Bone morphogenetic protein 7 (bmp-7) stimulates Proteoglycan synthesis in human osteoarthritic chondrocytes in vitro

Cartilage fragments combined with BMSCs-Derived exosomes can promote tendon-bone healing after ACL reconstruction

Anterior cruciate ligament reconstruction (ACLR) often fails due to the inability of tendon-bone integration to regenerate normal tissues and formation of fibrous scar tissues in the tendon-bone interface. Cartilage fragments and exosomes derived from bone mesenchymal stromal cells (BMSCs-Exos) can enhance enthesis healing. Nevertheless, the effects on the tendon-bone healing of ACLR remain unknown. This study found that BMSCs-Exos can promote the proliferation of chondrocytes in cartilage fragments, and activated the expression of chondro-related genes SOX9 and Aggrecan. The optimal effect concentration was 1012 events/uL. Besides, BMSCs-Exos could significantly upregulated the expression of BMP7 and Smad5 in cartilage fragments, and further enhanced the expression of chondrogenic genes. Moreover, this study established a rat model of ACLR and implanted the BMSCs-Exos/cartilage fragment complex into the femoral bone tunnel. Results demonstrated that the mean diameters of the femoral bone tunnels were significantly smaller in the BE-CF group than those in the CF group (p = 0.038) and control group (p = 0.007) at 8 weeks after surgery. Besides, more new bone formation was observed in the femoral tunnels in the BE-CF group, as demonstrated by a larger BV/TV ratio based on the reconstructed CT scans. Histological results also revealed the regeneration of tendon-bone structures, especially fibrocartilage. Thus, these findings provide a promising result that BMSCs-Exos/cartilage fragment complex can prevent the enlargement of bone tunnel and promote tendon-bone healing after ACLR, which may have resulted from the regulation of the BMP7/Smad5 signaling axis.

Potential of bone morphogenetic protein-7 in treatment of lupus nephritis: addressing the hurdles to implementation

Up to 50% of systemic lupus erythematosus (SLE) patients world-wide develop lupus nephritis (LN). In low to middle income countries and in particular in sub-Saharan Africa, where SLE is prevalent with a more aggressive course, LN and end stage renal disease is a major cause of mortality. While developed countries have the funding to invest in SLE and LN research, patients of African descent are often underrepresented in clinical trials. Thus, the complex influence of ethnicity and genetic background on outcome of LN and SLE as a whole, is not fully understood. Several pathophysiological mechanisms including major role players driving LN have been identified. A large body of literature suggest that prevention of fibrosis-which contributes to chronicity of LN-may significantly improve long-term prognosis. Bone morphogenetic protein-7 (BMP-7) was first identified as a therapeutic option in this context decades ago and evidence of its benefit in various conditions, including LN, is ever-increasing. Despite these facts, BMP-7 is not being implemented as therapy in the context of renal disease. With this review, we briefly summarise current understanding of LN pathology and discuss the evidence in support of therapeutic potential of BMP-7 in this context. Lastly, we address the obstacles that need to be overcome, before BMP-7 may become available as LN treatment.

Using Microphysiological System for the Development of Treatments for Joint Inflammation and Associated Cartilage Loss-A Pilot Study

Osteoarthritis (OA) is a painful and disabling joint disease affecting millions worldwide. The lack of clinically relevant models limits our ability to predict therapeutic outcomes prior to clinical trials, where most drugs fail. Therefore, there is a need for a model that accurately recapitulates the whole-joint disease nature of OA in humans. Emerging microphysiological systems provide a new opportunity. We recently established a miniature knee joint system, known as the miniJoint, in which human bone-marrow-derived mesenchymal stem cells (hBMSCs) were used to create an osteochondral complex, synovial-like fibrous tissue, and adipose tissue analogs. In this study, we explored the potential of the miniJoint in developing novel treatments for OA by testing the hypothesis that co-treatment with anti-inflammation and chondroinducing agents can suppress joint inflammation and associated cartilage degradation. Specifically, we created a "synovitis"-relevant OA model in the miniJoint by treating synovial-like tissues with interleukin-1β (IL-1β), and then a combined treatment of oligodeoxynucleotides (ODNs) suppressing the nuclear factor kappa beta (NF-κB) genetic pathway and bone morphogenic protein-7 (BMP-7) was introduced. The combined treatment with BMP-7 and ODNs reduced inflammation in the synovial-like fibrous tissue and showed an increase in glycosaminoglycan formation in the cartilage portion of the osteochondral complex. For the first time, this study demonstrated the potential of the miniJoint in developing disease-modifying OA drugs. The therapeutic efficacy of co-treatment with NF-κB ODNs and BMP-7 can be further validated in future clinical studies.

Application of Alginate Hydrogels for Next-Generation Articular Cartilage Regeneration

The articular cartilage has insufficient intrinsic healing abilities, and articular cartilage injuries often progress to osteoarthritis. Alginate-based scaffolds are attractive biomaterials for cartilage repair and regeneration, allowing for the delivery of cells and therapeutic drugs and gene sequences. In light of the heterogeneity of findings reporting the benefits of using alginate for cartilage regeneration, a better understanding of alginate-based systems is needed in order to improve the approaches aiming to enhance cartilage regeneration with this compound. This review provides an in-depth evaluation of the literature, focusing on the manipulation of alginate as a tool to support the processes involved in cartilage healing in order to demonstrate how such a material, used as a direct compound or combined with cell and gene therapy and with scaffold-guided gene transfer procedures, may assist cartilage regeneration in an optimal manner for future applications in patients.

Discovery of bone morphogenetic protein 7-derived peptide sequences that attenuate the human osteoarthritic chondrocyte phenotype

Treatment of osteoarthritis (OA) is mainly symptomatic by alleviating pain to postpone total joint replacement. Bone morphogenetic protein 7 (BMP7) is a candidate morphogen for experimental OA treatment that favorably alters the chondrocyte and cartilage phenotype. Intra-articular delivery and sustained release of a recombinant growth factor for treating OA are challenging, whereas the use of peptide technology potentially circumvents many of these challenges. In this study, we screened a high-resolution BMP7 peptide library and discovered several overlapping peptide sequences from two regions in BMP7 with nanomolar bioactivity that attenuated the pathological OA chondrocyte phenotype. A single exposure of OA chondrocytes to peptides p[63-82] and p[113-132] ameliorated the OA chondrocyte phenotype for up to 8 days, and peptides were bioactive on chondrocytes in OA synovial fluid. Peptides p[63-82] and p[113-132] required NKX3-2 for their bioactivity on chondrocytes and provoke changes in SMAD signaling activity. The bioactivity of p[63-82] depended on specific evolutionary conserved sequence elements common to BMP family members. Intra-articular injection of a rat medial meniscal tear (MMT) model with peptide p[63-82] attenuated cartilage degeneration. Together, this study identified two regions in BMP7 from which bioactive peptides are able to attenuate the OA chondrocyte phenotype. These BMP7-derived peptides provide potential novel disease-modifying treatment options for OA.

Knee Osteoarthritis: A Review of Pathogenesis and State-Of-The-Art Non-Operative Therapeutic Considerations

Being the most common musculoskeletal progressive condition, osteoarthritis is an interesting target for research. It is estimated that the prevalence of knee osteoarthritis (OA) among adults 60 years of age or older is approximately 10% in men and 13% in women, making knee OA one of the leading causes of disability in elderly population. Today, we know that osteoarthritis is not a disease characterized by loss of cartilage due to mechanical loading only, but a condition that affects all of the tissues in the joint, causing detectable changes in tissue architecture, its metabolism and function. All of these changes are mediated by a complex and not yet fully researched interplay of proinflammatory and anti-inflammatory cytokines, chemokines, growth factors and adipokines, all of which can be measured in the serum, synovium and histological samples, potentially serving as biomarkers of disease stage and progression. Another key aspect of disease progression is the epigenome that regulates all the genetic expression through DNA methylation, histone modifications, and mRNA interference. A lot of work has been put into developing non-surgical treatment options to slow down the natural course of osteoarthritis to postpone, or maybe even replace extensive surgeries such as total knee arthroplasty. At the moment, biological treatments such as platelet-rich plasma, bone marrow mesenchymal stem cells and autologous microfragmented adipose tissue containing stromal vascular fraction are ordinarily used. Furthermore, the latter two mentioned cell-based treatment options seem to be the only methods so far that increase the quality of cartilage in osteoarthritis patients. Yet, in the future, gene therapy could potentially become an option for orthopedic patients. In the following review, we summarized all of the latest and most important research in basic sciences, pathogenesis, and non-operative treatment.

Knee Osteoarthritis: A Review of Pathogenesis and State-Of-The-Art Non-Operative Therapeutic Considerations

Being the most common musculoskeletal progressive condition, osteoarthritis is an interesting target for research. It is estimated that the prevalence of knee osteoarthritis (OA) among adults 60 years of age or older is approximately 10% in men and 13% in women, making knee OA one of the leading causes of disability in elderly population. Today, we know that osteoarthritis is not a disease characterized by loss of cartilage due to mechanical loading only, but a condition that affects all of the tissues in the joint, causing detectable changes in tissue architecture, its metabolism and function. All of these changes are mediated by a complex and not yet fully researched interplay of proinflammatory and anti-inflammatory cytokines, chemokines, growth factors and adipokines, all of which can be measured in the serum, synovium and histological samples, potentially serving as biomarkers of disease stage and progression. Another key aspect of disease progression is the epigenome that regulates all the genetic expression through DNA methylation, histone modifications, and mRNA interference. A lot of work has been put into developing non-surgical treatment options to slow down the natural course of osteoarthritis to postpone, or maybe even replace extensive surgeries such as total knee arthroplasty. At the moment, biological treatments such as platelet-rich plasma, bone marrow mesenchymal stem cells and autologous microfragmented adipose tissue containing stromal vascular fraction are ordinarily used. Furthermore, the latter two mentioned cell-based treatment options seem to be the only methods so far that increase the quality of cartilage in osteoarthritis patients. Yet, in the future, gene therapy could potentially become an option for orthopedic patients. In the following review, we summarized all of the latest and most important research in basic sciences, pathogenesis, and non-operative treatment.

BMP7-overexpressing bone marrow-derived mesenchymal stem cells (BMSCs) are more effective than wild-type BMSCs in healing fractures

Bone fractures are a worldwide public health concern. Previous studies have demonstrated that bone morphogenetic protein-7 (BMP7) gene transfer or mesenchymal stem cells (MSCs) transplantation may be a promising novel therapeutic approach. Therefore, the aim of the present study was to observe the effect of bone BMP7 transfer to MSCs on fracture healing. Bone marrow-derived MSCs (BMSCs) from New Zealand white rabbits were isolated and identified using flow cytometry. A recombinant BMP7 overexpressing adenovirus vector (Adv) was constructed and transfected into BMSCs. The expression of BMP7 was detected by reverse transcription-polymerase chain reaction, immunofluorescence and western blotting. The present study additionally investigated the effect of BMP7 on the differentiation capacity of BMSCs. Finally, tissue-engineered bone was created with support material to verify the effect of BMP7-BMSCs on fracture healing. The results demonstrated that the expression of BMP7 was increased at the mRNA and protein levels in BMSCs following transfection with BMP7 overexpressing Adv. The results additionally demonstrated that the expression of BMP7 enhanced the differentiation capacity of bone marrow mesenchymal stem cells and had a promotional effect on fracture healing. Overall, these data suggest that Adv-BMP7 is useful for introducing foreign genes into BMSCs and will be a powerful gene therapy tool for bone regeneration and other tissue engineering applications in the future.

BMP-7-Loaded PGLA Microspheres as a New Delivery System for the Cultivation of Human Chondrocytes in a Collagen Type I Gel: The Common Nude Mouse Model

Purpose

Bone morphogenic protein 7 (BMP-7) released from polylactide (PLGA) microspheres has proven to be a potent system in cartilage tissue engineering in vitro. However, in vivo data are still lacking. The aim of this study was to investigate this BMP-7 release system utilizing the nude mouse as a small animal model.

Methods

Human osteoarthritic chondrocytes of 10 patients were enzymatically released and transferred into a collagen type-I gel. A concentration of 2×105 cells/mL was used. BMP-7 encapsulated in PGLA microspheres was added at an initial concentration of 500 ng BMP-7/mL gel. Untreated specimens and specimens with empty microspheres served as control. Samples were cultivated subcutaneously in nude mice for 6 weeks.

Results

After recovery, chondrocytes of all groups displayed a spheroid morphology without signs of dedifferentiation. The proteoglycan and collagen type II content of the control groups was restricted to the immediate pericellular region, whereas treatment group samples showed enhanced collagen type II production. Collagen type II and aggrecan gene expression was enhanced in treatment group samples with respect to the two control groups (mean ± SD: 0.268 ± 0.450 to 0.152 ± 0.129 and 0.155 ± 0.216 ng/ng β-actin for collagen type II; 0.535 ± 0.731 to 0.367 ± 0.651 and 0.405 ± 0.326 ng/ng β-actin for aggrecan), whereas collagen type I gene expression decreased by a factor of 10. Relative protein quantification of collagen type II, collagen type I and proteoglycan was in accordance.

Conclusions

Our data suggest that BMP-7 release from PGLA microspheres led to an improved tissue-engineered cartilage analogue in vivo with an increase in hyaline-cartilage-specific components.

Sprifermin (rhFGF18) enables proliferation of chondrocytes producing a hyaline cartilage matrix

OBJECTIVE

Fibroblast growth factor (FGF) 18 has been shown to increase cartilage volume when injected intra-articularly in animal models of osteoarthritis (OA) and in patients with knee OA (during clinical development of the recombinant human FGF18, sprifermin). However, the exact nature of this effect is still unknown. In this study, we aimed to investigate the effects of sprifermin at the cellular level.

DESIGN

A combination of different chondrocyte culture systems was used and the effects of sprifermin on proliferation, the phenotype and matrix production were evaluated. The involvement of MAPKs in sprifermin signalling was also studied.

RESULTS

In monolayer, we observed that sprifermin promoted a round cell morphology and stimulated both cellular proliferation and Sox9 expression while strongly decreasing type I collagen expression. In 3D culture, sprifermin increased the number of matrix-producing chondrocytes, improved the type II:I collagen ratio and enabled human OA chondrocytes to produce a hyaline extracellular matrix (ECM). Furthermore, we found that sprifermin displayed a 'hit and run' mode of action, with intermittent exposure required for the compound to fully exert its anabolic effect. Finally, sprifermin appeared to signal through activation of ERK.

CONCLUSIONS

Our results indicate that intermittent exposure to sprifermin leads to expansion of hyaline cartilage-producing chondrocytes. These in vitro findings are consistent with the increased cartilage volume observed in the knees of OA patients after intra-articular injection with sprifermin in clinical studies.

New scaffolds encapsulating TGF-β3/BMP-7 combinations driving strong chondrogenic differentiation

The regeneration of articular cartilage remains an unresolved question despite the current access to a variety of tissue scaffolds activated with growth factors relevant to this application. Further advances might result from combining more than one of these factors; here, we propose a scaffold composition optimized for the dual delivery of BMP-7 and TGF-β3, two proteins with described chondrogenic activity. First, we tested in a mesenchymal stem cell micromass culture with TGF-β3 whether the exposure to microspheres loaded with BMP-7 would improve cartilage formation. Histology and qRT-PCR data confirmed that the sustained release of BMP-7 cooperates with TGF-β3 towards chondrogenic differentiation. Then, we optimized a scaffold prototype for tissue culture and dual encapsulation of BMP-7 and TGF-β3. The scaffolds were prepared from poly(lactic-co-glycolic acid), and BMP-7/TGF-β3 were loaded as nanocomplexes with heparin and Tetronic 1107. The scaffolds showed the sustained release of both proteins over four weeks, with minimal burst effect. We finally cultured human mesenchymal stem cells on these scaffolds, in the absence of exogenous chondrogenic factor supplementation. The cells cultured on the scaffolds loaded with BMP-7 and TGF-β3 showed clear signs of cartilage formation macroscopically and histologically. RT-PCR studies confirmed a clear upregulation of cartilage markers SOX9 and Aggrecan. In summary, scaffolds encapsulating BMP-7 and TGF-β3 can efficiently deliver a cooperative growth factor combination that drives efficient cartilage formation in human mesenchymal stem cell cultures. These results open attractive perspectives towards in vivo translation of this technology in cartilage regeneration experiments.

Matrigel scaffold combined with Ad-hBMP7-transfected chondrocytes improves the repair of rabbit cartilage defect

The aim of this study was to explore an effective method for the repair of cartilage defects using chitosan/glycerophosphate (C/GP) gel- and Matrigel-engineered human bone morphogenetic protein 7 (hBMP7)-expressing chondrocytes. Rabbit chondrocytes were obtained, cultured in vitro and transfected with an adenovirus containing hBMP7 and green fluorescent protein (Ad-hBMP7-GFP). The expression of hBMP7 in the transfected cells was tested by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. The phenotype of the transfected cells was evaluated by detecting the yields of collagen II and hyaluronic acid using RT-PCR and enzyme-linked immunosorbent assay (ELISA). The growth of chondrocytes in the C/GP gel and Matrigel was accessed by measuring the cell growth rate, hematoxylin and eosin (H&E) staining and observation under a scanning microscope. Twelve adult male New Zealand white rabbits were randomly divided into three groups. Two cartilage defects were created in the rabbits' knees by aseptic surgery. Group A (n=4) did not receive any treatment, group B (n=4) were treated with C/GP gel and Matrigel-engineered Ad-mock-GFP-transfected chondrocytes, and group C (n=4) were treated with C/GP gel and Matrigel-engineered Ad-hBMP7-GFP-transfected chondrocytes. Rabbits were sacrificed at 4 weeks after transplantation, and the repair effect was measured by the Wakitani scoring method. On the basis of the RT-PCR and western blot results, hBMP7 was efficiently overexpressed in the Ad-hBMP7-GFP-transfected chondrocytes. The ELISA results showed that the yields of collagen II and hyaluronic acid in Ad-hBMP7-GFP-transfected chondrocytes were significantly higher than those in Ad-mock-GFP-transfected chondrocytes. Chondrocytes have a better morphology and arrangement in a Matrigel scaffold than in C/GP, as assessed by H&E staining and scanning microscopy. According to the Wakitani score, Matrigel combined with Ad-hBMP7-GFP-transfected chondrocytes successfully promoted the repair of cartilage defects in rabbit knees.

Lactoferricin enhances BMP7-stimulated anabolic pathways in intervertebral disc cells

Bone-morphogenetic protein-7 (BMP7) is a well-known anabolic and anti-catabolic growth factor on intervertebral disc (IVD) matrix and cell homeostasis. Similarly, Lactoferricin B (LfcinB) has recently been shown to have pro-anabolic, anti-catabolic, anti-oxidative and/or anti-inflammatory effects in bovine disc cells in vitro. In this study, we investigated the potential benefits of using combined peptide therapy with LfcinB and BMP7 for intervertebral disc matrix repair and to understand cellular and signaling mechanisms controlled by these factors. We studied the effects of BMP7 and LfcinB as individual treatments and combined therapy on bovine nucleus pulposus (NP) cells by assessing proteoglycan (PG) accumulation and synthesis, and the gene expression of matrix protein aggrecan and transcription factor SOX-9. We also analyzed the role of Noggin, a BMP antagonist, in IVD tissue and examined its effect after stimulation with LfcinB. To understand the molecular mechanisms by which LfcinB synergizes with BMP7, we investigated the ERK-SP1 axis as a downstream intracellular signaling regulator involved in BMP7 and LfcinB-mediated activities. Treatment of bovine NP cells cultured in alginate with LfcinB plus BMP7 synergistically stimulates PG synthesis and accumulation in part by upregulation of aggrecan gene expression. The synergism results from LfcinB-mediated activation of Sp1 and SMAD signaling pathways by (i) phosphorylation of SMAD 1/5/8; (ii) downregulation of SMAD inhibitory factors [i.e., noggin and SMAD6 (inhibitory SMAD)]; and (iii) upregulation of SMAD4 (universal co-SMAD). These data indicate that LfcinB-suppression of Noggin may eliminate the negative feedback of BMP7, thereby maximizing biological activity of BMP7 and ultimately shifting homeostasis to a pro-anabolic state in disc cells. We propose that combination growth factor therapy using BMP7 and LfcinB may be beneficial for treatment of disc degeneration.

Cell-free repair of small cartilage defects in the Goettinger minipig: The effects of BMP-7 continuously released by poly(lactic-co-glycolid acid) microspheres

Objective

Cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed after treatment with cell-free collagen type-I gel with or without additional BMP-7 loaded poly(lactic-co-glycolid acid) microspheres.

Methods

Two full-thickness chondral defects were created in the trochlear groove of one hind leg knee in six Goettinger minipigs. Six defects were treated with a cell-free collagen type-I gel plug of 10 mm, the corresponding six defects were treated with a cell-free collagen type-I plug with poly(lactic-co-glycolid acid) microspheres loaded with recombinant BMP-7 (100 ng/ml gel). After 1 year, the animals were sacrificed. Immediately after recovery, non-destructive biomechanical testing was performed. The repair tissue quality was evaluated by immunohistochemistry and the O’Driscoll score was calculated.

Results

After 1 year, a robust cellular migration into the cell-free collagen gel plugs occurred and a hyaline-like repair tissue was found. Collagen type-II production and cellular organisation were higher in the BMP-7 microsphere group. The determination of the E-modulus, creep and relaxation revealed that mechanical properties of the BMP-7 microsphere group in summary were closer to control hyaline cartilage.

Conclusions

While all specimens revealed a homogeneous cellular distribution, ECM production, cellular organisation and mechanical properties were enhanced by continuous BMP-7 release.

Effect of lyso-phosphatidylcholine and Schnurri-3 on osteogenic transdifferentiation of vascular smooth muscle cells to calcifying vascular cells in 3D culture

BACKGROUND

In vitro cell culture is a widely used technique for investigating a range of processes such as stem cell behavior, regenerative medicine, tissue engineering, and drug discovery. Conventional cell culture is performed in Petri dishes or flasks where cells typically attach to a flat glass or plastic surface as a cell monolayer. However, 2D cell monolayers do not provide a satisfactory representation of in vivo conditions. A 3D culture could be a much better system for representing the conditions that prevail in vivo.

METHODS AND RESULTS

To simulate 3D conditions, vascular smooth muscle cells (VSMCs) were loaded with gold-polyvmer-iron oxide hydrogel, enabling levitation of the cells by using spatially varying magnetic fields. These magnetically levitated 3D cultures appeared as freely suspended, clustered cells which proliferated 3-4 times faster than cells in conventional 2D cultures. When the levitated cells were treated with 10nM lysophosphatidylcholine (LPC), for 3days, cell clusters exhibited translucent extensions/rods 60-80μm wide and 200-250μm long. When 0.5μg/μl Schnurri-3 was added to the culture containing LPC, these extensions were smaller or absent. When excited with 590-650nm light, these extensions emitted intrinsic fluorescence at >667nm. When the 3D cultures were treated with a fluorescent probe specific for calcium hydroxyapatite (FITC-HABP-19), the cell extensions/rods emitted intensely at 518nm, the λmax for FITC emission. Pellets of cells treated with LPC were more enriched in calcium, phosphate, and glycosaminoglycans than cells treated with LPC and Schnurri-3.

CONCLUSIONS

In 3D cultures, VSMCs grow more rapidly and form larger calcification clusters than cells in 2D cultures. Transdifferentiation of VSMC into calcifying vascular cells is enhanced by LPC and attenuated by Schnurri-3.

GENERAL SIGNIFICANCE

The formation of calcified structures in 3D VSMC cultures suggests that similar structures may be formed in vivo.

Synergistic Effect of TGF-β1 And BMP-7 on Chondrogenesis and Extracellular Matrix Synthesis: An In Vitro Study

Introduction:

The purpose of the present study seeks to determine the signal timing of BMP–7 and TGF-β1 from a novel chitosan based hydrogel system that may affect chondrocyte proliferation resulting in the presence of a synergism seen conspicuously in consecutive controlled delivery.

Methods:

Four groups of cultured chondrocytes were seeded on a novel designed chitosan based hydrogel. The hydrogel was left empty (control) in one group and loaded with BMP–7, TGF-β1 and their combination in the other groups, respectively. Hydrogel structure was analyzed with scanning electron microscope. The release kinetics of Growth Factors (GFs) was determined with ELISA. Chondrocyte viability and toxicity after being tested with MTS and collagen type II synthesis, were quantified with western blotting. Canonical regression analysis was used for measuring statistical evaluation.

Results:

Chitosan based hydrogel allowed controlled release of GFs in different time intervals for BMP–7 and TGF-β1. Double peak concentration gradient was found to be present in the group loaded with both GFs. In this group, substantially higher chondrocyte growth and collagen synthesis were also detected.

Conclusions:

We concluded that, chitosan based hydrogel systems may be adjusted to release GFs consecutively during biodegradation at the layers of surface, which may increase the cell number and enhance collagen type II synthesis.

Effects of intermittent hydrostatic pressure and BMP-2 on osteoarthritic human chondrocyte metabolism in vitro

PURPOSE

This study examined effects of intermittent hydrostatic pressure (IHP) and a chondrogenic growth factor, bone morphogenetic protein-2 (BMP-2), on anabolic, catabolic, and other metabolic markers in human osteoarthritic (OA) chondrocytes in vitro.

METHODS

Articular chondrocytes, isolated from femoral OA cartilage and maintained in high-density monolayer culture, were examined for effects of BMP-2 and IHP on gene expression of matrix-associated proteins (aggrecan, type II collagen, and SOX9) and catabolic matrix metalloproteinases (MMP-2 and MMP-3) and culture medium levels of the metabolic markers MMP-2, nitric oxide (NO), and glycosaminoglycan (GAG). The results were analyzed using a mixed linear regression model to investigate the effects of load and growth factor concentration.

RESULTS

IHP and BMP-2 modulated OA chondrocyte metabolism in accordance with growth factor concentration independently, without evidence of synergism or antagonism. Each type of stimulus acted independently on anabolic matrix gene expression. Type II collagen and SOX9 gene expression were stimulated by both IHP and BMP-2 whereas aggrecan was increased only by BMP-2. IHP exhibited a trend to decrease MMP-2 gene expression as a catabolic marker whereas BMP-2 did not. NO production was increased by addition of BMP-2 and IHP exhibited a trend for increased levels. GAG production was increased by BMP-2.

CONCLUSIONS

This study confirmed the hypothesis that human OA chondrocytes respond to a specific type of mechanical load, IHP, through enhanced articular cartilage macromolecule gene expression and that IHP, in combination with a chondrogenic growth factor BMP-2, additively enhanced matrix gene expression without interactive effects.

Effects of recombinant adeno-associated viral vectors on angiopoiesis and osteogenesis in cultured rabbit bone marrow stem cells via co-expressing hVEGF and hBMP genes: a preliminary study in vitro

OBJECTIVE

VEGF and BMP play important roles in angiogenesis and osteogenesis. Combining these two factors may be a promising therapeutic strategy for avascular necrosis of the femoral head (ANFH).

METHODS

Rabbit bone marrow-derived mesenchymal stem cells (BMSCs) were isolated and purified by density gradient centrifugation combined with attachment culture methods. The purity and characteristics of the BMSCs were detected by cell surface antigen identification. The best MOI of BMSCs transfected with rAAV was detected by fluorescent cell counting, and cell viability was determined by MTT assay. Expression of the genes of interest was detected by GFP gene expression, RT-PCR assay, and ELISA assay. The biological activities of VEGF and BMP were detected by angiogenic and osteogenic assays.

RESULTS

The best MOI of BMSCs transfected with rAAV was 5 x 10(4)v.g./cell. Cell growth curves showed vigorous cell viability. Expressions of the GFP, VEGF165, and BMP(7) genes were detected 1 day post-transfection and peaked 14 days post-transfection. Expression of the genes of interest was sustained over 1 month. VEGF and BMP proteins secreted from BMSCs transfected with rAAV-hVEGF(165)-IRES-hBMP(7) enhanced angiogenesis and osteogenesis in vitro.

CONCLUSION

Recombinant adeno-associated viral vectors co-expressing the hVEGF(165) and hBMP(7) genes showed efficient gene expression ability. The VEGF(165) and BMP(7) proteins expressed from the vector have efficient biological activity in vitro.

Effects of Low Concentration BMP-7 on Human Osteoarthritic Chondrocytes: Comparison of Different Applications

While BMP-7 (OP-1) is one of the most potent growth factors in cartilage tissue engineering, the effects of exogenous low concentration BMP-7 on osteoarthritic chondrocytes are still unknown. Human osteoarthritic chondrocytes obtained from the femoral condyles of 10 patients were grown either in monolayer or in 3D collagen type-I gel culture in vitro. The growth factor was either given as a single dose of 50 ng/mL, a repeated dose, or continuously released from PGLA microspheres. Matrix formation was monitored by immunohistochemical staining and real-time PCR. In contrast to monolayer culture, the differentiated phenotype was prevailed in 3D culture. Collagen type-II protein production in the 3D group with a continuous BMP-7 release was enhanced in comparison to all other groups. Gene expression of collagen type-II and aggrecan was elevated in all treatment groups, with the highest extent in the BMP-7 microsphere group. In summary, treatment of articular chondrocytes with a low dose of BMP-7 leads to an elevated production of extracellular matrix components. This effect is further increased when BMP-7 is given repeatedly or continuously, which proved to be the most effective form of application.

Intra-articular injections of bone morphogenetic protein-7 retard progression of existing cartilage degeneration

We investigated the effect of weekly intra-articular injections of bone morphogenetic protein-7 (BMP-7) on prevention of progression of existing cartilage degeneration in an osteoarthritis model in rabbits. An anterior cruciate ligament transection (ACLT) model was used to create a progressive osteoarthritis model. BMP-7 was intra-articular injected weekly into the right knee and PBS into the left knee from 4 weeks after ACLT. Both sides of the knees were compared macroscopically, histologically, immunohistochemically, and by micro CT. Macroscopically, fibrillation in the femoral condyle was observed 4 weeks after ACLT. In the control knees, cartilage degeneration further progressed throughout the 12-week period. In the BMP-7 treated knee, osteoarthritis progression was milder than in the control knees. Histologically, safranin-O staining was decreased in the surgical knees at 4 weeks. Obvious erosions in both medial and lateral condyles were revealed in the control knees at 12 weeks, while cartilage matrix was predominantly retained in the BMP-7 treated knees. The macroscopic and microscopic OA score in the BMP-7 treated knee was better than that in the control in each rabbit. Immunohistochemical analysis demonstrated that both type II collagen and BMP-7 were more expressed in cartilage treated with BMP-7. Micro CT analysis showed that osteophytes were smaller in the BMP-7 treated knee compared to that of the control. Weekly intra-articular injections of BMP-7 inhibited progression of existing cartilage degeneration.

The role of BMP-7 in chondrogenic and osteogenic differentiation of human bone marrow multipotent mesenchymal stromal cells in vitro

This study addresses the role of bone morphogenetic protein-7 (BMP-7) in chondrogenic and osteogenic differentiation of human bone marrow multipotent mesenchymal stromal cells (BM MSCs) in vitro. BM MSCs were expanded and differentiated in the presence or absence of BMP-7 in monolayer and three-dimensional cultures. After 3 days of stimulation, BMP-7 significantly inhibited MSC growth in expansion cultures. When supplemented in commonly used induction media for 7-21 days, BMP-7 facilitated both chondrogenic and osteogenic differentiation of MSCs. This was evident by specific gene and protein expression analyses using real-time PCR, Western blot, histological, and immunohistochemical staining. BMP-7 supplementation appeared to enhance upregulation of lineage-specific markers, such as type II and type IX collagens (COL2A1, COL9A1) in chondrogenic and secreted phosphoprotein 1 (SPP1), osteocalcin (BGLAP), and osterix (SP7) in osteogenic differentiation. BMP-7 in the presence of TGF-beta3 induced superior chondrocytic proteoglycan accumulation, type II collagen, and SOX9 protein expression in alginate and pellet cultures compared to either factor alone. BMP-7 increased alkaline phosphatase activity and dose-dependently accelerated calcium mineralization of osteogenic differentiated MSCs. The potential of BMP-7 to promote adipogenesis of MSCs was restricted under osteogenic conditions, despite upregulation of adipocyte gene expression. These data suggest that BMP-7 is not a singular lineage determinant, rather it promotes both chondrogenic and osteogenic differentiation of MSCs by co-ordinating with initial lineage-specific signals to accelerate cell fate determination. BMP-7 may be a useful enhancer of in vitro differentiation of BM MSCs for cell-based tissue repair.

Angiopoiesis and bone regeneration via co-expression of the hVEGF and hBMP genes from an adeno-associated viral vector in vitro and in vivo

AIM

To investigate the therapeutic potential of adeno-associated virus (AAV)-mediated expression of vascular endothelial growth factor (VEGF) and bone morphogenetic protein (BMP).

METHODS

Four experimental groups were administered the following AAV vector constructs: rAAV-hVEGF(165)-internal ribosome entry site (IRES)-hBMP-7 (AAV-VEGF/BMP), rAAV-hVEGF(165)-GFP (AAV-VEGF), rAAV-hBMP-7-GFP (AAV-BMP), and rAAV-IRES-GFP (AAV-GFP). VEGF(165) and BMP-7 gene expression was detected using RT-PCR. The VEGF(165) and BMP-7 protein expression was determined by Western blotting and ELISA. The rabbit ischemic hind limb model was adopted and rAAV was administered intramuscularly into the ischemic limb.

RESULTS

Rabbit bone marrow-derived mesenchymal stem cells (BMSCs) were cultured and infected with the four viral vectors. The expression of GFP increased from the 7th day of infection and could be detected on the 28th day post-infection. In the AAV-VEGF/BMP group, the levels of VEGF165 and BMP-7 increased with prolonged infection time. The VEGF(165) and BMP-7 secreted from BMSCs in the AAV-VEGF/BMP group enhanced HUVEC tube formation and resulted in a stronger osteogenic ability, respectively. In rabbit ischemic hind limb model, GFP expression increased from the 4th week and could be detected at 8 weeks post-injection. The rAAV vector had superior gene expressing activity. Eight weeks after gene transfer, the mean blood flow was significantly higher in the AAV-VEGF/BMP group. Orthotopic ossification was radiographically evident, and capillary growth and calcium deposits were obvious in this group.

CONCLUSION

AAV-mediated VEGF and BMP gene transfer stimulates angiogenesis and bone regeneration and may be a new therapeutic technique for the treatment of avascular necrosis of the femoral head (ANFH).

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.

Periodic knee injections of BMP-7 delay cartilage degeneration induced by excessive running in rats

Strenuous running of rats enhances mechanical stress on the knee, thereby inducing degeneration of articular cartilage. Bone morphogenetic protein-7 (BMP-7) has an inhibitory effect on cartilage degeneration, suggesting its usefulness for human osteoarthritis patients. However, its mode of administration should be investigated. We examined whether weekly knee injections of BMP-7 delayed the progression of cartilage degeneration. Wistar rats were forced to run 30 km in 6 weeks on a rodent treadmill, and BMP-7 was injected weekly into the knee. Macroscopically and histologically, this strenuous running regimen induced cartilage degeneration. Weekly injections of 250 ng BMP-7 delayed the progression of cartilage degeneration. Immunohistochemically, in the control knee, type II collagen expression decreased, while BMP-7 expression in chondrocytes slightly increased. Interestingly, weekly injection of BMP-7 increased BMP-7 expression even 9 days after the final injection. Disulfate disaccharide keratan sulfate in serum transiently increased in the control group, while it remained at a low level in the BMP-7 group. Weekly BMP-7 injection increased BMP-7 expression in chondrocytes and its effect seemed to last more than 7 days. The effect of BMP-7 could be monitored by serum keratan sulfate concentration. Periodical injections of BMP-7 delayed progression of cartilage degeneration induced by excessive running in rats.

Cartilage repair: past and future--lessons for regenerative medicine

Since the first cell therapeutic study to repair articular cartilage defects in the knee in 1994, several clinical studies have been reported. An overview of the results of clinical studies did not conclusively show improvement over conventional methods, mainly because few studies reach level I of evidence for effects on middle or long term. However, these explorative trials have provided valuable information about study design, mechanisms of repair and clinical outcome and have revealed that much is still unknown and further improvements are required. Furthermore, cellular and molecular studies using new technologies such as cell tracking, gene arrays and proteomics have provided more insight in the cell biology and mechanisms of joint surface regeneration. Besides articular cartilage, cartilage of other anatomical locations as well as progenitor cells are now considered as alternative cell sources. Growth Factor research has revealed some information on optimal conditions to support cartilage repair. Thus, there is hope for improvement. In order to obtain more robust and reproducible results, more detailed information is needed on many aspects including the fate of the cells, choice of cell type and culture parameters. As for the clinical aspects, it becomes clear that careful selection of patient groups is an important input parameter that should be optimized for each application. In addition, the study outcome parameters should be improved. Although reduced pain and improved function are, from the patient's perspective, the most important outcomes, there is a need for more structure/tissue-related outcome measures. Ideally, criteria and/or markers to identify patients at risk and responders to treatment are the ultimate goal for these more sophisticated regenerative approaches in joint surface repair in particular, and regenerative medicine in general.

Weekly intra-articular injections of bone morphogenetic protein-7 inhibits osteoarthritis progression

Introduction

We investigated the ability of a weekly intra-articular injection of bone morphogenetic protein (BMP)-7 to prevent osteoarthritis in rabbits with anterior cruciate ligament transections.

Methods

First, 36 knee joints were randomly divided into four groups: 50, 500, 5,000 ng BMP-7, and control. Knee cartilage was evaluated at 4, 8, and 12 weeks. Then, in order to control for individual differences, 500 ng BMP-7 was injected into one knee and phosphate-buffered saline (PBS) into the other, and the two knees were compared at 4, 8, and 12 weeks (n = 5). For pharmacokinetic analysis, cartilage was harvested at 1 hour and 1, 2, 4, and 7 days after knee injection of 500 ng BMP-7 or PBS (n = 3).

Results

Histological scores in the 500 and 5,000 ng BMP-7 groups were significantly better than those in the other groups at 12 weeks. Matched pair analysis demonstrated that both macroscopic and histological scores in the 500 ng BMP-7 group were better than those in the control group. Immunohistochemical analysis revealed higher BMP-7 expression by chondrocytes in the BMP-7 injected knees. Histology of whole knee and quantitative micro computed tomography analysis showed that weekly injections of 500 ng BMP-7 did not induce synovial fibrosis, ectopic bone, or osteophyte formation. As detected by enzyme-linked immunosorbent assay, BMP-7 concentration in the cartilage tissue was still higher in the BMP-7 treated group 7 days after the injection.

Conclusions

Weekly intra-articular injections of BMP-7 inhibited progression of osteoarthritis. Obvious adverse effects were not observed. BMP-7 concentration and expression in cartilage were still higher 7 days after injection.