Cartilage-inducing factor-B is a unique protein structurally and functionally related to transforming growth factor-beta

Core needle biopsy changes the expression of TGFβ1 and TGFβRII at protein level, and the distribution of CD4 and CD8 positive T cells in primary breast cancer

Core needle biopsy (CNB) has become a paradigm in preoperative breast cancer (BC) diagnosis. Although considered safe, it is an invasive procedure, which changes the tumor microenvironment. It facilitates a tumor supportive immune response, induces epithelial-mesenchymal transition (EMT), and enables the release of circulating tumor cells. The cytokine Transforming Growth Factor β (TGFβ) with its pleiotropic immunologic functions has an important role in this process. The aim of this study was to clarify the specific impact of CNB on the activity of the TGFβ pathway in early BC. We compared formalin fixed paraffin embedded samples from CNBs to the corresponding surgical resection specimens (SRSs) of 49 patients with BC. We found that the expression of TGFβ1 at protein level was significantly higher in both tumor epithelial and benign stromal cells in the SRSs (p=0.001), whereas the expression of TGFβRII in tumor cells was lower (p=0.001). The frequency of intra tumoral CD8 and CD4 positive T lymphocytes was lower in SRSs (p=0081 and p=0001, respectively), while in the peripheral stroma their prevalence was increased (p=0001 and p=0012, respectively). Our results show that CNB changes the hallmarks of the TGFβ path way in early BC. These CNB-induced changes in the tumor and in its microenvironment suggest that the procedure may change the immunological anti-tumor response of the host.

Discovery of Heterotopic Bone-Inducing Activity in Hard Tissues and the TGF-β Superfamily

Bone is a unique organ because it can be experimentally induced in soft tissues by implanting a single growth factor, bone morphogenetic protein (BMP). Heterotopic bone-inducing activity was found in demineralized bone matrix in 1965. The characterization of this activity in bone enabled the purification and molecular cloning of BMPs and showed that they are members of the transforming growth factor-β (TGF-β) superfamily. Assay systems developed for this bone-inducing activity revealed the molecular mechanisms of the intracellular signaling of members of the superfamily, including BMPs. Moreover, they are being applied to elucidate molecular mechanisms and to develop novel therapeutics for a disease caused by an abnormality in BMP signaling.

Heterotopic bone induction via BMP signaling: Potential therapeutic targets for fibrodysplasia ossificans progressiva

More than 50years ago, Marshal M. Urist detected "heterotopic bone-inducing activity" in demineralized bone matrix. This unique activity was referred to as "bone morphogenetic protein (BMP)" because it was sensitive to trypsin digestion. Purification of the bone-inducing activity from demineralized bone matrix using a bone-inducing assay in vivo indicated that the original "BMP" consisted of a mixture of new members of the transforming growth factor-β (TGF-β) family. The establishment of new in vitro assay systems that reflect the bone-inducing activity of BMPs in vivo have revealed the functional receptors and downstream effectors of BMPs. Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by progressive heterotopic bone formation in soft tissues similar to the event induced by the transplantation of BMPs in skeletal muscle. In patients with FOP, genetic mutations have been identified in the ACVR1 gene, which encodes the BMP receptor ALK2. The mutations in ALK2 associated with FOP are hypersensitive to type II receptor kinases. Recently, activin A, a non-osteogenic member of the TGF-β family, was identified as the ligand of the mutant ALK2 in FOP, and various types of signaling inhibitors for mutant ALK2 are currently under development to establish effective treatments for FOP.

The cytokines and micro-environment of fracture haematoma: Current evidence

Fracture haematoma formation is the first and foremost important stage of fracture healing. It orchestrates the inflammatory and cellular processes leading to the formation of callus and the restoration of the continuity of the bone. Evidence suggests that blocking this initial stage could lead to an impairment of the overall bone healing process. This review aims to analyse the existing evidence of molecular contributions to bone healing within fracture haematoma and to determine the potential to modify the molecular response to fracture in the haematoma with the aim of improving union times. A comprehensive search of literature documenting fracture haematoma cytokine content was performed. Suitable papers according to prespecified criteria were identified and analysed according to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. A total of 89 manuscripts formed the basis of this analysis. Low oxygen tension, high acidity, and high calcium characterised initially the fracture haematoma micro-environment. In addition, a number of cytokines have been measured with concentrations significantly higher than those found in peripheral circulation. Growth factors have also been isolated, with an observed increase in bone morphogenetic proteins, platelet-derived growth factor, and transforming growth factor. Although molecular modification of fracture haematoma has been attempted, more research is required to determine a suitable biological response modifier leading to therapeutic effects. The cytokine content of fracture haematoma gives insight into processes occurring in the initial stages of fracture healing. Manipulation of signalling molecules represents a promising pathway to target future therapies aiming to upregulate the osteogenesis.

The Discovery and Early Days of TGF-β: A Historical Perspective

Transforming growth factors (TGFs) were discovered as activities that were secreted by cancer cells, and later by normal cells, and had the ability to phenotypically and reversibly transform immortalized fibroblasts. TGF-β distinguished itself from TGF-α because it did not bind to the same epidermal growth factor (EGF) receptor as TGF-α and, therefore, acted through different cell-surface receptors and signaling mediators. This review summarizes the discovery of TGF-β, the early developments in its molecular and biological characterization with its many biological activities in different cell and tissue contexts and its roles in disease, the realization that there is a family of secreted TGF-β-related proteins with many differentiation functions in development and activities in normal cell and tissue physiology, and the subsequent identification and characterization of the receptors and effectors that mediate TGF-β family signaling responses.

Growth factor directed chondrogenic differentiation of porcine bone marrow-derived progenitor cells

BACKGROUND

Despite advances in surgical technique, reconstruction of a mandibular condyle still causes significant donor-site morbidity. The purpose of this study was to compare the effect of 3 different growth factors and define optimal cell culture conditions for bone marrow-derived progenitor cells to differentiate into chondrocytes for mandibular condyle reconstruction.

METHODS

Porcine bone marrow-derived progenitor cells (pBMPCs) were cultured as a pellet for 2, 3, and 4 weeks under the following conditions: group 1, TGF-β3 + standard medium; group 2, TGF-β3 + BMP-2 + standard medium; group 3, TGF-β3 + IGF-1 + standard medium; and group 4, TGF-β3 + BMP-2 + IGF-1 + standard medium. Chondrogenic differentiation was evaluated using 3 lineage differentiation markers.

RESULTS

The mean type II collagen positive area increased over weeks 2, 3, and 4 in group 4 compared to all the other groups (ANOVA; P = 0.005). At week 4, there was significantly greater type II collagen production in group 4 compared to all the other groups (ANOVA; P = 0.003). The medium in group 4 produces the greatest amount of cartilage when compared to groups 1, 2, and 3, and that 4 weeks produces the greatest amount of type II collagen.

CONCLUSIONS

The results of this study indicate that the most efficacious medium for chondrogenic differentiation of pBMPCs was group 4 medium and the most type II collagen was produced at 4 weeks.

microRNA-495 inhibits chondrogenic differentiation in human mesenchymal stem cells by targeting Sox9

The chondrogenic differentiation process of human mesenchymal stem cells (hMSCs) passes through multiple stages, which are carried out by various factors and their interactions. Recently, microRNAs that regulate chondrogenic differentiation have been reported. However, microRNA that regulates SRY-related high mobility group-box gene 9 (Sox9), a chondrogenic key factor, has not been identified in hMSC. In this study, we identified that microRNA-495 (miR-495) is an important regulator of hMSC chondrogenic differentiation. In our microarray, miR-495 was downregulated during transforming growth factor (TGF)-β3-induced chondrogenic differentiation of hMSCs in vitro. We found that there is an miR-495 binding site in the 3' untranslated region (3'UTR) of Sox9. We confirmed opposite expression between miR-495 and Sox9 by using real-time polymerase chain reaction. Further, overexpression of miR-495 inhibited Sox9 expression, and repression of miR-495 increased expression of Sox9 in SW1353 cells and hMSCs. Additionally, luciferase analysis revealed that miR-495 directly binds to the Sox9 3'UTR, and we confirmed a seed sequence of miR-495 on the Sox9 3'UTR. Subsequently, overexpression of miR-495 repressed the expression of the extracellular matrix (ECM) protein, such as type II collagen (Col2A1), aggrecan, and proteoglycan products, whereas inhibition of miR-495 increased their expression. Collectively, this study indicates that miR-495 directly targets Sox9, ultimately leading to the regulation of chondrogenic differentiation in hMSCs.

Effects of low-dose microwave on healing of fractures with titanium alloy internal fixation: an experimental study in a rabbit model

Background

Microwave is a method for improving fracture repair. However, one of the contraindications for microwave treatment listed in the literature is surgically implanted metal plates in the treatment field. The reason is that the reflection of electromagnetic waves and the eddy current stimulated by microwave would increase the temperature of magnetic implants and cause heat damage in tissues. Comparing with traditional medical stainless steel, titanium alloy is a kind of medical implants with low magnetic permeability and electric conductivity. But the effects of microwave treatment on fracture with titanium alloy internal fixation invivo were not reported. The aim of this article was to evaluate the security and effects of microwave on healing of a fracture with titanium alloy internal fixation.

Methods

Titanium alloy internal fixation systems were implanted in New Zealand rabbits with a 3.0 mm bone defect in the middle of femur. We applied a 30-day microwave treatment (2,450MHz, 25W, 10 min per day) to the fracture 3 days after operation. Temperature changes of muscle tissues around implants were measured during the irradiation. Normalized radiographic density of the fracture gap was measured on the 10th day and 30th day of the microwave treatment. All of the animals were killed after 10 and 30 days microwave treatment with histologic and histomorphometric examinations performed on the harvested tissues.

Findings

The temperatures did not increase significantly in animals with titanium alloy implants. The security of microwave treatment was also supported by histology of muscles, nerve and bone around the implants. Radiographic assessment, histologic and histomorphometric examinations revealed significant improvement in the healing bone.

Conclusion

Our results suggest that, in the healing of fracture with titanium alloy internal fixation, a low dose of microwave treatment may be a promising method.

Outfits for different occasions: tissue-specific roles of Nuclear Envelope proteins

The Nuclear Envelope (NE) contains over 100 different proteins that associate with nuclear components such as chromatin, the lamina and the transcription machinery. Mutations in genes encoding NE proteins have been shown to result in tissue-specific defects and disease, suggesting cell-type specific differences in NE composition and function. Consistent with these observations, recent studies have revealed unexpected functions for numerous NE associated proteins during cell differentiation and development. Here we review the latest insights into the roles played by the NE in cell differentiation, development, disease and aging, focusing primarily on inner nuclear membrane (INM) proteins and nuclear pore components.

TGF-β but not BMP signaling induces prechondrogenic condensation through ATP oscillations during chondrogenesis

Although both TGF-β and BMP signaling enhance expression of adhesion molecules during chondrogenesis, TGF-β but not BMP signaling can initiate condensation of uncondensed mesenchymal cells. However, it remains unclear what causes the differential effects between TGF-β and BMP signaling on prechondrogenic condensation. Our previous report demonstrated that ATP oscillations play a critical role in prechondrogenic condensation. Thus, the current study examined whether ATP oscillations are associated with the differential actions of TGF-β and BMP signaling on prechondrogenic condensation. The result revealed that while both TGF-β1 and BMP2 stimulated chondrogenic differentiation, TGF-β1 but not BMP2 induced prechondrogenic condensation. It was also found that TGF-β1 but not BMP2 induced ATP oscillations and inhibition of TGF-β but not BMP signaling prevented insulin-induced ATP oscillations. Moreover, blockage of ATP oscillations inhibited TGF-β1-induced prechondrogenic condensation. In addition, TGF-β1-driven ATP oscillations and prechondrogenic condensation depended on Ca(2+) influx via voltage-dependent calcium channels. This study suggests that Ca(2+)-driven ATP oscillations mediate TGF-β-induced the initiation step of prechondrogenic condensation and determine the differential effects between TGF-β and BMP signaling on chondrogenesis.

Expression of TGF-beta 2 in human glioblastoma: a role in resistance to immune rejection?

Glioblastomas are among the most malignant tumours for which no curative treatment exists. A dysfunction of cellular immunity with decreased skin reactivity and lymphocyte blastogenesis has been described in patients with glioblastomas. In culture human glioblastoma cells release a factor termed glioblastoma-derived T cell suppressor factor (G-TsF) which inhibits the antigen-dependent growth of both helper and cytotoxic T cells. Purification and cloning indicated that G-TsF is a novel member of the TGF-beta family with a well-conserved mature sequence but less homology in the precursor segments. The factor was renamed TGF-beta 2. The two glioblastoma cell lines investigated expressed mRNAs for both G-TsF/TGF-beta 2 and TGF-beta 1 but only G-TsF/TGF-beta 2 protein was secreted. Neuroblastoma cells express only the mRNA for TGF-beta 1 but not the protein, nor the mRNA for G-TsF/TGF-beta 2. Recombinant G-TsF/TGF-beta 2 inhibits the generation of virus-specific cytotoxic T cells when injected into mice infected with lymphocytic choriomeningitis virus. Thus G-TsF/TGF-beta 2 might contribute to the impairment of tumour immune surveillance. Some T cell clones may escape the immunosuppressive effects of TGF-beta: ovalbumin-specific T helper cell lines that showed different degrees of susceptibility to TGF-beta contained clones which had lost receptor(s) for TGF-beta.

Polypeptide growth factors in bone matrix

The presence of many types of polypeptide growth factors in the mineralized extracellular matrix of bone is now well established. These factors are generally referred to as bone-derived growth factors (BDGFs), and are similar, or possibly identical, to the following species; platelet-derived growth factor (PDGF); acidic and basic forms of fibroblast growth factor (aFGF, bFGF); transforming growth factor beta (TGF-beta); and insulin-like growth factor 1 (IGF-1). Several osteoinductive factors, such as bone morphogenetic protein (BMP) and osteogenin, a skeletal growth factor (SGF), and osteoblast-derived BDGFs, have also been identified. Complete description of the biological functions of these BDGFs which are relevant to bone will ultimately require specific bioassays involving specific cell types in vitro, as well as in vivo animal implant models. Studies with primary rat osteoblast-like cells exposed either to mixed BDGFs, pure TGF-beta, or heparin-purified PDGF, aFGF, or bFGF from bovine bone have shown a general dose-dependent mitogenic effect. Phenotypic changes which accompany the BDGF-induced wave of proliferation include: decreased osteocalcin secretion and a reduction in 1,25-(OH)2 vitamin D3-stimulated osteocalcin synthesis; reduced alkaline phosphatase specific activity; decreased cyclic AMP responsiveness to parathyroid hormone (PTH); and increased collagen synthesis. Bone exhibits the most complex spectrum of growth factor activities of any tissue yet described. In bovine bone powder free of blood and cartilage contamination, the volume concentration of mitogens is up to 20 times greater than that in serum. Bone cells and other indigenous cell types must be considered as possible sources of the BDGFs, in addition to sequestration from blood. Mechanisms for the unmasking or release of BDGFs from the mineralized matrix that result in local action on osteoblasts, endothelial cells, and other target cells are undoubtedly important for the development and maintenance of bone tissue.

The effects of local platelet rich plasma delivery on diabetic fracture healing

Several studies have documented that diabetes impairs bone healing clinically and experimentally. The percutaneous delivery of platelet rich plasma (PRP) was used in the diabetic BB Wistar femur fracture model to investigate the use of PRP as a concentrated source of critical early growth factors on bone healing. PRP delivery at the fracture site normalized the early (cellular proliferation and chondrogenesis) parameters while improving the late (mechanical strength) parameters of diabetic fracture healing. These results suggest a role for PRP in mediating diabetic fracture healing and potentially other high risk fractures.

Expression and roles of connective tissue growth factor in Meckel's cartilage development

Meckel's cartilage is a prominent feature of the developing mandible, but its formation and roles remain unclear. Because connective tissue growth factor (CTGF, CCN2) regulates formation of other cartilages, we asked whether it is expressed and what roles it may have in developing mouse Meckel's cartilage. Indeed, CTGF was strongly expressed in anterior, central, and posterior regions of embryonic day (E) 12 condensing Meckel's mesenchyme. Expression decreased in E15 newly differentiated chondrocytes but surged again in E18 hypertrophic chondrocytes located in anterior region and most-rostral half of central region. These cells were part of growth plate-like structures with zones of maturation resembling those in a developing long bone and expressed such characteristic genes as Indian hedgehog (Ihh), collagen X, MMP-9, and vascular endothelial growth factor. At each stage examined perichondrial tissues also expressed CTGF. To analyze CTGF roles, mesenchymal cells isolated from E10 first branchial arches were tested for interaction and responses to recombinant CTGF (rCTGF). The cells readily formed aggregates in suspension culture and interacted with substrate-bound rCTGF, but neither event occurred in the presence of CTGF neutralizing antibodies. In good agreement, rCTGF treatment of micromass cultures stimulated both expression of condensation-associated macromolecules (fibronectin and tenascin-C) and chondrocyte differentiation. Expression of these molecules and CTGF itself was markedly up-regulated by treatment with transforming growth factor-beta1, a chondrogenic factor. In conclusion, CTGF is expressed in highly dynamic manners in developing Meckel's cartilage where it may influence multiple events, including chondrogenic cell differentiation and chondrocyte maturation. CTGF may aid chondrogenesis by acting down-stream of transforming growth factor-beta and stimulating cell-cell interactions and expression of condensation-associated genes.

Stem cell repair of physeal cartilage

To evaluate the ability of cultured mesenchymal stem cells (MSC) to repair physeal defects, MSC-matrix constructs with 5% gelatin (group A), 10% gelatin/Gelfoam (Pharmacia, Peapack, NJ) (group B), and MSC grown in the presence of TGF-beta3 with Gelfoam (group C) were implanted in proximal tibial physeal defects created in 20 immature rabbits. Control groups (untreated partial defect and partial defect treated with Gelfoam) showed bony bar formation with varus deformities of 30 degrees and 28 degrees, respectively. Group A had an average 23 degrees varus deformity with bony bridge formation, and group B had mild varus angulation (average 14 degrees) of the proximal tibia. In group C, there was no significant varus deformity (average 9 degrees), and histologic examination showed that some of the columnation areas interspersed with chondrocytes were irregularly arranged in the matrix. These findings suggest that repair of physeal defects can be enhanced by the implantation of MSC cultured with TGF-beta3.

Advances in drug delivery for articular cartilage

The complex structure of articular cartilage, the connective tissue lining diarthrodial joints, enables this tissue to dissipate compressive loads but also appears to hinder its repair ability. At best, both natural and surgical repair attempts replace the highly ordered extracellular matrix of native articular cartilage with fibrous repair tissue of inferior mechanical properties. Numerous bioactive molecules closely regulate the cellular processes in healthy and degenerative articular cartilage. Accordingly, this review outlines the roles of important signaling molecules in cartilage tissue. In addition, drug delivery strategies, aimed at utilizing these bioactive agents to prevent inflammation, to regulate extracellular matrix metabolism, and to control cellular activities, are discussed. As scientists gain further insight into the complex signaling cascades of articular cartilage, continued refinement of drug delivery systems is necessary to develop effective clinical therapies for articular cartilage repair.

Receptor-regulated and inhibitory Smads are critical in regulating transforming growth factor beta-mediated Meckel's cartilage development

The proper development of Meckel's cartilage is critical for craniofacial skeletogenesis, because it serves as the primordium for the formation of mandible, malleus, incus, and sphenomandibular ligament. Cranial neural crest (CNC) cells contribute significantly to the formation of Meckel's cartilage. Members of the transforming growth factor beta (TGF-beta) family control the proliferation and differentiation of CNC cells during craniofacial skeletogenesis. TGF-beta signaling is transduced from the cell membrane to the nucleus by means of specific type I and type II receptors and phosphorylated Smad proteins. Here we demonstrate that application of TGF-beta promotes chondrogenesis by specifically increasing proliferation of CNC-derived chondrocytes and production of extracellular matrix. To understand the molecular regulation of TGF-beta signaling, we have examined the biological function of both TGF-beta receptor-regulated and inhibitory Smads during Meckel's cartilage development. The expression patterns of Smad2, 3, and 7 are identical to the ones of endogenous TGF-beta and its cognate receptors during Meckel's cartilage development, establishing the potential that these intracellular signaling Smads may regulate TGF-beta-mediated chondrogenesis. Functional haploinsufficiency of Smad2 delays TGF-beta-mediated Meckel's cartilage development. Overproduction of Smad7 severely inhibits Meckel's cartilage formation, indicating a negative feedback on TGF-beta signaling by inhibitory Smad is critical in orchestrating TGF-beta-mediated gene regulation during embryonic chondrogenesis. The effectiveness of TGF-beta signaling is highly sensitive to the level of Smad gene expression.

Implantation of octacalcium phosphate combined with transforming growth factor-beta1 enhances bone repair as well as resorption of the implant in rat skull defects

In our previous study, we reported that synthetic octacalcium phosphate (OCP) enhances bone repair if implanted in rat skull defects. We hypothesized that OCP can be used as an effective carrier for transforming growth factor-beta1 (TGF-beta1) to promote bone repair. We designed the present study to investigate histomorphometrically whether combination with recombinant human TGF-beta1 could promote bone repair caused by OCP per se (Control/OCP). A full-thickness standardized trephine defect was made in the rat parietal bone and OCP combined with recombinant human TGF-beta1 (TGF-beta1/OCP) or Control/OCP was implanted into the defect. Four rats from each group were fixed at 2, 4, and 8 weeks after implantation. Histomorphometrical analysis of the percentage of newly formed bone (n-Bone %) and remaining implants (r-Imp %) in the defect was performed. The statistical analysis showed the n-Bone % of TGF-beta1/OCP was significantly higher than that of the Control/OCP in week 4, whereas the r-Imp % of TGF-beta1/OCP was significantly lower than that of the Control/OCP. The present study demonstrated that OCP can be used as an effective carrier for TGF-beta1 and their combination enhances bone repair as well as resorption of the carrier OCP in the early stage of bone formation.

Activation of latent transforming growth factor beta1 by stromelysin 1 in extracts of growth plate chondrocyte-derived matrix vesicles

Previous studies have shown that matrix vesicles isolated from cultures of costochondral growth zone chondrocytes and treated with 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] can activate recombinant human latent transforming growth factor beta1 (rhTGF-beta1). It is unknown what enzyme or other factor in the extracellular organelles is responsible for the activation. This study tested the hypothesis that enzymes present in matrix vesicles can activate latent TGF-beta1 and that this is regulated by 1alpha,25(OH)2D3. To do this, we examined the ability of matrix vesicle extracts to activate small latent rhTGF-beta1. In addition, enzymes previously determined to be present in matrix vesicles were screened for their ability to activate small latent rhTGF-beta1. Recombinant human matrix metalloproteinase 2 (rhMMP-2; 72 kDa gelatinase), rhMMP-3 (stromelysin 1), purified human plasminogen, and purified urokinase (plasminogen activator) were each tested at varying concentrations. To assess the role of cell maturation, we used a cell culture model in which chondrocytes are derived from two distinct zones of rat costochondral cartilage, the resting zone and the growth zone. Matrix vesicles were isolated from these cultures and then tested. The results showed that extracts of matrix vesicles produced by both growth zone and resting zone chondrocytes were able to activate small latent rhTGF-beta1. The effects were dose and time dependent, with greater activity being found in extracts of matrix vesicles from the growth zone chondrocyte cultures. Only rhMMP-3 was able to activate small latent rhTGF-beta1, indicating that stromelysin-1, but not MMP-2, plasminogen, or urokinase, was involved. As observed in the extracts, the effect of rhMMP-3 was time and dose dependent. When anti-MMP-3 antibody was added to matrix vesicle extracts from both cell types, activation of small latent rhTGF-beta1 was dose-dependently blocked. Neither 1alpha,25(OH)2D3 nor 24R,25(OH)2D3 had a direct effect on activation of small latent rhTGF-beta1 by the extracts. However, when intact matrix vesicles were treated with 1alpha,25(OH)2D3, their ability to activate small latent rhTGF-beta1 was increased. Inhibition of phospholipase A2 with quinacrine blocked the 1alpha,25(OH)2D3-dependent effect. These results suggest that the ability of 1alpha,25(OH)2D3-treated matrix vesicles to activate small latent TGF-beta1 is via action of the secosteroid on the matrix vesicle membrane, not on the enzymes responsible for activating latent TGF-beta1. Because matrix vesicles isolated from growth zone chondrocytes have been shown to contain increased phospholipase A2 activity after treatment with 1alpha,25(OH)2D3, it is likely that this secosteroid promotes loss of membrane integrity through phospholipase A2-dependent formation of lysophospholipids, resulting in the release of MMP-3 into the matrix, where latent TGF-beta1 is stored. Taken together, the results of the current study show that matrix vesicles produced by growth plate chondrocytes contain MMP-3, that this enzyme is at least partially responsible for activation of small latent TGF-beta1 in the matrix, and that 1alpha,25(OH)2D3 regulates MMP release from matrix vesicles.

Localization of specific binding sites for 125I-TGF-beta1 to fenestrated endothelium in bone and anastomosing capillary networks in enamel organ suggests a role for TGF-beta1 in angiogenesis

Previous studies have shown endothelial cells to be a major target for endocrine TGF-beta in several soft tissues in the normal growing rat. The potent effect of TGF-beta1 on bone formation prompted us to analyze in detail the localization of specific binding sites for endocrine TGF-beta in hard tissues. At 2.5 minutes after injection of 125I-TGF-beta1, specific binding, as demonstrated by quantitative radioautography, was localized to fenestrated endothelium participating in angiogenesis in the vascular invasion region of the growth plate in bone as well as to anatomizing capillary networks in the maturation zone of the enamel organ. At 15 minutes after injection, the bound ligand was internalized into endocytic vesicles of endothelial cells. In bone, quantitation revealed significant differences in receptor density between endothelia undergoing proliferation vs those in a state of elongation and anastomosis with neighboring endothelial cells. In the rat incisor, specific binding of 125I-TGF-beta1 to endothelium correlated with increased formation of anastomotic capillary networks. These studies identify differential specific binding sites of 125I-TGF-beta1 in angiogenically active endothelium, providing an important link between TGF-beta1, the endothelium, and hard tissue development.

Immunohistochemical expression of Smads 1-6 in the 15-day gestation mouse embryo: signaling by BMPs and TGF-betas

The eight mammalian Smad proteins mediate cellular signaling from members of the transforming growth factor-beta (TGF-beta), bone morphogenetic protein (BMP), and activin families. Smads 1, 5, and 8 transmit signals from BMPs, while Smads 2 and 3 transmit signals from TGF-betas and activin. Smad 4 is a common mediator of both pathways, while Smads 6 and 7 inhibit signaling. Signal transduction involves translocation of Smad complexes to the nucleus and subsequent gene activation. Little is known about the expression of endogenous Smad proteins during development. We identified commercially available Smad antibodies that specifically recognize a unique Smad protein and are suitable for immunohistochemistry. Here we compare the localization of Smads 1, 2, 3, 4, 5, and 6 in tissues of the 15-day gestation mouse embryo. Immunoreactive Smad proteins are seen in many tissues with differences in the localization being dependent upon the cell type. All tissues express Smad 4 and at least one each of the BMP-specific and TGF-beta-specific Smads, while expression of Smad 6 is more restricted. Differences are observed in the nuclear versus cytoplasmic localization among the Smads in different cell types or tissues, suggesting selective activation of Smads during this stage of development.

The influence of transforming growth factor beta1 on mesenchymal cell repair of full-thickness cartilage defects

To repair full-thickness articular cartilage defects in rabbit knees, we transplanted periosteal cells in a fibrin gel and determined the influence of transforming growth factor beta (TGF-beta) in vitro. Alginate served as a temporary supportive matrix component and was removed prior to transplantation. The defects were analyzed macroscopically, histologically, and electron microscopically, and evaluated with a semi-quantitative score system. Periosteal cell transplants showed a chondrogenic differentiation, which results in the development of embryonic-like cartilage tissue after 4 weeks and complete resurfacing of the patellar groove after 12 weeks. In the control groups, no repair was observed. Under the influence of TGF-beta1 we observed a reduction of the cartilage layer, whereas the osteochondral integration and the zonal architecture were improved. Periosteal cell-beads are stable cartilage transplants and have stiffness and elasticity enough for easy and sufficient transplant fixation. Further investigations are necessary to optimize the application of TGF-beta1 for cartilage repair.

TGF-beta2 is increased after fetal tracheal occlusion

BACKGROUND/PURPOSE

Fetal tracheal occlusion (TO) accelerates lung growth in normal and hypoplastic fetal lung. The mechanism of accelerated lung growth remains unknown but may be a result of growth factor induction. Previous studies of growth factors induced by tracheal ligation have characterized mRNA rather than protein expression. Although the transforming growth factor-beta (TGF-beta) family participates in normal lung morphogenesis, its role in lung growth after TO is unclear. The authors hypothesize that TGF-beta expression is increased with TO and may contribute to the accelerated lung growth seen after TO.

METHODS

Diaphragmatic hernia (DH) was created in 80-day-gestation sheep (n = 6; term, 145) by excising the left diaphragm. At 110 days, the trachea was occluded (n = 4) with a clip. DH controls (n = 2) were not occluded. Fetuses were killed at 139 days, and lung samples were snap frozen for tissue analysis. Non-DH control lungs were harvested from full-term animals (n = 2). TGF-beta mRNA was analyzed by semiquantitative reverse transcriptionase-polymerase chain reaction (RT-PCR). TGF-beta protein was assessed by Western blot analysis.

RESULTS

TGF-beta1 mRNA and protein were not increased with tracheal ligation compared with either non-DH or DH controls. TGF-beta2, however, was markedly increased, at both the mRNA and protein level, in ligated lungs compared with nonligated controls.

CONCLUSIONS

TGF-beta2 protein, but not TGF-beta1, is increased in the hypoplastic lungs of fetal sheep after tracheal occlusion. Increased TGF-beta2 expression appears to result from increased or prolonged expression of mRNA transcripts. This is the first study to document a change in growth factor protein levels after TO. Increased TGF-beta2 expression may contribute to accelerated lung growth and decreased surfactant production observed after tracheal occlusion.

Effects of filtration and gamma radiation on the accumulation of RANTES and transforming growth factor-beta1 in apheresis platelet concentrates during storage

BACKGROUND

Platelet-derived biologic response modifiers (BRMs) including RANTES and transforming growth factor (TGF)-beta1 accumulate in platelet components during storage because of platelet activation, and they may play a causative role in nonhemolytic febrile transfusion reactions. The majority of PCs with high unit values are provided by single donor apheresis in Japan.

STUDY DESIGN AND METHODS

RANTES and TGF-beta1 levels in platelet units prepared from single-donor apheresis platelet concentrates (apheresis PCs) and units from whole blood (buffy coat PCs) were investigated. The effects of prestorage and poststorage filtration and gamma radiation on the levels of RANTES and TGF-beta1 in the supernatant of apheresis PCs during storage were also examined.

RESULTS

The levels of RANTES and TGF-beta1 increased during storage from Day 0 to Day 5. The levels of RANTES and of TGF-beta1 correlated with the platelet concentration (p<0.01), but not with the residual white cell concentration in apheresis PCs that were not white cell reduced by filtration (p>0.05). In addition, there was a correlation between RANTES and TGF-beta1 levels (p<0.01). In white cell-reduced apheresis PCs using negatively charged filters as well as in gamma-radiated apheresis PCs, the levels of these two BRMs-did not differ at any storage time from those of untreated apheresis PCs. Filtration of apheresis PCs with negatively charged filters after 3 days of storage significantly (p<0.05) reduced the levels of RANTES, but not of TGF-beta1. There was no reduction in the levels of RANTES and TGF-beta1 levels by positively charged filters. The RANTES levels in buffy coat PCs were slightly higher than but not significantly different from those of apheresis PCs during storage, except for the level on Day 1. There were no differences in the TGF-beta1 levels in apheresis and buffy coat PCs during storage.

CONCLUSION

Prestorage filtration and gamma radiation had neither preventive effects on the accumulation of RANTES and TGF-beta1 nor adverse effects on platelet activation. Negatively charged filters might be useful for the reducing the levels of RANTES in stored apheresis PCs.

Transforming growth factor beta in fracture repair

Transforming growth factor betas are a group of polypeptide growth factors that have a wide range of activities in the musculoskeletal and immunological systems. They are thought to play an important role in the development, induction, and repair of bone. This family of closely related genes includes the five known transforming growth factor betas and also the bone morphogenetic proteins. With the development of new techniques to analyze gene expression, the broad range of cellular activities regulated by transforming growth factor beta is beginning to be understood. The critical role that transforming growth factor beta plays in the regulation and stimulation of mesenchymal precursor cells for chondrocytes, osteoblasts, and osteoclasts is now emerging based on a series of in vitro studies. Although transforming growth factor betas appear to stimulate proliferation of precursor cells, it appears that transforming growth factor betas have an inhibitory effect on mature cell lines. In vivo studies indicate the presence of transforming growth factor beta protein and transforming growth factor beta gene expression in normal fracture healing, whereas exogenous transforming growth factor beta administration stimulates the recruitment and proliferation of osteoblasts in fracture healing. Although the cascade of events that leads to bone formation and repair is not completely understood, transforming growth factor beta's central role in the regulation of fracture healing is not disputed.

Expression of cartilage extracellular matrix and potential regulatory genes in a new human chondrosarcoma cell line

A human chondrosarcoma cell line has been established from an aggressive chondrosarcoma. The cells grow in a monolayer culture (doubling time: 2 days) and form aggregates. The aggregates consist of a rim of cells surrounding a hollow core. The cell line exhibits a unique pattern of mRNA expression with several molecules characteristic of the chondrocyte phenotype. Consistent with the chondrocyte phenotype, mRNAs encoding types IX and XI collagens were present along with an abundant expression of mRNAs encoding the core protein of the cartilage proteoglycans biglycan and aggrecan. No expression of mRNAs encoding types I or II fibrillar collagens or the proteoglycan decorin was observed. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of [35S]sulfate-radiolabeled material confirmed the translation of proteoglycans containing glycosaminoglycan chains. The expression of molecules that contribute to cartilage development and tumorigenesis was examined. The cell line produces abundant mRNA that encodes transforming growth factor-beta1, a member of a family of cartilage and bone inductive proteins. The expression of mRNA encoding two proteins associated specifically with chondrogenesis was detected: Cart-1, a homeobox protein involved in cartilage differentiation, and CD-RAP, a secreted molecule restricted under normal conditions to differentiating chondrocytes and cartilage. Overexpression of p53, a tumor-suppressor gene, was detected. DNA analysis revealed a loss of heterozygosity at the chromosomal locus encoding p53, with the deletion of one p53 allele and the mutation of the remaining allele in both the parent tumor and the cell line. The malignant chondrosarcoma phenotype may be related to the unique gene expression pattern that is characteristic in many ways of differentiating chondroblasts, as well as to the inactivation of the p53 function that could contribute to the proliferative capacity of the cell line. This cell line may serve as a biological model for further investigation of the etiology of human chondrosarcomas and for the synthesis and regulation of cartilage-specific genes.

Anionic glycoconjugates from differentiated and dedifferentiated cultures of bovine articular chondrocytes: modulation by TGF-beta

Primary, high density bovine articular chondrocyte (BAC) cultures, stimulated with transforming growth factor-beta-1, elaborated a high molecular weight anionic glycoconjugate, kDa 540, which does not contain glycosaminoglycan chains (Chan and Anastassiades, 1996). The effect of exogenously added transforming growth factor-beta-1 on the elaboration of the high molecular weight glycoconjugate and of proteoglycans was studied during dedifferentiation of the chondrocytes, utilizing a serial subculture technique under anchorage-dependent conditions, up to four subcultures. The high molecular weight glycoconjugate was detected in the media of all growth-factor-stimulated chondrocyte subcultures, as well as stimulated primary cultures, but not in unstimulated primary cultures or subcultures. By contrast, a large proteoglycan, was only secreted by primary cultures and first subcultures, whether treated with transforming growth factor-beta-1 or untreated. This proteoglycan contained mostly chondroitin sulfate chains, whose hydrodynamic size was increased by the addition of transforming growth factor-beta-1. Further, the pattern of the proteoglycans appearing in the media of subcultures 2-4 was influenced by the addition of transforming growth factor-beta-1, so that while these control subcultures elaborated both the large and small chondroitin sulfate proteoglycans, the equivalent stimulated subcultures elaborated only intermediate sized chondroitin sulfate proteoglycan(s). These results suggest that while dedifferentiation of articular chondrocytes, achieved by subculturing, strongly modulates the effect of exogenously added transforming growth factor-beta-1 on the type of proteoglycan elaborated, the process of dedifferentiation does not influence the transforming-growth-factor-beta-dependent synthesis of the high molecular weight anionic glycoconjugate.

Electrical stimulation induces the level of TGF-beta1 mRNA in osteoblastic cells by a mechanism involving calcium/calmodulin pathway

It is well-known that electrical stimulation can prompt healing of bone fractures. However, the mechanism involved is less clear. In this study, we found that capacitively coupled electric field-induced proliferation of osteoblastic cells (MC3T3-E1) accompanied increased levels of transforming growth factor-beta 1 (TGF-beta1) mRNA determined by quantitative reverse transcription/polymerase chain reaction. Previous reports have shown that verapamil and W-7, both of which block voltage gated calcium channels and inhibit the activation of cytosolic calmodulin, respectively, blocked capacitively coupled electric field-induced proliferation of the osteoblast cells. Interestingly, we found that verapamil and W-7 can also block capacitively coupled electric field-induced elevation of TGF-beta1 mRNA. This result suggested that electrical stimulation induces the level of TGF-beta1 mRNA in osteoblastic cells by a mechanism involving calcium/calmodulin pathway. The potential roles of TGF-beta in the electrical signal-induced osteogenesis was discussed.

Transforming growth factor-beta 1 regulation of bone sialoprotein gene transcription: identification of a TGF-beta activation element in the rat BSP gene promoter

Transforming growth factor-beta (TGF-beta) increases steady-state mRNA levels of several extracellular matrix proteins in mineralized connective tissues. Bone sialoprotein (BSP) is a major constituent of the bone matrix, thought to initiate and regulate the formation of mineral crystals. To determine the molecular pathways of TGF-beta 1 regulation of bone proteins, we have analyzed the effects of the TGF-beta 1 on the expression of the BSP in the rat osteosarcoma cell line (ROS 17/2.8). TGF-beta 1 at 1 ng/ml, increased BSP mRNA levels in ROS 17/2.8 cells approximately 8-fold: the stimulation was first evident at 3 hr, reached maximal levels at 12 hr and slowly declined thereafter. Since the stability of the BSP mRNA was not significantly affected by TGF-beta 1, and nuclear "run-on" transcription analyses revealed only a approximately 2-fold increase in the transcription of the BSP gene, most of the increase in BSP mRNA appeared to involve a nuclear post-transcriptional mechanism. Moreover, the effects of TGF-beta 1 were indirect, since the increase in BSP mRNA was abrogated by cycloheximide (28 micrograms/ml). To identify the site of transcriptional regulation by TGF-beta 1, transient transfection analyses were performed using BSP gene promoter constructs linked to a luciferase reporter gene. Constructs that included nt -801 to -426 of the promoter sequence were found to enhance transcriptional activity approximately 1.8-fold in cells treated with TGF-beta 1. Within this sequence, approximately 500 nt upstream of the transcription start site, a putative TGF-beta activation element (TAE) was identified that contained the 5'-portion of the nuclear factor-1 (NF-1) canonical sequence (TTGGC) overlapping a consensus sequence for activator protein-2 (AP-2). The functionality of the TAE was shown by an increased binding of a nuclear protein from TGF-beta 1 stimulated cells in gel mobility shift assays and from the attenuation of TGF-beta 1-induced luciferase activity when cells were co-transfected with a double-stranded TAE oligonucleotide. Competition gel mobility shift analyses revealed that the nuclear protein that binds to the TAE has similar properties to, but is distinct from, NF-1 nuclear protein. These studies have therefore identified a TGF-beta activation element (TAE) in the rat BSP gene promoter that mediates the stimulatory effects of TGF-beta 1 on BSP gene transcription.

Osteoarthritis in the temporo-mandibular joint (TMJ) of aged mice and the in vitro effect of TGF-beta 1 on cell proliferation, matrix synthesis, and alkaline phosphatase activity

The temporo-mandibular joint of aged mice develops osteoarthritic (OA) degenerative lesions. Adult chondrocytes have a low rate of cell replication, and cartilage repair potential is very limited. One of the major problems in OA is the low rate of matrix synthesis and the inability of the chondrocytes to exceed the rate of matrix degradation. These combined factors lead to the overall destruction of the cartilage as seen in OA. Cartilage degradation is mediated by elevated proteolytic activity of enzymes. Among the enzymes degrading cartilage are the metalloproteinases, stromelysin and collagenase. Other proteinases that may potentially participate in matrix degradation are the lysosomal enzymes cathepsin B, D, and L, and acid phosphatase. On the other hand, alkaline phosphatase (ALP) is an enzyme that has been shown to be a marker for anabolic activity in skeletal tissues such as bone and cartilage. The cartilage of the mandibular condyle in the T-M-J from aged mice reveals OA lesions. An overall reduction of cell proliferation and sulfated proteoglycan synthesis has been also shown in this joint. In the present study the effects of hTGF-beta on the stimulation of DNA and sulfated GAG synthesis and ALP activity were studied. Mandibular condyle cartilage obtained from 12-month-old ICR male mice were cultured in BGJb serum-free medium for 24-72 hours, supplemented with 0.1-10 ng/ml hTGF-beta 1. 3H-thymidine and 35S-sulfate were added for the last 24 hours of the culture and their incorporation into DNA and sulfated GAGs respectively, as well as the activity of ALP, were determined. Results indicated that hTGF-beta 1 enhanced the incorporation of both 3H-thymidine and of 35S-sulfate into cartilage cultures of aged mice, and also induced ALP activity. It thus appeared that in OA degenerating articular cartilage, the chondrocytes could be stimulated in vitro to proliferate and to synthesize new matrix, thus indicating induced anabolic activity in the tissue.

Three-dimensional culture of bovine chondrocytes in rotating-wall vessels

The Rotating-Wall Vessel (RWV) was used to culture chondrocytes for 36 d to observe the influence of low-shear and quiescent culture conditions allowing three-dimensional freedom on growth, differentiation, and extracellular matrix formation. Chondrocytes were freshly isolated from bovine cartilage and placed into the RWV with Cytodex-3 microcarriers. Nonadherent petri dishes were initiated with microcarriers as representative of standard culture conditions. In the RWV, large three-dimensional aggregates (5-7 mm) were formed in suspension. In addition, a large sheet of matrix adhered to the oxygenator core and vessel endcaps. Petri dish culture resulted in the formation of sheets of chondrocytes with no matrix production. Immunocytochemical analyses on histologic sections of tissue obtained from the RWV and the petri dish controls were performed with antibodies against fibronectin, collagen II, chondroitin-4-sulfate, chondroitin-6-sulfate, and vimentin. Results demonstrated increased signal in the RWV material while the petri dishes demonstrated a slight decrease in signal. In addition, differentiated chondrocytes were observed in sections of RWV material through 36 d, while few were observed in the sections of petri dish material. These results indicate that the unique conditions provided by the RWV afford access to cellular processes that signify the initiation of differentiation as well as production of normal matrix material.

Studies in cranial suture biology: Part I. Increased immunoreactivity for TGF-beta isoforms (beta 1, beta 2, and beta 3) during rat cranial suture fusion

The mechanisms involved in normal cranial suture development and fusion as well as the pathophysiology of craniosynostosis, a premature fusion of the cranial sutures, are not well understood. Transforming growth factor-beta isoforms (TGF-beta 1, beta 2, and beta 3) are abundant in bone and stimulate calvarial bone formation when injected locally in vivo. To gain insight into the role of these factors in normal growth and development of cranial sutures and the possible etiology of premature cranial suture fusion, we examined the temporal and spatial expression of TGF-beta isoforms during normal cranial suture development in the rat. In the Sprague-Dawley rat, only the posterior frontal cranial suture undergoes fusion between 12 and 22 days of age, while all other cranial sutures remain patent. Therefore, immunohistochemical analysis of the fusing posterior frontal suture was compared with the patent sagittal suture at multiple time points from the fetus through adult. Whereas the intensity of immunostaining was the same in the posterior frontal and sagittal sutures in the fetal rat, there was increased immunoreactivity for TGF-beta isoforms in the actively fusing posterior frontal suture compared with the patent sagittal suture starting 2 days after birth and continuing until approximately 20 days. There were intensely immunoreactive osteoblasts present during fusion of the posterior frontal suture. In contrast, the patent sagittal suture was only slightly immunoreactive. A differential immunostaining pattern was observed among the TGF-beta isoforms; TGF-beta 2 was the most immunoreactive isoform and was also most strongly associated with osteoblasts adjacent to the dura and the margin of the fusing suture. Since the increased expression of TGF-beta 2 during suture fusion suggested a possible regulatory role, recombinant TGF-beta 2 was added directly to the posterior frontal and sagittal sutures in vivo to determine if suture fusion could be initiated. Exogenously added TGF-beta 2 stimulated fusion of the ectocranial surface of the posterior frontal suture. These data provide evidence for a regulatory role for these growth factors in cranial suture development and fusion. Additionally, the intense immunostaining for TGF-beta 2 in the dura mater underlying the fusing suture supports a role for the dura mater in suture fusion. It is possible that premature or excessive expression of these factors may be involved in the etiopathogenesis of craniosynostosis and that modulation of the growth factor profile at the suture site may have potential therapeutic value.

Expression of the gene for transforming growth factor-beta in avian dyschondroplasia

Previous immunolocalisation studies of dyschondroplasia have indicated that there is a reduction in the number of growth plate chondrocytes containing the protein transforming growth factor beta 3 (TGF-beta 3). The reduction in TGF-beta 3 in dyschondroplasia is likely to be a direct result of a reduction in the expression of the TGF-beta 3 gene. mRNA was extracted from small (0.09 g) samples of growth cartilage from the proximal tibiotarsus of three-week-old broiler chicks. The cartilage samples contained cells from all three zones of the growth plate (proliferative, transitional and upper hypertrophic) and were collected from normal and dyschondroplastic growth plates. The dyschondroplastic growth plates were identified by an accumulation of transitional chondrocytes which were considered to be a result of a failure to differentiate to the hypertrophic phenotype. A semi-quantitative polymerase chain reaction (PCR) was used to estimate the quantity of mRNA specific for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and for each of the three isoforms of TGF beta (TGF-beta 1, TGF-beta 2 and TGF-beta 3) in each of the cartilage samples. The levels of expression of mRNA for GAPDH, TGF-beta 1 and TGF-beta 2 were similar in the two groups, but the expression of TGF-beta 3 mRNA was significantly reduced in the samples from the dyschondroplastic growth plates. The reduction in TGF-beta 3 levels is thought to be associated with the failure of chondrocyte hypertrophy in dyschondroplasia, and provides in vivo evidence that TGF-beta 3 is part of the cascade of events associated with the differentiation of chondrocytes during endochondral ossification in the chick.

Limited chondro-osteogenesis by recombinant human transforming growth factor-beta 1 in calvarial defects of adult baboons (Papio ursinus)

The therapeutic utility of a single application of recombinant human transforming growth factor-beta (hTGF-beta) has not been previously tested in large osseous wounds in primates. Sixteen calvarial defects, 25 mm in diameter, were prepared in four adult male baboons (Papio ursinus). In each animal, three defects were treated with increasing doses of hTGF-beta 1 in conjunction with baboon insoluble collagenous bone matrix as carrier (5, 30, and 100 micrograms of hTGF-beta 1/g of matrix). The fourth defect was implanted with collagenous matrix without hTGF-beta 1 as control. Serial undecalcified sections were prepared from the specimens harvested on day 30. Islands of cartilage and endochondral osteogenesis were found in hTGF-beta 1-treated defects, irrespective of the doses used. Histomorphometry of the defect site showed no significant differences between control and hTGF-beta 1-treated specimens with regard to bone and osteoid volumes. However, analysis of the regenerated tissue in proximity to the defect margins only showed that, on average, greater amounts of bone formed in specimens that were treated with 5 and 30 micrograms of hTGF-beta 1 when compared with controls. This suggests a possible effect on osteoblastic cells originating from the periosteal and endosteal spaces of the severed calvaria. Overall, however, this difference has no therapeutic implications for the healing of large cranial wounds in primates. The present findings indicate that a single application of hTGF-beta 1, in conjunction with collagenous matrix, results in limited chondro-osteogenesis in defects of membranous bone of adult baboons.

Isolation and partial characterization of a high molecular weight anionic glycoconjugate from transforming growth factor-beta treated bovine articular chondrocyte cultures

A high molecular weight anionic glycoconjugate was isolated from the media of the transforming growth factor-beta treated chondrocyte cultures by anion-exchange chromatography on DEAE-Sephacel and Mono Q columns and was partially characterized. This high molecular weight anionic glycoconjugate was not detected in the non-treated (control) cultures. Characterization studies showed that the glycoconjugate is a non-reducible, non-collagenous glycoprotein containing O-linked, N-linked, and sialic acid substituted carbohydrate units. The isolated glycoconjugate stained "blue" with Stains All and migrated as a single band on sodium dodecyl sulfate gradient gels (2.5-10% acrylamide - diallyl tartardiamide) at an estimated molecular weight of 540 000. Amino acid and amino sugar analyses showed that it is rich in aspartic acid--asparagine, glutamic acid--glutamine, alanine, proline, and glycine, and contains galactosamine and glucoasmine. This transforming growth factor-beta inducible glycoprotein may be involved in cell differentiation and in the cartilage repair process. It may also be used as a marker to localize the biological activity of transforming growth factor-beta in articular cartilage.

Regulators of chondrocyte differentiation in tibial dyschondroplasia: an in vivo and in vitro study

Tibial dyschondroplasia (TD) is a disorder of endochondral bone growth and results in the retention of a mass of unmineralized, avascular cartilage extending into the metaphysis. We have studied various parameters of chondrocyte differentiation, both in isolated chick chondrocytes and growth plate sections, in an attempt to determine whether the inhibition in chondrocyte differentiation seen in TD is a consequence of an inherent incapability of chondrocytes to differentiate terminally and mineralize. Results from in vitro experiments indicated that both normal and lesion chondrocytes synthesized a matrix that stained with antibodies to types II and X collagen and displayed foci of mineralization. Alkaline phosphatase activity in lesion chondrocytes was significantly increased in comparison to that in normal hypertrophic chondrocytes. In addition, normal and lesion chondrocytes in culture synthesized transforming growth factor-beta and 24,25(OH)2D3 but not 1,25(OH)2D3. There was no significant difference in the production rate of these growth regulators between normal and lesion chondrocytes. In contrast, in growth plate sections, alkaline phosphatase activity was markedly reduced in the lesion chondrocytes and sites of mineralization were not evident. Type II collagen was located throughout the growth plate and lesion, but type X collagen was not present within the lesion except at sites of vascularization. These results indicate that, in culture, lesion chondrocytes have the ability to differentiate terminally and mineralize, and suggest that the primary abnormality in TD is related to a developmental fault which is only operative in vivo. This may include a defect in cartilage vascularization and/or impairment of chondrocyte differentiation by mechanisms that have not yet been elucidated but may involve the abnormal production of regulatory factors.

Formation of cartilage-like spheroids by micromass cultures of murine C3H10T1/2 cells upon treatment with transforming growth factor-beta 1

Formation of cartilage during both embryonic development and repair processes involves the differentiation of multipotential mesenchymal cells. The mouse cell line, C3H10T1/2, has been shown to be multipotential and capable of differentiating into various phenotypes normally derived from embryonic mesoderm, including myocytes, adipocytes and chondrocytes. In this study, we have analyzed the induction of chrondrogenesis in C3H10T1/2 cells by transforming growth factor-beta (TGF-beta 1, human recombinant form). Treatment of high-density micromass cultures of C3H10T1/2 cells with TGF-beta 1 resulted in the formation of a three dimensional spheroid structure, which exhibited cartilage-like histology. Extracellular matrix components characteristic of cartilage, type II collagen and cartilage link protein, were demonstrated by immunohistochemistry. TGF-beta 1 treatment increased collagen synthesis, and immunoblot analysis showed the presence of type II collagen in TGF-beta 1-treated micromass cultures, but not in TGF-beta 1-treated monolayer cultures nor in untreated cultures. An increase in radioactive sulfate uptake relative to DNA synthesis was also seen in TGF-beta 1-treated micromass cultures forming spheroids, indicating the increased synthesis of sulfated proteoglycans. These observations indicated that the spheroids formed are of a cartilaginous nature, and that multipotential C3H10T1/2 cells, which do not spontaneously enter the chondrogenic pathway, can be induced to undergo cellular differentiation towards chondrogenesis in vitro through culture in a favorable environment.

IL-1 beta and TGF-beta 1 modulate the sulphation grade of chondro-disaccharides in porcine articular cartilage: a capillary electrophoresis study

This report describes the effect of interleukin-1 beta (IL-1 beta) and transforming growth factor-beta 1 (TGF-beta 1) on proteoglycan release from cartilage explants and modification at the sulphation level. Matrix proteoglycans purified by ion-exchange chromatography were composed of two distinct peaks (1 and 2) each showing a different Kav value when they were subjected to size-exclusion chromatography on a Sepharose CL-2B column. Glycosaminoglycans (GAGs) of conditioned medium and extracellular matrix proteoglycans were digested by chondroitin ABC and AC lyase, suggesting that chondroitin sulphate (CS) is the major GAG present (80-90%). Structural analysis of disaccharides, by capillary zone electrophoresis, revealed a different pattern of sulphated glycosaminoglycans when cartilage was treated with either IL-1 beta or TGF-beta 1. Analysis of GAGs released into the medium from TGF-beta 1 treated cartilage showed a reduction in the level of 4-S-disaccharide (delta Di4S) and an increase in non-sulphated disaccharides (delta Di0S), while no significant changes were found in IL-1 beta treated cartilage. In the extracellular matrix, IL-1 beta and TGF-beta 1 induced a more complex rearrangement of the GAGs. The level of non-sulphated disaccharides was increased whereas that of total sulphated disaccharides was reduced. Taken together, these results suggest that both cytokines modify the structure of GAGs, probably by interfering with the activity or the synthesis of sulphotransferases involved in GAG turnover.

Processing of transforming growth factor beta 1 precursor by human furin convertase

Proteolytic processing of the transforming growth factor beta precursor (pro-TGF beta) is an essential step in the formation of the biologically active TGF beta homodimeric protein (TGF beta). The 361-amino-acid precursor pro-TGF beta 1 has within its primary structure the R-H-R-R processing signal found in many constitutively secreted precursor proteins and potentially recognized by members of the mammalian convertase family of endoproteases. To determine whether cleavage of pro-TGF beta 1 can be achieved by the furin convertase in vitro, purified precursor was incubated in the presence of a truncated/secreted form of the enzyme. Immunoblots showed that the 55-kDa pro-TGF beta 1 was converted into the 44 and 12.5 kDa bands corresponding to the pro-region and the mature monomer, respectively. Treatment of pro-TGF beta 1 with furin resulted in a 5-fold increase in the production of biologically active TGF beta 1. Furthermore, when expressed in the furin-deficient LoVo cells, no processing of pro-TGF beta 1 was observed. In contrast, efficient processing was observed when pro-TGF beta was coexpressed with the furin convertase. Collectively, these results provide evidence that in our experimental systems the TGF beta 1 precursor is efficiently and correctly processed by human furin thus permitting release of the biologically active peptide.

Isolation of a novel latent transforming growth factor-beta binding protein gene (LTBP-3)

This paper reports the molecular cloning of a novel gene in the mouse that shows structural similarities to the microfibril protein fibrillin and to the latent transforming growth factor-beta (TGF-beta) binding protein (LTBP), a component of the latent TGF-beta complex. The gene was initially isolated during a low stringency polymerase chain reaction screen of a NIH 3T3 cell cDNA library using primers that amplify a human fibrillin-1 epidermal growth factor-like repeat. Three lines of evidence suggest that the mouse gene is a third member of the LTBP gene family, which we designate LTBP-3. First, the deduced polypeptide, which consists of 15 epidermal growth factor-like repeats, 3 TGF binding protein repeats, and 2 proline- and glycine-rich sequences, shows 38.4% identity with LTBP-1 but only 27% identity with fibrillin-1. Second, the gene appears to be co-expressed in developing mouse tissues with TGF-beta. Third, immunoprecipitation studies using mouse preosteoblast MC3T3-E1 cells and a specific anti-peptide polyclonal antiserum reveal that the mouse polypeptide forms a complex with the TGF-beta 1 precursor. Finally, we note that the LTBP-3 gene was recently localized to a distinct genetic locus (Li, X., Yin, W., Perez-Jurado, L., Bonadio, J., and Francke, U. (1995) Mamm. Genome 6, 42-45). Identification of a third binding protein provides further insight into a mechanism by which latent TGF-beta complexes can be targeted to connective tissue matrices and cells.

Localization of Cytokines in Cholesteatoma Tissue

Acquired cholesteatoma is associated with an intense inflammatory reaction with resuitant tissue and bone destruction. Cytokines are molecules released by inflammatory cells at the site of infection and are potent mediators of inflammation and the immune response. Five cytokines, tumor necrosis factor-α, transforming growth factor-β1 and 2, and interleukin-1 and 6, were immunolocalized in human cholesteatoma epithelium and subepithelial stroma, with greater intensity of staining compared with noninflamed external auditory canal skin. Increased interleukin-6 activity in cholesteatoma epithelium and stroma correlated significantly with the presence of ossicular and bony erosion and granulation tissue noted intraoperatively. Transforming growth factor-β2 activity in cholesteatoma epithelium correlated significantly with bony erosion at surgery. Additionally, transforming growth factor-β1 activity in cholesteatoma epithelium correlated significantly with increased length of disease. Tumor necrosis factor-a, interleukin-1, and interleukin-6 appear to be involved in the inflammation and resultant remodeling associated with cholesteatoma. We hypothesized a protective function of transforming growth factor-β1 and 2 in the presence of cholesteatoma. The antiinflammatory and osteoclast and keratinocyte inhibitory actions of the transforming growth factor-βs could potentially slow the proliferation and resultant tissue destructiveness associated with Cholesteatoma.