage formation.

Effect of expansion medium on ex vivo gene transfer and chondrogenesis in type II collagen-glycosaminoglycan scaffolds in vitro

OBJECTIVE

Growth factors can profoundly affect the behaviour of chondrocytes during expansion and subsequent growth in three-dimensional (3-D) scaffolds. Prolonging such effects has stimulated investigation of the transfer of growth factor genes to chondrocytes. This study evaluated the effects of the monolayer expansion medium on the proliferation and cartilage matrix molecule synthesis of chondrocytes in 3-D pellet culture and in type II collagen-glycosaminoglycan (CG) scaffolds, and on ex vivo insulin-like growth factor-1 (IGF-1) gene transfer to articular chondrocytes in monolayer. The possibility of transfecting cells in 3-D culture using CG scaffolds was also investigated and the resulting effect of IGF-1 overexpression on glycosaminoglycan (GAG) biosynthesis in 3-D culture was assessed.

METHODS

Two expansion media were compared-one that has been widely used for growing chondrocytes (Medium 1) and one that has been found to increase chondrocyte proliferation rates and preserve the redifferentiation potential of monolayer-expanded chondrocytes when subsequently placed in pellet cultures (Medium 2). Chondrocytes were expanded in monolayer culture and then 1) redifferentiated in 3-D culture, or 2) infected with the IGF-1 gene in monolayer or in type II CG scaffolds.

RESULTS

The cell count for first passage chondrocytes was more than 3-fold higher when using Medium 2. In 3-D culture, cells expanded with Medium 2 and seeded in CG scaffolds produced more total GAG/DNA and displayed more intense immunohistochemical staining for collagen type II. Gene transfer and IGF-1 release kinetics from infected cells in monolayer were significantly affected by the composition of the expansion medium, the gene transfer method and time. IGF-1 gene transfer in CG scaffolds resulted in a 35-fold elevation in accumulated IGF-1 released from transfected Medium 2-expanded chondrocytes over controls, and resulted in a 40% increase in accumulated GAG/DNA.

CONCLUSION

The composition of the expansion medium significantly affects monolayer proliferation of adult canine chondrocytes, GAG synthesis when the cells are subsequently grown in CG scaffolds, and ex vivo IGF-1 gene transfer.

Gene therapy for cartilage defects

Focal defects of articular cartilage are an unsolved problem in clinical orthopaedics. These lesions do not heal spontaneously and no treatment leads to complete and durable cartilage regeneration. Although the concept of gene therapy for cartilage damage appears elegant and straightforward, current research indicates that an adaptation of gene transfer techniques to the problem of a circumscribed cartilage defect is required in order to successfully implement this approach. In particular, the localised delivery into the defect of therapeutic gene constructs is desirable. Current strategies aim at inducing chondrogenic pathways in the repair tissue that fills such defects. These include the stimulation of chondrocyte proliferation, maturation, and matrix synthesis via direct or cell transplantation-mediated approaches. Among the most studied candidates, polypeptide growth factors have shown promise to enhance the structural quality of the repair tissue. A better understanding of the basic scientific aspects of cartilage defect repair, together with the identification of additional molecular targets and the development of improved gene-delivery techniques, may allow a clinical translation of gene therapy for cartilage defects. The first experimental steps provide reason for cautious optimism.

Gene delivery strategies for cartilage tissue engineering

Tissue engineering is a multifaceted technology developed with a purpose of regenerating complex tissues and organs. Cartilage regeneration continues to challenge engineers and a new wave of efforts focus on developing strategies that provide sustained stimulation to cells by growth factors and other biological molecules to promote their differentiation into chondrocytes. Though significant research is dedicated to developing controlled release systems that deliver growth factors directly, a simpler approach to resolving this dilemma involves converting cells into protein producing factories. This is done through gene delivery. Gene Therapy studies published for articular diseases such as rheumatoid and osteoarthritis provide valuable information regarding different types of cells, gene delivery vectors and genes that can potentially be used to regenerate cartilage. Tissue engineering approaches provide the opportunity to combine two or more strategies used for Gene Therapy thus far and create a cohesive system that addresses both cartilage degeneration and synthesis simultaneously. Adopting gene transfer techniques for tissue engineering is a relatively novel approach, as non-viral gene delivery vectors are continually optimized for therapeutic purposes, and reservations about viral vectors have increasingly dampened their appeal. However, every element involved in gene transfection (i.e., the cell, vector and gene) is a variable which decides the physiological and biomechanical properties of the cartilage produced, and significant work still needs to be done in understanding the contribution of each of these factors to cartilage regeneration.

Combination of baculovirus-mediated gene transfer and rotating-shaft bioreactor for cartilage tissue engineering

We have previously demonstrated efficient baculovirus transduction of rat chondrocytes in 6-well plates. To further explore the potential of baculovirus in cartilage tissue engineering, the baculovirus-transduced chondrocytes were seeded into porous scaffolds and cultivated in a rotating-shaft bioreactor (RSB) which was developed for two-phase cultivation of tissue engineered cartilage. The baculovirus transduction resulted in efficiencies up to 90%, and affected neither cell adhesion to the scaffolds nor cell survival in the RSB. After 4-week RSB cultivation, the transduced cells remained highly differentiated and grew into constructs that resembled the untransduced constructs with regard to gross appearance, construct size, cell morphology, cell spatial distribution, glycosaminoglycan and collagen production and deposition. Importantly, baculovirus transduction did not alter the expression of chondrocytic genes. These data confirmed that baculovirus transduction neither harms chondrocytes nor retards the formation of cartilage-like tissues in the RSB, thus implicating the potentials of combining baculovirus-mediated gene transfer with RSB cultivation in in vitro cartilage tissue engineering.

Local stimulation of articular cartilage repair by transplantation of encapsulated chondrocytes overexpressing human fibroblast growth factor 2 (FGF-2) in vivo

BACKGROUND

Defects of articular cartilage are an unsolved problem in orthopaedics. In the present study, we tested the hypothesis that gene transfer of human fibroblast growth factor 2 (FGF-2) via transplantation of encapsulated genetically modified articular chondrocytes stimulates chondrogenesis in cartilage defects in vivo.

METHODS

Lapine articular chondrocytes overexpressing a lacZ or a human FGF-2 gene sequence were encapsulated in alginate and further characterized. The resulting lacZ or FGF-2 spheres were applied to cartilage defects in the knee joints of rabbits. In vivo, cartilage repair was assessed qualitatively and quantitatively at 3 and 14 weeks after implantation.

RESULTS

In vitro, bioactive FGF-2 was secreted, leading to a significant increase in the cell numbers in FGF-2 spheres. In vivo, FGF-2 continued to be expressed for at least 3 weeks without leading to differences in FGF-2 concentrations in the synovial fluid between treatment groups. Histological analysis revealed no adverse pathologic effects on the synovial membrane at any time point. FGF-2 gene transfer enhanced type II collagen expression and individual parameters of chondrogenesis, such as the cell morphology and architecture of the new tissue. Overall articular cartilage repair was significantly improved at both time points in vivo.

CONCLUSIONS

The data suggest that localized overexpression of FGF-2 enhances the repair of cartilage defects via stimulation of chondrogenesis, without adverse effects on the synovial membrane. These results may lead to the development of safe gene-based therapies for human articular cartilage defects.

The chrondoprotective actions of a natural product are associated with the activation of IGF-1 production by human chondrocytes despite the presence of IL-1beta

BACKGROUND

Cartilage loss is a hallmark of arthritis and follows activation of catabolic processes concomitant with a disruption of anabolic pathways like insulin-like growth factor 1 (IGF-1). We hypothesized that two natural products of South American origin, would limit cartilage degradation by respectively suppressing catabolism and activating local IGF-1 anabolic pathways. One extract, derived from cat's claw (Uncaria guianensis, vincaria), is a well-described inhibitor of NF-kappaB. The other extract, derived from the vegetable Lepidium meyenii (RNI 249), possessed an uncertain mechanism of action but with defined ethnomedical applications for fertility and vitality.

METHODS

Human cartilage samples were procured from surgical specimens with consent, and were evaluated either as explants or as primary chondrocytes prepared after enzymatic digestion of cartilage matrix. Assessments included IGF-1 gene expression, IGF-1 production (ELISA), cartilage matrix degradation and nitric oxide (NO) production, under basal conditions and in the presence of IL-1beta.

RESULTS

RNI 249 enhanced basal IGF-1 mRNA levels in human chondrocytes by 2.7 fold, an effect that was further enhanced to 3.8 fold by co-administration with vincaria. Enhanced basal IGF-1 production by RNI 249 alone and together with vincaria, was confirmed in both explants and in primary chondrocytes (P < 0.05). As expected, IL-1beta exposure completely silenced IGF-1 production by chondrocytes. However, in the presence of IL-1beta both RNI 249 and vincaria protected IGF-1 production in an additive manner (P < 0.01) with the combination restoring chondrocyte IGF-1 production to normal levels. Cartilage NO production was dramatically enhanced by IL-1beta. Both vincaria and RNI 249 partially attenuated NO production in an additive manner (p < 0.05). IL-1beta - induced degradation of cartilage matrix was quantified as glycosaminoglycan release. Individually RNI 249 or vincaria, prevented this catabolic action of IL-1beta.

CONCLUSION

The identification of agents that activate the autocrine production of IGF-1 in cartilage, even in the face of suppressive pro-inflammatory, catabolic cytokines like IL-1beta, represents a novel therapeutic approach to cartilage biology. Chondroprotection associated with prevention of the catabolic events and the potential for sustained anabolic activity with this natural product suggests that it holds significant promise in the treatment of debilitating joint diseases.

Effect of transforming growth factor-beta 1 (TGF-ß1) released from a scaffold on chondrogenesis in an osteochondral defect model in the rabbit

Articular cartilage repair might be stimulated by the controlled delivery of therapeutic factors. We tested the hypotheses whether TGF-ß1 can be released from a polymeric scaffold over a prolonged period of time in vitro and whether its transplantation modulates cartilage repair in vivo. Unloaded control or TGF-ß1 poly(ether-ester) copolymeric scaffolds were applied to osteochondral defects in the knee joints of rabbits. In vitro, a cumulative dose of 9 ng TGF-ß1 was released over 4 weeks. In vivo, there were no adverse effects on the synovial membrane. Defects treated with TGF-ß1 scaffolds showed no significant difference in individual parameters of chondrogenesis and in the average cartilage repair score after 3 weeks. There was a trend towards a smaller area (42.5 %) of the repair tissue that stained positive for safranin O in defects receiving TGF-ß1 scaffolds. The data indicate that TGF-ß1 is released from emulsion-coated scaffolds over a prolonged period of time in vitro and that application of these scaffolds does not significantly modulate cartilage repair after 3 weeks in vivo. Future studies need to address the importance of TGF-ß1 dose and release rate to modulate chondrogenesis.