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Tatsuo Tsukamoto

Publications and source records attributed to Tatsuo Tsukamoto.

8 recordsLinked to original sources
PubMed2003

Parathyroid hormone-Smad3 axis exerts anti-apoptotic action and augments anabolic action of transforming growth factor beta in osteoblasts.

Although several studies indicated that parathyroid hormone (PTH) exerted anabolic action on bone, its precise mechanisms have been unknown. On the other hand, transforming growth factor beta (TGF-beta), abundantly stored in bone matrix, stimulates bone formation with a local injection in rodents. Although our previous study suggested that Smad3 is an important molecule for the stimulation of bone formation, no reports have been available about the effects of PTH on Smad3. In this present study, we examined the effects of PTH on Smad3 and the physiological significance in mouse osteoblastic cells. PTH promoted the expression of Smad3 mRNA within 10 min and the protein level in a dose-dependent manner in MC3T3-E1 and rat osteoblastic UMR-106 cells. Protein kinase A (PKA) activator as well as protein kinase C (PKC) activators increased Smad3 protein level, and both PKA and PKC inhibitors antagonized PTH-induced Smad3, indicating that PTH promotes the production of Smad3 through both PKA and PKC pathways. Next, we examined anti-apoptotic effects of PTH and Smad3 in these cells, employing trypan blue, transferase-mediated nick end labeling, and Hoechst staining. Pretreatment with PTH or overexpression of Smad3 decreased the number of apoptotic cells induced by dexamethasone and etoposide. Moreover, a dominant negative mutant, Smad3DeltaC, abrogated PTH-induced anti-apoptotic effects. On the other hand, PTH augmented TGF-beta-induced transcriptional activity. Furthermore, PTH enhanced TGF-beta-induced production of type I collagen, whereas it did not affect TGF-beta-reduced proliferation in MC3T3-E1 cells. These observations indicated that PTH amplified the anabolic effects of TGF-beta by accelerating the transcriptional activity of Smad3. In conclusion, we first demonstrated that PTH-Smad3 axis exerts anti-apoptotic effects in osteoblasts and reinforces the anabolic action by TGF-beta in osteoblasts. Hence, PTH-Smad3 axis might be involved in the bone anabolic action of PTH.

Animals↗
PubMed2003

Inactivation of menin, the product of the multiple endocrine neoplasia type 1 gene, inhibits the commitment of multipotential mesenchymal stem cells into the osteoblast lineage.

The physiological roles of menin, the product of the multiple endocrine neoplasia type 1 gene, are not known. Homozygous menin knockout mice exhibit cranial and facial hypoplasia. We, therefore, investigated the role of menin in the regulation of osteoblastic differentiation. Menin antisense oligonucleotides (AS-oligo) reduced endogenous menin expression in the C3H10T1/2 (10T1/2) mouse mesenchymal stem cells and antagonized alkaline phosphatase (ALP) activity and the expression of type I collagen, Runx2/cbfa1 (Runx2), and osteocalcin (OCN) induced by bone morphogenetic protein 2 (BMP-2). AS-oligo did not affect adipogenic markers (Oil red staining and PPARgamma expression) and chondrogenic markers (Alcian blue staining and type IX collagen) induced by BMP-2 in 10T1/2 cells. Menin co-immunoprecipitated with Smad1 and Smad5, and inactivation of menin antagonized BMP-2-induced transcriptional activity of Smad1/5. In osteoblastic MC3T3-E1 cells, AS-oligo affected neither BMP-2-stimulated ALP activity nor the expression of Runx2 and OCN. Stable inactivation of menin in MC3T3-E1 cells increased ALP activity, mineralization, and the expression of type I collagen and OCN. In 21-day cultures of MC3T3-E1 cells and BMP-2-treated 10T1/2 cells, endogenous menin expression increased up to day 14 and declined thereafter. These data indicate that menin inactivation specifically inhibits the commitment of pluripotent mesenchymal stem cells to the osteoblast lineage, mediated by menin and Smad1/5 interactions. Menin is important for both early differentiation of osteoblasts and inhibition of their later differentiation, and it might be crucial for intramembranous ossification.

3T3 Cells↗
PubMed2003

Efficacy of direct injection of calcitriol into the parathyroid glands in uraemic patients with moderate to severe secondary hyperparathyroidism.

INTRODUCTION: Secondary hyperparathyroidism (2HPT) is a common complication in uraemic patients. When medical therapy, including high doses of intravenous calcitriol, fails to suppress the pathological secretion of parathyroid hormone (PTH), one of the newly developed interventional techniques, such as percutaneous ethanol injection therapy (PEIT), is an option before taking the surgical solution. A protocol for direct calcitriol injection therapy and a discussion of its effectiveness and limitations for an enlarged parathyroid gland(s) are presented. METHODS: Nine patients were selected according to the Japanese Guideline for Selective PEIT. Using the same technique as PEIT, a dose of calcitriol that was approximately 200-300% of the calculated volume of the selected parathyroid gland was injected directly into the gland under ultrasonographic guidance. RESULTS: In six cases, the intact PTH concentration decreased to <360 pg/ml. The total volume of the enlarged parathyroid gland(s) also decreased to 54.7% of the initial volume. The blood supply to the treated glands, as evaluated by colour Doppler imaging, appeared to diminish transiently after injection, probably from the volume effect of this procedure. The number of enlarged parathyroid glands was not a limiting factor for this therapy; however, a grossly enlarged parathyroid gland (>2000 mm(3)) appeared to be resistant to this intervention and an intrathoracic parathyroid gland was found in a non-responsive case. None of the patients had any severe complications, such as nerve palsy or massive haemorrhage. CONCLUSION: This new approach to the control of 2HPT is recommended as an alternative pharmacological parathyroidectomy to surgical therapy.

Calcitriol↗
PubMed2003

Effects of an excess and a deficiency of endogenous parathyroid hormone on volumetric bone mineral density and bone geometry determined by peripheral quantitative computed tomography in female subjects.

Peripheral quantitative computed tomography (pQCT) is useful for evaluating volumetric bone mineral density (vBMD) as well as bone mineral density (BMD) of cortical and trabecular bones separately. Although PTH affects cortical and trabecular bones differently, the effects of endogenous PTH on vBMD and bone geometry have not previously been examined with pQCT. We, therefore, investigated the effects of an excess and a deficiency of endogenous PTH on bone by employing dual-energy x-ray absorptiometry and pQCT in 36 female patients with primary hyperparathyroidism (hyper), nine female patients with idiopathic or postoperative hypoparathyroidism (hypo), and 100 normal controls matched to age, gender, and body size (cont). Lumbar BMD by dual-energy x-ray absorptiometry was higher in the order: hypo > cont = hyper, and radius-1/3 BMD was significantly higher in the order: hypo > cont > hyper. The area of radius-1/3 was significantly higher in hyper than in cont. As for pQCT, trabecular vBMD was significantly higher in the order: hypo > cont > hyper at the 4% site (hypo, 157.5 +/- 36.7 mg/cm(3); cont, 123.4 +/- 47.5 mg/cm(3); hyper, 98.4 +/- 41.7 mg/cm(3)). Cortical vBMD was higher in the order: hypo > cont > hyper at the 20% site (hypo, 1141.1 +/- 53.1 mg/cm(3); cont, 1090.2 +/- 72.9 mg/cm(3); hyper, 1038.6 +/- 89.1 mg/cm(3)). Total bone area and endosteal and periosteal circumferences were significantly higher in hyper than in cont and hypo. Cortical area and thickness were higher in the order: hypo > cont > hyper. Bone strength indices were not significantly different among the three groups. In conclusion, vBMD evaluation revealed that an excess of endogenous PTH was catabolic for both cortical and trabecular bones, and that bone mass (especially trabecular bone mass) was preserved under a condition of deficient endogenous PTH. An excess of endogenous PTH stimulated periosteal bone formation, which might partly compensate for a decrease in bone strength induced by low BMD.

Absorptiometry, Photon↗
PubMed2003

Functional giant parathyroid cyst with high concentration of CA19-9 in cystic fluid.

A 63-year-old man was admitted to our hospital for the evaluation of hypercalcemia and anterior neck mass. Laboratory findings revealed hypercalcemia, hypophosphatemia, and hypercalciuria, as well as elevated serum levels of parathyroid hormone (PTH) and alkaline phosphatase. Computerized tomography and magnetic resonance images showed that the mass contained a cystic area. Parathyroid scintigraphy using either 99mTc-sestamibi alone or 201Tl-chloride in conjunction with 99mTc-pertechnetate for thyroid image subtraction showed uptake of the radioactivity into the cyst wall, suggesting that the mass originated from the parathyroid. Fine needle aspiration biopsy revealed that the cyst fluid was serous and bloody with extremely high concentrations of both PTH and CA19-9. The patient was diagnosed as primary hyperparathyroidism caused by parathyroid cyst and cervical exploration was performed. The cyst was dissected away along with the right lobe of the thyroid gland. After tumor removal, serum calcium and PTH levels were normalized. Histological study showed that the tumor possessed malignant potential with capsular invasion as well as moderate cellular atypia with trabecular pattern in arrangement. Parathyroid cells in the wall of the cystic tumor were immunostained positively for CA19-9, suggesting that CA19-9 in the cyst fluid was produced from the cells.

CA-19-9 Antigen↗
PubMed2003

Decrease in vitamin D receptor and calcium-sensing receptor in highly proliferative parathyroid adenomas.

OBJECTIVE: A significant decrease in vitamin D receptor (VDR) and calcium-sensing receptor (CaSR) protein expression has been demonstrated recently in parathyroid (PT) adenomas. In this study, we investigated the relationships between the proliferative activity of parathyroid glands (PTGs) and the expression of VDR as well as CaSR, and compared it with the clinical severity in patients with primary hyperparathyroidism (1 degrees HPT). DESIGN: Seven patients with 1 degrees HPT were included in this study. Four patients with thyroid carcinoma served as controls. METHODS: Immunohistochemical staining was performed on serial sections of PTGs with specific antibodies against CaSR, VDR, and Ki67. Areas examined in each section were selected at random in relation to the gland size. The number of Ki67-positive cells was expressed as a labeling index (LI; positive cells per 1000 PT cells). The expression of CaSR and VDR was semi-quantitatively analyzed based on the intensity of staining. After averages of the scores from all areas were calculated, CaSR and VDR scores, and Ki67 LI were assigned to each gland for use in statistical analyses. RESULTS: In PT adenomas, scores of VDR and CaSR were markedly lower than in normal PTGs (P<0.01), while the proportion of Ki67-positive cells in PT adenomas was significantly higher than in normal PTGs (P<0.01). Single regression analyses revealed that Ki67 LI was positively correlated with serum levels of intact parathyroid hormone and Ca, and PTG weight (R=0.70, P<0.05, R=0.78, P<0.01 and R=0.84, P<0.05 respectively). Ki67 LI was negatively correlated with CaSR and VDR scores (R=-0.78, P<0.01 and R=-0.72, P<0.05 respectively). Moreover, there was a strong positive relationship between CaSR and VDR expression (R=0.95, P<0.001). CONCLUSIONS: Marked decreases in VDR and CaSR expression could, at least in part, be responsible for the high proliferation of PT cells and the pathological progression of 1 degree HPT.

Adenoma↗