Search

Background: After the discovery of the Klotho gene, phosphate came into focus as a pathogenetic aging agent. Phosphate homeostasis is controlled by phosphate-regulating hormones: fibroblast growth factor 23 (FGF23), vitamin D 3 , and parathyroid hormone. This study investigated the relationship between the deterioration in phosphate homeostasis and arterial stiffness by measuring serum FGF23 concentrations. Methods and Results: The study subjects comprised 82 hospitalized patients (31 males, 51 females; mean [±SD] age 78.6±10.5 years). All patients underwent chest computed tomography, measurement of central blood pressure (BP), and blood chemistry tests. Arterial calcification and/or stiffness was evaluated using the Agatston calcification score (ACS) and pulse wave velocity (PWV). PWV was significantly correlated with age (t=23.47, P<0.0001), estimated glomerular filtration rate (eGFR; t=-4.40, P<0.0001), and ACS (t=4.36, P<0.0001). Serum FGF23 concentrations were significantly correlated with age (t=2.52, P=0.014), eGFR (t=-3.37, P<0.001), serum inorganic phosphorus concentrations (t=3.49, P<0.001), serum vitamin D 3 concentrations (t=-4.57, P<0.001), ACS (t=2.30, P=0.025), augmentation pressure (t=2.48, P=0.015), central systolic BP (t=2.00, P=0.049), plasma B-type natriuretic peptide (BNP) concentrations (t=3.48, P<0.001), and PWV (t=2.99, P=0.004). PWV was positively related to augmentation pressure (t=4.09, P<0.001), central systolic BP (t=3.13, P=0.002), and plasma BNP concentrations (t=3.54, P<0.001). Conclusions: This study shows that the increase in serum FGF23 concentrations reflects deterioration of phosphate homeostasis and is an important predictor for arterial stiffness, which intensifies cardiac afterload., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2023, THE JAPANESE CIRCULATION SOCIETY.)

β-Blocker (BB) use is a mainstay for the treatment of heart failure (HF) with reduced ejection fraction (HFrEF), whereas its efficacy for heart failure with preserved ejection fraction (HFpEF) remains controversial. Women outnumber men in HFpEF, whereas men outnumber women in HFrEF. Plasma B-type natriuretic peptide (BNP) is established as a biomarker for HF. We examined whether BB use is associated with plasma BNP levels differently in men and women with HFpEF. The study subjects comprised 721 patients with HFpEF [left ventricular ejection fraction (LVEF) ≥ 50%] (184 men, mean age 78.2 ± 9.2 yr and 537 women, mean age 83.1 ± 8.8 yr), 179 on BB (66 men and 113 women) and 542 no BB (118 men and 424 women), 583 in sinus rhythm (SR) and 138 in atrial fibrillation (AF). A multivariable logistic regression test was used. Plasma BNP levels were higher ( P = 0.0005), systolic blood pressure and LVEF lower ( P = 0.0003, and P = 0.0059, respectively) on BBs than on no BBs in women, whereas in men, plasma BNP levels, systolic blood pressure, and LVEF were not altered significantly ( P = 0.0849, P = 0.9129, and P = 0.4718, respectively) on BBs compared with no BBs in patients with SR. Multivariable logistic regression analysis revealed that BB use and women were a positive and a negative predictor for high BNP levels ( P = 0.003 and P = 0.032, respectively) in SR but not in AF. BB use was associated with high-plasma BNP levels and lower LVEF in women but not in men with HFpEF and SR, suggesting that the pathogenesis and treatment of HFpEF may differ in men and women in SR. NEW & NOTEWORTHY Pathogenesis and treatment for heart failure with preserved ejection fraction (HFpEF) may differ in men and women in sinus rhythm (SR).

Background: Aldehyde dehydrogenase 2 (ALDH2) plays a central role in the biotransformation of glyceryl trinitrate (GTN) or nitroglycerin, which is widely used for the treatment of coronary artery disease (CAD). The deficient variant ALDH2 genotype (ALDH2*2) is prevalent among East Asians. This study examined whether there are differences in nitroglycerine-mediated dilation (NMD) and flow-mediated dilation (FMD) response between wildALDH2*1/*1and variantALDH2*2patients with CAD., Methods and results: The study subjects comprised 55 coronary spastic angina (CSA) patients, confirmed by coronary angiography and intracoronary injection of acetylcholine (42 men and 13 women, mean age 68.0±9.0 years). They underwent NMD and FMD tests in the morning before and after continuous transdermal GTN administration for 48 h. NMD was lower at baseline inALDH2*2than in theALDH2*1/*1group (P=0.0499) and decreased significantly in both groups (P<0.0001 and P<0.0001, respectively) after GTN, with significantly lower levels in theALDH2*2group (P=0.0002). FMD decreased significantly in bothALDH2*1/*1andALDH2*2groups (P<0.0001and P=0.0002, respectively) after continuous GTN administration, with no significant differences between the 2 groups both before and after GTN., Conclusions: Continuous administration of GTN produced endothelial dysfunction as well as nitrate tolerance in bothALDH2*1/1andALDH2*2patients with CSA.ALDH2*2attenuated GTN response and exacerbated GTN tolerance, but not endothelial dysfunction, as compared toALDH2*1/*1in patients with CSA.

Background: Prevalence of heart failure with preserved ejection fraction (HFpEF) increases with advancing age, particularly among women. Plasma levels of B-type natriuretic peptide (BNP), a surrogate marker of heart failure, have consistently been shown to be higher in women in the general populations. Whether BNP levels differ as per the sex of HFpEF patients remains largely unknown., Materials and Methods: The study subjects were 733 HFpEF patients (204 men and 529 women, aged 80.9 ± 9.6 years) who underwent echocardiography and routine clinical examination, including plasma BNP level evaluation. These parameters were compared between women and men., Results: Plasma levels of BNP were significantly lower in women than in men (104 [61, 192] versus 133 [78, 255] pg/mL, P < 0.001), just as hemoglobin, atrial fibrillation, diabetes mellitus, beta-blockers, left ventricular diastolic dimension, left ventricular mass index, left ventricular eccentric hypertrophy and left atrial dimension were. Age, systolic blood pressure, pulse pressure, heart rate, left ventricular relative wall thickness, left ventricular ejection fraction and left ventricular concentric hypertrophy were higher in women than in men. Multiple regression analyses revealed that left ventricular mass index, body mass index, the ratio of early diastolic mitral flow velocity to tissue annular motion velocity divided by left ventricular diastolic dimension, estimated glomerular filtration rate, beta-blockers, left atrial dimensions, female sex and atrial fibrillation were significant predictors for BNP levels (t = 5.41, P < 0.001; t = -4.06, P < 0.001; t = 3.76, P < 0.001; t = -3.68, P < 0.001; t = 3.32, P = 0.001; t = 3.11, P = 0.002; t = -3.07, P = 0.002; and t = 2.65, P = 0.008, respectively)., Conclusions: Plasma BNP levels were lower in women and were related to left ventricular concentric remodeling and hypertrophy among HFpEF patients, contrary to those in the general population., (Copyright © 2018 Southern Society for Clinical Investigation. Published by Elsevier Inc. All rights reserved.)

Introduction: Although initial treatments for pyogenic spondylitis include conservative approaches such as rest and antibiotics, some cases are refractory to conservative therapy. The objective of this study was to clarify the predictors for achievement of C-reactive protein (CRP) normalization in pyogenic spondylitis by conservative therapy., Methods: In the present study, we enrolled 83 patients (51 men and 32 women) with conservatively treated pyogenic spondylitis from 2006 to 2015. Multiple logistic regression analysis was used to examine the association of achievement of CRP normalization with the number of infected vertebrae, bacterial strain, blood data, and the expansion of abscess to the epidural space by using functional magnetic resonance imaging., Results: We found significant differences in the subjects with and without achievement of CRP normalization with respect to age, the number of affected vertebrae, ratio of resistant pathogenic bacteria, ratio of expansion of abscess to the epidural space, and blood data such as Hb, ALB, eGFR, Cr, and ALP levels. After adjustment for age and sex, the number of infected vertebral bodies, resistant bacteria, expansion of abscess to the epidural space, and Hb level showed significant associations with the normalization of CRP. In addition, we used multiple logistic regression analysis with age, sex, number of infected vertebral bodies, resistant bacteria, expansion of abscess to the epidural space, and serum Hb level as explanatory variables. We found that expansion of the abscess to the epidural and paravertebral spaces was significantly associated with the normalization of CRP level., Conclusions: The number of infected vertebral bodies, resistant strains of pathogenic bacteria, expansion of abscess to the epidural and paravertebral spaces, and serum Hb level predicts the prognosis of patients with pyogenic spondylitis. Particularly, expansion of abscess to the epidural and paravertebral spaces was strongly associated with the achievement of CRP normalization., Competing Interests: Conflicts of Interest: No conflicts of interest and no financial support.

Background: Diabetic heart is characterized by failure of insulin to increase glucose uptake and increasingly relies on free fatty acids (FFAs) as a source of fuel in animal models. However, it is not well known how cardiac energy metabolism is altered in diabetic hearts in humans. We examined cardiac fuel metabolism in the diabetics as compared to non-diabetics who underwent cardiac catheterization for heart diseases., Material and Methods: The study subjects comprised 81 patients (male 55, female 26, average age 63.0±10.0years) who underwent the cardiac catheterization for heart diseases. Thirty-six patients were diagnosed as diabetics (diabetic group) and 45 as non-diabetics (non-diabetic group). Blood samplings were done in both the aortic root (Ao) and coronary sinus (CS) simultaneously and the plasma levels of FFAs, glucose, lactate, pyruvate, total ketone bodies and β-hydroxybutyrate were measured and compared between the two groups., Results: The myocardial uptake of glucose, lactate and pyruvate were decreased, whereas those of total ketone bodies, β-hydroxybutyrate and acetoacetate were increased in the diabetics as compared to the non-diabetics. However, the myocardial uptakes of FFAs were not significantly increased in the diabetics as compared to the non-diabetics., Conclusions: Cardiac uptakes of carbohydrate (glucose, lactate and pyruvate) were decreased, whereas those of total ketone bodies and β-hydroxybutyrate were increased in the diabetics as compared to the non-diabetics in humans. Ketone bodies therefore are utilized as an energy source partially replacing glucose in the human diabetic heart., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Heart failure (HF) with preserved ejection fraction (HFpEF) is increasing with aging of the population. Plasma levels of B-type natriuretic peptide (BNP) increase in proportion to the severity of left ventricular (LV) dysfunction. The object of this study was to examine the plasma levels of BNP in HFpEF to better understand the pathogenesis of HFpEF as compared with HF with reduced EF (HFrEF)., Methods and results: The study subjects comprised 468 HFpEF patients (158 men, 310 women, mean age 81.3±9.6 years) and 126 HFrEF patients (77 men, 49 women, mean age 75.4±12.0 years) who underwent echocardiography and routine clinical examinations including plasma BNP. Age, female prevalence, systolic blood pressure and pulse pressure were higher in the HFpEF patients than in the HFrEF patients (P<0.0001, P<0.001, P<0.0001, and P<0.0001, respectively). Plasma BNP levels, LV diastolic dimensions, and LV mass index (LVMI) were lower (P<0.0001, P<0.0001, and P<0.0001, respectively), while relative wall thickness was higher (P<0.0001) in the HFpEF patients than in the HFrEF patients. Multiple regression analysis revealed that LVMI, EF, plasma levels of albumin, C-reactive protein, and uric acid were the predictors of BNP levels (P<0.001, P<0.001, P=0.009, P=0.012, and P=0.018, respectively)., Conclusions: Plasma BNP levels were lower and related to aging-related LV concentric remodeling/hypertrophy in HFpEF patients as compared with HFrEF patients, who were associated predominantly with eccentric LV hypertrophy.

To elucidate the molecular mechanism underlying the endochondral ossification process during the skeletal growth and osteoarthritis (OA) development, we examined the signal network around CCAAT/enhancer-binding protein-β (C/EBPβ, encoded by CEBPB), a potent regulator of this process. Computational predictions and a C/EBP motif-reporter assay identified RUNX2 as the most potent transcriptional partner of C/EBPβ in chondrocytes. C/EBPβ and RUNX2 were induced and co-localized in highly differentiated chondrocytes during the skeletal growth and OA development of mice and humans. The compound knockout of Cebpb and Runx2 in mice caused growth retardation and resistance to OA with decreases in cartilage degradation and matrix metalloproteinase-13 (Mmp-13) expression. C/EBPβ and RUNX2 cooperatively enhanced promoter activity of MMP13 through specific binding to a C/EBP-binding motif and an osteoblast-specific cis-acting element 2 motif as a protein complex. Human genetic studies failed to show the association of human CEBPB gene polymorphisms with knee OA, nor was there a genetic variation around the identified responsive region in the human MMP13 promoter. However, hypoxia-inducible factor-2α (HIF-2α), a functional and genetic regulator of knee OA through promoting endochondral ossification, was identified as a potent and functional inducer of C/EBPβ expression in chondrocytes by the CEBPB promoter assay. Hence, C/EBPβ and RUNX2, with MMP-13 as the target and HIF-2α as the inducer, control cartilage degradation. This molecular network in chondrocytes may represent a therapeutic target for OA.

Objective: To examine the role of the phosphoinositide-dependent serine/threonine protein kinase Akt1 in chondrocytes during endochondral ossification., Methods: Skeletal phenotypes of homozygous Akt1-deficient (Akt1(-/-)) mice and their wild-type littermates were compared in radiologic and histologic analyses. An experimental osteoarthritis (OA) model was created by surgically inducing instability in the knee joints of mice. For functional analyses, we used primary costal and articular chondrocytes from neonatal mice and mouse chondrogenic ATDC5 cells with retroviral overexpression of constitutively active Akt1 or small interfering RNA (siRNA) for Akt1., Results: Among the Akt isoforms (Akt1, Akt2, and Akt3), Akt1 was the most highly expressed in chondrocytes, and the total level of Akt protein was decreased in Akt1(-/-) chondrocytes, indicating a dominant role of Akt1. Akt1(-/-) mice exhibited dwarfism with normal proliferative and hypertrophic zones but suppressed cartilage calcification in the growth plate compared with their wild-type littermates. In mice with surgically induced OA, calcified osteophyte formation, but not cartilage degradation, was prevented in the Akt1(-/-) joints. Calcification was significantly suppressed in cultures of Akt1(-/-) chondrocytes or ATDC5 cells overexpressing siRNA for Akt1 and was enhanced in ATDC5 cells overexpressing constitutively active Akt1. Neither proliferation nor hypertrophic differentiation was affected by the gain or loss of function of Akt1. The expression of ANK and nucleotide pyrophosphatase/phosphodiesterase 1, which accumulate pyrophosphate, a crucial calcification inhibitor, was enhanced by Akt1 deficiency or siRNA for Akt1 and was suppressed by constitutively active Akt1., Conclusion: Our findings indicate that Akt1 in chondrocytes controls cartilage calcification by inhibiting pyrophosphate during endochondral ossification in skeletal growth and during osteophyte formation in OA.

We sought to evaluate whether thienopyridine low responsiveness, a predictor of stent thrombosis, is found in hemodialysis patients. We measured platelet aggregation at the site of implantation of drug-eluting stents in 333 patients with angina pectoris undergoing dual anti-platelet therapy. Thirty-one patients were on hemodialysis (HD group), and 302 were not (N-HD group). We used a novel whole-blood aggregometer. The aggregometer used the screen filtration method, with adenosine diphosphate as an agonist. The concentration of agonist required to induce 50% of the maximum pressure rate was calculated and indicated as the platelet aggregatory threshold index (PATI). Low responsiveness for thienopyridine was defined if the PATI levels were <4 μmol/l. PATI levels (μmol/l) were significantly lower in the HD group than in the N-HD group (6.8 ± 4.8 vs. 9.1 ± 5.4, P = 0.023), and the rate of low responsiveness for thienopyridine was significantly higher in the HD group than in the N-HD group (45.7 vs. 26.8%, P = 0.019). Non-fatal myocardial infarction and stent thrombosis occurred in three of the HD group and in nine of the N-HD group (P = 0.122). Late stent thrombosis occurred at a significantly higher rate in the HD group than in the N-HD group (P = 0.002). The rate of target lesion revascularization was significantly higher in the HD group than in the N-HD group (38 vs. 11.8%, P = 0.0001). In conclusion, low responsiveness to thienopyridine, as an indicator of platelet reactivity, is found more frequently in hemodialysis patients.

Background: Although transition from proliferation to hypertrophic differentiation of chondrocytes is a crucial step for endochondral ossification in physiological skeletal growth and pathological disorders like osteoarthritis, the underlying mechanism remains an enigma. This study investigated the role of the transcription factor CCAAT/enhancer-binding protein beta (C/EBPbeta) in chondrocytes during endochondral ossification., Methodology/principal Findings: Mouse embryos with homozygous deficiency in C/EBPbeta (C/EBPbeta-/-) exhibited dwarfism with elongated proliferative zone and delayed chondrocyte hypertrophy in the growth plate cartilage. In the cultures of primary C/EBPbeta-/- chondrocytes, cell proliferation was enhanced while hypertrophic differentiation was suppressed. Contrarily, retroviral overexpression of C/EBPbeta in chondrocytes suppressed the proliferation and enhanced the hypertrophy, suggesting the cell cycle arrest by C/EBPbeta. In fact, a DNA cell cycle histogram revealed that the C/EBPbeta overexpression caused accumulation of cells in the G0/G1 fraction. Among cell cycle factors, microarray and real-time RT-PCR analyses have identified the cyclin-dependent kinase inhibitor p57(Kip2) as the transcriptional target of C/EBPbeta. p57(Kip2) was co-localized with C/EBPbeta in late proliferative and pre-hypertrophic chondrocytes of the mouse growth plate, which was decreased by the C/EBPbeta deficiency. Luciferase-reporter and electrophoretic mobility shift assays identified the core responsive element of C/EBPbeta in the p57(Kip2) promoter between -150 and -130 bp region containing a putative C/EBP motif. The knockdown of p57(Kip2) by the siRNA inhibited the C/EBPbeta-induced chondrocyte hypertrophy. Finally, when we created the experimental osteoarthritis model by inducing instability in the knee joints of adult mice of wild-type and C/EBPbeta+/- littermates, the C/EBPbeta insufficiency caused resistance to joint cartilage destruction., Conclusions/significance: C/EBPbeta transactivates p57(Kip2) to promote transition from proliferation to hypertrophic differentiation of chondrocytes during endochondral ossification, suggesting that the C/EBPbeta-p57(Kip2) signal would be a therapeutic target of skeletal disorders like growth retardation and osteoarthritis.

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 (Krüppel-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.

cGMP-dependent protein kinase II (cGKII; encoded by PRKG2) is a serine/threonine kinase that is critical for skeletal growth in mammals; in mice, cGKII deficiency results in dwarfism. Using radiographic analysis, we determined that this growth defect was a consequence of an elongated growth plate and impaired chondrocyte hypertrophy. To investigate the mechanism of cGKII-mediated chondrocyte hypertrophy, we performed a kinase substrate array and identified glycogen synthase kinase-3beta (GSK-3beta; encoded by Gsk3b) as a principal phosphorylation target of cGKII. In cultured mouse chondrocytes, phosphorylation-mediated inhibition of GSK-3beta was associated with enhanced hypertrophic differentiation. Furthermore, cGKII induction of chondrocyte hypertrophy was suppressed by cotransfection with a phosphorylation-deficient mutant of GSK-3beta. Analyses of mice with compound deficiencies in both protein kinases (Prkg2(-/-)Gsk3b(+/-)) demonstrated that the growth retardation and elongated growth plate associated with cGKII deficiency were partially rescued by haploinsufficiency of Gsk3b. We found that beta-catenin levels decreased in Prkg2(-/-) mice, while overexpression of cGKII increased the accumulation and transactivation function of beta-catenin in mouse chondroprogenitor ATDC5 cells. This effect was blocked by coexpression of phosphorylation-deficient GSK-3beta. These data indicate that hypertrophic differentiation of growth plate chondrocytes during skeletal growth is promoted by phosphorylation and inactivation of GSK-3beta by cGKII.

Hedgehog (Hh)-Patched1 (Ptch1) signaling plays essential roles in various developmental processes, but little is known about its role in postnatal homeostasis. Here, we demonstrate regulation of postnatal bone homeostasis by Hh-Ptch1 signaling. Ptch1-deficient (Ptch1+/-) mice and patients with nevoid basal cell carcinoma syndrome showed high bone mass in adults. In culture, Ptch1+/- cells showed accelerated osteoblast differentiation, enhanced responsiveness to the runt-related transcription factor 2 (Runx2), and reduced generation of the repressor form of Gli3 (Gli3rep). Gli3rep inhibited DNA binding by Runx2 in vitro, suggesting a mechanism that could contribute to the bone phenotypes seen in the Ptch1 heterozygotes. Moreover, systemic administration of the Hh signaling inhibitor cyclopamine decreased bone mass in adult mice. These data provide evidence that Hh-Ptch1 signaling plays a crucial role in postnatal bone homeostasis and point to Hh-Ptch1 signaling as a potential molecular target for the treatment of osteoporosis.

Bone mass and turnover are maintained by the coordinated balance between bone formation by osteoblasts and bone resorption by osteoclasts, under regulation of many systemic and local factors. Phosphoinositide-dependent serine-threonine protein kinase Akt is one of the key players in the signaling of potent bone anabolic factors. This study initially showed that the disruption of Akt1, a major Akt in osteoblasts and osteoclasts, in mice led to low-turnover osteopenia through dysfunctions of both cells. Ex vivo cell culture analyses revealed that the osteoblast dysfunction was traced to the increased susceptibility to the mitochondria-dependent apoptosis and the decreased transcriptional activity of runt-related transcription factor 2 (Runx2), a master regulator of osteoblast differentiation. Notably, our findings revealed a novel role of Akt1/forkhead box class O (FoxO) 3a/Bim axis in the apoptosis of osteoblasts: Akt1 phosphorylates the transcription factor FoxO3a to prevent its nuclear localization, leading to impaired transactivation of its target gene Bim which was also shown to be a potent proapoptotic molecule in osteoblasts. The osteoclast dysfunction was attributed to the cell autonomous defects of differentiation and survival in osteoclasts and the decreased expression of receptor activator of nuclear factor-kappaB ligand (RANKL), a major determinant of osteoclastogenesis, in osteoblasts. Akt1 was established as a crucial regulator of osteoblasts and osteoclasts by promoting their differentiation and survival to maintain bone mass and turnover. The molecular network found in this study will provide a basis for rational therapeutic targets for bone disorders.

Despite accumulated knowledge of various signalings regulating bone formation, the molecular network has not been clarified sufficiently to lead to clinical application. Here we show that heterozygous glycogen synthase kinase-3beta (GSK-3beta)-deficient mice displayed an increased bone formation due to an enhanced transcriptional activity of Runx2 by suppressing the inhibitory phosphorylation at a specific site. The cleidocranial dysplasia in heterozygous Runx2-deficient mice was significantly rescued by the genetic insufficiency of GSK-3beta or the oral administration of lithium chloride, a selective inhibitor of GSK-3beta. These results establish GSK-3beta as a key attenuator of Runx2 activity in bone formation and as a potential molecular target for clinical treatment of bone catabolic disorders like cleidocranial dysplasia.

To effectively treat serious bone defects using bone regenerative medicine, there is a need for the development of a small chemical compound that potently induces bone formation. We now report a novel osteogenic helioxanthin-derivative, TH. TH induced osteogenic differentiation in MC3T3-E1 cells, mouse primary osteoblasts, and mouse embryonic stem cells. The combination of TH and bone morphogenetic protein (BMP) 2 induced the mRNA expression of osteoblast marker genes and calcification in primary fibroblasts. The TH induced the mRNA of the inhibitor of DNA-binding 1 (Id-1), and its osteogenic effect was inhibited by Smad6 or Noggin. Furthermore, TH induced the mRNA expression of Bmp4 and Bmp6. These data suggest that TH exerts its potent osteogenic effect in a BMP-dependent manner by enhancing the effects of the existing BMPs and/or increasing the expression of Bmp4 and Bmp6. TH may help establish a more efficient bone regeneration system.

To identify potent bioactive factors for in vivo tissue regeneration by comprehensive screening remains a challenge for regenerative medicine. Here we report the development of an ES cell-based monitoring system for osteogenic differentiation, the identification of a potent combination of osteogenic genes using such a system, and an evaluation of its therapeutic potentials. ES cells were isolated from mice carrying a transgene expressing GFP driven by the 2.3 kb fragment of rat type I collagen alpha1 promoter. Using these cells engineered to fluoresce on osteogenic differentiation, we screened cDNA libraries and combinations of major osteogenesis-related genes. Among them, the combination of constitutively active activin receptor-like kinase 6 (caALK6) and runt-related transcription factor 2 (Runx2) was the minimal unit that induced fluorescence. The combination efficiently induced osteogenic differentiation in various cell types, including terminally differentiated nonosteogenic cells. The cooperative action of the combination occurred through protein stabilization of core binding factor beta (Cbfb), induction of Runx2-Cbfb complex formation, and its DNA binding. Furthermore, transplantation of a monolayer sheet of fibroblasts transduced with the combination achieved bone regeneration within 4 wk in mouse calvarial bone defects. Thus, we successfully identified the potent combination of genes for bone regeneration, which helped broaden cell sources.

FK506 is an immunosuppressant that exerts effects by binding to FK506-binding protein 12 (FKBP12). Recently, FK506 has also been reported to promote osteogenic differentiation when administered locally or in vitro in combination with bone morphogenetic proteins (BMPs), although the underlying mechanism remains unclarified. The present study initially showed that FK506 alone at a higher concentration (1muM) induced osteogenic differentiation of mesenchymal cell lines, which was suppressed by adenoviral introduction of Smad6. FK506 rapidly activates the BMP-dependent Smads in the absence of BMPs, and the activation was blocked by Smad6. Overexpression of FKBP12, which was reported to block the ligand-independent activation of BMP type I receptor A (BMPRIA), suppressed Smad signaling induced by FK506, but not that induced by BMP2. BMPRIA and FKBP12 bound to each other, and this binding was suppressed by FK506. These data suggest that FK506 promotes osteogenic differentiation by activating BMP receptors through interacting with FKBP12.

Although accumulated evidence has shown the bone anabolic effects of bone morphogenetic proteins (BMPs) that were exogenously applied in vitro and in vivo, the roles of endogenous BMPs during bone formation remain to be clarified. This study initially investigated expression patterns of BMPs in the mouse long bone and found that BMP2 and BMP6 were the main subtypes expressed in hypertrophic chondrocytes that induce endochondral bone formation. We then examined the involvement of the combination of these BMPs in bone formation in vivo by generating the compound-deficient mice (Bmp2+/-;Bmp6-/-). Under physiological conditions, these mice exhibited moderate growth retardation compared with the wild-type (WT) littermates during the observation period up to 52 weeks of age. Both the fetal and adult compound-deficient mice showed a reduction in the trabecular bone volume with suppressed bone formation, but normal bone resorption, whereas the single deficient mice (Bmp2+/- or Bmp6-/-) did not. When a fracture was created at the femoral midshaft and the bone healing was analyzed, the endochondral bone formation, but not intramembranous bone formation, was impaired by the compound deficiency. In the cultures of bone marrow cells, however, there was no difference in osteogenic differentiation between WT and compound-deficient cells in the presence or absence of the exogenous BMP2. We thus concluded that endogenous BMP2 and BMP6 cooperatively play pivotal roles in bone formation under both physiological and pathological conditions.

We present two patients who developed bilateral border zone brain infarctions after massive bleeding. Patient 1 was a 46-year old woman who developed bilateral visual disturbance and left hand monoparesis after excessive menstruation with severe anemia. Diffusion-weighted MRI of brain showed multiple border zone infarcts bilaterally in cerebral and cerebellar hemispheres while brain MRA was normal. Patient 2 was a 67-year old man who developed disturbance of consciousness and right hemiplegia after upper gastrointestinal tract bleeding. Diffusion-weighted MRI of brain showed bilateral multiple border zone infarcts in cerebral hemispheres, although he had asymptomatic occlusion of the left internal carotid artery. The bilateral multiple border zone infarcts are one of the key findings suggesting the presence of anemic hypoxia as a result of global brain hypoperfusion caused by massive blood loss.

To better understand the role of the canonical Wnt signaling pathway in cartilage development, we adenovirally expressed a constitutively active (ca) or a dominant negative (dn) form of lymphoid enhancer factor-1 (LEF-1), the main nuclear effector of the pathway, in undifferentiated mesenchymal cells, chondrogenic cells, and primary chondrocytes, and examined the expression of markers for chondrogenic differentiation and hypertrophy. caLEF-1 and LiCl, an activator of the canonical pathway, promoted both chondrogenic differentiation and hypertrophy, whereas dnLEF-1 and the gene silencing of beta-catenin suppressed LiCl-promoted effects. To investigate whether these effects were dependent on Sox9, a master regulator of cartilage development, we stimulated Sox9-deficient ES cells with the pathway. caLEF-1 and LiCl promoted both chondrogenic differentiation and hypertrophy in wild-type, but not in Sox9-deficient, cells. The response of Sox9-deficient cells was restored by the adenoviral expression of Sox9. Thus, the canonical Wnt signaling pathway promotes chondrocyte differentiation in a Sox9-dependent manner.

During vertebrate skeletal development, the appendicular skeleton forms through endochondral ossification, which involves the intricately regulated multistep differentiation of mesenchymal cells. During this process, mesenchymal condensations initially differentiate into chondrocytes. Then chondrocytes in the center further differentiate into hypertrophic chondrocytes. Hypertrophic chondrocytes express a number of osteogenic factors and induce bone formation. Although numerous studies have provided novel insights into the regulation and function of cartilage development, little is known about the intracellular signaling pathways regulating chondrocyte hypertrophy. Recent study revealed that cyclic guanosine monophosphate (cGMP)-dependent protein kinase II (cGKII) coupled the stop of proliferation and the start of hypertrophic differentiation of chondrocytes. Herein, we review the molecular mechanism of regulation of chondrocyte hypertrophy by cGKII and the interaction between cGKII and other signaling pathways.

The Komeda miniature rat Ishikawa (KMI) is a naturally occurring mutant caused by an autosomal recessive mutation mri, which exhibits longitudinal growth retardation. Here we identified the mri mutation as a deletion in the rat gene encoding cGMP-dependent protein kinase type II (cGKII). KMIs showed an expanded growth plate and impaired bone healing with abnormal accumulation of postmitotic but nonhypertrophic chondrocytes. Ex vivo culture of KMI chondrocytes reproduced the differentiation impairment, which was restored by introducing the adenovirus-mediated cGKII gene. The expression of Sox9, an inhibitory regulator of hypertrophic differentiation, persisted in the nuclei of postmitotic chondrocytes of the KMI growth plate. Transfection experiments in culture systems revealed that cGKII attenuated the Sox9 functions to induce the chondrogenic differentiation and to inhibit the hypertrophic differentiation of chondrocytes. This attenuation of Sox9 was due to the cGKII inhibition of nuclear entry of Sox9. The impaired differentiation of cultured KMI chondrocytes was restored by the silencing of Sox9 through RNA interference. Hence, the present study for the first time shed light on a novel role of cGKII as a molecular switch, coupling the cessation of proliferation and the start of hypertrophic differentiation of chondrocytes through attenuation of Sox9 function., (Copyright 2004 Cold Spring Harbor Laboratory Press)

Bone Morphogenetic Proteins (BMPs) are secreted proteins that represent a group of the transforming growth factor-beta. BMPs were identified as molecules that induce ectopic bone formation in muscles of mice. The homo- or heterodimetric BMP proteins, which bind to serine/threonine protein-kinase receptor and activate smad and p38MAPK signal transductions, function as potent osteogenic factors. In vivo, it is not clear which BMPs play crucial roles in regulating osteogenesis. Clinical uses of rhBMP-2 and rhBMP-7 have been performed, but we need numerous rhBMPs, which is very expensive, to induce osteogenesis in humans.

During endo chondral bone development, parathyroid hormone-related peptide(PTHrP)is expressed by the perichondrial cells and proliferating chondrocytes in the periarticular region. PTHrP mRNA expression is increased by Indian Hedgehog(Ihh), which is expressed by prehypertrophic and hypertrophic chondrocytes. PTHrP acts directly on columnar proliferating chondrocytes to prevent hypertrophic differentiation. This prevention indirectly results in less Ihh signaling by decreasing the number of prehypertrophic and hypertrophic chondrocytes expressing Ihh. This negative feedback loop serves to regulate the balance of differentiation and proliferation of growth plate chondrocytes. Gs, cAMP, Sox9 and CREB seem to act downstream of PTHrP, while Patched, smoothened, Gli appear to act downstream of Ihh.