[Dopamine modified and cartilage derived morphogenetic protein 1 laden polycaprolactone-hydroxyapatite composite scaffolds fabricated by three-dimensional printing improve chondrogenic differentiation of human bone marrow mesenchymal stem cells]

Objective

To prepare dopamine modified and cartilage derived morphogenetic protein 1 (CDMP1) laden polycaprolactone-hydroxyapatite (PCL-HA) composite scaffolds by three-dimensional (3D) printing and evaluate the effect of 3D scaffolds on in vitro chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs).

Methods

A dimensional porous PCL-HA scaffold was fabricated by 3D printing. Dopamine was used to modify the surface of PCL-HA and then CDMP-1 was loaded into scaffolds. The surface microstructure was observed by scanning electron microscope (SEM) and porosity and water static contact angle were also detected. The cytological experiment in vitro were randomly divided into 3 groups: group A (PCL-HA scaffolds), group B (dopamine modified PCL-HA scaffolds), and group C (dopamine modified and CDMP-1 laden PCL-HA scaffolds). The hBMSCs were seeded into three scaffolds, in chondrogenic culture conditions, the cell adhesive rate, the cell proliferation (MTT assay), and cell activity (Live-Dead staining) were analyzed; and the gene expressions of collagen type Ⅱ and Aggrecan were detected by real-time fluorescent quantitative PCR.

Results

The scaffolds in 3 groups were all showed a cross-linked and pore interconnected with pore size of 400-500 μm, porosity of 56%, and fiber orientation of 0°/90°. For dopamine modification, the scaffolds in groups B and C were dark brown while in group A was white. Similarly, water static contact angle was from 76° of group A to 0° of groups B and C. After cultured for 24 hours, the cell adhesion rate of groups A, B, and C was 34.3%±3.5%, 48.3%±1.5%, and 57.4%±2.5% respectively, showing significant differences between groups ( P<0.05). Live/Dead staining showed good cell activity of cells in 3 groups. MTT test showed that hBMSCs proliferated well in 3 groups and the absorbance ( A) value was increased with time. The A value in group C was significantly higher than that in groups B and A, and in group B than in group A after cultured for 4, 7, 14, and 21 days, all showing significant differences ( P<0.05). The mRNA relative expression of collagen type Ⅱ and Aggrecan increased gradually with time in 3 groups. The mRNA relative expression of collagen type Ⅱafter cultured for 7, 14, and 21 days, and the mRNA relative expression of Aggrecan after cultured for 14 and 21 days in group C were significantly higher than those in groups A and B, and in group B than in group A, all showing significant differences ( P<0.05).

Conclusion

Co-culture of dopamine modified and CDMP1 laden PCL-HA scaffolds and hBMSCs in vitro can promote hBMSCs' adhesion, proliferation, and chondrogenic differentiation.

Pullulan microbeads/Si-HPMC hydrogel injectable system for the sustained delivery of GDF-5 and TGF-β1: new insight into intervertebral disc regenerative medicine

Discogenic low back pain is considered a major health concern and no etiological treatments are today available to tackle this disease. To clinically address this issue at early stages, there is a rising interest in the stimulation of local cells by in situ injection of growth factors targeting intervertebral disc (IVD) degenerative process. Despite encouraging safety and tolerability results in clinic, growth factors efficacy may be further improved. To this end, the use of a delivery system allowing a sustained release, while protecting growth factors from degradation appears of particular interest. We propose herein the design of a new injectable biphasic system, based on the association of pullulan microbeads (PMBs) into a cellulose-based hydrogel (Si-HPMC), for the TGF-β1 and GDF-5 growth factors sustained delivery. We present for the first time the design and mechanical characterization of both the PMBs and the called biphasic system (PMBs/Si-HPMC). Their loading and release capacities were also studied and we were able to demonstrate a sustained release of both growth factors, for up to 28 days. Noteworthy, the growth factors biological activity on human cells was maintained. Altogether, these data suggest that this PMBs/Si-HPMC biphasic system may be a promising candidate for the development of an innovative bioactive delivery system for IVD regenerative medicine.

Laryngotracheal Stenosis Repair Using Cartilage-Derived Morphogenic Proteins: A Pilot Study

Objectives:

This pilot study evaluated the role of cartilage-derived morphogenic proteins (CDMPs) as promoters of cartilage growth and differentiation and as a possible alternative to autologous cartilage grafts in laryngotracheal reconstruction.

Methods:

In phase 1, 6 New Zealand rabbits underwent subperichondrial injection of CDMP-1, CDMP-2, or CDMP-3 in the right thyroid ala and normal saline solution in the left thyroid ala as controls. In phase 2, 14 rabbits underwent anterior cricoid split and interposition of a fibrillar collagen sponge saturated with normal saline solution, CDMP-2, or CDMP-3.

Results:

In both phases, saline solution failed to induce new cartilage or bone growth. Small foci of cartilage and/or bone formation were observed within the thyroid subperichondria of those rabbits injected with CDMP-2 or CDMP-3. In phase 2, a few small foci of new cartilage and/or bone formation were observed at the edges of the cricoid split with CDMP-2 and CDMP-3.

Conclusions:

A different carrier of CDMP, a change in dosage, or a combination of CDMPs might yield more significant neochondrification. The role of CDMPs as promoters of cartilage and differentiation could not be disqualified in this study and should be further investigated.

[Progress of research in osteoarthritis. Recent advance in the study of susceptibility genes for osteoarthritis]

Osteoarthritis (OA) is a polygenic disease based on genetic and environmental factors. Identification of its genetic factor, i.e., the susceptibility genes for OA is rapidly in progress. Recent advance in the study of OA susceptibility genes is reviewed with focus on the genome-wide association study and the large-scale replication study.

The effects of GDF-5 and uniaxial strain on mesenchymal stem cells in 3-D culture

Recent endeavors in tissue engineering have attempted to identify the optimal parameters to create an artificial ligament. Both mechanical and biochemical stimulation have been used by others to independently modulate growth and differentiation, although few studies have explored their interactions. We applied previously described fabrication techniques to create a highly porous (90%-95% porosity, 212-300 microm), 3-D, bioabsorbable polymer scaffold (polycaprolactone). Scaffolds were coated with bovine collagen, and growth and differentiation factor 5 (GDF-5) was added to half of the scaffolds. Scaffolds were seeded with mesenchymal stem cells and cultured in a custom bioreactor under static or cyclic strain (10% strain, 0.33 Hz) conditions. After 48 hours, both mechanical stimulation and GDF-5 increased mRNA production of collagen I, II, and scleraxis compared to control; tenascin C production was not increased. Combining stimuli did not change gene expression; however, cellular metabolism was 1.7 times higher in scaffolds treated with both stimuli. We successfully grew a line of mesenchymal stem cells in 3-D culture, and our initial data indicate mechanical stimulation and GDF-5 influenced cellular activity and mRNA production; we did not, however, observe additive synergism with the mechanical and biological stimuli.

Adenovirus-mediated expression of growth and differentiation factor-5 promotes chondrogenesis of adipose stem cells

The repair of articular cartilage injuries is impeded by the avascular and non-innervated nature of cartilage. Transplantation of autologous chondrocytes has a limited ability to augment the repair process due to the highly differentiated state of chondrocytes and the risks of donor-site morbidity. Mesenchymal stem cells can undergo chondrogenesis in the presence of growth factors for cartilage defect repair. Growth and differentiation factor-5 (GDF5) plays an important role in chondrogenesis. In this study, we examined the effects of GDF5 on chondrogenesis of adipose-derived stem cells (ADSCs) and evaluate the chondrogenic potentials of GDF5 genetically engineered ADSCs using an in vitro pellet culture model. Rat ADSCs were grown as pellet cultures and treated with chondrogenic media (CM). Induction of GDF5 by an adenovirus (Ad-GDF5) was compared with exogenous supplementation of GDF5 (100 ng/ml) and transforming growth factor-beta (TGF-beta1; 10 ng/ml). The ADSCs underwent chondrogenic differentiation in response to GDF5 exposure as demonstrated by production of proteoglycan, and up-regulation of collagen II and aggrecan at the protein and mRNA level. The chondrogenic potential of a one-time infection with Ad-GDF5 was weaker than exogenous GDF5, but equal to that of TGF-beta1. Stimulation with growth factors or CM alone induced transient expression of the mRNA for collagen X, indicating a need for optimization of the CM. Our findings indicate that GDF5 is a potent inducer of chondrogenesis in ADSCs, and that ADSCs genetically engineered to express prochondrogenic growth factors, such as GDF5, may be a promising therapeutic cell source for cartilage tissue engineering.

Differentially regulated expression of growth differentiation factor 5 and bone morphogenetic protein 7 in articular cartilage and synovium in murine chronic arthritis: potential importance for cartilage breakdown and synovial hypertrophy

OBJECTIVE

To examine whether the endogenous expression of growth differentiation factor 5 (GDF-5) and bone morphogenetic protein 7 (BMP-7) is altered in the cartilage and synovium of human tumor necrosis factor alpha (TNFalpha)-transgenic (hTNFtg) mice with chronic arthritis, and to investigate the response of hTNFtg chondrocytes as well as fibroblast-like synoviocytes (FLS) to these morphogens in vitro.

METHODS

Analyses were performed in hTNFtg mice with chronic destructive arthritis and in wild-type (WT) mice as controls. Expression of GDF-5 and BMP-7 in the articular cartilage and synovium was examined by real-time polymerase chain reaction and immunohistochemistry. Human TNFtg cartilage explants, chondrocytes, and FLS monolayer cultures were assessed for basal matrix biosynthesis as well as growth factor responsiveness, using (35)S-sulfate incorporation assays. In addition, the DNA content/cell proliferation rate was measured.

RESULTS

The expression of GDF-5 and BMP-7 was decreased in articular cartilage from hTNFtg mice, whereas expression of both morphogens was increased in arthritic synovium from hTNFtg mice, as compared with the levels in WT controls. Isotope incorporation revealed a marked reduction of matrix synthesis in hTNFtg cartilage as well as a decrease in responsiveness to GDF-5 and BMP-7. The DNA content did not change in arthritic cartilage as compared with WT cartilage. In hTNFtg FLS, growth factor stimulation increased the rate of cell proliferation and the production of extracellular matrix.

CONCLUSION

In this murine model of TNFalpha-mediated arthritis, the expression of GDF-5 and BMP-7 is regulated differentially in articular cartilage and synovium. In articular cartilage, the down-regulation of GDF-5 and BMP-7, which function to maintain matrix integrity, could potentially compromise tissue repair, whereas in synovium, the increased expression of GDF-5 and BMP-7 might contribute to synovial hypertrophy.

Heterotypy in the N-terminal region of growth/differentiation factor 5 (GDF5) mature protein during teleost evolution

Heterotypy is now recognized as a generative force in the formation of new proteins through modification of existing proteins. We report that heterotypy in the N-terminal region of the mature growth/differentiation factor 5 (GDF5) protein occurred during evolution of teleosts. N-terminal length variation of GDF5 was found among teleost interfamilies and interorders but not within teleost families or among tetrapods. We further show that increase of proline and glutamine to the N-terminal region of mature GDF5 occurred in Eurypterygii, the higher lineage of teleosts. Because the basic amino acids, believed to control diffusion, are conserved in this region across all species examined, we suggest that the N-terminal elongation of the mature GDF5 protein during evolution has altered the protein diffusion in Eurypterygii, leading to high concentrations of the protein in the joint of the pharyngeal skeleton, the location of cartilage formation during development.

[Genomic approaches to bone and joint diseases. Current status of genetic study of osteoarthritis]

Osteoarthritis (OA) is the most common human arthritis characterized by the degeneration of articular cartilage. OA is a major concern for aging societies worldwide. Epidemiological and genetic studies have revealed that OA is a polygenic disease. Growth differentiation factor 5 (GDF5 ) is a good candidate gene for OA. We have recently found a novel ENU-mutagenesis mouse that presents early onset OA in the elbow joint in homozygotes. Through case-control association studies, we have found that GDF5 is associated with OA in the Japanese population. A single nucleotide polymorphism (SNP) in the 5'-UTR of GDF5 (+ 104T/C ; rs143383) showed a significant association (p = 1.8 x 10(- 13)) in hip OA. This association was replicated for knee OA in both Japanese and Han Chinese populations as well as in West European Caucasians. This SNP is located in the core promoter of GDF5 and exerted allelic differences on transcription, with the susceptibility allele showing reduced transcriptional activity. Our findings implicate GDF5 as a susceptibility gene for OA in worldwide populations and suggest that decreased GDF5 expression is involved in OA pathogenesis.

The growth differentiation factor 5 (GDF5) core promoter polymorphism is not associated with knee osteoarthritis in the Greek population

Genetic factors have been shown to play an important role in the etiology of osteoarthritis (OA). A functional single nucleotide polymorphism (SNP) +104T/C; rs143383 in the 5' UTR of the GDF5 gene was recently associated with susceptibility to osteoarthritis in the Japanese and Chinese population. Our objective was to assess whether this SNP was also associated with knee OA in a Greek Caucasian population sample. The +104T/C SNP was genotyped in a total of 519 case-control cohort; 251 patients with idiopathic knee OA and 268 controls were used. No significant differences were found in genotype or allele frequencies of the +104T/C SNP of GDF5 gene between cases and controls (p < 0.05). Also, no significant differences in allelic and genotypic frequencies were found when the individuals were stratified by sex. Our data implied that the +104T/C; rs143383 GDF5 core promoter polymorphism is not a risk factor for OA etiology in Greek Caucasians. Our study highlights the heterogeneous nature of OA genetic susceptibility.

Effect of transforming growth factor-beta and growth differentiation factor-5 on proliferation and matrix production by human bone marrow stromal cells cultured on braided poly lactic-co-glycolic acid scaffolds for ligament tissue engineering

Tissue engineering of ligaments based on biomechanically suitable biomaterials combined with autologous cells may provide a solution for the drawbacks associated with conventional graft material. The aim of the present study was to investigate the contribution of recombinant human transforming growth factor beta 1 (rhTGF-beta1) and growth differentiation factor (GDF)-5, known for their role in connective tissue regeneration, to proliferation and matrix production by human bone marrow stromal cells (BMSCs) cultured onto woven, bioabsorbable, 3-dimensional (3D) poly(lactic-co-glycolic acid) scaffolds. Cells were cultured for 12 days in the presence or absence of these growth factors at different concentrations. Human BMSCs attached to the suture material, proliferated, and synthesized extracellular matrix rich in collagen type I and collagen III. No differentiation was demonstrated toward cartilage or bone tissue. The addition of rhTGF-beta1 (1-10 ng/mL) and GDF-5 (10-100 ng/mL) increased cell content (p < 0.05), but only TGF-beta1 also increased total collagen production (p < 0.05) and collagen production per cell, which is a parameter indicating differentiation. In conclusion, stimulation with rhTGF-beta1, and to a lesser extent with GDF-5, can modulate human BMSCs toward collagenous soft tissue when applied to a 3D hybrid construct. The use of growth factors could play an important role in the improvement of ligament tissue engineering.

A novel dominant-negative mutation in Gdf5 generated by ENU mutagenesis impairs joint formation and causes osteoarthritis in mice

Growth and differentiation factor 5 (GDF5) has been implicated in chondrogenesis and joint formation, and an association of GDF5 and osteoarthritis (OA) has been reported recently. However, the in vivo function of GDF5 remains mostly unclarified. Although various human GDF5 mutations and their phenotypic consequences have been described, only loss-of-function mutations that cause brachypodism (shortening and joint ankylosis of the digits) have been reported in mice. Here, we report a new Gdf5 allele derived from a large-scale N-ethyl-N-nitrosourea mutagenesis screen. This allele carries an amino acid substitution (W408R) in a highly conserved region of the active signaling domain of the GDF5 protein. The mutation is semi-dominant, showing brachypodism and ankylosis in heterozygotes and much more severe brachypodism, ankylosis of the knee joint and malformation with early-onset OA of the elbow joint in homozygotes. The mutant GDF5 protein is secreted and dimerizes normally, but inhibits the function of the wild-type GDF5 protein in a dominant-negative fashion. This study further highlights a critical role of GDF5 in joint formation and the development of OA, and this mouse should serve as a good model for OA.

An SNP in the 5′-UTR of GDF5 is associated with osteoarthritis susceptibility in Europeans and with in vivo differences in allelic expression in articular cartilage

A compelling genetic association with osteoarthritis (OA) of a functional SNP (rs143383, T/C) in the 5'-UTR of the GDF5 gene was recently reported in case-control cohorts from Japan and China. GDF5 is a pro-chondrogenic growth factor. The T-allele frequency of the gene was elevated in cases, with an odds ratio (OR) of 1.79, and in vitro functional studies demonstrated that this allele mediated a moderate but significant reduction in the activity of the GDF5 promoter in several cell lines. Our initial objective was to assess whether the SNP was also associated with OA in a broad European population by genotyping the SNP in 2487 cases and 2018 age-matched controls from the UK and Spain. The T-allele was associated with OA (P = 0.03, OR = 1.10) as was carrier status for this allele (P = 0.004, OR = 1.28), demonstrating that the SNP is associated with OA in two diverse ethnic groups, Asians and Europeans. We subsequently assessed the functional effect of the SNP on GDF5 allelic expression using RNA extracted from the cartilage of OA patients who had undergone joint-replacement surgery. The associated T-allele showed up to a 27% reduction in expression relative to the C-allele (P = 0.00007), revealing that the functional effect mediated by SNP rs143383 on GDF5 expression is active in patients who have severe disease up to the point at which they require surgery. A small but persistent imbalance of GDF5 expression throughout life therefore appears to render an individual more susceptible to OA.

Analysis of osteochondro-induction using growth and differentiation factor-5 in rat muscle

Growth and differentiation factor-5 (GDF-5) belongs to the TGF-beta super family, and reportedly plays an important role in cartilage development and differentiation. In this study, we implanted GDF-5 in rat leg muscle, and evaluated its in vivo osteochondro-inducing activity by histological and X-ray examinations. GDF-5 (0, 100, 300, and 500 microg) and the carrier type I collagen were mixed, and the mixture was implanted into rat leg muscle. Three weeks later, the site of implantation was examined by soft X-ray, and examined histologically. The GDF-5 0 and 100 microg groups showed no osteochondro-induction. The GDF-5 300 microg group showed aggregates of cartilage and some bone tissue in the carrier. The GDF-5 500 microg group revealed bone and no cartilage. This is the first report of the dose-dependent effect of GDF-5 inducing osteochondrogenesis or osteogenesis.

The effect of growth differentiation factor-5-coated sutures on tendon repair in a rat model

Tendon ruptures are common injuries that are often treated surgically. Growth Differentiation Factor-5 (GDF-5) has been shown to accelerate tendon healing with varying degrees of success. We used a novel technique to apply recombinant human GDF-5 (rhGDF-5) to suture and hypothesized that controlled, local delivery of rhGDF-5 can be used to enhance tendon repair. Tendons of 92 rats were transected and repaired with sutures. All researchers were blinded to the following treatment groups (24 rats in each group): 0 rhGDF (control), 24 ng/cm rhGDF, 55 ng/cm rhGDF, and 556 ng/cm rhGDF. Rats were euthanized at 3 weeks (n = 48) and at 6 weeks (n = 48). Sutures were coated with rhGDF-5 using a novel dip-coat technique. Enzyme-linked immunosorbent assay confirmed consistent and reproducible delivery of rhGDF-5. Within each group, 8 were tested biomechanically, and 4 were assessed histologically. Histologic grading at 3 weeks showed improved healing in tendons repaired with coated suture versus controls. By 6 weeks, there were no significant differences. At 3 weeks, minimal isolated cartilage formation was observed; 6-week samples showed more extensive presence, typically surrounding suture fibers. At 3 weeks, tendons repaired with rhGDF-5-coated sutures resulted in significantly higher ultimate tensile load and stiffness compared with control sutures (P < .05) At 6 weeks, there were no significant differences in the mechanical properties of repaired tendons. At 3 weeks, rhGDF-5 induced significant tendon hypertrophy that was more pronounced than at 6 weeks. In addition, tendons repaired with rhGDF-5 showed an increased rate of healing versus control repairs at 3 weeks. This study showed that a novel dip-coating technique can be used to deliver growth factors in varying concentrations to local repair sites to accelerate tendon healing.

Developmental failure of the intra-articular ligaments in mice with absence of growth differentiation factor 5

OBJECTIVE

To show the phenotypic characteristics of the knee joints in brachypodism mice (bp mice), which carry a functional null mutation of the growth differentiation factor 5 (GDF5) gene, we investigated the adult and embryonic bp mice.

METHOD

Radiographic and macroscopic examinations of the knee joint of adult bp mice were performed. A histological examination of the knee joint of bp mice from E12.5 to E18.5 was also performed.

RESULTS

Radiographic and macroscopic examinations of the adult bp mice showed anterior dislocation, hypoplastic condyles, and absence of the intra-articular ligaments. Safranin O staining of knee joints of the embryonic bp mice showed severe hypoplasty of the chondroepiphyses and intra-articular ligaments at E16.5. There was no difference in the number and location of 5-bromo-2'-deoxyuridine (BrdU)-positive cells between wild-type and bp mice through E12.5 to E14.5. A terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) study showed excessive cell death of mesenchymal cells of the future knee joint in bp mice at E12.5 and E13.5.

CONCLUSION

bp mice exhibit developmental failure of the condyles and intra-articular ligament of the knee joints.

A functional polymorphism in the 5′ UTR of GDF5 is associated with susceptibility to osteoarthritis

Osteoarthritis (MIM 165720), characterized by degeneration of articular cartilage, is the most common form of human arthritis and a major concern for aging societies worldwide. Epidemiological and genetic studies have shown that osteoarthritis is a polygenic disease. Here, we report that the gene encoding growth differentiation factor 5 (GDF5) is associated with osteoarthritis in Asian populations. A SNP in the 5' UTR of GDF5 (+104T/C; rs143383) showed significant association (P = 1.8 x 10(-13)) with hip osteoarthritis in two independent Japanese populations. This association was replicated for knee osteoarthritis in Japanese (P = 0.0021) and Han Chinese (P = 0.00028) populations. This SNP, located in the GDF5 core promoter, exerts allelic differences on transcriptional activity in chondrogenic cells, with the susceptibility allele showing reduced activity. Our findings implicate GDF5 as a susceptibility gene for osteoarthritis and suggest that decreased GDF5 expression is involved in the pathogenesis of osteoarthritis.

Expression of Dlx5 and Dlx6 during specification of the elbow joint

The onset of elbow joint formation in the developing limb is characterized morphologically by the conversion of differentiated chondrocytes at the site of incipient joint formation into the densely packed flattened cells of the joint interzone. However, experimental studies have indicated that the elbow joint is specified well before joint interzone formation by a distinctive population of precursor cells located at the site in the developing limb bud at which the elbow joint will subsequently form. Here we show that during specification of the elbow joint in the chick limb bud, the homeodomain transcription factors Dlx5 and Dlx6 are highly expressed by a discrete group of cells that encompass the prospective elbow joint. The Dlx5- and Dlx6-expressing cells at the prospective elbow joint are located where the differentiating humerus branches into the radius and ulna. Thus, Dlx5 and Dlx6 are the earliest molecular markers of the presumptive elbow joint yet described. The onset of Dlx5 expression in the region of the presumptive elbow joint is shortly followed by the initiation of expression amongst the Dlx5-expressing cells of Gdf5, which encodes a secreted signaling molecule that is involved in regulating the onset of joint formation. These results suggest that Dlx genes may be involved in specification of the elbow joint and/or in providing positional information that specifies the site at which the elbow joint will form.

Transcription factor ERG and joint and articular cartilage formation during mouse limb and spine skeletogenesis

Articular cartilage and synovial joints are critical for skeletal function, but the mechanisms regulating their development are largely unknown. In previous studies we found that the ets transcription factor ERG and its alternatively-spliced variant C-1-1 have roles in joint formation in chick. Here, we extended our studies to mouse. We found that ERG is also expressed in developing mouse limb joints. To test regulation of ERG expression, beads coated with the joint master regulator protein GDF-5 were implanted close to incipient joints in mouse limb explants; this led to rapid and strong ectopic ERG expression. We cloned and characterized several mammalian ERG variants and expressed a human C-1-1 counterpart (hERG3Delta81) throughout the cartilaginous skeleton of transgenic mice, using Col2a1 gene promoter/enhancer sequences. The skeletal phenotype was severe and neonatal lethal, and the transgenic mice were smaller than wild type littermates and their skeletons were largely cartilaginous. Limb long bone anlagen were entirely composed of chondrocytes actively expressing collagen IX and aggrecan as well as articular markers such as tenascin-C. Typical growth plates were absent and there was very low expression of maturation and hypertrophy markers, including Indian hedgehog, collagen X and MMP-13. The results suggest that ERG is part of molecular mechanisms leading chondrocytes into a permanent developmental path and become joint forming cells, and may do so by acting downstream of GDF-5.

Growth and differentiation factor-5 (GDF-5) stimulates osteogenic differentiation and increases vascular endothelial growth factor (VEGF) levels in fat-derived stromal cells in vitro

Fat-derived adult mesenchymal stem cells can differentiate into different phenotypes reflecting their potential to regenerate various skeletal tissues. These properties together with the association of adipose with skeletal tissues formed the basis of our study to establish an experimental model for using fat-derived stromal cells to undergo osteogenic differentiation in vitro under the influence of either growth and differentiation factor-5 (GDF-5) or bone morphogenetic protein-2 (BMP-2). Members of the BMP/GDF family of proteins are known for their ability to elicit skeletal morphogenesis, but little is known about the mechanism whereby these morphogens exert their effect on the osteogenic differentiation of fat-derived stromal cells. We compared the effects of GDF-5 and BMP-2 in their recombinant forms to qualitatively and quantitatively determine their influence on the osteogenic differentiation of fat derived stromal cells by examining the effects on mineralization, extracellular matrix, cell proliferation, biochemistry, and gene expression. We identified that GDF-5 not only promotes osteogenic differentiation of rat fat-derived stromal cells, but also may promote angiogenic activity of stromal cells by increasing vascular endothelial growth factor (VEGF) gene expression in vitro. These data suggest that several distinct regulatory mechanisms may exist in association with osteogenic differentiation.

Local application of a collagen type I/hyaluronate matrix and growth and differentiation factor 5 influences the closure of osteochondral defects in a minipig model by enchondral ossification

This pilot study evaluated the effect of growth and differentiation factor-5 (rhGDF-5) combined with a collagen type I/hyaluronate matrix (c/h) on osteochondral defect repair in a minipig model. Defects created in both medial femoral condyles of 20 minipigs were treated with c/h (n = 10), c/h + rhGDF-5 (n = 10) or were left empty. After 3 and 12 months, five animals of each group were sacrificed. Evaluation included macroscopic and histological scoring and quantitative histomorphometry of synthesized bone. C/h and c/h + rhGDF-5 treatment increased trabecular bone formation in the upper third of the defect compared to empty controls, showing significance for c/h + rhGDF-5 (p = 0.05) but not between c/h and c/h + rhGDF-5 treatment. Cartilage regeneration and macroscopic outcome were not improved by c/h or c/h + rhGDF-5 treatment. Since c/h remnants were seen even one year postoperatively in the defect, possibly inhibiting further bone and cartilage healing, other matrices in combination with rhGDF-5 may provide further improvement in osteochondral defect treatment.

Potential involvement of BMP receptor type IB activation in a synergistic effect of chondrogenic promotion between rhTGFbeta3 and rhGDF5 or rhBMP7 in human mesenchymal stem cells

Chondrogenic promotion by rhGDF5 with or without rhTGFbeta3 was studied in pellet culture of human mesenchymal stem cells (HMSCs). A synergy between rhGDF5 and rhTGFbeta3 was observed in promoting chondrogenesis. rhBMP2, rhBMP6, rhBMP7 and rhTGFbeta1 were further tested and showed the same effect. To explore the mechanism, the expression of TGFbetatype I and II receptors, ALK5, ALK2, ALK3, ALK6, TGFbetaRII, BMPRII, ActRII was studied. ALK6 showed increase by the rhTGFbeta1 or rhTGFbeta3 treatment. ALK6 protein expression also showed increase by rhTGFbeta3. rhTGFbeta1/rhTGFbeta3 induced ALK6 up-regulation was inhibited by SD-208, a TGFbeta type I receptor inhibitor. Chondrogenesis by rhTGFbetal/rhTGFbeta3 or the combination between rhTGFbetal/rhTGFbeta3 and rhGDF5 also was diminished by SD-208. SMAD1/5/8 phosphorylation in nascent human mesenchymal stem cells (HMSCs) was stimulated weakly by rhGDF5 but strongly by rhBMP7. The rhGDF5 stimulated SMAD1/5/8 phosphorylation was enhanced by rhTGFbetal/rhTGFbeta3 but inhibited by SD-208. The rhBMP7 stimulated SMAD1/5/8 phosphorylation did not show influence by rhTGFbeta3 and SD-208. Our results indicated the potential involvement of ALK6 activation by rhTGFbetas in the synergy between rhTGFbetas and rhBMPs.

Effects of growth differentiation factor-5 on the intervertebral disc--in vitro bovine study and in vivo rabbit disc degeneration model study

STUDY DESIGN

In vitro studies on the effects of recombinant human growth and differentiation factor-5 (rhGDF-5) on matrix metabolism of bovine intervertebral disc cells and an in vivo study on the effect of rhGDF-5 in the rabbit anular puncture model.

OBJECTIVE

To determine the reparative capacity of rhGDF-5 on the intervertebral disc.

SUMMARY OF BACKGROUND DATA

The in vitro and in vivo effects of rhGDF-5, a crucial protein in the developing musculoskeletal system, on repair of the degenerated intervertebral disc remain unidentified.

METHODS

In vitro, bovine nucleus pulposus and anulus fibrosus cells were cultured with or without rhGDF-5 (100 or 200 ng/mL). On days 7, 14, and 21, the contents of deoxyribonucleic acid and proteoglycan, and the synthesis of proteoglycan and collagen were assessed. In vivo, 16 adolescent New Zealand white rabbits received anular punctures in 2 lumbar discs. Four weeks later, phosphate buffered saline or rhGDF-5 (10 ng, 1 and 100 mug) was injected into the nucleus pulposus. The rabbits were followed up for 16 weeks for disc height, magnetic resonance imaging, and histologic grading.

RESULTS

In vitro, rhGDF-5 increased the deoxyribonucleic acid and proteoglycan contents of both cell types significantly after day 14. rhGDF-5 at 200 ng/mL significantly stimulated proteoglycan synthesis (nucleus pulposus: +138%, anulus fibrosus: +24%) and collagen synthesis (nucleus pulposus: +95%, anulus fibrosus: +23%) at day 21. In vivo, the injection of rhGDF-5 resulted in a restoration of disc height, improvement of magnetic resonance imaging scores, and histologic grading scores with statistical significance (P < 0.05-0.001).

CONCLUSION

A single injection of rhGDF-5 has a reparative capacity on intervertebral discs, presumably based on its effects to enhance extracellular matrix production in vitro.

Role of canonical Wnt-signalling in joint formation

The individual elements of the vertebrate skeleton are separated by three different types of joints, fibrous, cartilaginous and synovial joints. Synovial joint formation in the limbs is coupled to the formation of the prechondrogenic condensations, which precede the formation of the joint interzone. We are beginning to understand the signals involved in the formation of prechondrogenic condensations and the subsequent differentiation of cells within the condensations into chondrocytes. However, relatively little is known about the molecules and molecular pathways involved in induction of the early joint interzone and the subsequent formation of the synovial joints. Based on gain-of function studies Wnt-signalling, in particular the canonical pathway, has been implicated in the joint induction process. Here we provide genetic evidence from loss-of function analysis of embryos lacking either the central player of the canonical Wnt-pathway, beta-catenin, in the limb mesenchyme or the two ligands, Wnt9a and Wnt4, demonstrating that canonical Wnt-signalling plays an important role in suppressing the chondrogenic potential of cells in the joint thereby actively allowing joint formation. Furthermore our data show that the beta-catenin activity is not essential for the induction of molecular markers expressed in the joint interzone. Thus, suggesting that canonical Wnt-signalling is not required for the induction, but for the subsequent maintenance of the fate of the joint interzone cells.

Osteogenic differentiation of adipose-derived stromal cells treated with GDF-5 cultured on a novel three-dimensional sintered microsphere matrix

BACKGROUND CONTEXT

It is well known that under the proper conditions multipotential bone marrow stromal cells are capable of osteogenic differentiation. Recently studies have demonstrated that an analogous subpopulation of cells exist within adipose tissue. Although early studies characterizing these adipose-derived stromal (ADS) cells in culture exist, investigations exploring the characteristics and viability of these cells cultured on a three-dimensional sintered microsphere matrix are absent.

PURPOSE

To characterize and investigate the viability of ADS cells cultured on bioengineered three-dimensional sintered microsphere matrices (SMM).

STUDY DESIGN

Basic science, laboratory study.

PATIENT SAMPLE

Sixty SMM total. Six underwent examination by scanning electron microscopy, 18 for cellular viability, 18 for biochemical assay, and 18 for evaluation by gene expression.

OUTCOME MEASURES

The SMM were examined under scanning electron microscopy to evaluate for adherence, migration, and proliferation at 7, 14, and 28 days. Cellular viability was assessed using colorimetric assay for mitochondrial dehydrogenases activity in viable cells (MTS [3-(4,5-dimethylthiazol-2-yl)5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay) at each corresponding time point. Osteoblastic differentiation was determined using biochemical assays for alkaline phosphatase activity and gene expression for alkaline phosphatase (ALP), osteocalcin (OC), and core binding factor alpha-1 (Cbfa1).

METHODS

Multipotential ADS cells from adult Sprague Dawley rats were isolated and maintained in media. Sintered microsphere matrices of poly(lactide-co-glycolide) [85:15] were prepared using solvent evaporation technique followed by mechanical sieving and fabricated by heating in metal molds. ADS cells were then seeded on the SMM and cultured in media with growth and differentiation factor-5 (GDF-5). Treated samples and controls were evaluated at 7, 14, and 28 days. Statistical significance was set at p<.05.

RESULTS

Multipotential ADS cells were capable of being isolated from adipose tissue. Scanning electron microscopy evaluation revealed cells adherent to the scaffold surface in a monolayer by 7 days. Cytoplasmic extensions were seen linking the cells on adjacent microspheres. Migration and proliferation resulting in extension of the cellular elements into the scaffold was apparent by 14 days. MTS confirmed cell viability within the scaffold throughout the 28-day study. Osteoblastic differentiation was confirmed using biochemical assays for alkaline phosphatase activity and gene expression for ALP, OC, and Cbfa1.

CONCLUSIONS

This is the first study to investigate the fate of ADS seeded on a three-dimensional sintered microsphere matrix. The results of this study confirm that ADS cells, when treated with GDF-5, are not only capable of adhering to the bioengineered scaffold, but also remain viable and demonstrated the ability to migrate, proliferate, and subsequently undergo osteogenic differentiation under the conditions described. These early findings support the concept that ADS cells cultured on a SMM may serve as a viable alternative to more traditional methods of bone graft materials.

A novel mutation in GDF5 causes autosomal dominant symphalangism in two Chinese families

Proximal symphalangism (SYM1) is an autosomal dominant disorder characterized by ankylosis of the proximal interphalangeal joints and fusion of carpal and tarsal bones. We identified and characterized two five-generation Chinese families with SYM1. The two families share some similarities (e.g., osseous fusion of interphalangeal joints of the 2-4 fingers) with SYM1 families with mutations in the NOG gene or the family with mutation R438L recently reported in the GDF5 gene (encoding a bone morphogenetic protein family member). However, they show some unique features including the absence of cuboid bone, the lack of shortness of the first and fifth metacarpal bones, and manifestation of flat feet. Genome-wide linkage analysis of the two families mapped the disease gene to marker D20S112 with a combined LOD score of 4.32. Mutational analysis revealed a novel E491K mutation in the GDF5 gene in both families. The mutation occurs at a highly conserved residue in the TGF-beta domain of GDF5 and represents the second GDF5 mutation identified for SYM1 to date. The E491K mutation co-segregated with the affected individuals in the two families, and did not exist in unaffected family members or 200 normal controls. These results indicate that defects in GDF5 can cause SYM1 in the Chinese population, and expand the spectrum of clinical phenotypes associated with mutant GDF5.

Establishment of immortalized dental follicle cells for generating periodontal ligament in vivo

The dental follicle is a mesenchymal tissue that surrounds the developing tooth germ. During tooth root formation, periodontal components, viz., cementum, periodontal ligament (PDL), and alveolar bone, are created by dental follicle progenitors. Here, we report the presence of PDL progenitors in mouse dental follicle (MDF) cells. MDF cells were obtained from mouse incisor tooth germs and immortalized by the expression of a mutant human papilloma virus type 16 E6 gene lacking the PDZ-domain-binding motif. MDF cells expressing the mutant E6 gene (MDF( E6-EGFP ) cells) had an extended life span, beyond 150 population doublings (PD). In contrast, normal MDF cells failed to proliferate beyond 10 PD. MDF( E6-EGFP ) cells expressed tendon/ligament phenotype-related genes such as Scleraxis (Scx), growth and differentiation factor-5, EphA4, Six-1, and type I collagen. In addition, the expression of periostin was observed. To elucidate the differentiation capacity of MDF( E6-EGFP ) cells in vivo, the cells were transplanted into severe combined immunodeficiency mice. At 4 weeks, MDF( E6-EGFP ) cell transplants had the capacity to generate a PDL-like tissue that expressed periostin, Scx, and type XII collagen and the fibrillar assembly of type I collagen. Our findings suggest that MDF( E6-EGFP ) cells can act as PDL progenitors, and that these cells may be a useful research tool for studying PDL formation and for developing regeneration therapies.

Expression of bone morphogenetic proteins in human lung carcinomas

BACKGROUND

The bone morphogenetic proteins (BMP) are phytogenetically conserved proteins, which are essential for embryonic development. Bone morphogenetic protein-2 (BMP-2) was recently shown to be expressed in a small sample of lung carcinomas. Studies have suggested that BMP-2 may enhance tumor growth. The present study examined which BMP family members are expressed in non-small cell lung carcinomas (NSCLC). Furthermore, the frequency of BMP-2 overexpression and the types of lung carcinomas expressing BMP-2 were determined.

METHODS

Tissue samples were obtained from the operating room and frozen in liquid nitrogen. Samples included metastatic NSCLC, benign lung tumors, adenocarcinoma, squamous cell carcinoma, bronchioloalveolar, and neuroendocrine carcinomas. Paired normal lung tissues served as the controls. The BMP-2, BMP-4, BMP-6, BMP-7, and growth differentiation factor 5 (GDF-5) expressions were examined by Western blot analysis.

RESULTS

The BMP-4, BMP-6, BMP-7, and GDF-5 were infrequently expressed in NSCLC. The BMP-2 was expressed in 41 of 42 NSCLC with minimal expression in normal lung tissue; BMP-2 was expressed 17 fold higher than that of normal lung tissue. The BMP-2 was over-expressed in all subtypes of NSCLC, including neuroendocrine carcinomas. The BMP-2 expression was similar between squamous cell carcinomas and adenocarcinomas; however, bronchioloalveolar carcinomas tended to have a lower level of expression. The BMP-2 was not significantly expressed in benign lung tumors.

CONCLUSIONS

Bone morphogenetic protein-2 is the predominant family member expressed in NSCLC. The BMP-2 is overexpressed in the majority of human lung carcinomas independent of cell type.

Healos/recombinant human growth and differentiation factor-5 induces posterolateral lumbar fusion in a New Zealand white rabbit model

STUDY DESIGN

Posterolateral lumbar spine fusions in New Zealand white rabbits.

OBJECTIVE

To evaluate the efficacy of recombinant human growth and differentiation factor-5 (rhGDF-5) lyophilized to a Healos carrier (cross-linked type I collagen with hydroxyapatite coating; DePuy Spine, Inc., Raynham, MA) in inducing fusion.

SUMMARY OF BACKGROUND DATA

Bone graft substitutes have become an area of considerable interest. rhGDF-5 is one such product. Limited lumbar preclinical studies have been performed with this product.

METHODS

Single-level, intertransverse process fusions were performed in 67 rabbits using iliac crest autograft (n = 13), Healos alone (n = 13), or 0.5, 1.0, or 1.5 mg/cc rhGDF-5 lyophilized to Healos (n = 13 per group). At 8 weeks, the rabbits were euthanized. Fusion masses were assessed.

RESULTS

There were 2 animals (3%) lost to complication. Manual palpation revealed fusion rates for autograft of 38% (5/13), Healos alone of 0% (0/13), and each of the Healos/rhGDF-5 groups of 100% (13/13). Histologic analyses were 95% sensitive and 95% specific for confirming fusion. Histologic differences were found among the treatment groups.

CONCLUSIONS

In this rabbit fusion model, Healos/rhGDF-5 induced fusion in 100% of the rabbits studied. This rate was significantly higher than the fusion rate induced by autograft (38%). Overall, these results support continued research of Healos/rhGDF-5 as a potential bone graft alternative.

Superior Effect of MD05, Beta-Tricalcium Phosphate Coated With Recombinant Human Growth/Differentiation Factor-5, Compared to Conventional Bone Substitutes in the Rat Calvarial Defect Model

BACKGROUND

MD05 consists of beta-tricalcium phosphate (beta-TCP) coated with recombinant human growth/differentiation factor-5 (rhGDF-5) and is under evaluation as an osteoinductive and osteoconductive bone graft material for use in dental and maxillofacial applications. The objective of this study was to compare the bone regenerative properties of MD05 with those of conventional commercially available bone substitutes.

METHODS

Full-thickness, 6-mm diameter, calvarial critical-size defects (two per animal) were created in adult Sprague-Dawley rats. Groups of rats were implanted with the following: 1) MD05; 2) bovine bone mineral; 3) bovine bone mineral with collagen; 4) bovine bone mineral with synthetic peptide, 5) beta-TCP (from two different manufacturers); or 6) no filling material (sham controls). Blinded macroscopic analysis, histopathologic analysis, and histomorphometric analysis were carried out 6 weeks after implantation.

RESULTS

New bone formation assessed histomorphometrically was about five times greater with MD05 than with the other bone substitutes tested, and bone repair was well advanced in MD05-filled defects after 6 weeks. The extent of fibrous tissue and residual implant were significantly lower in the MD05 group. In contrast to the other materials, the use of MD05 was associated with the complete osseous bridging of the defect and with the presence of normal bone marrow. The osteoinductive effect of rhGDF-5 was apparent from the more pronounced bone ingrowth observed with MD05 compared to the beta-TCP carrier alone. All implants showed good biocompatibility.

CONCLUSION

MD05 achieved superior bone regeneration compared to conventional materials and is a promising new bone substitute for dental and maxillofacial applications.

CDMP1/GDF5 Has Specific Processing Requirements That Restrict Its Action to Joint Surfaces

CDMP1/GDF5 has not demonstrated biological activity in Xenopus embryos when overexpressed by mRNA injection. We provide biological and biochemical evidence that to become active, the protein requires cleavage by two distinct proteolytic enzymes. We demonstrate a specific overlap in the expression patterns of CDMP1/GDF5 with the proteases required to release the mature peptide at the location of the future articular surface but not in the future joint space. Taken together, these observations provide a plausible mechanism for local action of CDMP1/GDF5 consistent with requirements imposed by current models of pattern formation in the developing limb.

Advances in osteobiologics in spine surgery

In spine surgery, fixation devices that revolutionized spinal fusion are becoming mature technologies, and new tools derived from biologics are becoming more important in clinical practice. Thus, surgeons need to become more sophisticated in evaluating and using these new biologics, which are rapidly entering the market. The majority of these biologics are aimed at enhancing spinal fusion and can be called osteobiologics. Osteobiologic products vary from recombinant proteins to specially prepared allograft or autograft materials. Their financial costs are considerable, and the level of proof for the efficacy and safety of these products varies widely. In this article, I delineate useful principles that can be used to evaluate current and future generations of osteobiologic products, and I discuss the most pertinent examples of specific osteobiologics.

The role of growth/differentiation factor 5 (GDF5) in the induction and survival of midbrain dopaminergic neurones: relevance to Parkinson's disease treatment

Growth/differentiation factor-5 (GDF5) is a member of the transforming growth factor-beta superfamily which has potent effects on dopaminergic neurones in vitro and in vivo. GDF5 is under investigation as a potential therapeutic agent for Parkinson's disease (PD), which is caused by the progressive degeneration of dopaminergic neurones projecting from the substantia nigra (SN) to the striatum. In the rat ventral mesencephalon (VM; the developing SN), GDF5 expression peaks at embryonic day 14, the time at which dopaminergic neurones undergo terminal differentiation. Addition of GDF5 protein to cultures of embryonic rat VM increases the survival and improves the morphology of dopaminergic neurones in these cultures. GDF5 treatment also increases the number of cells which adopt a dopaminergic phenotype in cultures of VM progenitor cells. Intracerebral administration of GDF5 has potent neuroprotective and restorative effects on the nigrostriatal pathway in animal models of PD. Furthermore, addition of GDF5 protein to embryonic rat dopaminergic neuronal transplants improves their survival and function in a rat model of PD. Thus, GDF5 has potential applications to PD therapy as a dopaminergic neuroprotective agent and as a factor that may induce a dopaminergic neuronal fate in unrestricted progenitor cells.

A homozygous BMPR1B mutation causes a new subtype of acromesomelic chondrodysplasia with genital anomalies

We present a patient with acromesomelic chondrodysplasia and genital anomalies caused by a novel homozygous mutation in BMPR1B, the gene coding for bone morphogenetic protein receptor 1B. The 16 year old girl, the offspring of a multiconsanguinous family, showed a severe form of limb malformation consisting of aplasia of the fibula, severe brachydactyly, ulnar deviation of the hands, and fusion of carpal/tarsal bones. In addition, she presented with hypoplasia of the uterus and ovarian dysfunction resulting in hypergonadotrophic hypogonadism. Mutation analysis of BMPR1B revealed a homozygous 8 bp deletion (del359-366). This mutation is expected to result in a loss of function and is thus different from the heterozygous missense mutations in BMPR1B recently shown to cause brachydactyly type A2 through a dominant negative effect. The patient's skeletal phenotype shows an overlap with the clinical spectrum of the acromesomelic chondrodysplasias of the Grebe, Hunter-Thompson, and DuPan types caused by homozygous mutations in the gene coding for growth differentiation factor 5 (GDF5) which is a high-affinity ligand to BMPR1B. However, the phenotype described here differs from GDF5 associated chondrodysplasias because of the additional presence of genital anomalies and the distinct limb phenotype.

Forced chondrocyte expression of sonic hedgehog impairs joint formation affecting proliferation and apoptosis

Proliferation and apoptosis are two fundamental processes that occur during limb development, and in particular in joint formation. To study the role of hedgehog proteins in limbs, we have misexpressed Sonic Hedgehog specifically in chondrocytes. We found that the appendicular skeleton was severely misshapen while pelvic and shoulder girdles developed normally. In particular, we detected fusion of the elbow/knee joint, no definite carpal/tarsal, metacarpal/metatarsal bones and absence of distinct phalanges, fused in a continuous cartilaginous rod. Molecular markers of joints, such as Gdf5 and sFrp2 were absent at presumptive joint sites and Tenascin C, a molecule associated with joint formation and expressed in permanent cartilage, was expressed in a wider region in transgenic animals as compared to the wild type. The ratio of proliferating to non-proliferating chondrocytes was about two times higher in transgenic developing cartilage as compared to the wild type. Accordingly, the proapoptotic gene Bax was barely detectable in the growth plate of transgenic mice and Tunel assay showed the absence of apoptosis in presumptive joints at E15.5. Taken together, these results suggest that misexpression of Sonic Hedgehog causes apoptosis and proliferation defects leading to the lack of joint cavity and fusion of selected limb skeletal elements.

Upregulation of ID protein by growth and differentiation factor 5 (GDF5) through a smad-dependent and MAPK-independent pathway in HUVSMC

GDF5 (growth and differentiation factor five), a member of the TGF-beta superfamily, binds specifically to BMPR1b, BMPR2 and ACTR2a receptors forming a heterodimeric complex, thereby inducing phosphorylation of smad1, 5, 8 and translocation to the nucleus. ID1 (inhibitor of differentiation or DNA binding) is essential for G1 to S phase transition inhibiting DNA binding thereby playing an important role in the control of differentiation, proliferation and angiogenesis. The objective of this study was, therefore, to characterize the signal transduction pathway of GDF5, especially the involvement of ID1, in human umbilical vein smooth muscle cells (HUVSMC). We observed the expression of BMPR1a, BMPR1b, BMPR2, ACTR2a, smad1, smad 5, ID1, ID2 and ID3 in HUVSMC. Application of GDF5 upregulated ID1 and ID3 expression by involvement of the smad signaling pathway. GDF5 caused phorsphorylation of smad1 followed by upregulation of ID1 and ID3. Co-incubation with anti-GDF5 prevented these effects. GDF5 significantly inhibited phosphorylation of p38 MAPK and induced phosphorylation of ERK. The specific inhibitor of p38 MAPK or ERK, SB203580 or U0126 did not induce ID protein expression. Smad1 siRNA transfection inhibited the upregulation of ID protein. GDF5 had chemotactic activity in HUVSMC; this effect was partly blocked by transfection of smad1 or ID1 siRNA. Our results indicate that GDF5 induces ID1 and ID3 in HUVSMC by a smad-dependent, MAPK-independent pathway. GDF5 binds to specific receptors, thereby inducing phosphorylation and translocation of smad1 to the nucleus where it is involved in the regulation of transcription. Since ID1 has been shown to be crucial for cell cycle control, we propose that GDF5 could be involved in the process of angiogenesis.

Monomeric and dimeric GDF-5 show equal type I receptor binding and oligomerization capability and have the same biological activity

Growth and differentiation factor 5 (GDF-5) is a homodimeric protein stabilized by a single disulfide bridge between cysteine 465 in the respective monomers, as well as by three intramolecular cysteine bridges within each subunit. A mature recombinant human GDF-5 variant with cysteine 465 replaced by alanine (rhGDF-5 C465A) was expressed in E. coli, purified to homogeneity, and chemically renatured. Biochemical analysis showed that this procedure eliminated the sole interchain disulfide bond. Surprisingly, the monomeric variant of rhGDF-5 is as potent in vitro as the dimeric form. This could be confirmed by alkaline phosphatase assays and Smad reporter gene activation. Furthermore, dimeric and monomeric rhGDF-5 show comparable binding to their specific type I receptor, BRIb. Studies on living cells showed that both the dimeric and monomeric rhGDF-5 induce homomeric BRIb and heteromeric BRIb/BRII oligomers. Our results suggest that rhGDF-5 C465A has the same biological activity as rhGDF-5 with respect to binding to, oligomerization of and signaling through the BMP receptor type Ib.

The effect of intracavernosal growth differentiation factor-5 therapy in a rat model of cavernosal nerve injury

OBJECTIVE

To determine whether the intracavernosal application of growth differentiation factor-5 (GDF-5) influences nerve regeneration and erectile function after cavernosal nerve injury in a rat model.

MATERIALS AND METHODS

Thirty-two male Sprague-Dawley rats were randomly divided into four equal groups: eight had a sham operation (uninjured controls), while 24 had bilateral cavernosal nerve crush. The crush-injury groups were treated at the time of injury with an impregnated collagen sponge implanted into the right corpus cavernosum. The sponge contained no GDF-5 (injured controls), 2 microg (low concentration), or 20 microg GDF-5 (high concentration). Erectile function was assessed by cavernosal nerve electrostimulation at 8 weeks. Midshaft penile tissue samples were histochemically evaluated for neuronal nitric oxide synthase (nNOS)-containing fibres in the dorsal penile nerve.

RESULTS

There was no erectile dysfunction in the uninjured control group, as shown by a mean (sem) maximal increase in intracavernosal pressure (ICP) of 149.5 (17.0) cmH(2)O on stimulation. By comparison, the ICP decreased in the injured control group, by 21.3 (6.7) cmH(2)O. After cavernosal nerve injury, the recovery of erectile function was greatest in the low-concentration GDF-5 group; the maximum ICP increase was 40.8 (13.3) cmH(2)O, vs 24.3 (5.9) cmH(2)O for 20 microg GDF-5. Histologically, the low-concentration group had significantly more nNOS-containing nerve fibres, at 163 (24.7), than the high-concentration group, at 76 (17.3), or injured controls, at 67 (23.8). By contrast, the uninjured controls had a mean of 538 (40.6) nerve fibres in the dorsal nerve.

CONCLUSION

Bilateral cavernosal nerve crush resulted in erectile dysfunction with accompanying neurological changes in the rat. The intracavernosal application of GDF-5 enhanced the recovery of erectile function and n-NOS nerve preservation, with a 2-microg dose giving the most promising results.

Asymmetric expression of the BMP antagonists chordin and gremlin in the sea anemone Nematostella vectensis: implications for the evolution of axial patterning

The evolutionary origin of the anterior-posterior and the dorsoventral body axes of Bilateria is a long-standing question. It is unclear how the main body axis of Cnidaria, the sister group to the Bilateria, is related to the two body axes of Bilateria. The conserved antagonism between two secreted factors, BMP2/4 (Dpp in Drosophila) and its antagonist Chordin (Short gastrulation in Drosophila) is a crucial component in the establishment of the dorsoventral body axis of Bilateria and could therefore provide important insight into the evolutionary origin of bilaterian axes. Here, we cloned and characterized two BMP ligands, dpp and GDF5-like as well as two secreted antagonists, chordin and gremlin, from the basal cnidarian Nematostella vectensis. Injection experiments in zebrafish show that the ventralizing activity of NvDpp mRNA is counteracted by NvGremlin and NvChordin, suggesting that Gremlin and Chordin proteins can function as endogenous antagonists of NvDpp. Expression analysis during embryonic and larval development of Nematostella reveals asymmetric expression of all four genes along both the oral-aboral body axis and along an axis perpendicular to this one, the directive axis. Unexpectedly, NvDpp and NvChordin show complex and overlapping expression on the same side of the embryo, whereas NvGDF5-like and NvGremlin are both expressed on the opposite side. Yet, the two pairs of ligands and antagonists only partially overlap, suggesting complex gradients of BMP activity along the directive axis but also along the oral-aboral axis. We conclude that a molecular interaction between BMP-like molecules and their secreted antagonists was already employed in the common ancestor of Cnidaria and Bilateria to create axial asymmetries, but that there is no simple relationship between the oral-aboral body axis of Nematostella and one particular body axis of Bilateria.

Differential regulation of GDF-5 and FGF-2/4 by immobilisation in ovo exposes distinct roles in joint formation

Members of the fibroblast growth factor (FGF) family and growth and differentiation factor 5 (GDF-5) have been implicated in joint specification, but their roles in subsequent cavity formation are not defined. Cavity formation (cavitation) depends upon limb movement in embryonic chicks and factors involved in joint formation are often identified by their expression at the joint-line. We have sought support for the roles of FGF-2, FGF-4, and GDF-5 in cavitation by defining expression patterns, immunohistochemically, during joint formation and establishing whether these are modified by in ovo immobilisation. We found that FGF-2 exhibited low level nuclear expression in chondrocytes and fibrocartilage cells close to presumptive joints, but showed significantly higher expression levels in cells at, and directly bordering, the forming joint cavity. This high-level joint line FGF-2 expression was selectively diminished in immobilised limbs. In contrast, we show that FGF-4 does not exhibit differential joint-line expression and was unaffected by immobilisation. GDF-5 protein also failed to show joint-line selective labelling, and although immobilisation induced a cartilaginous fusion across presumptive joints, it did not affect cellular GDF-5 expression patterns. Examining changes in GDF-5 expression in response to a direct mechanical strain stimulus in primary embryonic chick articular surface (AS) cells in vitro discloses only small mechanically-induced reductions in GDF-5 expression, suggesting that GDF-5 does not exert a direct positive contribution to the mechano-dependent joint cavitation process. This notion was supported by retroviral overexpression of UDPGD, a characteristic factor involved in hyaluronan (HA) accumulation at presumptive joint lines, which was also found to produce small decreases in AS cell GDF-5 expression. These findings support a direct mechano-dependent role for FGF-2, but not FGF-4, in the cavitation process and indicate that GDF-5 is likely to influence chondrogenesis positively without contributing directly to joint cavity formation.

The influence of surface coatings of dicalcium phosphate (DCPD) and growth and differentiation factor-5 (GDF-5) on the stability of titanium implants in vivo

Mechanical stability of implants is usually tested by pull out or push out tests which destroy the interface between the implant and bone. Pull out tests do not ideally reflect the clinical situation. In contrast, applying submaximal load leads to more physiologic micro-displacement between implant and bone. The aim of this study was to evaluate a new non-destructive mechanical testing device on different modifications of titanium implants. In 18 rabbits we investigated the influence of a dicalcium phosphate (DCPD) coating, or of a growth and differentiation factor-5 (GDF-5) coating, or a combination of both on the stability of titanium implants. The stability of implant was assessed by a non-destructive micro-measurement. In the same specimens the interface was investigated by micro-CT and histological evaluation. Surface modifications had a positive effect on the implant stability regarding displacement (p=0.001). Mechanical stability correlated with the quality of peri-implant tissue. Micro-displacement correlated negatively with the bone formation around the implants in histomorphometric evaluation (p=0.02). Amount of peri-prosthetic soft tissue showed a positive correlation with micro-displacement (p=0.01). Our findings indicate the positive effect of DCPD and GDF-5 coatings on stability of titanium implants. Results demonstrate the non-destructive testing to be an effective method to evaluate mechanical stability of implants.

Recombinant human growth/differentiation factor-5 (rhGDF-5) induced bone formation in murine calvariae

OBJECTIVES

Growth/differentiation factor-5 (GDF-5), a member of the transforming growth factor-beta superfamily, shows a close structural relationship to bone morphogenetic proteins and plays crucial roles in skeletal morphogenesis. Recombinant human (rh) GDF-5 was reported as a suitable factor for enhancing healing in bone defect and inducing ectopic bone formation. The purpose of the present study was to investigate the mechanism of bone formation induced by rhGDF-5 in murine calvariae by radiological, histological and immunohistochemical methods. Cell proliferation was also examined in vitro.

MATERIAL AND METHODS

Cells including primary osteoblasts, periosteum cells and connective tissue fibroblasts were isolated enzymatically from neonatal murine calvariae or head skin. In the presence or absence of rhGDF-5, cell proliferation was estimated by tetrazolium reduction assay. To examine the mechanism of osteoinduction, rhGDF-5/atelocollagen (AC) composite or 0.01 N HCl/AC composite were injected into murine calvariae subcutaneously. Tissue was examined radiologically, histologically and immunohistochemically.

RESULTS

In the presence of rhGDF-5, proliferation of primary osteoblasts, periosteum cells, and connective tissue fibroblasts was increased significantly in culture. Immunohistochemical observations showed cells at the site injected with rhGDF-5/AC displayed immunoreactivity for proliferating cell nuclear antigen (PCNA). Newly formed bone- and cartilage-like tissue contained chondrocyte osteocyte and osteoclastic cells, and were immunoreactive for both type I and II collagen.

CONCLUSION

Exposure to GDF-5 promotes proliferation and differentiation of calvarial cells, which give rise to ectopic bone formation.

GDF5 is a second locus for multiple-synostosis syndrome

Multiple-synostosis syndrome is an autosomal dominant disorder characterized by progressive symphalangism, carpal/tarsal fusions, deafness, and mild facial dysmorphism. Heterozygosity for functional null mutations in the NOGGIN gene has been shown to be responsible for the disorder. However, in a cohort of six probands with multiple-synostosis syndrome, only one was found to be heterozygous for a NOGGIN mutation (W205X). Linkage studies involving the four-generation family of one of the mutation-negative patients excluded the NOGGIN locus, providing genetic evidence of locus heterogeneity. In this family, polymorphic markers flanking the GDF5 locus were found to cosegregate with the disease, and sequence analysis demonstrated that affected individuals in the family were heterozygous for a novel missense mutation that predicts an R438L substitution in the GDF5 protein. Unlike mutations that lead to haploinsufficiency for GDF5 and produce brachydactyly C, the protein encoded by the multiple-synostosis-syndrome allele was secreted as a mature GDF5 dimer. These data establish locus heterogeneity in multiple-synostosis syndrome and demonstrate that the disorder can result from mutations in either the NOGGIN or the GDF5 gene.

Du Pan syndrome phenotype caused by heterozygous pathogenic mutations in CDMP1 gene

Du Pan syndrome is a rare acromesomelic dysplasia with characteristic clinical and radiographic findings. It is inherited as an autosomal recessive trait. Almost all the patients reported have been from Muslim countries. We report on a female and her child with Du Pan syndrome from a Caucasian, Polish family. Three new heterozygous mutations clustered on one allele of the CDMP1 gene were identified in the affected individuals resulting in the first familial case with dominant Du Pan syndrome. A possible synergistic effect of the cis-acting mutations located in the active domain of the mature CDMP1 protein is likely to be responsible for the clinical expression of the disorder.

Combination of engineered neural cell adhesion molecules and GDF-5 for improved neurite extension in nerve guide concepts

Current therapeutical approaches for the treatment of severe lesions in the peripheral nervous system rely on the use of autologous tissue or the body's own Schwann cells. However, these approaches are limited and alternative strategies for peripheral nerve regeneration are required. Here we evaluate combinations of a variety of neuronal regeneration factors including engineered cell adhesion molecules and growth factors in embryonic model neurons to test the possible improvement of artificial nerve guides by cooperative mechanisms. Cell adhesion molecules L1 and neurofascin synergistically promote neurite elongation. The outgrowth promoting properties of both proteins can be combined and further increased within one chimeric protein. Addition of growth and differentiation factor 5 (GDF-5) further enhances neurite outgrowth in a substrate-independent manner. This effect is not due to a protective mode of action of GDF-5 against pro-apoptotic stimuli. Consequently, the study supports the idea that different modes of action of pro-regenerative factors may contribute synergistically to neurite outgrowth and emphasizes the applicability of combinations of proteins specifically involved in development of the nervous system for therapeutical approaches.

Involvement of Notch signaling in initiation of prechondrogenic condensation and nodule formation in limb bud micromass cultures

Notch signaling is an evolutionarily conserved mechanism that plays a critical role in the determination of multiple cellular differentiation pathways and morphogenesis during embryogenesis. The limb bud high-density culture is an established model that recapitulates mesenchymal condensation and chondrocyte differentiation. Reverse transcription-polymerase chain reaction (RT-PCR) showed that Notch and its related genes were expressed in such cultures on day 1 and reached a peak between day 3 and day 5, when cell condensation and nodule formation were initiated. Immunohistochemical experiments revealed that the expression of Notch1 was initially localized within the nodules and shifted to their peripheral region as the cell differentiation progressed. We disrupted Notch signaling by using a gamma-secretase inhibitor, N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT), to analyze the function of Notch signaling in the culture system. The blocking of Notch signaling by DAPT apparently promoted the initiation of prechondrogenic condensation and fusion of the nodules, and such an effect was reversed by exogenous expression of the Notch cytoplasmic domain. DAPT treatment also induced chondrogenic markers and bone morphogenetic protein (BMP)-related molecules, including type II collagen, Sox9, GDF5, and Id1. These observations imply that the Notch signal may have an important role in chondrogenic differentiation by negatively regulating the initiation of prechondrogenic condensation and nodule formation.

Effect of GDF-5 on ligament healing

The effects of growth and differentiation factor-5 (GDF-5) on ligament healing were studied using a gap injury model of the medial collateral ligament in rat knee joints. The administration of GDF-5 once at the time of surgery significantly improved the mechanical properties of the femur-ligament-tibia complex. At 3 weeks after surgery, 30 microg of GDF-5 improved the ultimate tensile strength of the complex by 41%, and the stiffness by 60%, compared with the vehicle control (p < 0.05 for both; Fisher's PLSD test). The observation with a transmission electron microscopy revealed that GDF-5 increased the diameter of collagen fibrils in the repair tissue, which was considered to be a possible mechanism for the positive result in the biomechanical testing. Quantitative PCR and in situ hybridization revealed enhanced type I procollagen expression by GDF-5, and the PCR analysis also revealed that the GDF-5 treatment reduced the expression of type III procollagen relative to type I procollagen. The PCR analysis further showed that the expression of decorin and fibromodulin was relatively reduced against type I procollagen by the growth factor, which was considered to be responsible for the increase of collagen fibril diameter in the repair tissue. No adverse effects were observed, and the use of GDF-5 was considered a promising approach to facilitate ligament healing.

Identification of Mutation in the Growth Differentiation Factor 5 (Gdf5) Gene in NC-brp/brp Mice

A brachypodism (brp) mutation arose spontaneously in the inbred NC mouse strain, producing a phenotype similar to that caused by bp mutation; therefore, it is strongly suggested that brp and bp are allelic. A series of bp mutations are due to defects in the growth differentiation factor 5 (Gdf5) gene. Nucleotide sequence analysis on the Gdf5 gene in NC-brp/brp mice revealed that an irregular insertion of a unit ;GGCAGCC' in exon 2 caused a frame shift leading to a premature stop codon. In addition to the known physiologic roles of brp, I found that brp significantly reduced the litter size. The brp is a novel mutant allele at the Gdf5 gene locus; I would like to name this allele Gdf5(brp).

Recombinant growth/differentiation factor-5 stimulates osteogenic differentiation of fat-derived stromal cells in vitro

Fat-derived stromal cells can differentiate into various skeletal tissues. Currently the mechanism that determines whether stromal cells differentiate into osteoblasts is unclear and the role of growth/differentiation factor (GDF)-5 in differentiation of fat-derived stromal cells is not fully understood. It appears that the differentiation of stromal cells is greatly enhanced by GDF-5 that plays a role in a variety of musculoskeletal processes such as joint formation, tendon maintenance, and bone formation. Our study showed that GDF-5 promotes the differentiation of rat fat-derived stromal cells into osteogenic lineages in vitro. Furthermore, these findings were confirmed by histology, biochemical assay for alkaline phosphatase activity, and analysis of gene expression. The ability to preferentially stimulate fat-derived stromal cells down the osteogenic pathway holds significance in a variety of clinical scenarios.