Angiopoietin-like protein 2 promotes chronic adipose tissue inflammation and obesity-related systemic insulin resistance

Recent studies of obesity have provided new insights into the mechanisms underlying insulin resistance and metabolic dysregulation. Numerous efforts have been made to identify key regulators of obesity-linked adipose tissue inflammation and insulin resistance. We found that angiopoietin-like protein 2 (Angptl2) was secreted by adipose tissue and that its circulating level was closely related to adiposity, systemic insulin resistance, and inflammation in both mice and humans. Angptl2 activated an inflammatory cascade in endothelial cells via integrin signaling and induced chemotaxis of monocytes/macrophages. Constitutive Angptl2 activation in vivo induced inflammation of the vasculature characterized by abundant attachment of leukocytes to the vessel walls and increased permeability. Angptl2 deletion ameliorated adipose tissue inflammation and systemic insulin resistance in diet-induced obese mice. Conversely, Angptl2 overexpression in adipose tissue caused local inflammation and systemic insulin resistance in nonobese mice. Thus, Angptl2 is a key adipocyte-derived inflammatory mediator that links obesity to systemic insulin resistance.

Angiopoietins and Angiopoietin-Like Proteins in Angiogenesis

Vascular network formation requires several endothelial cell growth factors. These factors have a potent angiogenic effect, and their precise coordination is essential for vascular development. Among them, angiopoietins function through the Tie2 receptor, whose signaling is critical to regulate vascular stabilization and remodeling. It has been reported that the angiopoietin/Tie2 signal is involved in survival and migration of endothelial cells and regulates vascular remodeling and maintenance of vascular integrity. More recent studies demonstrate that angiopoietin/Tie2 signaling is also required for lymphangiogenesis. The authors and several other groups have identified six angiopoietin-like proteins (Angptls) containing a coiled-coil domain and a fibrinogen-like domain, both of which are characteristic of angiopoietins. Interestingly, Angptls also function in angiogenesis through regulating survival and migration of endothelial cells, although Angptls do not bind the angiopoietin receptor Tie2. Currently, Angptls are orphan ligands, but they have been reported to have pleiotropic effects not only on vascular cells but also on metabolism and tumor biology. Here, the authors review current findings relating to the roles of angiopoietins and Angptls in vascular biology and discuss molecular mechanisms relevant to these factors and angiogenesis.

M-CSF inhibition selectively targets pathological angiogenesis and lymphangiogenesis

Antiangiogenic therapy for the treatment of cancer and other neovascular diseases is desired to be selective for pathological angiogenesis and lymphangiogenesis. Macrophage colony-stimulating factor (M-CSF), a cytokine required for the differentiation of monocyte lineage cells, promotes the formation of high-density vessel networks in tumors and therefore possesses therapeutic potential as an M-CSF inhibitor. However, the physiological role of M-CSF in vascular and lymphatic development, as well as the precise mechanisms underlying the antiangiogenic effects of M-CSF inhibition, remains unclear. Moreover, therapeutic potential of M-CSF inhibition in other neovascular diseases has not yet been evaluated. We used osteopetrotic (op/op) mice to demonstrate that M-CSF deficiency reduces the abundance of LYVE-1⁺ and LYVE1⁻ macrophages, resulting in defects in vascular and lymphatic development. In ischemic retinopathy, M-CSF was required for pathological neovascularization but was not required for the recovery of normal vasculature. In mouse osteosarcoma, M-CSF inhibition effectively suppressed tumor angiogenesis and lymphangiogenesis, and it disorganized extracellular matrices. In contrast to VEGF blockade, interruption of M-CSF inhibition did not promote rapid vascular regrowth. Continuous M-CSF inhibition did not affect healthy vascular and lymphatic systems outside tumors. These results suggest that M-CSF–targeted therapy is an ideal strategy for treating ocular neovascular diseases and cancer.

Cancer stem cells and their niche

The unique characteristics of stem cells, specifically pluripotency and self-renewal, are critical for sustaining the lifelong functionality of organs. Stem cells reside in a special microenvironment called the niche. Stem cells interact with the niche via adhesion molecules and exchange molecular signals that maintain the specific features of stem cells. A better understanding of the nature of stem cells and their niches is expected to provide an alternative approach to the treatment of various serious diseases, including cancer, in clinical practice. It has been suggested that tumor tissue contains a type of stem cell referred to as a cancer stem cell. Interestingly, there are a number of molecules that are commonly expressed in normal and cancer stem cells that lead to different phenomena depending on the local conditions. In this review, the hematopoietic system is used as an example to show how stem cells interact with different niches. The regulatory mechanisms of two kinds of bone marrow niche, osteoblastic and vascular, are covered in this review. Furthermore, the involvement of the niche in cancer stem cell regulation, tumor invasion and metastasis, and its response to oxidative stress is described, and novel therapeutic approaches involving the interactions between cancer stem cells and their niches are addressed.

Bidirectional signaling through ephrinA2-EphA2 enhances osteoclastogenesis and suppresses osteoblastogenesis

Bone is remodeled constantly throughout life by bone-resorbing osteoclasts and bone-forming osteoblasts. To maintain bone volume and quality, differentiation of osteoclasts and osteoblasts is tightly regulated through communication between and within these two cell lineages. Previously we reported that cell-cell interaction mediated by ephrinB2 ligand on osteoclasts and EphB4 receptor on osteoblasts generates bidirectional anti-osteoclastogenic and pro-osteoblastogenic signals into respective cells and presumably facilitates transition from bone resorption to bone formation. Here we show that bidirectional ephrinA2-EphA2 signaling regulates bone remodeling at the initiation phase. EphrinA2 expression was rapidly induced by receptor activator of NF-kappaB ligand in osteoclast precursors; this was dependent on the transcription factor c-Fos but independent of the c-Fos target gene product NFATc1. Receptor EphA2 was expressed in osteoclast precursors and osteoblasts. Overexpression experiments revealed that both ephrinA2 and EphA2 in osteoclast precursors enhanced differentiation of multinucleated osteoclasts and that phospholipase Cgamma2 may mediate ephrinA2 reverse signaling. Moreover, ephrinA2 on osteoclasts was cleaved by metalloproteinases, and ephrinA2 released in the culture medium enhanced osteoclastogenesis. Interestingly, differentiation of osteoblasts lacking EphA2 was enhanced along with alkaline phosphatase, Runx2, and Osterix expression, indicating that EphA2 on osteoblasts generates anti-osteoblastogenic signals presumably by up-regulating RhoA activity. Therefore, ephrinA2-EphA2 interaction facilitates the initiation phase of bone remodeling by enhancing osteoclast differentiation and suppressing osteoblast differentiation.

First demonstration of electron scattering using a novel target developed for short-lived nuclei

We carried out a demonstrative electron scattering experiment using a novel ion-trap target exclusively developed for short-lived highly unstable nuclei. Using stable 133Cs ion as a target, this experiment completely mimicked electron scattering off short-lived nuclei. Achieving a luminosity higher than 10;{26} cm;{-2} s;{-1} with around only 10;{6} trapped ions on the electron beam, the angular distribution of elastic scattering was successfully measured. This experiment clearly demonstrates that electron scattering off rarely produced short-lived nuclei is practical with this target technique.

1-Alpha, 25-dihydroxy vitamin D3 inhibits osteoclastogenesis through IFN-beta-dependent NFATc1 suppression

1-Alpha, 25-dihydroxy vitamin D(3) (1alpha,25(OH)(2)D(3)), an active form of vitamin D(3), plays a critical role in calcium and bone metabolism. Although 1alpha,25(OH)(2)D(3) has been used for osteoporosis therapy, the direct role of 1alpha,25(OH)(2)D(3) on human osteoclastogenesis has not been well characterized. Here we show that 1alpha,25(OH)(2)D(3) treatment significantly inhibited human osteoclast formation at the early stage of differentiation in a concentration-dependent manner. 1alpha,25(OH)(2)D(3) inhibited the expression of nuclear factor of activated T cells c1 (NFATc1, also referred as NFAT2), an essential transcription factor for osteoclast differentiation, and upregulated the expression of interferon-beta (IFN-beta), a strong inhibitor of osteoclastogenesis in osteoclast progenitors. Inhibitory effects of 1alpha,25(OH)(2)D(3) on osteoclastogenesis and NFATc1 expression were restored by treatment with an antibody against IFN-beta, suggesting that upregulation of IFN-beta by 1alpha,25(OH)(2)D(3) treatment results in inhibition of NFATc1 expression, in turn interfering with osteoclast formation. Thus, our study may provide a molecular basis for the treatment of human bone diseases by 1alpha,25(OH)(2)D(3) through regulation of the IFN-beta and NFATc1 axis.

Involvement of regulatory elements on corticotropin-releasing factor gene promoter in hypothalamic 4B cells

INTRODUCTION

Corticotropin-releasing factor (CRF) plays a central role in controlling the hypothalamic-pituitary-adrenal (HPA) axis during stressful periods. CRF is synthesized and secreted in the hypothalamic paraventricular nucleus (PVN) in response to stress, and stimulates ACTH in the pituitary corticotrophs. ACTH stimulates the release of glucocorticoids from the adrenal glands, and glucocorticoids sequentially inhibit hypothalamic PVN production of CRF and pituitary production of ACTH. The effects of glucocorticoids on CRF gene regulation, however, are possibly tissue-specific since glucocorticoids stimulate CRF gene expression in the placenta and the bed nucleus of the stria terminalis, while they inhibit it in the hypothalamus.

METHODS AND RESULTS

In a hypothalamic cell line, 4B, we found that forskolin-stimulated CRF gene transcription was mediated by a functional cAMP-response element (CRE), which included -220 to -233 bp on the CRF 5'-promoter region. Protein kinase A, protein kinase C, and p38 mitogen-activated protein kinase pathways contributed to forskolin-induced transcriptional activity of CRF in hypothalamic 4B cells. Glucocorticoid-dependent repression of cAMP-stimulated transcriptional activity of CRF was localized to promoter sequences between -278 and -233 bp, which included a glucocorticoid regulatory element and a serum response element.

CONCLUSION

Taken together, these findings indicate that the regulatory elements, including CRE, negative glucocorticoid regulatory element, and a serum response element on the promoter, contribute to the regulation of CRF gene transcription in hypothalamic 4B cells.

Reconstitution activity of hypoxic cultured human cord blood CD34-positive cells in NOG mice

Hematopoietic stem cells (HSCs) reside in hypoxic areas of the bone marrow. However, the role of hypoxia in the maintenance of HSCs has not been fully characterized. We performed xenotransplantation of human cord blood cells cultured in hypoxic or normoxic conditions into adult NOD/SCID/IL-2Rgamma(null) (NOG) mice. Hypoxic culture (1% O(2)) for 6 days efficiently supported the maintenance of HSCs, although cell proliferation was suppressed compared to the normoxic culture. In contrast, hypoxia did not affect in vitro colony-forming ability. Upregulation of a cell cycle inhibitor, p21, was observed in hypoxic culture. Immunohistochemical analysis of recipient bone marrow revealed that engrafted CD34(+)CD38(-) cord blood HSCs were hypoxic. Taken together, these results demonstrate the significance of hypoxia in the maintenance of quiescent human cord blood HSCs.

Foxo3a is essential for maintenance of the hematopoietic stem cell pool

The mobilization of hematopoietic stem cells does not require osteoclasts, which may even have an inhibitory effect.

Hematopoietic stem cells (HSCs) are maintained in a specific bone marrow (BM) niche in cavities formed by osteoclasts. Osteoclast-deficient mice are osteopetrotic and exhibit closed BM cavities. Osteoclast activity is inversely correlated with hematopoietic activity; however, how osteoclasts and the BM cavity potentially regulate hematopoiesis is not well understood. To investigate this question, we evaluated hematopoietic activity in three osteopetrotic mouse models: op/op, c-Fos-deficient, and RANKL (receptor activator of nuclear factor kappa B ligand)-deficient mice. We show that, although osteoclasts and, by consequence, BM cavities are absent in these animals, hematopoietic stem and progenitor cell (HSPC) mobilization after granulocyte colony-stimulating factor injection was comparable or even higher in all three lines compared with wild-type mice. In contrast, osteoprotegerin-deficient mice, which have increased numbers of osteoclasts, showed reduced HSPC mobilization. BM-deficient patients and mice reportedly maintain hematopoiesis in extramedullary spaces, such as spleen; however, splenectomized op/op mice did not show reduced HSPC mobilization. Interestingly, we detected an HSC population in osteopetrotic bone of op/op mice, and pharmacological ablation of osteoclasts in wild-type mice did not inhibit, and even increased, HSPC mobilization. These results suggest that osteoclasts are dispensable for HSC mobilization and may function as negative regulators in the hematopoietic system.

Leukemia inhibitory factor regulates microvessel density by modulating oxygen-dependent VEGF expression in mice

To meet tissue requirements for oxygen, capillaries must be properly distributed without excess or shortage. In this process, tissue oxygen concentration is well known to determine capillary density via the hypoxia-induced cascade, in which HIFs and VEGF play key roles. However, some additional mechanisms modulating this cascade are suggested to be involved in precise capillary network formation. Here, we showed that leukemia inhibitory factor (LIF) was predominantly expressed in developing endothelium, while its receptor was expressed in surrounding cells such as retinal astrocytes. The retinas of Lif(-/-) mice displayed increased microvessel density accompanied by sustained tip cell activity, due to increased VEGF expression by astrocytes in the vascularized area. Lif(-/-) mice resisted hyperoxygen insult in the oxygen-induced retinopathy model, whereas they paradoxically had increased numbers of neovascular tufts. In an in vitro study, LIF inhibited hypoxia-induced VEGF expression and proliferation in cultured astrocytes. Lif(-/-) mice also exhibited similarly increased microvessel density and upregulated VEGF in various tissues outside the retina. Together, these findings suggest that tissues and advancing vasculature communicate to ensure adequate vascularization using LIF as well as oxygen, which suggests a new strategy for antiangiogenic therapy in human diseases such as diabetic retinopathy and cancer.

Effects of combined PPARgamma and PPARalpha agonist therapy on reverse cholesterol transport in the Zucker diabetic fatty rat

AIM

We investigated the effects of the combined therapy of PPARgamma and PPARalpha agonists on HDL metabolism, especially concerning reverse cholesterol transport (RCT), using Zucker diabetic fatty rats (ZDF/Crl-Lepr fa rats) that are the rodent model for type 2 diabetes with obesity, hyperlipidaemia and insulin resistance.

METHODS

The ZDF rats were divided into four medicated groups as follows: pioglitazone as a PPARgamma agonist (5 mg/kg/day; P group, n = 6), fenofibrate as a PPARalpha agonist (30 mg/kg/day; F group, n = 6), both these medications (P + F group, n = 6) and no treatment (UNT group, n = 6). Non-diabetic rats (ZDF/GmiCrl-lean, CON group, n = 6) served as controls. We evaluated HDL particle size and messenger RNA (mRNA) levels of the following factors: liver X receptor alpha (L x R alpha), ATP-binding cassette A1 (ABCA1) and ABCG1 which are regulated by PPARs and are related to early stage RCT.

RESULTS

The significant increase in HDL particle size was demonstrated in rats of the F and P + F groups, although changes in plasma HDL-cholesterol levels were not significant. In accordance with this finding, mRNA levels of ABCG1 in the liver increased significantly.

CONCLUSIONS

These findings suggest the efficacy of combined therapy with PPARgamma and PPARalpha in improving lipid metabolism, partly through the enhanced RCT, and insulin resistance in type 2 diabetes mellitus.

Role of fibroblast growth factor 8 (FGF8) in animal models of osteoarthritis

INTRODUCTION

Fibroblast growth factor 8 (FGF8) is isolated as an androgen-induced growth factor, and has recently been shown to contribute to limb morphogenesis. The aim of the present study was to clarify the role of FGF8 in animal models of osteoarthritis (OA).

METHODS

The expression of FGF8 in the partial meniscectomy model of OA in the rabbit knee was examined by immunohistochemistry. The effect of intraperitoneal administration of anti-FGF8 antibody was tested in a model of OA that employed injection of monoiodoacetic acid or FGF8 into the knee joint of rats. The effect of FGF8 was also tested using cultured chondrocytes. Rabbit articular chondrocytes were treated with FGF8 for 48 hours, and the production of matrix metalloproteinase and the degradation of sulfated glycosaminoglycan in the extracellular matrix (ECM) were measured.

RESULTS

The expression of FGF8 in hyperplastic synovial cells and fibroblasts was induced in the meniscectomized OA model, whereas little or no expression was detected in normal synovium. Injection of FGF8 into rat knee joints induced the degradation of the ECM, which was suppressed by anti-FGF8 antibody. In the monoiodoacetic acid-induced arthritis model, anti-FGF8 antibody reduced ECM release into the synovial cavity. In cultured chondrocytes, FGF8 induced the release of matrix metalloproteinase 3 and prostaglandin E2, and caused degradation of the ECM. The combination of FGF8 and IL-1alpha accelerated the degradation of the ECM. Anti-FGF8 antibody suppressed the effects of FGF8 on the cells.

CONCLUSION

FGF8 is produced by injured synovium and enhances the production of protease and prostaglandin E2 from inflamed synoviocytes. Degradation of the ECM is enhanced by FGF8. FGF8 may therefore participate in the degradation of cartilage and exacerbation of osteoarthritis.

The role of DC-STAMP in maintenance of immune tolerance through regulation of dendritic cell function

Regulation of dendritic cell (DC) function is critical for maintaining self-tolerance and preventing autoimmunity. The dendritic cell-specific transmembrane protein (DC-STAMP) plays a key role in cell-cell fusion of osteoclasts and foreign body giant cells, but though originally identified in DCs, its specific roles there remain undefined. Here, we report that aged DC-STAMP-deficient mice display several systemic autoimmune symptoms such as spontaneous lymphoproliferation, splenomegaly associated with infiltration of T cells in several organs and increased serum anti-double-stranded DNA antibody production. Although a lack of DC-STAMP did not inhibit DC differentiation or proliferation, antigen presentation activity of DC-STAMP-deficient DCs was significantly up-regulated in both class I and II pathways through increased phagocytotic activity compared with wild-type DCs, an activity likely leading to autoimmunity. Our results indicate that DC-STAMP is required for proper regulation of DC activity and maintenance of immune self-tolerance.

Ontogeny and multipotency of neural crest-derived stem cells in mouse bone marrow, dorsal root ganglia, and whisker pad

Although recent reports have described multipotent, self-renewing, neural crest-derived stem cells (NCSCs), the NCSCs in various adult rodent tissues have not been well characterized or compared. Here we identified NCSCs in the bone marrow (BM), dorsal root ganglia, and whisker pad and prospectively isolated them from adult transgenic mice encoding neural crest-specific P0-Cre/Floxed-EGFP and Wnt1-Cre/Floxed-EGFP. Cultured EGFP-positive cells formed neurosphere-like structures that expressed NCSC genes and could differentiate into neurons, glial cells, and myofibroblasts, but the frequency of the cell types was tissue source dependent. Interestingly, we observed NCSCs in the aorta-gonad-mesonephros region, circulating blood, and liver at the embryonic stage, suggesting that NCSCs migrate through the bloodstream to the BM and providing an explanation for how neural cells are generated from the BM. The identification of NCSCs in accessible adult tissue provides a new potential source for autologous cell therapy after nerve injury or disease.

Vascular endothelial growth factor-A is a survival factor for nucleus pulposus cells in the intervertebral disc

The intervertebral disc (IVD) is composed of two avascular tissue types, the nucleus pulposus (NP) and the annulus fibrosus (AF). IVDs is the largest avascular tissue in the human body, however, how these tissues are maintained without a blood supply is poorly understood. Here we show that vascular endothelial growth factor-A (VEGF-A) is highly expressed in NP and that VEGF-A plays a role in NP survival. High VEGF-A expression in NP was detected by microarray analysis, and NP was positive for the hypoxic probe pimonidazole and hypoxia-responsive genes. VEGF-A expression in NP was promoted by hypoxic conditions in vitro. NP cells also expressed the membrane-bound VEGF receptor-1 (VEGFR-1), and the number of apoptotic cells in cultured cell model of NP increased following treatment with VEGFR-1-Fc, which traps VEGF-A in NP. These results indicate that NP is a hypoxic tissue, and that VEGF-A functions in NP survival in an autocrine/paracrine manner.

Novel internal target for electron scattering off unstable nuclei

A novel internal target has been developed, which will make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. An "ion trapping" phenomenon in the electron storage ring was successfully utilized for the first time to form the target for electron scattering. Approximately 7 x 10(6) stable 133Cs ions were trapped along the electron beam axis for 85 ms at an electron beam current of 80 mA. The collision luminosity between the stored electrons and trapped Cs ions was determined to be 2.4(8) x 10(25) cm(-2) s(-1) by measuring elastically scattered electrons.

Ras signaling directs endothelial specification of VEGFR2+ vascular progenitor cells

Vascular endothelial growth factor receptor 2 (VEGFR2) transmits signals of crucial importance to vasculogenesis, including proliferation, migration, and differentiation of vascular progenitor cells. Embryonic stem cell–derived VEGFR2⁺ mesodermal cells differentiate into mural lineage in the presence of platelet derived growth factor (PDGF)–BB or serum but into endothelial lineage in response to VEGF-A. We found that inhibition of H-Ras function by a farnesyltransferase inhibitor or a knockdown technique results in selective suppression of VEGF-A–induced endothelial specification. Experiments with ex vivo whole-embryo culture as well as analysis of H-ras^−/− mice also supported this conclusion. Furthermore, expression of a constitutively active H-Ras[G12V] in VEGFR2⁺ progenitor cells resulted in endothelial differentiation through the extracellular signal-related kinase (Erk) pathway. Both VEGF-A and PDGF-BB activated Ras in VEGFR2⁺ progenitor cells 5 min after treatment. However, VEGF-A, but not PDGF-BB, activated Ras 6–9 h after treatment, preceding the induction of endothelial markers. VEGF-A thus activates temporally distinct Ras–Erk signaling to direct endothelial specification of VEGFR2⁺ vascular progenitor cells.

Fbxw7 acts as a critical fail-safe against premature loss of hematopoietic stem cells and development of T-ALL

Common molecular machineries between hematopoietic stem cell (HSC) maintenance and leukemia prevention have been highlighted. The tumor suppressor Fbxw7 (F-box and WD-40 domain protein 7), a subunit of an SCF-type ubiquitin ligase complex, induces the degradation of positive regulators of the cell cycle. We demonstrate that inactivation of Fbxw7 in hematopoietic cells causes premature depletion of HSCs due to active cell cycling and p53-dependent apoptosis. Interestingly, Fbxw7 deletion also confers a selective advantage to cells with suppressed p53 function, eventually leading to development of T-cell acute lymphoblastic leukemia (T-ALL). Thus, Fbxw7 functions as a fail-safe mechanism against both premature HSC loss and leukemogenesis.

Mycobacterium avium complex disease: prognostic implication of high-resolution computed tomography findings

To evaluate the prognostic implications of computed tomography (CT) findings in assessing responses to treatment in Mycobacterium avium complex (MAC) pulmonary disease without underlying lung disease, high-resolution (HR)CT findings were correlated based on the results of sputum conversion after anti-MAC therapy. A total of 59 patients underwent HRCT before treatment and the therapeutic efficacy was evaluated by the results of sputum conversion. Atelectasis, cavities and pleural thickening on HRCT were significantly more frequent and extensive among patients in the sputum nonconverted group than among those in the converted group. Furthermore, bronchiectasis was also significantly more extensive among patients in the nonconverted group, even though there was no significant difference in frequency between these two groups. These results suggest that high-resolution computed tomography findings are good predictors of response to treatment in Mycobacterium avium complex pulmonary disease.

The CYP2A6*4 allele is determinant of S-1 pharmacokinetics in Japanese patients with non-small-cell lung cancer

S-1 is an oral fluorouracil anticancer drug that contains the 5-FU prodrug tegafur. Tegafur has been shown to be converted enzymatically to 5-FU to exert its antitumor effect, and this conversion is principally catalyzed by CYP2A6. Forty-six non-small-cell lung cancer patients were enrolled. The frequencies of the CYP2A6*4C, CYP2A6*7, and CYP2A6*9 alleles were 17.4, 19.6, and 15.2%, respectively. In the S-1 pharmacokinetic analysis, the area under the concentration-time curve from 0 to 10 h (AUC(0-10)) ratios of 5-FU/tegafur showed large interindividual variabilities, ranging from 5.14 to 112.6. The AUC(0-10) for tegafur was 1.5-fold higher in patients with the CYP2A6*4C allele than in patients without the CYP2A6*4C allele P < 0.05). Furthermore, patients with the CYP2A6*4C allele had a significantly lower maximum plasma concentration (102.6 +/- 32.9 ng/ml) for 5-FU than patients without the CYP2A6*4C allele (157.0 +/- 65.5 ng/ml, P < 0.05). Genotyping of CYP2A6 polymorphisms may provide vital information for effective cancer therapy using S-1.

VEGFR1 tyrosine kinase signaling promotes lymphangiogenesis as well as angiogenesis indirectly via macrophage recruitment

OBJECTIVE

Angiogenesis and lymphangiogenesis are complex phenomena that involve the interplay of several growth factors and receptors. Recently, we have demonstrated that in Keratin-14 (K14) promoter-driven Vegf-A transgenic (Tg) mice, not only angiogenesis but also lymphangiogenesis is stimulated. However, the mechanism by which VEGFR1 is involved in lymphangiogenesis remains unclear.

METHODS AND RESULTS

To examine how important the tyrosine kinase (TK) of VEGFR1 is in lymphangiogenesis in K14 Vegf-A Tg mice, we crossed the K14 Vegf-A Tg mice with VEGFR1-TK-deficient mice to generate double mutant K14 Vegf-A Tg Vegfr1 tk(-/-) mice. K14 Vegf-A Tg Vegfr1 tk(-/-) mice exhibit a remarkable decrease in lymphangiogensis as well as angiogenesis in subcutaneous tissues. To address the mechanism underlying the decrease in lymphangiogensis, we investigated the recruitment of monocyte-macrophage-lineage cells into the skin. The recruitment of VEGFR1-expressing macrophages driven by VEGF-A was reduced in K14 Vegf-A Tg Vegfr1 tk(-/-) mice. Vegf-A Tg mice that received VEGFR1-TK-deficient bone marrow showed a reduction of macrophage recruitment, lymphangiogenesis and angiogenesis compared with those in K14 Vegf-A Tg mice.

CONCLUSIONS

VEGFR1 signaling promotes lymphangiogenesis as well as angiogenesis mainly by increasing bone marrow-derived macrophage recruitment.

A case of thyrotropin-producing pituitary adenoma, accompanied by an increase in anti-thyrotropin receptor antibody after tumor resection

We describe a rare, but interesting, case of TSH-producing adenoma (TSHoma), accompanied by increases in both anti-TSH receptor antibody (TRAb) and thyroid-stimulating antibody (TSAb) after tumor resection. A 21-yr-old woman was referred to our department for further evaluation of pituitary tumor. In a nearby hospital, she had been diagnosed as having pituitary tumor. Her serum free T4, free T3, and TSH levels were all elevated concomitantly. On the basis of a diagnosis of pituitary adenoma with TSH production, transsphenoidal resection of the pituitary adenoma was performed. Two weeks after the operation, the blood concentrations of TSH were undetectable, whereas both TRAb and TSAb levels were elevated. TSAb levels gradually increased further from 2 weeks to 3 months after the operation, accompanied by an increase in TSH and free T4 levels. TSH is an important hormone in maintaining physiology and regulating immunomodulators in thyrocytes, as it can influence a variety of immune-regulating cytokine-like activities and inhibit expressions of Fas antigen, intracellular adhesion molecule-1, and class II trans-activator. Changes in TSH would modulate the immune circumstances in the thyroid, and then induce TRAb and TSAb. Autoimmune parameters with thyroid function should be observed carefully when managing patients with TSHoma.

Bone marrow long label-retaining cells reside in the sinusoidal hypoxic niche

In response to changing signals, quiescent hematopoietic stem cells (HSCs) can be induced to an activated cycling state and provide multi-lineage hematopoietic cells to the whole body via blood vessels. However, the precise localization of quiescent HSCs in bone marrow microenvironment is not fully characterized. Here, we performed whole-mount immunostaining of bone marrow and found that BrdU label-retaining cells (LRCs) definitively reside in the sinusoidal hypoxic zone distant from the "vascular niche". Although LRCs expressed very low level of a well-known HSC marker, c-kit in normal circumstances, myeloablation by 5-FU treatment caused LRCs to abundantly express c-kit and proliferate actively. These results demonstrate that bone marrow LRCs reside in the sinusoidal hypoxic niche, and function as a regenerative cell pool of HSCs.

Osteoblast-specific Angiopoietin 1 overexpression increases bone mass

Although osteoblasts express the angiogenic protein Angiopoietin 1 (Ang1), the role of Ang1 in bone formation remains largely unknown. Here we report that Ang1 overexpression in osteoblasts driven by the osteoblast-specific 2.3 kb alpha 1 type 1 collagen promoter results in increased bone mass in vivo. In Ang1-transgenic mice (Ang1-Tg), bone volume and bone parameters increased significantly compared with wild-type littermates, although the Ang1 receptor, Tie2 was not expressed in osteoblasts. Tie2 is primarily expressed in vascular endothelial cells, and Ang1-Tie2 signaling is reportedly crucial for angiogenesis. We found that the number of vascular endothelial cells was significantly elevated in Ang1-Tg mice compared with that of wild-type littermates, an increase accompanied by increased alkaline-phosphatase activity, a marker of osteoblast activation. The number of osteoclasts in the bone of Ang1-Tg mice did not differ from wild-type littermates. These results indicate that angiogenesis induced by Ang1 expressed in osteoblasts is coupled with osteogenesis.

Function of oxidative stress in the regulation of hematopoietic stem cell-niche interaction

During postnatal life, the bone marrow (BM) supports both self-renewal and differentiation of hematopoietic stem cells (HSCs) in specialized niches, such as osteoblastic niche and vascular niche. A cell adhesion molecule, N-cadherin expressed in the HSCs and osteoblasts, suggesting that homophylic binding of N-cadherin induce the adhesion of HSCs to the niche cells. Here we demonstrate that an anti-cancer drug, 5-fuluorouracil induces reactive oxygen species (ROS) in HSCs, which suppressed N-cadherin expression. These events result in the shift of side population (SP) cells to non-SP cells, indicating that quiescent HSCs are detached from the niche. Administration of a potent anti-oxidant, N-acetyl cystein (NAC) suppressed the shift from SP cells. These data suggest that ROS suppressed the N-cadherin-mediated cell adhesion, and induce the exit of HSCs from the niche.

Osteoclastic activity induces osteomodulin expression in osteoblasts

Bone resorption by osteoclasts stimulates bone formation by osteoblasts. To isolate osteoblastic factors coupled with osteoclast activity, we performed microarray and cluster analysis of 8 tissues including bone, and found that among 10,490 genes, osteomodulin (OMD), an extracellular matrix keratan sulfate proteoglycan, was simultaneously induced with osteoclast-specific markers such as MMP9 and Acp5. OMD expression was detected in osteoblasts and upregulated during osteoblast maturation. OMD expression in osteoblasts was also detected immunohistochemically using a specific antibody against OMD. The immunoreactivity against OMD decreased in op/op mice, which lack functional macrophage colony stimulating factor (M-CSF) and are therefore defective in osteoclast formation, when compared to wild-type littermates. OMD expression in op/op mice was upregulated by M-CSF treatment. Since the M-CSF receptor c-Fms was not expressed in osteoblasts, it is likely that OMD is an osteoblast maturation marker that is induced by osteoclast activity.

Association of novel promoter single nucleotide polymorphisms in vasopressin V1a receptor gene with essential hypertension in nonobese Japanese

We studied the association between four novel single nucleotide polymorphisms (SNPs) in the promoter region of V1aR gene and essential hypertension in 620 Japanese subjects (365 hypertensives and 255 healthy). A significant association was found between one of the genotypes and alleles at SNP -6951 and hypertension in a subsample of nonobese individuals. This association demonstrated an independent risk for nonobese hypertension.

Induction of DC-STAMP by alternative activation and downstream signaling mechanisms

DC-STAMP is essential for fusion of osteoclasts and foreign body giant cells; however, it is not known whether dc-stamp expression in these two cell types is differentially regulated. Here, we show that dc-stamp expression and cell-cell fusion are regulated in a cell type-specific manner.

INTRODUCTION

The transcription factors c-Fos and NFATc1 cooperate to regulate osteoclast differentiation, whereas PU.1 and NF-kappaB are activated in macrophages and osteoclasts or in both cell types. Thus, we asked what role c-Fos, NFATc1, PU.1, and NF-kappaB played in regulating dendritic cell-specific transmembrane protein (dc-stamp) expression and fusion of osteoclasts and macrophage giant cells.

MATERIALS AND METHODS

Transcriptional activation by c-Fos and NFATc1 was examined by dc-stamp promoter analysis. Multinuclear cell formation was analyzed in cells from c-Fos-deficient mice or in wildtype cells treated with the NFAT inhibitor FK506. The role of DC-STAMP in cell fusion was examined in vitro in a macrophage giant cell formation assay using DC-STAMP-deficient cells. Recruitment of c-Fos, NFATc1, PU.1, and NF-kappaB to the dc-stamp promoter in osteoclasts and macrophage giant cells was analyzed by chromatin-immunoprecipitation analysis.

RESULTS

Both activator protein-1 (AP-1) and NFAT binding sites in the dc-stamp promoter were needed for dc-stamp expression after RANKL stimulation of osteoclasts. dc-stamp expression was induced in osteoclasts and macrophage giant cells, and cells from DC-STAMP-deficient mice failed to form either multinuclear osteoclasts or macrophage giant cells. In contrast, c-Fos is indispensable for dc-stamp expression and cell-cell fusion under conditions favoring in vitro and in vivo induction of osteoclasts but not macrophage giant cells. Consistently, an NFAT inhibitor suppressed multinuclear osteoclast formation but not macrophage giant cell formation. In addition, PU.1 and NF-kappaB binding sites were detected in the dc-stamp promoter, and both PU.1 and NF-kappaB were recruited to the dc-stamp promoter after granulocyte-macrophage colony stimulating factor (GM-CSF) + interleukin (IL)-4 stimulation.

CONCLUSIONS

dc-stamp expression is regulated differently in osteoclasts and macrophage giant cells. c-Fos and NFATc1, both of which are essential for osteoclast differentiation, are needed for dc-stamp expression and cell-cell fusion in osteoclasts, but both factors are dispensable for giant cell formation by macrophages. Because PU.1 and NF-kappaB are recruited to the dc-stamp promoter after stimulation with GM-CSF + IL-4, dc-stamp transcription is regulated in a cell type-specific manner.

Reactive oxygen species induce chondrocyte hypertrophy in endochondral ossification

Chondrocyte hypertrophy during endochondral ossification is a well-controlled process in which proliferating chondrocytes stop proliferating and differentiate into hypertrophic chondrocytes, which then undergo apoptosis. Chondrocyte hypertrophy induces angiogenesis and mineralization. This step is crucial for the longitudinal growth and development of long bones, but what triggers the process is unknown. Reactive oxygen species (ROS) have been implicated in cellular damage; however, the physiological role of ROS in chondrogenesis is not well characterized. We demonstrate that increasing ROS levels induce chondrocyte hypertrophy. Elevated ROS levels are detected in hypertrophic chondrocytes. In vivo and in vitro treatment with N-acetyl cysteine, which enhances endogenous antioxidant levels and protects cells from oxidative stress, inhibits chondrocyte hypertrophy. In ataxia telangiectasia mutated (Atm)–deficient (Atm^−/−) mice, ROS levels were elevated in chondrocytes of growth plates, accompanied by a proliferation defect and stimulation of chondrocyte hypertrophy. Decreased proliferation and excessive hypertrophy in Atm^−/− mice were also rescued by antioxidant treatment. These findings indicate that ROS levels regulate inhibition of proliferation and modulate initiation of the hypertrophic changes in chondrocytes.

Regulation of reactive oxygen species by Atm is essential for proper response to DNA double-strand breaks in lymphocytes

The ataxia telangiectasia-mutated (ATM) gene plays a pivotal role in the maintenance of genomic stability. Although it has been recently shown that antioxidative agents inhibited lymphomagenesis in Atm(-/-) mice, the mechanisms remain unclear. In this study, we intensively investigated the roles of reactive oxygen species (ROS) in phenotypes of Atm(-/-) mice. Reduction of ROS by the antioxidant N-acetyl-l-cysteine (NAC) prevented the emergence of senescent phenotypes in Atm(-/-) mouse embryonic fibroblasts, hypersensitivity to total body irradiation, and thymic lymphomagenesis in Atm(-/-) mice. To understand the mechanisms for prevention of lymphomagenesis, we analyzed development of pretumor lymphocytes in Atm(-/-) mice. Impairment of Ig class switch recombination seen in Atm(-/-) mice was mitigated by NAC, indicating that ROS elevation leads to abnormal response to programmed double-strand breaks in vivo. Significantly, in vivo administration of NAC to Atm(-/-) mice restored normal T cell development and inhibited aberrant V(D)J recombination. We conclude that Atm-mediated ROS regulation is essential for proper DNA recombination, preventing immunodeficiency, and lymphomagenesis.

Maintenance of quiescent hematopoietic stem cells in the osteoblastic niche

Hematopoietic stem cells (HSCs) are responsible for blood cell production throughout an individual's lifetime. Interaction of HSCs with their specific microenvironments, known as stem cell niches, is critical for maintaining stem cell properties, including self-renewal capacity and the ability to differentiate into multiple lineages. During postnatal life, the bone marrow (BM) supports both self-renewal and differentiation of HSCs in specialized microenvironmental niches. In the adult BM, HSCs are located in the trabecular endosteum (osteoblastic niche) or sinusoidal perivascular (vascular niche) areas. Here we show that osteoblastic cells (OBs) are a critical component for sustaining slow-cycling or quiescent HSCs. Interaction of HSCs with OBs through signaling and cell adhesion molecules maintains the balance in HSCs between cell division/proliferation and quiescence. In particular, the quiescent state is thought to be an essential mechanism to protect HSCs from stress and to sustain long-term hematopoiesis.