Effects of growth/differentiation factor 5 on the survival and morphology of embryonic rat midbrain dopaminergic neurones in vitro

Growth/differentiation factor 5 (GDF5) is a member of the transforming growth factor-beta superfamily that is expressed in the developing CNS, including the ventral mesencephalon (VM). GDF5 has been shown to increase the survival of dopaminergic neurones in animal models of Parkinson's disease. This study was aimed at characterising the effects of GDF5 on dopaminergic neurones in vitro. Treatment with GDF5 induced a three-fold increase in the number of dopaminergic neurones in embryonic day 14 rat VM cultures after six days in vitro. A significant increase was also observed in the numbers of astrocytes in GDF5-treated cultures. GDF5 treatment also had significant effects on the morphology of dopaminergic neurones in these cultures; total neurite length, number of branch points and somal area were all significantly increased after six days in vitro. Analysis of neurite length and numbers of branch points at each level of the neuritic field revealed that the most pronounced effects of GDF5 were on the secondary and tertiary levels of the neuritic field. The specific type I receptor for GDF5, bone morphogenetic protein receptor (BMPR)-Ib, was found to be strongly expressed in freshly-dissected E14 VM tissue, but its expression was lost with increasing time in culture. Accordingly, treatment with GDF5 for 24 h from the time of plating induced increases in the numbers of dopaminergic neurones, while treatment with GDF5 for 24 h after six days in vitro did not. This study shows that GDF5 can promote both the survival and morphological differentiation of VM dopaminergic neurones in vitro, lending support to its potential as a candidate dopaminergic neurotrophin for use in the treatment of Parkinson's disease.

[Cartilage-derived morphogenetic protein 1 initiates chondrogenic differentiation of human dermal fibroblasts in vitro]

OBJECTIVE

To investigate the feasibility of human dermal fibroblasts in vitro differentiation into chondrogenic phenotype with induction of cartilage-derived morphogenetic protein (CDMP) growth factor.

METHODS

Human dermal fibroblasts were isolated from foreskin and cultured in monolayer ex vivo. Dermal fibroblasts of passage2 was plated at density of 1 x 10(4) cells/cm(2) and induced with CDMP1 (100 ng/ml) in medium of F12 + 10% FBS. After 7 days of induction, morphology of cells was observed under phase-contrast microscopy and the length:width ratio of cells was calculated by Image Plus software analysis. Expression of type I, II, III collagen was detected by immunofluorescence and observed with confocal microscopy. The method of Western-Blot was applied to detect secretion of collagen type II. mRNA expression of chondrogenic related Sox9, Aggrecan as well as collagen type II, IX was detected by RT-PCR. The osteogenic related expression of collagen type X, Alkaline Phosphatase (AKP) was also detected by RT-PCR. Pellet cultured dermal fibroblasts at a density of 2 x 10(7) cells/ml was observed respectively for proteoglycan and collagen type II expression with Alcian blue and immunohistochemistry staining.

RESULTS

With the induction of CDMP1, the morphology of cells changed from spindle fibroblastic appearance to that of typical chondrocyte-like polygon shape. By Image Plus software analysis, it was found that the length/width ratio changed significantly from 7.40 +/- 1.30 of preinduction to 1.40 +/- 0.15 of post-induction (P < 0.05). No significant difference was found between the postinduction and normal chondrocyte (1.29 +/- 0.24). By confocal microscope observation, expression of collagen type II was found intracellularly in CDMP1 treated fibroblasts. Western-Blot detection confirmed collagen type II expression by 7 days induction. RT-PCR gene expression analysis of characteristic chondrogenic related genes, such as Sox9, Aggrecan as well as collagen type II, IX, revealed induction of chondrocytic phenotype in monolayered culture upon stimulation with CDMP1 for 7 days. While osteogenic related gene expression of collagen type X, AKP was not detected by RT-PCR, which indicates that osteogenic differentiation was not initiated by CDMP1 in 7 days culture. Histological staining of proteoglycan with Alcian blue and immunohistochemical staining cartilage specific type II collagen revealed deposition of typical cartilage extracellular matrix deposition in pellet cultured fibroblasts.

CONCLUSION

These results suggests human dermal derived fibroblast could be differentiated into chondrogenic phenotype with CDMP1 induction in vitro.

Expression of growth differentiation factor-5 in the developing and adult rat brain

Expression of the dopaminergic neurotrophin GDF-5 in developing rat ventral mesencephalon (VM) was found to begin at embryonic day (E) 12 and peak on E14, when dopaminergic neurones undergo terminal differentiation. In the adult rat, GDF-5 was found to be restricted to heart and brain, being expressed in many areas of the brain, including striatum and midbrain. This indicates a role for GDF-5 in the development and maintenance of dopaminergic neurones.

Repair of articular cartilage defects in rabbits using CDMP1 gene-transfected autologous mesenchymal cells derived from bone marrow

OBJECTIVE

Cartilage-derived morphogenetic protein 1 (CDMP1), which is a member of the transforming growth factor-beta superfamily, is an essential molecule for the aggregation of mesenchymal cells and acceleration of chondrocyte differentiation. In this study, we investigated whether CDMP1-transfected autologous bone marrow-derived mesenchymal cells (BMMCs) enhance in vivo cartilage repair in a rabbit model.

METHODS

BMMCs, which had a fibroblastic morphology and pluripotency for differentiation, were isolated from bone marrow of the tibia of rabbits, grown in monolayer culture, and transfected with the CDMP1 gene or a control gene (GFP) by the lipofection method. The autologous cells were then implanted into full-thickness articular cartilage defects in the knee joints of each rabbit.

RESULTS

During in vivo repair of full-thickness articular cartilage defects, cartilage regeneration was enhanced by the implantation of CDMP1-transfected autologous BMMCs. The defects were filled by hyaline cartilage and the deeper zone showed remodelling to subchondral bone over time. The repair and reconstitution of zones of hyaline articular cartilage was superior to simple BMMC implantation. The histological score of the CDMP1-transfected BMMC group was significantly better than those of the control BMMC group and the empty control group.

CONCLUSION

Modulation of BMMCs by factors such as CDMP1 allows enhanced repair and remodelling compatible with hyaline articular cartilage.

Altered hypertrophic chondrocyte kinetics in GDF-5 deficient murine tibial growth plates

The growth/differentiation factors (GDFs) are a subgroup of the bone morphogenetic proteins best known for their role in joint formation and chondrogenesis. Mice deficient in one of these signaling proteins, GDF-5, exhibit numerous skeletal abnormalities, including shortened limb bones. The primary aim of this study was determine whether GDF-5 deficiency would alter the growth rate in growth plates from the long bones in mice and, if so, how this is achieved. Stereologic and cell kinetic parameters in proximal tibial growth plates from 5-week-old female GDF-5 -/- mice and control littermates were examined. GDF-5 deficiency resulted in a statistically significant reduction in growth rate (-14%, p=0.03). The effect of genotype on growth rate was associated with an altered hypertrophic phase duration, with hypertrophic cells from GDF-5 deficient mice exhibiting a significantly longer phase duration compared to control littermates (+25%, p=0.006). These data suggest that one way in which GDF-5 might modulate the rate of endochondral bone growth could be by affecting the duration of the hypertrophic phase in growth plate chondrocytes.

[Growth and differentiation factor 5 (GDF-5) composite improves the healing of necrosis of the femoral head in a sheep model. Analysis of an animal model]

MATERIALS AND METHODS

After creation of necrosis in 23 sheep, the composites were implanted in half of the animals. The animals were sacrificed 6 and 12 weeks after implantation and the femora were harvested. The specimens were investigated by microradiography, computed tomography, and histologically.

RESULTS

The GDF-5 composites were effective in the necrosis model. Osseous regeneration of the necrosis and the drill track were accelerated and enhanced by the composites. In treated animals the necrosis was nearly healed and the drill track was filled with bone after 12 weeks. In the control group the track was partially filled with fibrous tissue and necrotic lesions were still present. Specific side effects of the growth factor or the matrix were not documented. This was documented by histological scoring and CT investigation.

DISCUSSION

The application of an absorbable GDF-5 composite in combination with a core decompression procedure may enhance the healing of devitalized bone defects and is a promising approach for further studies.

Bapx1 regulates patterning in the middle ear: altered regulatory role in the transition from the proximal jaw during vertebrate evolution

The middle ear apparatus is composed of three endochondrial ossicles (the stapes, incus and malleus) and two membranous bones, the tympanic ring and the gonium, which act as structural components to anchor the ossicles to the skull. Except for the stapes, these skeletal elements are unique to mammals and are derived from the first and second branchial arches. We show that, in combination with goosecoid (Gsc), the Bapx1 gene defines the structural components of the murine middle ear.

During embryogenesis, Bapx1 is expressed in a discrete domain within the mandibular component of the first branchial arch and later in the primordia of middle ear-associated bones, the gonium and tympanic ring. Consistent with the expression pattern of Bapx1, mouse embryos deficient for Bapx1 lack a gonium and display hypoplasia of the anterior end of the tympanic ring. At E10.5, expression of Bapx1partially overlaps that of Gsc and although Gsc is required for development of the entire tympanic ring, the role of Bapx1 is restricted to the specification of the gonium and the anterior tympanic ring. Thus, simple overlapping expression of these two genes appears to account for the patterning of the elements that compose the structural components of the middle ear and suggests that they act in concert.

In addition, Bapx1 is expressed both within and surrounding the incus and the malleus. Examination of the malleus shows that the width, but not the length, of this ossicle is decreased in the mutant mice. In non-mammalian jawed vertebrates, the bones homologous to the mammalian middle ear ossicles compose the proximal jaw bones that form the jaw articulation(primary jaw joint). In fish, Bapx1 is responsible for the formation of the joint between the quadrate and articular (homologues of the malleus and incus, respectively) enabling an evolutionary comparison of the role of a regulatory gene in the transition of the proximal jawbones to middle ear ossicles. Contrary to expectations, murine Bapx1 does not affect the articulation of the malleus and incus. We show that this change in role of Bapx1 following the transition to the mammalian ossicle configuration is not due to a change in expression pattern but results from an inability to regulate Gdf5 and Gdf6, two genes predicted to be essential in joint formation.

[The effect of growth/differentiation factor-5 (GDF-5) on genotype and phenotype in human adult mesenchymal stem cells]

AIM

To evaluate the effects of GDF-5 on genotype and phenotype of human mesenchymal stem cells (hMSC).

HYPOTHESIS

GDF-5 leads to up-regulation of the Type I-collagen (Col) gene without altering bone marker genes or alkaline phosphatase activity.

METHODS

To test our hypothesis hMSC were treated with rmGDF-5. Using quantitative real-time PCR we analyzed mRNA for Col, Runx2 and Osterix (Osx). Furthermore, we analyzed alkaline phosphatase activity (ALP) as a phenotypical bone marker. ANOVA and post hoc statistical analyses were used to determine differences among treatments (p < 0.05).

RESULTS

HMSC showed a biphasic response in both Col and Runx2 after rmGDF-5. Initial up-regulation was followed by a significant down-regulation below controls. Interestingly, the controls presented with changes for Col and Runx2 over time. There was no Osx expression in either treated hMSC or controls. No significant differences could be detected in ALP.

CONCLUSION

Increased expression of Col and Runx2 might indicate differentiation towards both osteoblast and fibroblast lineage. However, no Osx expression and no change in ALP support the assumption that rmGDF-5 does not lead to an osteoblast phenotype in hMSC. Our in vitro studies confirm a possible therapeutic benefit of GDF-5 in the treatment of tendon and ligament injuries and tissue engineering approaches. Further research is necessary to prove its clinical value.

Multiple Effects of GDF-5 Deficiency on Skeletal Tissues: Implications for Therapeutic Bioengineering

The growth/differentiation factors (GDFs) are a subfamily of the highly conserved group of bone morphogenetic protein (BMP) signaling molecules known to play a diverse set of roles in the skeletal system. GDFs 5, 6, and 7 in particular have been grouped together on the basis of the high degree of amino acid sequence homology in the C-terminal signaling region of these proteins. The existence of several naturally occurring and engineered mouse models with functional null mutations in these GDFs has led to a variety of investigations into the effects of GDF deficiency on skeletal tissues and processes. The best characterized of these models to date is the GDF-5-deficient brachypod (bp) mouse. In this paper, a comprehensive review of the studies performed on the bp mouse is provided in an effort to elucidate implications for potential therapeutic bioengineering applications using GDF-5. On the basis of the available evidence to date, GDF-5 may hold promise as a possible therapeutic agent for applications involving tendon/ligament repair as well as perhaps intervertebral disk degeneration, cartilage repair, and bone augmentation, although further detailed interventional studies will be required to investigate these potential applications.

Effects of local application of growth and differentiation factor-5 (GDF-5) in a full-thickness cartilage defect model

Our purpose in this study was to investigate the effects of growth and differentiation factor-5 (GDF-5) on cartilage and subchondral bone in a rabbit model harboring an osteochondral defect for a period of 6 months. Absorbable composites were implanted in adult rabbits (18 controls, 18 animals with collagen-I matrix, and 18 animals with matrix plus GDF-5). After 4, 8, or 24 weeks the specimens were studied by histology, microcomputed tomography (microCT) and flow-cytometric analysis (FACS). Implantation of GDF-5 resulted in an improved histological appearance. This was the result of significantly improved defect filling at 4 and 8 weeks. At 24 weeks, however, there was no difference between the groups. The histological examination disclosed a predominance of fibrocartilage, and remodeled subchondral bone was also observed. MicroCT documented normal bone density in all groups, excluding subchondral sclerosis. At 24 weeks, FACS analysis revealed high apoptotic activity in the GDF-5-treated group. As far as we are aware, this is the first report of the effects of GDF-5 in a full-thickness cartilage defect model. We assume that recombinant GDF-5 contained on the carrier is probably able to accelerate the regeneration of the osteochondral defect owing to its availability. However, control of the protein delivery may require further investigation.

Neuroprotective effects of delayed administration of growth/differentiation factor-5 in the partial lesion model of Parkinson's disease

Neurotrophic factors have the potential for therapeutic use in Parkinson's disease (PD) to support the remaining dopaminergic neurons and protect them against the ongoing disease process. We have examined the effects of the neurotrophin growth and differentiation factor-5 (GDF-5) in a rat model of Parkinson's disease, the intrastriatal 6-hydroxydopamine (6-OHDA) lesion. GDF-5 (25 microg) was injected into either the striatum or substantia nigra (SN) of adult rats at 1 or 2 weeks after 6-hydroxydopamine administration. The behavioral effects of GDF-5 treatment were examined in vivo by amphetamine-induced rotational testing. Injection of GDF-5 into the nigra at either 1 or 2 weeks, or into the striatum at 1 week, after the lesion induced significant decreases in rotations. Post-mortem immunocytochemistry after 6 weeks showed that GDF-5 administration into either site protected dopaminergic cell bodies of the nigra when injected at 1 but not 2 weeks after 6-hydroxydopamine. However, no significant protection of striatal dopaminergic fiber density was observed after GDF-5 treatment. This study shows that the delayed administration of a single dose of GDF-5 has significant protective effects on the damaged adult rat nigrostriatal pathway, reinforcing its therapeutic potential for Parkinson's disease.

Release of active and depot GDF-5 after adenovirus-mediated overexpression stimulates rabbit and human intervertebral disc cells

To develop new therapeutic options for the treatment of disc degeneration we tested the possibility of overexpression of active growth and differentiation factor (GDF) 5 and of transforming growth factor (TGF) beta(1) by adenoviral gene transfer and characterized its effect on cell proliferation and matrix synthesis of cultured rabbit and human intervertebral disc cells. Recombinant adenovirus encoding for GDF-5 or TGF-beta(1) was developed and transgene expression characterized by RT-PCR, western blot and ELISA. Growth and matrix synthesis of transduced cells was measured by [(3)H]thymidine or [(35)S]sulfate incorporation. Disc cells expressed the receptors BMPR1A, BMPR1B, and BMPR2, which are relevant for GDF-5 action. Adenovirus efficiently transferred the GDF-5 gene or the TGF-beta(1) gene to rabbit and human intervertebral disc cells. About 50 ng GDF-5 protein/10(6 )cells per 24 h or 7 ng TGF-beta(1) protein/10(6 )cells per 24 h was produced. According to western blotting, two GDF-5 forms, with molecular weights consistent with the activated GDF-5 dimer and the proform, were secreted over the 3 weeks following gene transfer. Overexpressed GDF-5 and TGF-beta(1) were bioactive and promoted growth of rabbit disc cells in monolayer culture. Our results suggest that ex vivo gene delivery of GDF-5 and TGF-beta(1) is an attractive approach for the release of mature and pre-GDF-5 in surrounding tissue. This leads us to hope that it will prove possible to improve the treatment of degenerative disc disease by means of ex vivo gene transfer of single or multiple growth factors.

In vivo growth factor treatment of degenerated intervertebral discs

STUDY DESIGN

An in vivo model was used to investigate the response of degenerated discs to various exogenous growth factors.

OBJECTIVES

To study growth factor-induced alterations of the spatial and temporal patterns of disc cellularity and matrix gene expression.

SUMMARY OF BACKGROUND DATA

Cell proliferation and proteoglycan synthesis have been stimulated by growth factors in normal disc cells, suggesting that growth factors may play a therapeutic role for degeneration. However, the response in situ in degenerated discs has not been characterized.

METHODS

Degeneration was induced in murine caudal discs by static compression. Degenerated discs were given single or multiple injections of growth and differentiation factor-5, transforming growth factor-beta, insulin-like growth factor-1, basic fibroblast growth factor, or saline as control. Comparisons of disc morphology, anular cell density, proliferating cells, disc height, and aggrecan and type II collagen gene expression were made either 1 week or 4 weeks after treatment.

RESULTS

In some growth and differentiation factor-5 and transforming growth factor-beta treated discs, expansion of inner anular fibrochondrocyte populations into the nucleus was observed. The cells actively expressed aggrecan and type II collagen mRNA. A lesser effect was observed for insulin-like growth factor-1 and little or no effect for basic fibroblast growth factor. Differences in cell density and proliferating cells were not significant between treatments but suggested a trend of increased cellularity and proliferation following growth factor treatment. A statistically significant increase in disc height 4 weeks after growth and differentiation factor-5 treatment was measured.

CONCLUSIONS

Anular fibrochondrocytes in degenerated discs are responsive to some growth factors in vivo. The results have implications in the early intervention of disc degeneration to arrest or slow the degenerative process.

Endoscopic Instrumented Posterolateral Lumbar Fusion with Healos and Recombinant Human Growth/Differentiation Factor-5

OBJECTIVE

The goal of this study was to use a minimally invasive endoscopic surgical technique in a sheep model to evaluate the efficacy of an osteoinductive growth factor, recombinant human growth/differentiation factor-5 (also designated MP52), and an osteoconductive matrix formulation (Healos; DePuy AcroMed, Inc., Mountain View, CA) for inducing and facilitating bone formation.

METHODS

Twelve mature sheep underwent bilateral posterolateral lumbar fusion and pedicle screw fixation via a posterior endoscopic approach. Each sheep received two different types of graft material, autogenous iliac crest bone, or a bone graft substitute (MP52 with Healos), inserted into the right and left sides of the spine in an alternating fashion. Groups of four sheep were killed at 2, 4, and 6 months postoperatively for manual, radiographic, and histological evaluation.

RESULTS

No neurological impairments, infections, or other complications were observed. After 2 months, partial fusion on both sides was observed, but radiographic evaluation showed greater bone growth on the side that received the bone graft substitute. Solid posterolateral fusion was observed in both autograft and bone graft substitute sites at 4 and 6 months, and autograft and Healos MP52 fusion sites were essentially the same at histological examination. There was no abnormal overgrowth of new bone from either of these two materials.

CONCLUSION

Endoscopic posterolateral lumbar arthrodesis and instrumentation is feasible, safe, and effective in a sheep model. Healos is a useful bonding agent that mimics natural bone in posterolateral intertransverse fusion sites. Combined with MP52, it produced fusion comparable to that of autogenous bone graft. Minimally invasive techniques and bone graft substitutes could eliminate morbidity and increase the likelihood of successful fusion.

Cloning of integral mature peptide gene of human GDF-5

The integral mature peptide gene of human growth differentiation factor-5 (GDF-5) was cloned to provide the essential foundation for study on the biological characteristics of GDF-5 at gene and protein levels. Two primers were chemosynthesized according to the hGDF-5 sequence reported in Genbank. The hGDF-5 gene was gained by RT-PCR methods from the total RNA extracted from human fetus cartilage tissue, and was cloned into vector pMD18-T. The sequence of recombinant plasmid pMD18-T-hGDF-5 was analyzed by sequence analysis. DNA agarose gel electrophoresis showed that the product of RT-PCR was about 380bp, and double enzyme digestion of the recombinant plasmid corresponded with it. The result of sequence assay was in agreement with the reported hGDF-5 sequence in Genbank. Our results showed that the integral mature peptide gene of human GDF-5 was cloned successfully from human fetal cartilage tissue, and totally identified with the sequence of human GDF-5 in Genbank.

Distinct functions of BMP4 and GDF5 in the regulation of chondrogenesis

Bone morphogenetic protein 4 (BMP4) and growth/differentiation factor 5 (GDF5) are closely related protein family members and regulate early cartilage patterning and differentiation. In this study, we compared the functional outcome of their actions systematically at various stages of chondrogenesis in mouse embryonic limb bud mesenchyme grown in micromass cultures. Overall, both growth factors enhanced cartilage growth and differentiation in these cultures. Uniquely, BMP4 not only accelerated the formation and maturation of cartilaginous nodules, but also induced internodular mesenchymal cells to express cartilage differentiation markers. On the other hand, GDF5 increased the number of prechondrogenic mesenchymal cell condensation and cartilaginous nodules, without altering the overall pattern of differentiation. In addition, GDF5 caused a more sustained elevated expression level of Sox9 relative to that associated with BMP4. BMP4 accelerated chondrocyte maturation throughout the cultures and sustained an elevated level of Col10 expression, whereas GDF5 caused a transient increase in Col10 expression. Taken together, we conclude that BMP4 is instructive to chondrogenesis and induces mesenchymal cells toward the chondrogenic lineage. Furthermore, BMP4 accelerates the progression of cartilage differentiation to maturation. GDF5 enhances cartilage formation by promoting chondroprogenitor cell aggregation, and amplifying the responses of cartilage differentiation markers. These differences may serve to fine-tune the normal cartilage differentiation program, and can be exploited for the molecular manipulation in biomimetics.

Cartilage-derived morphogenetic proteins enhance the osteogenic protein-1-induced osteoblastic cell differentiation of C2C12 cells

Previous studies have shown that osteogenic protein-1 (OP-1; also known as BMP-7) induces differentiation of the pluripotent mesenchymal cell line C2C12 into osteoblastic cells. OP-1 also alters the steady-state levels of messenger RNA (mRNA) encoding for the cartilage-derived morphogenetic proteins (CDMPs) in C2C12 cells. In the present study, the effects of exogenous CDMPs on bone cell differentiation induced by OP-1 in C2C12 cells were examined. Exogenous CDMP-1, -2, and -3 synergistically and dose-dependently enhanced OP-1 action in stimulating alkaline phosphatase (AP) activity and osteocalcin (OC) mRNA expression. AP staining studies revealed that the combination of OP-1 and CDMP enhanced OP-1 action by stimulating those cells that had responded to OP-1 and not by activating additional cells. The combination did not change the mRNA expression of the BMPs and their receptors. CDMP-1 enhanced the suppression of the OP-1-induced expression of the myogeneic differentiation regulator MyoD. CDMP-1 and OP-1 alone stimulated Smad5 protein expression, but the combination of OP-1 and CDMP-1 stimulated synergistically Smad5 protein expression. Thus, one mechanism of the observed synergy involved enhancement of the induced Smad5 protein expression. At the same protein concentration, CDMP-1 is most potent in enhancing OP-1 activity in inducing osteoblastic cell differentiation of C2C12 cells. CDMP-3 is about 80% as potent as CDMP-1, and CDMP-2 is the least potent (about 50% of CDMP-1).

Correlation of GDF5 and connexin 43 mRNA expression during embryonic development

Growth/differentiation factor 5 (GDF5) regulates connexin expression and enhances embryonic chondrogenesis in a gap junction-dependent manner, suggesting that GDF5 action on developmental skeletogenesis is coordinated with gap junction activities. The results shown here demonstrate concordance between the mRNA expression profiles of GDF5 and the gap junction gene, Cx43, in the mouse embryonic limb, spine, and heart, consistent with coordinated functions for these gene products during developmental organogenesis.

Effects of growth/differentiation factor-5 on human periodontal ligament cells

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, tendon, and ligament morphogenesis. The mRNA encoding GDF-5 is also expressed during odontogenesis, especially in dental follicle tissue. While this suggests that GDF-5 participates in the formation of alveolar bone and the periodontal ligament, cementum, and dental root, the physiologic role of GDF-5 in these tissues in adulthood remains unclear. We therefore investigated GDF-5 effects upon cultures of human periodontal ligament (HPDL) cells.

MATERIAL AND METHODS

HPDL cells were obtained from healthy periodontal ligaments of individuals. Tetrazolium reduction assay was carried out for cell proliferation assay. Alkaline phosphatase (ALP) activity was estimated by measuring light absorbance at 405 nm. Reverse transcription-polymerase chain reaction (RT-PCR) and northern analysis were performed for gene expression in cultured HPDL cells. Sulfated glycosaminoglycan (sGAG) synthesis was evaluated by histochemical staining and a quantitative dye-binding method.

RESULTS

Expression of GDF-5 and its receptor was demonstrated in HPDL cells by RT-PCR. ALP activity in HPDL cells was significantly decreased by addition of rhGDF-5 at 10-1000 ng/ml (p < 0.05). Although northern analysis showed little change in gene expression for collagen alpha2(I) in rhGDF-5-stimulated HPDL cells, rhGDF-5 dose-dependently enhanced cell proliferation. This proliferative effect persisted for 16 d. Alcian blue staining and dye-binding assays indicated that sGAG synthesis was enhanced by rhGDF-5.

CONCLUSION

rhGDF-5 may provide an environment fostering periodontal healing or regeneration by affecting extracellular matrix metabolism.

Expression of the BMP antagonist Dan during murine forebrain development

Dan (Differential screening-selected gene aberrative in neuroblastoma, also known as N03) is a member of a class of glycoproteins shown to be secreted inhibitors of the transforming growth factor-beta (TGF-beta) and bone morphogenic protein pathways. We examined Dan expression during murine forebrain development from embryonic day 10.5 to postnatal day 14 and found that Dan was expressed in highly specific spatiotemporal patterns. In early telencephalic development, Dan is highly expressed in the fibroblasts covering the cortex. From E12.5-E14.5, Dan is also weakly expressed in a region of neuroepithelium at the medial margin of the telencephalon called the cortical hem. From E17.5 on, Dan is expressed strongly in CA3 pyramidal neurons of the hippocampus as well as in the developing thalamus and amygdala. To determine if Dan expression is correlated with the expression of any of its known ligand targets, we examined the expression of GDF-5, -6 and -7 in the forebrain and found that GDF-5 is expressed in Cajal-Retzius cells in Layer I of cortex, immediately adjacent to the expression of Dan in the meninges.

Receptor cluster formation during activation by bacterial products

The recognition of bacterial products, such as lipopolysaccharide (LPS) by the innate immune system lead to a strong pro-inflammatory response that can eventually lead to fatal sepsis syndrome in humans. Although CD14 and TLR4 have been identified as the key molecules involved in LPS-induced signal transduction, accumulating evidence indicates that multiple receptors are also involved. Our group has recently identified a cluster of receptors, involving heat-shock proteins 70 and 90, chemokine receptor 4 as well as growth differentiation factor 5, that are formed following LPS stimulation. In addition, we present data demonstrating that these molecules associate with TLR4 and accumulate in membrane microdomains following LPS ligation. Our results suggest that the entire bacterial recognition is based around the recruitment of multiple signalling molecules, in addition to CD14 and TLRs, within the lipid rafts. We propose that different combinational associations of receptors within activation clusters determine the different responses to a variety of bacterial stimuli.

Growth/differentiation factor 5 enhances chondrocyte maturation

Growth/differentiation factor 5 (GDF5) is required for limb mesenchymal cell condensation and joint formation during skeletogenesis. Here, we use a model consisting of long-term, high-density cultures of chick embryonic limb mesenchymal cells, which undergo the entire life history of chondrocyte development, to examine the effects of GDF5 overexpression on chondrocyte maturation. Exposure to GDF5 significantly enhanced chondrocyte hypertrophy and maturation, as determined by the presence of alkaline phosphatase activity, collagen type X protein production, and the presence of a sulfated proteoglycan-rich extracellular matrix. Histologic analysis also revealed an increase in cell volume and cellular encasement in larger lacunae in GDF5-treated cultures. Taken together, these results support a role for GDF5 in influencing chondrocyte maturation and the induction of hypertrophy in the late stages of embryonic cartilage development, and provide additional mechanistic insights into the role of GDF5 in skeletal development.

GDF-5 deficiency in mice delays Achilles tendon healing

The aim of this study was to examine the role of one of the growth/differentiation factors, GDF-5, in the process of tendon healing. Specifically, we tested the hypothesis that GDF-5 deficiency in mice would result in delayed Achilles tendon repair. Using histologic, biochemical, and ultrastructural analyses, we demonstrate that Achilles tendons from 8-week-old male GDF-5 -/- mice exhibit a short-term delay of 1-2 weeks in the healing process compared to phenotypically normal control littermates. Mutant animals took longer to achieve peak cell density, glycosaminoglycan content, and collagen content in the repair tissue, and the time course of changes in collagen fibril size was also delayed. Revascularization was delayed in the mutant mice by 1 week. GDF-5 deficient Achilles tendons also contained significantly more fat within the repair tissue at all time points examined, and was significantly weaker than control tissue at 5 weeks after surgery, but strength differences were no longer detectable by 12-weeks. Together, these data support the hypothesis that GDF-5 may play an important role in modulating tendon repair, and are consistent with previously posited roles for GDF-5 in cell recruitment, migration/adhesion, differentiation, proliferation, and angiogenesis.

Clinical and molecular analysis of Grebe acromesomelic dysplasia in an Omani family

Grebe syndrome is a rare autosomal recessive acromesomelic dysplasia. The syndrome was studied clinically, radiographically, and genetically in an Omani family with four affected children. The affected persons had normal axial skeletons, severely shortened, and deformed limbs with severity increasing in a proximo-distal gradient, and subluxated joints. The humeri and femora were hypoplastic with distal malformations. The radii/ulnae were shortened and deformed whereas carpal bones were invariably rudimentary or absent. The tibiae appeared rudimentary; fibulae were absent in two children, and some tarsal and metatarsal bones were absent. The proximal and middle phalanges were absent while the distal phalanges were present. The father and mother had short first metacarpal and middle phalynx of the fifth finger and hallux valgus respectively. Transition A1137G and deletion delG1144 mutations in the gene encoding the cartilage-derived morphogenetic protein-1 (CDMP-1) were identified in this family. The A1137G is a silent mutation coding for lysine, whereas the delG1144 predicts a frameshift mutation resulting in a presumable loss of the CDMP-1 biologically active carboxy-terminal domain. The affected siblings were homozygous for the delG1144 mutation while parents were heterozygous.

Bone augmentation using rhGDF-5-collagen composite

The aim of this study was to evaluate the effectiveness of local application of growth differentiation factor-5 (GDF-5)-collagen composite on bone augmentation on the rat calvaria. GDF-5-collagen composite is made from recombinant human GDF-5 (rhGDF-5) and purified bovine type I atelocollagen. The GDF-5 solution was mixed with 0.3% atelocollagen acid solution, and the mixture was lyophilized. The spongy lyophilized material was pressed into the shape of a minidisk to make the GDF-5-collagen composite. The GDF-5-collagen composite contained 1, 10, or 100-microg rhGDF-5. The control collagen composite contained 0-microg rhGDF-5. The GDF-5-collagen composite or control collagen composite was inserted beneath the calvarial periosteum of 4-week-old rats. At 3 weeks after implantation, the implants containing 1-microg rhGDF-5 had mostly induced new bone formation on the cranial side. In the implants containing 10- microg rhGDF-5, bone formation had proceeded to the center of the GDF-5-collagen composite from the periosteal and the cranial sides, and bone marrow was seen focally. The augmented bone showed a connected trabecular structure with abundant vascularization. The implants containing 100-microg rhGDF-5 were nearly entirely replaced by new bone with bone marrow, and the augmented bone was firmly connected with the original bone. Neither cartilage nor bone formation was found in the control collagen composite. Thus, we conclude that the GDF-5-collagen composite may be a superior biomaterial for bone augmentation and this composite could be useful as a local osteoinductive device.