眞鍋 一郎

Although degradation of cartilage matrix has been suggested to be a rate-limiting step for endochondral ossification during skeletal development, little is known about the transcriptional regulation. This study investigated the involvement of KLF5 (Kruppel-like factor 5), an Sp/KLF family member, in the skeletal development. KLF5 was expressed in chondrocytes and osteoblasts but not in osteoclasts. The heterozygous deficient (KLF5(+/-)) mice exhibited skeletal growth retardation in the perinatal period. Although chondrocyte proliferation and differentiation were normal, cartilage matrix degradation was impaired in KLF5(+/-) mice, causing delay in replacement of cartilage with bone at the primary ossification center in the embryonic limbs and elongation of hypertrophic chondrocyte layer in the neonatal growth plates. Microarray analyses identified MMP9 (matrix metalloproteinase 9) as a transcriptional target, since it was strongly up-regulated by adenoviral transfection of KLF5 in chondrogenic cell line OUMS27. The KLF5 overexpression caused gelatin degradation by stimulating promoter activity of MMP9 without affecting chondrocyte differentiation or vascular endothelial growth factor expression in the culture of chondrogenic cells; however, in osteoclast precursors, it affected neither MMP9 expression nor osteoclastic differentiation. KLF5 dysfunction by genetic heterodeficiency or RNA interference was confirmed to cause reduction of MMP9 expression in cultured chondrogenic cells. MMP9 expression was decreased in the limbs of KLF5(+/-) embryos, which was correlated with suppression of matrix degradation, calcification, and vascularization. We conclude that KLF5 causes cartilage matrix degradation through transcriptional induction of MMP9, providing the first evidence that transcriptional regulation of a proteinase contributes to endochondral ossification and skeletal development.

Self-renewal of embryonic stem cells (ESCs) is maintained by a complex regulatory mechanism involving transcription factors Oct3/4 (Pou5f1), Nanog and Sox2. Here, we report that Klf5, a Zn-finger transcription factor of the Kruppel-like family, is involved in ESC self-renewal. Klf5 is expressed in mouse ESCs, blastocysts and primordial germ cells, and its knockdown by RNA interference alters the molecular phenotype of ESCs, thereby preventing their correct differentiation. The ability of Klf5 to maintain ESCs in the undifferentiated state is supported by the finding that differentiation of ESCs is prevented when Klf5 is constitutively expressed. Maintenance of the undifferentiated state by Klf5 is, at least in part, due to the control of Nanog and Oct3/4 transcription, because Klf5 directly binds to the promoters of these genes and regulates their transcription.

Obesity and metabolic syndrome are increasingly recognized as major risk factors for cardiovascular disease. Herein we show that Kruppel-like transcription factor 5 (KLF5) is a crucial regulator of energy metabolism. Klf5(+/-) mice were resistant to high fat-induced obesity, hypercholesterolemia and glucose intolerance, despite consuming more food than wild-type mice. This may in part reflect their enhanced energy expenditure. Expression of the genes involved in lipid oxidation and energy uncoupling, including those encoding carnitine-palmitoyl transferase-1b (Cpt1b) and uncoupling proteins 2 and 3 (Ucp2 and Ucp3), was upregulated in the soleus muscles of Klf5(+/-) m ice. Under basal conditions, KLF5 modified with small ubiquitin-related modifier (SUMO) proteins was associated with transcriptionally repressive regulatory complexes containing unliganded peroxisome proliferator-activated receptor-delta (PPAR-delta) and co-repressors and thus inhibited Cpt1b, Ucp2 and Ucp3 expression. Upon agonist stimulation of PPAR-delta, KLF5 was deSUMOylated, and became associated with transcriptional activation complexes containing both the liganded PPAR-delta and CREB binding protein (CBP). This activation complex increased the expression of Cpt1b, Ucp2 and Ucp3. Thus, SUMOylation seems to be a molecular switch affecting function of KLF5 and the transcriptional regulatory programs governing lipid metabolism.

A phenotypic change of smooth muscle cells (SMCs) is considered to be critical in the pathogenesis of atherosclerotic lesions such as coronary artery disease (CAD). Mrf-2/ARID5B, a member of the AT-rich interaction domain family of transcription factors, is highly expressed in the cardiovascular system and is believed to play essential roles in the phenotypic change of SMCs through its regulation of SMC differentiation. In addition, recent studies on gene-engineered mice suggested that this transcriptional factor is involved in obesity and adipogenesis, which are critical aspects for the pathogenesis of atherosclerosis. Thus, we hypothesized that genetic variations of the Mrf-2 gene might be associated with susceptibility to CAD.We investigated 11 common genetic variations of Mrf-2 to determine whether they were associated with susceptibility to CAD in 475 CAD subjects and 3 10 control Subjects. The prevalence of homozygotes for the minor allele G of SNP4 (rs2893890) and minor allele G of SNP6 (rs7087507) were significantly more frequent in the control Subjects than in patients with CAD (P = 0.0002, rs2893880, P = 0.0058, rs7087507). Four nearby SNPs (SNP4 to SNP7) (rs2893880, rs10740055, rs7087507 and rs10761600) showed almost complete linkage disequilibrium, and haplotype analysis revealed that the haplotype G (rs2893880)-C (rs10740055)-G (rs7087507)-A (rs10761600) was also significantly negatively associated with susceptibility to CAD (P = 0.049). Moreover, these negative disease associations still existed after logistic regression analysis was taken into account to eliminate confounding conventional coronary risk factors.The results implicate possible disease relevance of the polymorphisms in the Mrf-2 gene with Susceptibility to CAD. However, a larger scale prospective study is needed to clarify these findings.

To assess physiological and pathophysiological events that involve dynamic interplay between multiple cell types, real-time, in vivo analysis is necessary. We developed a technique based on confocal laser microscopy that enabled us to analyze and compare the 3-dimensional structures, cellular dynamics, and vascular function within mouse lean and obese adipose tissue in vivo with high spatiotemporal resolution. We found increased leukocyte-EC-platelet interaction in the microcirculation of obese visceral adipose tissue in ob/ob and high-fat diet-induced obese mice. These changes were indicative of activation of the leukocyte adhesion cascade, a hallmark of inflammation. Local platelet activation in obese adipose tissue was indicated by increased P-selectin expression and formation of monocyte-platelet conjugates. We observed upregulated expression of adhesion molecules on macrophages and ECs in obese visceral adipose tissue, suggesting that interactions between these cells contribute to local activation of inflammatory processes. Furthermore, administration of anti-ICAM-1 antibody normalized the cell dynamics seen in obese visceral fat. This imaging technique to analyze the complex cellular interplay within obese adipose tissue allowed us to show that visceral adipose tissue obesity is an inflammatory disease. In addition, this technique may prove to be a valuable tool to evaluate potential therapeutic interventions.

In this paper, we have driven polydimethylsiloxane (PDMS) micropillars by us-ing vascular smooth muscle cells (SMCs) on them. SMCs could both drive and re-turn micropillars by only chemical stimuli. From this result, the principle of an SMC-based bio-microactuator was demonstrated.

We have demonstrated the working principle of a bio-microactuator using smooth muscle cells (SMCs) by driving micropillars coupled to cultured SMCs and controlled pillar displacements by chemical stimuli; the generated driving force was estimated to be over 1.1 mu N.

Cardiovascular diseases are closely related to circadian rhythm, which is under the control of an internal biological clock mechanism. Although a biological clock exists not only in the hypothalamus but also in each peripheral tissue, the biological relevance of the peripheral clock remains to be elucidated. In this study we searched for clock- controlled genes in vascular endothelial cells using microarray technology. The expression of a total of 229 genes was up- regulated by CLOCK/ BMAL2. Among the genes that we identified, we examined the thrombomodulin ( TM) gene further, because TM is an integral membrane glycoprotein that is expressed primarily in vascular endothelial cells and plays a major role in the regulation of intravascular coagulation. TM mRNA and protein expression showed a clear circadian oscillation in the mouse lung and heart. Reporter analyses, gel shift assays, and chromatin immunoprecipitation analyses using the TM promoter revealed that a heterodimer of CLOCK and BMAL2 binds directly to the E- box of the TM promoter, resulting in TM promoter transactivation. Indeed, the oscillation of TM gene expression was abolished in clock mutant mice, suggesting that TM expression is regulated by the clock gene in vivo. Finally, the phase of circadian oscillation of TM mRNA expression was altered by temporal feeding restriction, suggesting TM gene expression is regulated by the peripheral clock system. In conclusion, these data suggest that the peripheral clock in vascular endothelial cells regulates TM gene expression and that the oscillation of TM expression may contribute to the circadian variation of cardiovascular events.

Objectives-Angiotensin II (ATII) type 1 receptor (AT1R) blocker (ARB) has been shown to inhibit neointimal formation. Bone marrow-derived mononuclear cells (BM-MNCs) give rise to smooth muscle (SM)-like cells at injured arterial wall and contribute to neointimal formation. However, role of the renin-angiotensin system in the homing process of SM-like cells during neointimal formation is unknown.Material and Methods-When human BM-MNCs and peripheral blood MNCs (PB-MNCs) were cultured under treatment with PDGF-BB and bFGF, these cells gave rise to SM-like cells with expression of alpha SMA, SMemb, and SM1 proteins. RT-PCR showed the expression of AT1R, ATII type 2 receptor (AT2R), alpha SMA, and SMemb mRNAs. ATII accelerated the differentiation of SM-like cells, which was inhibited by an ARB CV11974 (P<0.05). We then examined the effects of ATII, CV11974, and AT2R antagonist PD123319 on neointimal formation and BM-derived SM-like cell incorporation at injured arteries in vivo. BM from green fluorescence protein (GFP)-transgenic mice was transplanted to irradiated WT mice. GFP-BM chimera mice were subjected to wire injury on the left femoral artery. ATII (100 ng/kg/min) stimulated whereas CV11974 (1 mg/kg/d) inhibited neointimal formation. Number of GFP(+) alpha SMA(+) cells at neointima correlated with the intima/media ratio (r = 0.69, P<0.05).Conclusion-BM-derived SM-like progenitor cells contributed to the neointimal formation after arterial injury. ATII accelerated whereas ARB suppressed this process. These are new aspects of the ARB-mediated inhibition of atherosclerotic disease progression.

OBJECTIVE-The expansion of adipose tissue mass seen in obesity involves both hyperplasia and hypertrophy of adipocytes. However, little is known about how adipocytes, adipocyte precursors, blood vessels, and stromal cells interact with one another to achieve adipogenesis.RESEARCH DESIGN AND METHODS-We have developed a confocal microscopy-based method of three-dimensional visualization of intact living adipose tissue that enabled us to simultaneously evaluate angiogenesis and adipogenesis in db/db mice.RESULTS-We found that adipocyte differentiation takes place within cell clusters (which we designated adipogenic/angiogenic cell clusters) that contain multiple cell types, including endothelial cells and stromal cells that express CD34 and CD68 and bind lectin. There were close spatial and temporal interrelationships between blood vessel formation and adipogenesis, and the sprouting of new blood vessels from preexisting vasculature was coupled to adipocyte differentiation. CD34(+) CD68(+) lectin-binding cells could clearly be distinguished from CD34(-) CD68(+) macrophages, which were scattered in the stroma and did not bind lectin. Adipogenic/angiogenic cell clusters can morphologically and immunohistochemically be distinguished from crown-like structures frequently seen in the late stages of adipose tissue obesity. Administration of anti-vascular endothelial growth factor (VEGF) antibodies inhibited not only angiogenesis but also the formation of adipogenic/angiogenic cell clusters, indicating that the coupling of adipogenesis and angiogenesis is essential for differentiation of adipocytes in obesity and that VEGF is a key mediator of that process.CONCLUSIONS-Living tissue imaging techniques provide novel evidence of the dynamic interactions between differentiating adipocytes, stromal cells, and angiogenesis in living obese adipose tissue.

Objective - Vascular disease alters and reduces connexin expression and a reduction in connexin 43 (Cx43) expression diminishes the extent of atherosclerosis observed in a high-cholesterol diet murine model. We hypothesized that connexins might play a role in the smooth muscle cell response to vascular injury.Methods and Results - We therefore studied a line of smooth muscle cell-specific, Cx43 gene knockout mice (SM Cx43 KO) in which the carotid arteries were injured, either by vascular occlusion or by a wire injury. In the SM Cx43 KO mice both types of injury manifested accelerated growth of the neointima and of the adventitia. Isolated vascular smooth muscle cells from the SM Cx43 KO mice grew at a slightly faster rate in culture, and to marginally higher saturation densities than those of control mice, but these changes were not adequate to explain the large changes in the injured vessels.Conclusions - These observations provide direct evidence that smooth muscle Cx43 gap junctions play a multi-faceted role in modulating the in vivo growth response of vascular smooth muscle cells to vascular injury.

Adipocyte-derived adiponectin has an antiatherosclerotic effect that acts independently of its antidiabetic effect. Plasma adiponectin levels are generally low in subjects with coronary artery disease. In this study, the relationship between the plasma adiponectin level and the severity of coronary artery disease, as assessed using the Gensini score, an index for the severity of coronary artery stenosis, was investigated. The subjects of the study were 104 patients (72 men and 32 women; BMI, 23.5 +/- 3.3 kg/m(2); age, 63.6 +/- 10.1 years) admitted to Tokyo University Hospital for coronary angiography. Plasma adiponectin levels were inversely correlated with the insulin resistance index HOMA-IR (P =0.0127). The plasma adiponectin level was significantly associated with the Gensini score (P = 0.0332). After adjustment for conventional risk factors for cardiovascular diseases, the plasma adiponectin level tended to be inversely correlated with the Gensini score (P = 0.087). The measurement of plasma adiponectin levels may be useful for predicting the severity of coronary artery stenosis.

動脈硬化、狭心症、肥満などの生活習慣病に関連する因子として、転写因子KLF5を同定し、生活習慣病の関連臓器、組織の発生や病態の発症にKLF5がどのように関わるかをこれまで同定してきた。転写因子は創薬のターゲットになりにくいとされているが、KLF5の共役核内受容体に対するリガンドを用いた治療や、KLF5に対するsiRNAを用いた新たな臨床応用法の開発を行い、転写因子研究を治療に発展させる新たなアプローチを試みている。(著者抄録)

The Notch signaling pathway plays a crucial role in specifying cellular fates by interaction between cellular neighbors; however, the molecular mechanism underlying smooth muscle cell (SMC) differentiation by Notch signaling has not been well characterized. Here we demonstrate that Jagged1-Notch signaling promotes SMC differentiation from mesenchymal cells. Overexpression of the Notch intracellular domain, an activated form of Notch, up-regulates the expression of multiple SMC marker genes including SMC-myosin heavy chain (Sm-mhc) in mesenchymal 10T1/2 cells, but not in non-mesenchymal cells. Physiological Notch stimulation by its ligand Jagged1, but not Dll4, directly induces Sm-mhc expression in 10T1/2 cells without de novo protein synthesis, indicative of a ligand-selective effect. Jagged1-induced expression of SM-MHC was blocked by gamma-secretase inhibitor, N-(N-(3,5-difluorophenyl)-L-alanyl)-S-phenylglycine t-butyl ester, which impedes Notch signaling. Using Rbp-j kappa-deficient cells and site-specific mutagenesis of the SM-MHC gene, weshow that such an induction is independent of the myocardin-serum response factor-CArG complex, but absolutely dependent on RBP-J kappa, a major mediator of Notch signaling, and its cognate binding sequence. Of importance, Notch signaling and myocardin synergistically activate SM-MHC gene expression. Taken together, these data suggest that the Jagged1-Notch pathway constitutes an instructive signal for SMC differentiation through an RBP-J kappa-dependent mechanism and augments gene expression mediated by the myocardin-SRF-CArG complex. Given that Notch pathway components are expressed in vascular SMC during normal development and disease, Notch signaling is likely to play a pivotal role in such situations to modulate the vascular smooth muscle cell phenotype.

Adipose tissue expression and circulating concentrations of monocyte chemoattractant protein-1 (MCP-1) correlate positively with adiposity. To ascertain the roles of MCP-1 overexpression in adipose, we generated transgenic mice by utilizing the adipocyte P2 (aP2) promoter (aP2-MCP-1 mice). These mice had higher plasma MCP-1 concentrations and increased macrophage accumulation in adipose tissues, as confirmed by immunochemical, flow cytometric, and gene expression analyses. Tumornecrosis factor-alpha and interleukin-6 mRNA levels in white adipose tissue and plasma non-esterified fatty acid levels were increased in transgenic mice. aP2-MCP-1 mice showed insulin resistance, suggesting that inflammatory changes in adipose tissues may be involved in the development of insulin resistance. Insulin resistance in aP2-MCP-1 mice was confirmed by hyperinsulinemic euglycemic clamp studies showing that transgenic mice had lower rates of glucose disappearance and higher endogenous glucose production than wild-type mice. Consistent with this, insulin-induced phosphorylations of Akt were significantly decreased in both skeletal muscles and livers of a P2-MCP-1 mice. MCP-1 pretreatment of isolated skeletal muscle blunted insulin-stimulated glucose uptake, which was partially restored by treatment with the MEK inhibitor U0126, suggesting that circulating MCP-1 may contribute to insulin resistance in aP2MCP-1 mice. We concluded that both paracrine and endocrine effects of MCP-1 may contribute to the development of insulin resistance in aP2-MCP-1 mice.

Alteration in the differentiated state of smooth muscle cells (SMCs) is known to be integral to vascular development and the pathogenesis of vascular disease. However, it is still largely unknown how environmental cues translate into transcriptional control of SMC genes. We found that delta EF1 is upregulated during SMC differentiation and selectively transactivates the promoters of SMC differentiation marker genes, SM alpha-actin and SM myosin heavy chain (SM-MHC). delta EF1 physically interacts with SRF and Smad3, resulting in a synergistic activation of SM a-actin promoter. Chromatin immunoprecipitation assays and knockdown experiments showed that delta EF1 is involved in the control of the SMC differentiation programs induced by TGF-beta signaling. Overexpression of delta EF1 inhibited neointima formation and promoted SMC differentiation, whereas heterozygous dEF1 knockout mice exhibited exaggerated neointima formation. It thus appears delta EF1 mediates SMC differentiation via interaction with SRF and Smad3 during development and in vascular disease.

社会技術研究ミッションプログラムI医療安全研究グループにおいては，大学医学部附属病院における理論構築環境（研究）と，技術実装環境（大学医学部附属病院）を活用して，他の研究グループと連携を図りつつ，医療安全向上を目的とした包括的，かつ多層的なアプローチで研究を行った．その中でも，社会技術としては，医師-患者間，医師間，医療機関間において，臨床判断に資する情報共有，コミュニケーションを促進するツールとしての診療ナビゲーションシステムを開発し，東京大学医学部附属病院循環器内科において実装した．