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T K Sampath

Publications and source records attributed to T K Sampath.

At least 37 records · Page 2Linked to original sources
PubMed1997

Expression and localization of bone morphogenetic proteins (BMPs) and BMP receptors in ossification of the ligamentum flavum.

To clarify the pathogenesis of ossification of the ligamentum flavum (OLF), we examined the expression and localization of bone morphogenetic proteins (BMPs) and their receptors (BMPRs) in the ligamentum flavum of the patients with OLF by immunohistochemical staining and compared them with staining patterns in control patients. The BMPRs appeared extensively in mature and immature chondrocytes around the calcified zone and in spindle-shaped cells and round cells in the remote part from ossified foci in examined tissue of OLF. The ligands for BMPRs, BMP-2/-4 and osteogenic protein-1 (OP-1)/BMP-7, colocalized in OLF patients. In the control cases, expression of BMPs and BMPRs was observed around the calcified zone at the insertion of the ligamentum flavum to the bone, and limited expression was found in the smaller range. Thus, the expression profile of BMPs and BMPRs in OLF patients was entirely different from the control patients, suggesting that BMPs may be involved in promoting endochondral ossification at ectopic ossification sites in OLF, and that ossification activity is continuous in these patients.

Activin Receptors↗
PubMed1997

Osteogenic protein-1 stimulates production of insulin-like growth factor binding protein-3 nuclear transcripts in human osteosarcoma cells.

To begin delineating molecular mechanisms by which osteogenic protein-1 (OP-1) modulates its effect on the insulin-like growth factor (IGF) system in human skeletal cells, we evaluated time-course effects of OP-1 on the expression of IGFBP-3 messenger RNA (mRNA) in human SaOS-2 osteosarcoma cells and found that 100 ng/ml of OP-1 increased (maximum 10.7-fold at 24 h; P < 0.01) the level of IGFBP-3 mRNA in a time-dependent manner (from 3-36 h; treatment x time interaction, P < 0.001). The stimulatory effect of OP-1 on IGFBP-3 mRNA was not promoted by transcript stabilization; actually, OP-1 treatment selectively increased the decay of mRNA for IGFBP-3 (T1/2 = 5 h vs. 24 h for OP-1 and controls), but not for IGFBP-4 or beta-actin. Conversely, OP-1 acutely increased IGFBP-3 nuclear transcript abundance in total RNA samples ranging between 1-24 h of treatment. After 6 h of treatment, OP-1 produced an average 4-fold increase (P < 0.02; n = 4 experiments) in the level of IGFBP-3 nuclear transcripts vs. a 3-fold increase (P < 0.01; n = 2 experiments) in mRNA abundance. The OP-1 stimulated induction of IGFBP-3 nuclear transcript and mRNA expression was dependent on de novo protein synthesis. Transient transfection experiments were undertaken to isolate putative OP-1 stimulatory cis-elements within 1.8-kb of the IGFBP-3 5'-flanking region in SaOS-2 and TE-85 osteosarcoma cells. In these experiments, OP-1 did not stimulate IGFBP-3 proximal promoter activity in either cell line, thus suggesting that OP-1 reactive domains may be located either beyond the currently established 5'-flanking region, or within internal exon/intron regions of the IGFBP-3 gene. In conclusion, OP-1 treatment stimulates IGFBP-3 expression in human osteoblastic cells by a mechanism that largely promotes the production of IGFBP-3 nuclear transcripts, a process that requires de novo protein synthesis, and overrides an OP-1-induced targeted degradation of IGFBP-3 steady-state mRNA.

Actins↗
PubMed1997

Osteogenic protein-1 up-regulation of the collagen X promoter activity is mediated by a MEF-2-like sequence and requires an adjacent AP-1 sequence.

Bone morphogenetic proteins induce chondrogenesis and osteogenesis in vivo. To investigate molecular mechanisms involved in chondrocyte induction, we examined the effect of osteogenic protein (OP)-1/bone morphogenetic protein-7 on the collagen X promoter. In rat calvaria-derived chondrogenic C5.18 cells, OP-1 up-regulates collagen X mRNA levels and its promoter activity in a cell type- specific manner. Deletion analysis localizes the OP-1 response region to 33 bp (-310/-278), which confers OP-1 responsiveness to both the minimal homologous and heterologous Rous sarcoma virus promoter. Transforming growth factor-beta2 or activin, which up-regulates the expression of a transforming growth factor-beta-inducible p3TP-Lux construct, has little effect on collagen X mRNA and on this 33-bp region. Mutational analysis shows that both an AP-1 like sequence (-294/-285, TGAATCATCA) and an A/T-rich myocyte enhancer factor (MEF)-2 like sequence (-310/-298, TTAAAAATAAAAA) in the 33-bp region are necessary for the OP-1 effect. Gel shift assays show interaction of distinct nuclear proteins from C5.18 cells with the AP-1-like and the MEF-2-like sequences. OP-1 rapidly induces nuclear protein interaction with the MEF-2-like sequence but not with the AP-1 like sequence. MEF-2-like binding activity induced by OP-1 is distinct from the MEF-2 family proteins present in C2C12 myoblasts, in which OP-1 does not induce collagen X mRNA or up-regulate its promoter activity. In conclusion, we identified a specific response region for OP-1 in the mouse collagen X promoter. Mutational and gel shift analyses suggest that OP-1 induces nuclear protein interaction with an A/T-rich MEF-2 like sequence, distinct from the MEF-2 present in myoblasts, and up-regulates collagen X promoter activity, which also requires an AP-1 like sequence.

Activins↗
PubMed1997

Role of BMP-2 and OP-1 (BMP-7) in programmed cell death and skeletogenesis during chick limb development.

Bone Morphogenetic Protein 2 (BMP-2) and Osteogenic Protein 1 (OP-1, also termed BMP-7) are members of the transforming growth factor beta superfamily. In the present study, we have analyzed the effects of administering them locally at different stages and locations of the chick limb bud using heparin beads as carriers. Our results show that these BMPs are potent apoptotic signals for the undifferentiated limb mesoderm but not for the ectoderm or the differentiating chondrogenic cells. In addition, they promote intense radial growth of the differentiating cartilages and disturb the formation of joints accompanied by alterations in the pattern of Indian hedgehog and ck-erg expression. Interestingly, the effects of these two BMPs on joint formation were found to be different. While the predominant effect of BMP-2 is alteration in joint shape, OP-1 is a potent inhibitory factor for joint formation. In situ hybridizations to check whether this finding was indicative of specific roles for these BMPs in the formation of joints revealed a distinct and complementary pattern of expression of these genes during the formation of the skeleton of the digits. While Op-1 exhibited an intense expression in the perichondrium of the developing cartilages with characteristic interruptions in the zones of joint formation, Bmp-2 expression was a positive marker for the articular interspaces. These data suggest that, in addition to the proposed role for BMP-2 and OP-1 in the establishment of the anteroposterior axis of the limb, they may also play direct roles in limb morphogenesis: (i) in regulating the amount and spatial distribution of the undifferentiated prechondrogenic mesenchyme and (ii) in controlling the location of the joints and the diaphyses of the cartilaginous primordia of the long bones once the chondrogenic aggregates are established.

Animals↗
PubMed1997

Establishment and characterization of conditionally immortalized stromal cell lines from a temperature-sensitive T-Ag transgenic mouse.

We established bone marrow stromal cell lines from a transgenic mouse that harbors a temperature-sensitive mutant of the simian virus 40-derived large T-antigen under the control of a major histocompatibility complex (MHC) I promotor. These cell lines were screened for their ability to induce the formation of osteoclasts in a spleen cell/stromal cell coculture system. By means of this screen, five clones, referred to as marine bone marrow stromal clone 1 (mBMS-B1) mBMS-B2, mBMS-B14, mBMS-B18, and mBMS-B21, were selected for detailed characterization. Cell growth depends on culture conditions, i.e., cells grow at 33 degrees C in the presence of murine interferon-gamma, whereas cell proliferation ceases at 39 degrees C. The phenotype of the cells is also correlated with the culture conditions because the osteoclast inductive capacity is only seen at 39 degrees C, indicating that the cells undergo differentiation when the transforming agent is inactivated. These conditionally immortalized stromal cells can be induced to express a variety of markers that are typical for mature osteoblasts, e.g., alkaline phosphatase activity and expression of functional parathyroid hormone receptor after stimulation with soluble osteogenic protein 1 (sOP-1). mRNA analysis revealed the expression and regulation of osteopontin, osteonectin, and collagen alpha 1(I) as well as the inducibility of osteocalcin upon treatment with sOP-1. The cells have the potential to form mineralized nodules in supplemented medium. We observed expression of vascular cell adhesion molecule-1, which is stimulated upon treatment of the cells with 1 alpha,25-dihydrocholecalciferol after 4 days, indicating the presence of the receptor for this steroid. These cell lines represent a model to study mechanisms and factors involved in osteoblast differentiation.

Alkaline Phosphatase↗
PubMed1997

Stimulation of proteoglycan synthesis in explants of porcine articular cartilage by recombinant osteogenic protein-1 (bone morphogenetic protein-7).

UNLABELLED: Osteogenic protein-1 (also known as bone morphogenetic protein-7) is a member of the bone morphogenetic protein family. Bone morphogenetic proteins and related members of the TGF-beta (transforming growth factor-beta) superfamily are involved in the development and repair of bone. Recombinant bone morphogenetic proteins induce the formation of new cartilage and bone at heterotopic sites. We investigated the influence of recombinant osteogenic protein-1 (at doses of three, ten, thirty, or 100 nanograms per milliliter) on the synthesis and release of proteoglycans and the maintenance of a steady-state concentration of proteoglycans in explants of porcine articular cartilage that were maintained in chemically defined serum-free medium. We found a dose-dependent stimulation of proteoglycan synthesis and a concurrent decrease in the rate of release of proteoglycans from the explants. The size of the proteoglycan monomers and the composition of the glycosaminoglycan chains in the untreated articular cartilage were similar to those in the articular cartilage treated with osteogenic protein-1. The capacity of the newly synthesized proteoglycan monomers to form aggregates with exogenous hyaluronic acid was found to be similar to that of proteoglycans in bovine nasal cartilage. Our results demonstrated that osteogenic protein-1 stimulated the synthesis of proteoglycans and diminished the release of proteoglycans from explants of porcine articular cartilage. CLINICAL RELEVANCE: The maintenance and repair of articular cartilage is a formidable challenge in clinical orthopaedics. The stimulation of proteoglycan synthesis by osteogenic protein-1 (bone morphogenetic protein-7) in explants of cartilage maintained in chemically defined serum-free medium implies that recombinant osteogenic protein-1 may play a role in the maintenance of a steady-state concentration of proteoglycans in articular cartilage, a desirable prerequisite for optimum repair of cartilage. Osteogenic protein-1 can initiate the formation of cartilage from mesenchymal cells. Once new cartilage has formed at the site of repair, osteogenic protein-1 also may maintain the synthesis of proteoglycans.

Animals↗
PubMed1997

Osteochondral allografts with an intramedullary muscle flap in rabbits.

A model for hemijoint reconstruction using partially demineralized and lyophilized osteochondral allografts combined with an intramedullary muscle flap is described. The proximal 2/3 of the humerus was resected in 10 rabbits. The remaining defect was reconstructed with either a control lyophilized osteochondral allograft or a lyophilized allograft with a muscle flap filling the marrow cavity. Graft healing was followed by serial radiographs and magnetic resonance imaging. The grafts were harvested at 5 weeks for histologic analysis. By 5 weeks, 4 of 5 control allografts had fractured. In contrast, only 1 allograft with an intramedullary muscle flap showed evidence of a cortical break. Magnetic resonance imaging of control allografts showed a persistent large dead space within the marrow cavity and callus formation only at the outer cortical surface. Magnetic resonance imaging of allografts with an intramedullary muscle flap showed muscle obliterating the marrow cavity and areas of callus formation at both the outer and inner cortical surfaces. Histologically, graft incorporation was occurring at the outer cortical surface of the control allografts. In contrast, graft incorporation was occurring at both the outer and inner cortical surfaces of the allografts with an intramedullary muscle flap. The articular surface of the control allografts was severely degenerated. In allografts with an intramedullary muscle flap, the articular surface was smoother. Joints reconstructed with allografts with an intramedullary muscle flap had a significantly better range of motion at 5 weeks compared with control allografts. These results suggest that an intramedullary muscle flap can improve the functional results of joints reconstructed with partially demineralized and lyophilized osteochondral allografts by providing both vascularity and an increased population of mesenchymal stem cells capable of responding to bone morphogenetic proteins that reside in the partially demineralized allograft.

Animals↗
PubMed1997

Bone morphogenetic protein receptors and activin receptors are highly expressed in ossified ligament tissues of patients with ossification of the posterior longitudinal ligament.

Ossification of the posterior longitudinal ligament (OPLL) is a pathological ossification in the spinal ligament, with formation of ectopic bone mainly through endochondral ossification. Bone morphogenetic proteins (BMPs) and activins are multifunctional proteins that belong to the transforming growth factor-beta superfamily and that have been implicated in the formation of new bone and cartilage. BMPs and activins signal via type I and type II receptors for BMPs (BMPRs) and activins (ActRs), respectively. OP-1/BMP-7 binds to BMPR-II and ActR-II and forms complexes with BMPR-IA and -IB and ActR-I. We studied the expression of BMPR-IA, -IB, and -II, ActR-I, ActR-II, and OP-1/BMP-7 by immunohistochemistry in ossified ligament tissues of patients with OPLL and control ligament tissues from patients with cervical disc herniation. The expression of BMPRs and ActRs was elevated in OPLL compared with controls. Expressions of BMPR-IA, -IB, and -II were observed not only in chondrocytes at the fibrocartilage tissue around the calcified zone but also in fibroblast-like spindle cells at the nonossified ligament. ActR-I and -II were found co-localized in the hypertrophic chondrocytes near the calcified zone and in the ossified tissue. OP-1/BMP-7 was expressed in chondrocytes near the calcified zone. In the control cases, the BMPRs and ActRs were only weakly expressed in the fibrocartilage tissue at the site of ligament attachments to bone and OP-1/BMP-7 was not detected. Enhanced expression of BMPRs at the nonossified ligament in OPLL patients suggests that these cells have a greater potential to differentiate into osteogenic cells than ligament cells from non-OPLL patients. The high expression of BMPRs and ActRs in the ectopic ossified ligament suggests that BMPs and activin may be tightly involved in the pathological ossification process of OPLL.

Activin Receptors↗
PubMed1997

[Functions of the transforming growth factor-beta superfamily in eyes].

One human body is composed of 6 x 10(13) cells, and eyes are also composed of many cells of different functions. The cellular functions and intercellular interaction are regulated by many regulators including cytokines and growth factors to maintain the homeostasis. The transforming growth factor-beta (TGF-beta) superfamily, a large family of multifunctional factors, regulates various cellular functions, including cellular proliferation, migration, differentiation, apoptosis and extracellular matrix production. The TGF-beta superfamily contains about 30 multifunctional factors, and is divided into several families according to the sequence homology. The TGF-beta family, the activin family, and bone morphogenic proteins belong to the TGF-beta superfamily. TGF-beta superfamily members transduce signals through type I and type II serine/threonine type transmembrane receptors. The signals are transduced from receptors through nuclei by Smad family members, which are phosphorylated by the activated type I receptors and translocate from cytoplasm into nuclei. TGF-beta family members and the TGF-beta superfamily receptor family are expressed in ocular tissues including the cornea, ciliary epithelium, lens epithelium, retina, and blood vessels. This observation suggests the importance of the TGF-beta superfamily in eyes. Smad family members (Smad 1, Smad 2, Smad 3 and Smad 4) are expressed in the cultured retinal pigmant epithelial cell line (D407), in which TGF-beta and activin A stimulate the translocation of Smad 2, but not Smad 1 into nuclei, whereas bone morphogenetic protein (BMP) stimulates that of Smad 1, but not Smad 2. TGF-beta superfamily members play important roles in the pathogenesis of retinal neovascularization and in the wound healing process of corneal tissue. TGF-beta inhibits the endothelial functions, but, stimulates angiogenesis in vivo. TGF-beta is involved in the formation of abnormal connective tissue in corneal wound healing. In these processes, many cytokines and growth factors are involved, interacting with each other and forming networks. It is mandatory to clarify the networks to investigate molecular pathogenesis and new therapeutic agents.

Diabetic Retinopathy↗
PubMed1996

Induction of nephrogenic mesenchyme by osteogenic protein 1 (bone morphogenetic protein 7).

The definitive mammalian kidney forms as the result of reciprocal interactions between the ureteric bud epithelium and metanephric mesenchyme. As osteogenic protein 1 (OP-1/bone morphogenetic protein 7), a member of the TGF-beta superfamily of proteins, is expressed predominantly in the kidney, we examined its involvement during metanephric induction and kidney differentiation. We found that OP-1 mRNA is expressed in the ureteric bud epithelium before mesenchymal condensation and is subsequently seen in the condensing mesenchyme and during glomerulogenesis. Mouse kidney metanephric rudiments cultured without ureteric bud epithelium failed to undergo mesenchymal condensation and further epithelialization, while exogenously added recombinant OP-1 was able to substitute for ureteric bud epithelium in restoring the induction of metanephric mesenchyme. This OP-1-induced nephrogenic mesenchyme differentiation follows a developmental pattern similar to that observed in the presence of the spinal cord, a metanephric inducer. Blocking OP-1 activity using either neutralizing antibodies or antisense oligonucleotides in mouse embryonic day 11.5 mesenchyme, cultured in the presence of metanephric inducers or in intact embryonic day 11.5 kidney rudiment, greatly reduced metanephric differentiation. These results demonstrate that OP-1 is required for metanephric mesenchyme differentiation and plays a functional role during kidney development.

Animals↗
PubMed1996

Three-dimensional structure of recombinant human osteogenic protein 1: structural paradigm for the transforming growth factor beta superfamily.

We report the three-dimensional structure of osteogenic protein 1 (OP-1, also known as bone morphogenetic protein 7) to 2.8-A resolution. OP-1 is a member of the transforming growth factor beta (TGF-beta) superfamily of proteins and is able to induce new bone formation in vivo. Members of this superfamily share sequence similarity in their C-terminal regions and are implicated in embryonic development and adult tissue repair. Our crystal structure makes possible the structural comparison between two members of the TGF-beta superfamily. We find that although there is limited sequence identity between OP-1 and TGF-beta 2, they share a common polypeptide fold. These results establish a basis for proposing the OP-1/TGF-beta 2 fold as the primary structural motif for the TGF-beta superfamily as a whole. Detailed comparison of the OP-1 and TGF-beta 2 structures has revealed striking differences that provide insights into how these growth factors interact with their receptors.

Base Sequence↗
PubMed1996

Osteogenic protein-1 is required for mammalian eye development.

Osteogenic Protein-1 (OP-1/BMP-7) is a bone morphogenetic protein in the transforming growth factor-beta superfamily and has been shown to be expressed temporally and spatially during epithelial-mesenchymal interactions mediating tissue morphogenesis in early embryogenesis. In order to identify the primary role(s) for OP-1 in development, we carried out whole rat embryo cultures, over a 72-h period from primitive streak stages to early limb bud stages, in rat sera containing either OP-1 blocking antibodies (10 micrograms/ml) or nonreactive IgG. Rat embryos cultured with control antibodies developed normally, while those cultured with anti-OP-1 antibodies consistently exhibited over-all reduced size and absence of eyes. Histological sections revealed a greater reduction in neural retina development in the embryos treated with anti-OP-1 blocking antibodies. In situ hybridization and immunolocalization analyses indicate that OP-1 is expressed in the neuroepithelium of the optic vesicle at E11.5, is limited to the presumptive neural retina and developing lens placode, and is subsequently expressed in the neural retina, lens and developing cornea at E12.5-E13.5. Our results indicate that OP-1 mediates the inductive signals involved in mammalian eye development.

Animals↗
PubMed1996

Human osteogenic protein-1 induces chondroblastic, osteoblastic, and/or adipocytic differentiation of clonal murine target cells.

Osteogenic protein-1 (OP-1, BMP-7), a bone morphogenetic protein in the transforming growth factor-beta superfamily, induces endochondral bone formation in vivo, but the mechanism of action of OP-1 in osteogenesis is not yet established. Three murine clonal cell lines in different stages of differentiation exhibit graded responses to recombinant human OP-1: the mouse embryonal carcinoma ATDC5 cell, with potential for chondroblastic differentiation; the osteoblast-like MC3T3-E1 cell derived from mouse calvaria; and the multipotent fibroblastic C3H10T1/2 cell derived from mouse embryo connective tissue. We show that OP-1 acts on early stage mesenchymal progenitor cells (ATDC5, C3H10T1/2) to induce chondroblastic differentiation, while OP-1 strongly enhances the osteoblastic phenotype of committed osteoblasts (MC3T3-E1), possibly explaining its induction of the endochondral ossification cascade in vivo. Markers of osteoblastic, chondroblastic, and adipocytic differentiation are compared. OP-1 is strongly mitogenic for ATDC5, showing dose-dependent (2.5-80 ng/ml) induction of Alcian blue staining, alkaline phosphatase activity, and mRNA expression for collagen types II and IX, and matrix Gla protein. MC3T3-E1 cells do not proliferate or stain with Alcian blue in response to OP-1, but express elevated levels of alkaline phosphatase and osteocalcin. While low-dose OP-1 treatment of C3H10T1/2 induces only adipocyte-like cells filled with lipid droplets, a high dose (500 ng/ml) causes the same cells to also exhibit chondrocytic properties. Thus, OP-1 can induce differentiation along elements of the endochondral ossification pathway according to the stage and potential of the target cell.

Adipocytes↗
PubMed1996

Recombinant human osteogenic protein 1 is a potent stimulator of the synthesis of cartilage proteoglycans and collagens by human articular chondrocytes.

OBJECTIVE: To study the effects of recombinant human osteogenic protein-1 (rHuOP-1; bone morphogenetic protein-7) on proteoglycan and collagen synthesis by human articular chondrocytes. METHODS: Articular chondrocytes from fetal, adolescent, and adult human donors were cultured in alginate beads for 4 days in a mixture of Ham's F-12, Dulbecco's modified Eagle's medium, 10% fetal bovine serum (FBS), then for an additional 3-10 days in the presence and absence of rHuOP-1, with and without FBS. Chondrocyte synthetic activity was measured as the amount of incorporation of 35S-sulfate into proteoglycans and 3H-proline into hydroxyproline. Sieve chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis were performed to identify specific proteoglycans and collagens. RESULTS: Recombinant human OP-1 markedly stimulated the synthesis of proteoglycans (mostly aggrecan) and collagens (predominantly type II) by all chondrocyte preparations. This did not require the presence of FBS and was associated with continued expression of the chondrocyte phenotype. CONCLUSION: Recombinant human OP-1 is a more potent stimulator of the synthesis of cartilage-specific molecules by human articular chondrocytes than are other factors tested for comparison, including TGF beta 1 and activin A.

Activins↗
PubMed1996

Induction of cementogenesis by recombinant human osteogenic protein-1 (hop-1/bmp-7) in the baboon (Papio ursinus).

Recombinant human osteogenic protein-1 (hOP-1), a member of the bone morphogenetic protein family, was examined for its efficacy in periodontal regeneration. Twelve furcation defects, surgically prepared in the first and second mandibular molars, were treated with bovine insoluble collagenous matrix in conjunction with 0.0 (control), 100 and 500 mu g of recombinant hOP-1 per g of matrix. After 60 days of healing, histological and histometric analyses on serial, undemineralized sections cut at 7 mu m showed substantial cementogenesis on the exposed dentine of furcations treated with both doses of hOP-1 (p < 0.01 vs control). Foci of nascent mineralization were seen within the newly deposited cementoid along the coronal areas of hOP-1-treated defects. Within the furcations, there were substantial amounts of residual collagenous carrier, interspersed with a mineralized matrix having histological features of cementum. This mineralized cementum-like material was predominantly deposited around the carrier, and blended into newly formed cementum along the root surfaces. In the apical area, the cementum-like material and the remaining alveolar bony housing were not connected; indeed the two components were separated by a fibrovascular tissue that had numerous features of the periodontal ligament space. Formation and insertion of Sharpey's fibres into newly formed root cementum were also observed. It is likely that the expression of specific cell phenotypes by hOP-1 is regulated, in part, by the extracellular matrix microenvironment, including dentine. Thus, exposed dentine, in the presence of exogenous hOP-1 at the doses tested, may preferentially modulate the expression of the cementogenic phenotype. These findings in a non-human primate show that hOP-1, at the doses tested, induced cementogenesis on surgically denuded root surfaces, indicating a specific function during repair and regeneration of periodontal tissues.

Alveolar Process↗
PubMed1996

Subcloning of three osteoblastic cell lines with distinct differentiation phenotypes from the mouse osteoblastic cell line KS-4.

Three distinct osteoblastic cell lines (KS418, KS460, and KS483) were subcloned from the mouse osteoblastic KS-4 cells, which possessed the abilities not only to differentiate into mature osteoblasts, but also to support osteoclast differentiation in coculture with spleen cells. The order of the magnitude of the basal alkaline phosphatase (ALP) activity was KS483 > KS418 > KS460. KS483 cells were also more differentiated than KS418 and KS460 in terms of ALP activity and osteocalcin production, when cultured in growth medium containing 10% fetal bovine serum. In long-term culture, KS418 and KS483 apparently differentiated into mature osteoblasts and formed calcified nodules without addition of beta-glycerophosphate. Electron microscopic analysis demonstrated that calcification occurring in the nodules was initiated in the matrix vesicles as observed in bone formation in vivo. Nodule formation and mineral deposition occurred simultaneously in the presence of beta-glycerophosphate, but the former always preceded the latter without addition of beta-glycerophosphate. In contrast, KS460 cells did not show time-dependent increases of ALP activity, type I collagen expression and osteocalcin production, which were induced by treatment with recombinant osteogenic protein-1 (OP-1). The three cell lines similarly supported osteoclast differentiation in coculture with spleen cells in response to 1,25-dihydroxyvitamin D3. These results indicate that the three cell lines subcloned from the original KS-4 cells represent phenotypically distinct osteoblasts during osteoblast differentiation, but are equipped similarly with the capacity to support osteoclast differentiation. The subcloned cells of the KS-4 series may provide useful systems in which to study osteoblast differentiation and function.

Actins↗
PubMed1996

Bone morphogenetic protein type IB receptor is progressively expressed in malignant glioma tumours.

The distribution of bone morphogenetic protein (BMP) type I receptors and the activin type I receptor (ActR-I) was investigated in 16 cases of human glioma and five cases of non-tumourous gliosis tissue by immunohistochemical technique. Both BMP type IA (BMPR-IA) and the type IB (BMPR-IB) receptors were detected in human glioma cells. A significant increase in BMPR-IB in tumour cells was observed in malignant glioma compared with both low-grade astrocytomas (n=16, P<0.005) and gliosis (n=13, P<0.001). However, enhancement of BMPR-IA staining was moderate and ActR-I staining was only weakly expressed in the malignant glioma tumours. Osteogenic protein (OP)-1/BMP-7, which is known to bind BMPR-IA, BMPR-IB and ActR-I, was expressed in nervous tissue and was also detected in anaplastic areas of malignant glioma. In contrast to the tissue materials, BMPR-IA was expressed to a stronger degree than BMPR-IB in human glioma cell lines; the growth of these cells was suppressed by OP-1. These results suggest the presence of BMP receptors and a functional role for BMPs in malignant glioma.

Activin Receptors↗