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Biomedical subjects

T Komori

Publications and source records attributed to T Komori.

At least 109 records · Page 6Linked to original sources
PubMed1999

Excessive extramedullary hematopoiesis in Cbfa1-deficient mice with a congenital lack of bone marrow.

Cbfa1, a transcriptional factor that belongs to the runt-domain gene family, plays a pivotal role in osteogenesis. Cbfa1-deficient mice completely lacked both intramembranous and endochondral bone formation owing to the maturational arrest of osteoblasts, resulting in a total lack of bone marrow throughout the entire skeleton. To investigate the development of hematopoiesis in Cbfa1-deficient mice, hematopoietic tissues and peripheral blood were examined. Colony-forming assays of yolk sac at embryonic day 10.5 (E10.5) and liver at E12.5 showed normal numbers of hematopoietic precursors in the mutant embryos. Further, histological examination and flow-cytometric analysis showed normal hematopoietic development of liver and spleen in the mutant embryos until E17.5. However, mutant embryos at E18.5 showed large hematopoietic foci in the periportal area of liver and mild splenomegaly with dilated vessels, and an increase of myeloid cells was observed in both organs. Flow-cytometric analysis also demonstrated a relative increase of granulocytes and a relative decrease of B-cells reciprocally in the livers and spleens of the mutant embryos. Colony-forming assays showed that the frequency of colony-forming unit-culture (CFU-C) was elevated in liver, and both the frequency and total number of CFU-C were increased in spleen of mutant embryos at E18.5. Moreover, leukoerythroblastosis was observed in peripheral blood of the mutant embryos. These data demonstrate that the congenital lack of bone marrow caused excessive levels of extramedullary hematopoiesis in both liver and spleen at the late embryonic stage.

Animals↗
PubMed1999

Maturational disturbance of chondrocytes in Cbfa1-deficient mice.

Cbfa1, a transcription factor that belongs to the runt-domain gene family, plays an essential role in osteogenesis. Cbfa1-deficient mice completely lacked both intramembranous and endochondral ossification, owing to the maturational arrest of osteoblasts, indicating that Cbfa1 has a fundamental role in osteoblast differentiation. However, Cbfa1 was also expressed in chondrocytes, and its expression was increased according to the maturation of chondrocytes. Terminal hypertrophic chondrocytes expressed Cbfa1 extensively. The significant expression of Cbfa1 in hypertrophic chondrocytes was first detected at embryonic day 13.5 (E13.5), and its expression in hypertrophic chondrocytes was most prominent at E14.5-16.5. In Cbfa1-deficient mice, whose entire skeleton was composed of cartilage, the chondrocyte differentiation was disturbed. Calcification of cartilage occurred in the restricted parts of skeletons, including tibia, fibula, radius, and ulna. Type X collagen, BMP6, and Indian hedgehog were expressed in their hypertrophic chondrocytes. However, osteopontin, bone sialoprotein, and collagenase 3 were not expressed at all, indicating that they are directly regulated by Cbfa1 in the terminal hypertrophic chondrocytes. Chondrocyte differentiation was severely disturbed in the rest of the skeleton. The expression of PTH/PTHrP receptor, Indian hedgehog, type X collagen, and BMP6 was not detected in humerus and femur, indicating that chondrocyte differentiation was blocked before prehypertrophic chondrocytes. These findings demonstrate that Cbfa1 is an important factor for chondrocyte differentiation.

Animals↗
PubMed1999

An aldose redutase inhibitor prevents the intimal thickening in coronary arteries of galactose-fed beagle dogs.

AIMS/HYPOTHESIS: Although increased polyol pathway activity has been implicated in the pathogenesis of diabetic microangiopathy, the relation with diabetic macroangiopathy remains unclear. Galactose feeding is known to stimulate the polyol pathway and to develop abnormalities similar to those in diabetic microangiopathy. Our study was conducted to investigate whether an activation of polyol pathway by long-term treatment with galactose produced morphological changes in coronary arteries of dogs and the effect of an aldose reductase inhibitor, epalrestat, was also studied. METHODS: Dogs received either normal chow or chow containing 30% galactose with or without epalrestat given orally (20 or 50 mg x kg(-1)). After 44 months, morphometric analyses of coronary arteries were carried out and the galactitol contents in aortas were measured. RESULTS: The ratio of areas of the intimal layer to those of the medial layer, an indicator of intimal thickening, was statistically significantly increased in galactose-fed dogs compared with control dogs. Galactose-fed dogs had a remarkable accumulation of galactitol in their aortas. These morphological and biochemical deficits were reduced by treatment with epalrestat. CONCLUSION/INTERPRETATION: This report morphologically shows diabetes-like macrovascular abnormalities in galactosaemic animals, suggesting that polyol pathway hyperactivity is closely related to the development of diabetic macroangiopathy, which could be prevented by aldose reductase inhibition.

Aldehyde Reductase↗
PubMed1999

Large motor neuron involvement in Stiff-man syndrome: a qualitative and quantitative study.

Stiff-man syndrome (SMS) is characterized by fluctuating muscular rigidity and spasm. Recently, antibodies against glutamic acid decarboxylase (GAD), the enzyme catalyzing the synthesis of y-amino butyric acid (GABA), have been detected in SMS patients. An autoimmune mechanism against GAD was thus proposed for the suppression of GABAergic inhibitory interneurons, resulting in rigidity and spasm. We conducted quantitative investigations on the ventral horn of the spinal cord and its GAD immunoreactivity, post mortem, in a SMS patient and four controls. In the spinal cord of the SMS patient, we found a 70%, 33% and 27% reduction (P < 0.05) in the density of neurons with somal areas of 1000-1500 microm2, 500-1000 microm2, and 0-500 microm2, respectively. The density of neurons with a somal area greater than 1500 microm2 was not reduced, although some neurons in this class showed central chromatolytic changes. The affected muscles exhibited neurogenic atrophy. GAD-like immunoreactivity in the spinal gray matter was not significantly decreased. The density of Purkinje cells, known to contain high amounts of GAD, was not significantly reduced. While the co-occurrence of elevation of anti-GAD antibody in the serum and reduction in the density of small spinal neurons was confirmed, that of smaller alpha-motor neurons and gamma-motor neurons, the qualitative changes in larger alpha-motor neurons, and the preservation of spinal GAD-like immunoreactivity and non-spinal GAD-containing neurons suggest the involvement of factors other than autoimmune mechanisms through anti-GAD antibodies. More diverse mechanisms may be associated in the pathogenesis of SMS.

Cell Count↗
PubMed1999

Advanced glycation endproducts are deposited in neuronal hyaline inclusions: a study on familial amyotrophic lateral sclerosis with superoxide dismutase-1 mutation.

To determine the role of advanced glycation endproducts (AGE) in the pathogenesis of familial amyotrophic lateral sclerosis (ALS) with superoxide dismutase-1 (SOD1) mutation, we investigated the immunohistochemical localization of N(epsilon)-carboxymethyl-lysine (CML), one of the major AGE structures, in spinal cords from three familial ALS patients with a heterozygous Ala to Val substitution at codon 4 in the gene for SOD1. Neuronal hyaline inclusions (NHIs), the abnormal structures seen in some of the remaining lower motor neurons of familial ALS patients with SOD1 mutation, were intensely stained by a monoclonal antibody specific for CML in contrast to the only weakly stained cytoplasm. Immunoelectron microscopy depicted the CML determinants restricted to the granule-associated thick linear structures that mainly compose the NHIs. The NHIs were also recognized by antibodies to SOD1, phosphorylated neurofilament protein and ubiquitin. No focal collection of either CML or SOD1 was found in neurons of the control individuals. Our results indicate that CML is a component of the NHIs of familial ALS patients with SOD1 mutation, and suggest that the CML formation may be mediated by protein glycoxidation or lipid peroxidation in the presence of oxidative stress from mutant SOD1, in association with motor neuron degeneration.

Adult↗
PubMed1999

Tumor-doubling time and onset of pulmonary metastasis from adenoid cystic carcinoma of the salivary gland.

Adenoid cystic carcinoma (ACC), an uncommon malignancy in the head and neck region, invades diffusely and often metastasizes to the lung, although the growth rate is very slow. A retrospective study was conducted in 30 patients with ACC to ascertain the frequency of pulmonary metastasis, the doubling time of metastatic tumor deposits, and the time of onset for pulmonary metastasis. The following results were obtained: (1) Of 30 patients with ACC, 21 had pulmonary metastases (4 initially and 17 during observation), 7 were free of metastases but have not been observed for 5 years, and 2 were free of metastases for more than 5 years but less than 10 years after the initial treatment. The cumulative metastasis rate at 5 and 10 years for this group of patients was 70% and 100%, respectively. (2) Patients with T1 or T2 tumors that have a tubular or cribriform histopathologic pattern showed pulmonary metastases about 20 months later than those with T3 or T4 tumors and a solid pattern. However, the final metastasis rate did not differ between the 2 groups after a long period. (3) The tumor doubling time of the metastatic deposits of ACC was 86 to 1064 days with an average of 393 days, which was much longer than that of most other malignant neoplasms reported previously. (4) The time of onset of pulmonary metastasis was calculated to be much earlier (average of 227 months) before the first visit. These findings suggest that the treatment method for ACC should be chosen with the consideration that many of the patients may have occult pulmonary metastases at the time of their initial evaluation.

Carcinoma, Adenoid Cystic↗
PubMed1999

Morphological characterization of skeletal cells in Cbfa1-deficient mice.

To clarify the mechanisms by which core-binding factor-alpha1 (Cbfa1), an essential transcription factor in osteogenesis, functions in osteoblast matrix formation, as well as in chondrocyte differentiation and osteoclastic bone resorption, Cbfa1-deficient embryonic mice were investigated ultrastructurally and histocytochemically at 18.5 days postcoitum. In homozygotic mice, both endochondral and intramembranous ossification were arrested, although bone tissue had already formed at this stage in the wild type. The tibiae of homozygotic mice were characterized by calcified cartilage and alkaline phosphatase (ALP)-positive perichondrium, whereas membranous structures indicating the presence of ALP activity in the lateral portion were observed in the calvariae, rather than the bone tissue. Most of the ALP-positive perichondrial cells in homozygotic tibiae possessed a spindle-shaped cell contour and small cytoplasm, the extracellular matrix of which contained neither type I collagen nor calcifying matrix vesicles. In contrast, some perichondrial cells at the very middle part of tibiae became flattened. In the vicinity of these cells, a thin layer of type I collagen-based calcified matrix, containing osteopontin, bone sialoprotein, or osteocalcin, was observed. In the cartilage of mutant mice, we observed a hypoplasic zone of proliferative chondrocytes, the flattening of hypertrophic chondrocyte-like cells, and calcified chondrocytes which, while not degraded, did display a high level of cell function. Mononuclear osteoclastic cells were found in the perichondrium, near calcified chondrocytes, in mutant mice. Multinuclear osteoclasts possessing H+-ATPase and ruffled borders were also present, although only in limited numbers. Neither the development of ruffled borders nor intracellular polarization was complete. Because the majority of osteogenic cells in Cbfa1-deficient mice can neither form nor calcify the bone matrix, Cbfa1 principally plays essential roles in osteoblastic differentiation and bone matrix formation. Cbfa1 also affects both the proliferation and the differentiation of chondrocytes, whereas its absence prevents normal osteoclast formation and related functions.

Animals↗
PubMed1999

Ultrastructural localization of E-cadherin and alpha-/beta-catenin in adenoid cystic carcinoma.

AIMS: To investigate the disturbance of intercellular adhesion in adenoid cystic carcinoma (ACC), we examined the ultrastructural localization of E-cadherin (E-cad), alpha-catenin (alpha-cat) and beta-catenin (beta-cat) in ACC, and compared it with that in the normal labial gland. METHODS AND RESULTS: Using immuno-electron microscopy, in the normal labial gland, E-cad was found to be uniformly distributed along the plasmalemma, where cells were in close contact with each other, with junctional complexes, desmosomes and interdigitations; expression of alpha-cat and beta-cat was also detected. In ACC, which was classified into tubular, cribriform and trabecular types, E-cad expression seemed not to be uniform, but was observed to be along the plasmalemma where cell-to-cell contact was made. On the other hand, expression of alpha-cat or beta-cat was uneven in the trabecular-type cells which were very slender and grew in an infiltrative scattered pattern into the extracellular matrix; that was absent in the cribriform-type cells which made contact with each other mostly at the tip of the cytoplasmic processes. CONCLUSION: These findings suggest that the neoplastic cells of ACC express E-cad for use in intercellular adhesion, but the cadherin-catenin complex might not operate properly, which is the cause of neoplastic cell dissociation, followed by invasion and metastasis.

Adult↗
PubMed1999

Tau-positive glial inclusions in progressive supranuclear palsy, corticobasal degeneration and Pick's disease.

The presence of tau-positive glial inclusions has been recently found a consistent feature in the brains of patients with progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and Pick's disease (PiD). These inclusions are classified based on cellular origin as tau-positive astrocytes, presumably either fibrillary or protoplasmic, coiled bodies and glial threads. Immunohistochemically, their major structural component is abnormal tau proteins, similar to those found in Alzheimer's disease. Nevertheless, their morphology, including ultrastructural profile, has been suggested to be distinctive for each disease. The profile and extent of particular glial inclusions correlate well with disease phenotype. Highly characteristic correlations include tufts of abnormal fibers in PSP, astrocytic plaques and dense glial threads in CBD and ramified astrocytes and small Pick body-like inclusions in PiD. The significance of the inclusions in disease pathogenesis and their biochemical characteristics remain to be clarified. Nevertheless, these distinctive glial lesions most likely reflect fundamental alterations in isoform composition of tau as well as its specific cellular and regional expression in sporadic tauopathies.

Humans↗
PubMed1999

Collagenase 3 is a target of Cbfa1, a transcription factor of the runt gene family involved in bone formation.

Collagenase 3 (MMP-13) is a recently identified member of the matrix metalloproteinase (MMP) gene family that is expressed at high levels in diverse human carcinomas and in articular cartilage from arthritic patients. In addition to its expression in pathological conditions, collagenase 3 has been detected in osteoblasts and hypertrophic chondrocytes during fetal ossification. In this work, we have evaluated the possibility that Cbfa1 (core binding factor 1), a transcription factor playing a major role in the expression of osteoblastic specific genes, is involved in the expression of collagenase 3 during bone formation. We have functionally characterized a Cbfa motif present in the promoter region of collagenase 3 gene and demonstrated, by cotransfection experiments and gel mobility shift assays, that this element is involved in the inducibility of the collagenase 3 promoter by Cbfa1 in osteoblastic and chondrocytic cells. Furthermore, overexpression of Cbfa1 in osteoblastic cells unable to produce collagenase 3 leads to the expression of this gene after stimulation with transforming growth factor beta. Finally, we show that mutant mice deficient in Cbfa1, lacking mature osteoblasts but containing hypertrophic chondrocytes which are also a major source of collagenase 3, do not express this protease during fetal development. These results provide in vivo evidence that collagenase 3 is a target of the transcriptional activator Cbfa1 in these cells. On the basis of these transcriptional regulation studies, together with the potent proteolytic activity of collagenase 3 on diverse collagenous and noncollagenous bone and cartilage components, we proposed that this enzyme may play a key role in the process of bone formation and remodeling.

3T3 Cells↗
PubMed1999

The mechanisms of immune suppression by high-pressure stress in mice.

The effects of high-pressure stress on the induction of anti-sheep red blood cells (SRBC) and of plaque-forming cells (PFC), and on thymus weight, were studied in BALB/c mice in-vivo and in-vitro. The efficacy of high-pressure stress in suppressing PFC and thymic involution was maximum when the stress was applied 1 h day(-1) for 2 days before immunization with SRBC. Both effects were blocked by administration of indomethacin, atropine, naloxone or phentolamine before the first application of stress, whereas hexamethonium and propranolol had no such effect. Hexamethonium, naloxone and propranolol administered before the second application of high-pressure stress blocked both effects. Prostaglandin and acetylcholine given 24 h before application of high-pressure stress caused a marked reduction in PFC count, but not in thymus weight. The reduced PFC count caused by acetylcholine was blocked by pretreatment with indomethacin. When adrenaline was injected 24 h after application of high-pressure stress a marked reduction in PFC was observed, but without thymic involution. When adrenaline was injected 24 h after prostaglandin injection the PFC count was also markedly reduced, but not thymus weight. The decrease in PFC caused by two exposures to stress or one exposure to stress plus injection of adrenaline was blocked by diethylcarbamazine before the second exposure to stress or the injection of adrenaline. In addition, normal spleen cells, were induced as suppressor cells when incubated with the serum of stressed mice, but not when supplemented with anti-leukotriene C4, D4 antibody. These data suggest that mice fall into a pre-stress condition via the release of prostaglandin after the first stress, and then immunosuppression is induced in these prestressed mice via the release of leukotriene C4, D4, caused by the activation of the autonomic nervous system by the second exposure to stress.

Animals↗
PubMed1999

A trans-acting enhancer modulates estrogen-mediated transcription of reporter genes in osteoblasts.

The presence of bone-specific estrogen agonists and discovery of the osteoblast-specific transcription factor (TF), Cbfa1, together with the discovery of synergism between a TF Pit-1 and estrogen receptor alpha (ERalpha) on rat prolactin gene, led to investigation of Cbfa1 in the modulation of osteoblast-specific actions of estrogen. Reverse transcribed-polymerase chain reaction demonstrated expression of Cbfa1 in the osteoblastic cell lines, MG63, ROS17/2.8, and MC3T3E1, but not in nonosteoblastic cell lines, MCF7, C3H10T1/2, and HeLa. An ER expression vector and a series of luciferase (Luc) reporter plasmids harboring the Cbfa1 binding site OSE2 (the osteoblast-specific cis element in the osteocalcin promoter) and palindromic estrogen response elements (EREs) were cotransfected into both osteoblastic and nonosteoblastic cells. OSE2 worked as a cis- acting element in osteoblastic cells but not nonosteoblastic cells, whereas EREs were cis- acting in all cell lines. Synergistic transactivation was observed in osteoblastic cells only when both ERE and OSE2 were placed in juxtaposition to the promoter. Forced expression of Cbfa1 in C3H10T1/2 cells also induced synergism. Tamoxifen, a partial agonist/antagonist of estrogen, acted as an osteoblast-specific agonist in cells transfected with a promoter containing ERE and acted synergistically with a promoter containing the ERE-OSE2 enhancer combination. These results support the idea that bone-specific TFs modulate the actions of estrogen in a tissue-specific manner.

Animals↗
PubMed1999

[Evaluation of 99mTc-MAG3 (mercaptoacetyltriglycine) renography for pediatric patients].

It is difficult to evaluate renal function with 99mTc-MAG3 renography in both adult and pediatric patients. We examined 109 pediatric patients with various renal diseases using 99mTc-MAG3 renography. Tenal diseases were classified as follows: 9 vesicoureteral reflux, 4 ureteropelvic junctional stenosis, 3 double pelvis, 23 hydronephrosis, 4 glomerulonephritis, 4 nephrotic syndrome, 24 hemolytic uremic syndrome, 10 others; and 24 patients without abnormal findings on other examinations. After hydration and sedation, 100-200 MBq of 99mTe-MAG3 was injected intravenously. All patients were placed in the supine position, and dynamic data acquisition at 12 sec/frame x 100 frames was performed from the back. The renograms were prepared with the ROIs (regions of interest) set to include the entire kidney. Tmax and T1/2 of renograms were measured for 26 kidneys with no abnormal findings. The correlations between Tmax or T1/2 and age (days after birth) were determined by a linear or logarithmic function. The logarithmic function (Y = 7.49 - 0.56 logeX, r2 = 0.134) yielded a higher correlation than did the linear function (Y = 5.16 - 0.00194X, r2 = 0.089) between Tmax and age. For T1/2 and age (days after birth), the linear function (Y = 8.07 - 0.00451X, r2 = 0.222) yielded a higher correlation than the logarithmic function (Y = 11.9 - 0.986 logeX, r2 = 0.192). Our findings suggest that prolonged Tmax is normalized more rapidly than T1/2 after birth in infants. A delayed excretion phase is not suggestive of renal dysfunction, but is characteristic of renograms in pediatric patients. Abnormality was detected in all patients with hydronephrosis using 99mTc-MAG3 renography. On the other hand, a quantitative study was required because renography detected no abnormality for some of patients with disorders of renal parenchyma.

Adolescent↗
PubMed1999

[Quantitative assessment of 201Tl-SPECT in tumors of bone and soft tissue].

201Tl-SPECT was performed to diagnose the malignancy of bone and soft tissue tumors by visual and quantitative assessment in 48 patients (17 malignant lesions and 31 benign lesions). SPECT images were obtained in the early phase (15 min after injection) and the delayed phase (240 min). By visual assessment a tumor was considered malignant if high accumulation was found in the tumor in the early phase and the accumulation was confirmed in the delayed phase. Tumors which did not meet these criteria were considered benign. For quantitative assessment, the ROI (region of interest) accumulation ratios of the tumor to the contralateral normal tissue in the early phase (ER) and in the delayed phase (DR), the ROI accumulation ratio of the delayed phase to the early phase of the tumor (Td/Te), and the ROI accumulation ratio of the delayed phase to the early phase of the contralateral normal tissue (Nd/Ne) were obtained. Sixteen patients with malignant tumors each had a high accumulation each but 12 of 31 benign lesions had no high accumulation on visual assessment. Furthermore, the accuracy was 85.4%, sensitivity 94.1%, and specificity 80.6%. Quantitative assessment was performed for 36 cases of high accumulation. The ER of malignant and benign lesions was 5.51 +/- 3.73 and 2.75 +/- 2.17, respectively, and the ER of malignant lesions was significantly higher than that of benign lesions. The DR did not demonstrate a significant difference. If the tumor having an ER greater than 3.9 was assumed to be malignant, the accuracy for differentiating malignant lesions from benign lesions was 85.4%. The Td/Te of benign lesions (0.97 +/- 0.28) was higher than that of malignant lesions (0.77 +/- 0.09). The Nd/Ne of normal tissue which contained muscles in both lesions were higher than 1.4. In conclusion, 201Tl-SPECT was very useful for the differential diagnosis of benign or malignant bone and soft tissue tumors. The ER was important for quantitative assessment, but a delayed image was necessary for visual assessment.

Adolescent↗
PubMed1999

Effect of various properties of hydroxyapatite ceramics on osteoconduction and stability.

Hydroxyapatite ceramics (HA) are widely used for clinical applications as a bone substitute or dental implant because they have been shown to be biocompatible and exhibit excellent osteoconductivity when grafted into the bone tissue. However, the influence of the physical properties of HA on the osteoconduction and stability remains unclear. We examined here the effect of various properties of HA granules on osteoconduction and stability using 6 types of HA granules. The HA granules were grafted into the rabbit tibia and the initial bone formation and long-term stability of the new bone were studied histologically. The following results were obtained; 1. Osteoconduction of the HA granule was influenced by the shape. Multi-nuclear granules with continuous pores ranging from 30 to 200 microns in diameter showed both excellent osteoconduction and stability. 2. Solubility behavior of HA granules, which was effected by the relative surface area sizes, also seemed to be an important factor for osteoconduction and stability. 3. Stable bi-phase ceramics with HA and beta TCP were produced at the sintering temperature of 1200 degrees C when Mg was added. The beta TCP and Mg content did not negatively influence the initial osteoconduction or long-term stability.

Animals↗
PubMed1998

Potential role of cbfa1, an essential transcriptional factor for osteoblast differentiation, in osteoclastogenesis: regulation of mRNA expression of osteoclast differentiation factor (ODF).

The role of Cbfa1 (core binding factor alpha1), an essential transcriptional factor for osteoblast differentiation, in osteoclastogenesis was investigated in vitro and in vivo using Cbfa1-deficient calvarial cells and mice. Co-cultures of calvarial cells isolated from embryos with three different Cbfa1 genotypes (Cbfa1+/+, Cbfa1+/- and Cbfa1-/-) and normal spleen cells generated TRAP-positive multinucleated osteoclast-like cells (OCLs) in response to 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] and dexamethasone, but the number and bone-resorbing activity of OCLs formed in co-culture with Cbfa1-/- calvarial cells were significantly decreased in comparison with those formed in co-cultures with Cbfa1+/+ or Cbfa1+/- calvarial cells. The expression of osteoclast differentiation factor/osteoprotegerin ligand (ODF/OPGL) mRNA was increased by the treatment with 1alpha, 25(OH)2D3 and dexamethasone in calvarial cells from Cbfa1+/+ and Cbfa1+/- mouse embryos, but not from Cbfa1-/- embryos. In contrast, the expression of osteoprotegerin/osteoclastogenesis inhibitory factor (OPG/OCIF) mRNA was inhibited by 1alpha,25(OH)2D3 and dexamethasone similarly in all three types of calvarial cells. ODF/OPGL and OPG/OCIF mRNAs were highly expressed in the tibia and femur of Cbfa1+/+ and Cbfa1+/- embryos. In the tibia and femur of Cbfa1-/- embryos, however, ODF/OPGL mRNA was undetectable and the expression of OPG/OCIF mRNA was also decreased compared with those in Cbfa1+/+ and Cbfa1+/- embryos. These results suggested that Cbfa1 is somehow involved in osteoclastogenesis through regulation of ODF/OPGL.

Animals↗
PubMed1998

Smad2 overexpression enhances Smad4 gene expression and suppresses CBFA1 gene expression in osteoblastic osteosarcoma ROS17/2.8 cells and primary rat calvaria cells.

Mothers against decapentaplegic-related proteins (Smads) are essential intracellular components for the signal transduction of transforming growth factor-beta (TGF-beta) family members. Smad1 mediates bone morphogenetic protein (BMP) signals, whereas Smad2 functions downstream of TGF-beta. TGF-beta is expressed in osteoblastic cells and acts as an autocrine and/or paracrine factor in regulation of osteoblastic functions. In this study, we examined the levels and functions of Smad2 in osteoblastic cells. Smad2 mRNA expression was hardly detectable by Northern blot analysis in an osteoblast-like cell line, ROS17/2.8, as well as in primary rat calvaria (PRC) cells. Overexpression of Smad2 gene enhanced endogenous Smad4 gene expression in both ROS17/2.8 and PRC cells, while Smad3 levels were not altered. Smad2 overexpression suppressed osteocalcin mRNA expression in ROS17/2.8 cells. Furthermore, Smad2 overexpression also suppressed transcriptional activity of the 1-kilobase pair osteocalcin gene promoter, which was linked to chloramphenicol acetyltransferase reporter gene in both ROS and PRC cells. Since core binding factor A1 (CBFA1) is involved in osteocalcin gene expression, we further examined CBFA1 expression in the Smad2-overexpressing ROS17/2.8 and PRC cells. The levels of CBFA1 mRNA were suppressed by the overexpression of Smad2 by about 50% in both ROS17/2.8 and PRC cells. TGF-beta treatment enhanced Smad4 expression in PRC cells, and this TGF-beta effect was blocked by the cotreatment with BMP, indicating that TGF-beta signaling pathway is interfered by BMP. These data indicate that Smad2 regulates Smad4 specifically and that CBFA1 gene is one of the downstream targets of Smad2.

Animals↗