Circulating osteoblast-lineage cells.
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Animals↗
Biomedical subjects
Kimie Tanaka
Publications and source records attributed to Kimie Tanaka.
Age-associated aortic stenosis in apolipoprotein E-deficient mice.
OBJECTIVES: The present study was designed to assess aortic valve morphology and function in mice of advanced age. We also evaluated the potential contribution of bone-marrow-derived cells to the pathogenesis of aortic stenosis. BACKGROUND: Age-associated valvular degeneration is characterized by lipid accumulation, collagen deposition, and calcification containing smooth muscle-like cells and osteoblast-like cells. Cellular and molecular factors that mediate these changes remain unknown. METHODS: We extensively examined the aortic valves of senile wild-type and apolipoprotein E (ApoE)-/- mice with echocardiography. The aortic valves were analyzed by immunohistochemistry and electron microscopy. The bone marrow of wild-type and ApoE-/- mice was reconstituted with that of green fluorescent protein (GFP) or beta-galactosidase (LacZ) mice, which expressed GFP or LacZ ubiquitously. RESULTS: Transaortic flow velocity was correlated with age in wild-type and ApoE-/- mice. The aortic valves of old ApoE-/- mice showed sclerosis that resembled the pathology of human aortic stenosis. A significant number of GFP-positive cells (10.7 +/- 4.1%) in the sclerotic valves of ApoE-/- mice expressed alpha-smooth muscle actin, whereas most of the GFP-positive cells were identified as endothelial cells or macrophages in wild-type mice. There were bone-marrow-derived cells that were positive for osteoblast-related proteins near the sites of ectopic calcification. The sclerotic valves displayed frequent apoptotic cell death and chemokine expression. CONCLUSIONS: Senile ApoE-deficient mice display aortic valve sclerosis that is similar to that observed in humans. The sclerotic valves displayed frequent apoptotic cell death and chemokine expression. Smooth muscle-like cells observed in degenerative valves might derive, at least in part, from bone marrow.
Age Factors↗
Comparison of various bone marrow fractions in the ability to participate in vascular remodeling after mechanical injury.
In contrast to conventional assumption, recent reports propose the possibility that hematopoietic stem cells (HSCs) may have broader potential to differentiate into various cell types. Here, we tested the pluripotency of HSCs by comparing vascular lesions induced by mechanical injury after bone marrow reconstitution with total bone marrow (TBM) cells, c-Kit+ Sca-1+ Lin- (KSL) cells, or a single HSC cell (Tip-SP CD34-KSL cell, CD34- c-Kit+ Sca-1+ Lin- cell with the strongest dye-efflux activity) harboring green fluorescent protein (GFP). The lesions contained a significant number of GFP-positive cells in the TBM and KSL groups, whereas GFP-positive cells were rarely detected in the HSC group. These results suggest that transdifferentiation of a highly purified HSC seems to be a rare event, if it occurs at all, whereas bone marrow cells including the KSL fraction can give rise to vascular cells that substantially contribute to repair or lesion formation after mechanical injury.
Animals↗
Potent inhibitory effect of sirolimus on circulating vascular progenitor cells.
BACKGROUND: Neointimal hyperplasia is the major cause of in-stent restenosis (ISR). The sirolimus-eluting stent (SES) has emerged as a promising therapy to prevent ISR; however, the exact mechanism by which locally delivered sirolimus, an immunosuppressive agent, prevents ISR remains unknown. Recent evidence suggests that circulating progenitor cells may contribute to neointimal formation. METHODS AND RESULTS: Mononuclear cells (MNCs) were isolated from peripheral blood of healthy human volunteers. Smooth muscle (SM)-like cells outgrew from the culture of MNCs (1x10(6)) in the presence of platelet-derived growth factor-BB and basic fibroblast growth factor, whereas endothelial cell-like cells were obtained in the presence of vascular endothelial growth factor. Sirolimus potently inhibited SM-like cell outgrowth. The number of SM-like cells was significantly reduced at a concentration as low as 0.1 ng/mL (15.9+/-5.8% of control, P<0.001). Sirolimus also exerted an inhibitory effect on endothelial cell-like cells that originated from MNCs. Wire-mediated vascular injury was induced in femoral arteries of bone marrow chimeric mice. Either vehicle or sirolimus was administered locally to the perivascular area of the injured arteries. Sirolimus significantly reduced neointima hyperplasia at 4 weeks (intima/media ratio 2.0+/-0.3 versus 1.0+/-0.2, P<0.05) with a decreased number of bone marrow-derived SM-like cells and hematopoietic cells in the lesion. Reendothelialization was retarded in the arteries treated with sirolimus. CONCLUSIONS: The potent inhibitory effects of sirolimus on circulating smooth muscle progenitor cells may mediate the clinical efficacy of SES, at least in part. Sirolimus potentially may affect reendothelialization after stent implantation.
Animals↗
Cell size and nucleoid organization of engineered Escherichia coli cells with a reduced genome.
The minimization of a genome is necessary to identify experimentally the minimal gene set that contains only those genes that are essential and sufficient to sustain a functioning cell. Recent developments in genetic techniques have made it possible to generate bacteria with a markedly reduced genome. We developed a simple system for formation of markerless chromosomal deletions, and constructed and characterized a series of large-scale chromosomal deletion mutants of Escherichia coli that lack between 2.4 and 29.7% of the parental chromosome. Combining deletion mutations changes cell length and width, and the mutant cells with larger deletions were even longer and wider than the parental cells. The nucleoid organization of the mutants is also changed: the nucleoids occur as multiple small nucleoids and are localized peripherally near the envelope. Inhibition of translation causes them to condense into one or two packed nucleoids, suggesting that the coupling of transcription and translation of membrane proteins peripherally localizes chromosomes. Because these phenotypes are similar to those of spherical cells, those may be a consequence of the morphological change. Based on the nucleoid localization observed with these mutants, we discuss the cellular nucleoid dynamics.
Cell Nucleus↗
Statins augment collateral growth in response to ischemia but they do not promote cancer and atherosclerosis.
3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, or statins, are widely prescribed to lower cholesterol. Recent reports suggest that statins may promote angiogenesis in ischemic tissues. It remains to be elucidated whether statins potentially enhance unfavorable angiogenesis associated with tumor and atherosclerosis. Here, we induced hind limb ischemia in wild-type mice by resecting the right femoral artery and subsequently inoculated cancer cells in the same animal. Cerivastatin enhanced blood flow recovery in the ischemic hind limb as determined by laser Doppler imaging, whereas tumor growth was significantly retarded. Cerivastatin did not affect capillary density in tumors. Cerivastatin, pitavastatin, and fluvastatin inhibited atherosclerotic lesion progression in apolipoprotein E-deficient mice, whereas they augmented blood flow recovery and capillary formation in ischemic hind limb. Low-dose statins were more effective than high-dose statins in both augmentation of collateral flow recovery and inhibition of atherosclerosis. These results suggest that statins may not promote the development of cancer and atherosclerosis at the doses that augment collateral flow growth in ischemic tissues.
Animals↗
Diverse contribution of bone marrow cells to neointimal hyperplasia after mechanical vascular injuries.
We and others have suggested that bone marrow-derived progenitor cells may contribute to the pathogenesis of vascular diseases. On the other hand, it was reported that bone marrow cells do not participate substantially in vascular remodeling in other experimental systems. In this study, three distinct types of mechanical vascular injuries were induced in the same mouse whose bone marrow had been reconstituted with that of GFP or LacZ mice. All injuries are known to cause smooth muscle cell (SMC) hyperplasia. At 4 weeks after wire-mediated endovascular injury, a significant number of the neointimal and medial cells derived from bone marrow. In contrast, marker-positive cells were seldom detected in the lesion induced by perivascular cuff replacement. There were only a few bone marrow-derived cells in the neointima after ligation of the common carotid artery. These results indicate that the origin of intimal cells is diverse and that contribution of bone marrow-derived cells to neointimal hyperplasia depends on the type of model.
Actins↗
Absence of p53 leads to accelerated neointimal hyperplasia after vascular injury.
OBJECTIVE: It has been suggested that deregulated expression of the tumor suppressor protein p53 may play a role in the pathogenesis of occlusive vascular remodeling. However, the role of p53 in cell proliferation and apoptosis in vascular lesions has been controversial. METHODS AND RESULTS: We tested the potential involvement of p53-mediated molecular signaling in lesion formation using a mouse model of vascular injury that may resemble balloon angioplasty. A large wire was inserted into the femoral artery of p53+/+ and p53-/- mice. There was no significant difference in the occurrence of rapid-onset apoptosis, that is, 4 hours after injury. At 2 weeks, the number of proliferating cells in the lesion of p53-/- mice was significantly higher than that observed in p53+/+ mice. The frequency of apoptotic cells was significantly lower in p53-/- mice than in p53+/+ mice. At 4 weeks, the neointimal hyperplasia of p53-/- mice was greater than that of p53+/+ mice. There was no significant difference in the frequency of apoptosis in the lesions. CONCLUSIONS: These results indicate a crucial role of p53 in pathological vascular remodeling after mechanical injury and provide the basis for the development of new therapies targeting p53 for a prophylactic treatment of vascular diseases.
Actins↗
Origin of smooth muscle progenitor cells: different conclusions from different models.
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Animals↗
Mouse genetic evidence that tranilast reduces smooth muscle cell hyperplasia via a p21(WAF1)-dependent pathway.
OBJECTIVE: N-(3'4'-dimethoxycinnamoyl)-anthranilic acid (tranilast) is a drug that has been shown to reduce the incidence of restenosis after angioplasty in middle-scale clinical trials. Despite clinical interest in this drug, the pharmacological actions of tranilast remain relatively unexplored at a molecular level. METHODS AND RESULTS: We evaluated the effects of tranilast on vascular smooth muscle cell (VSMC) proliferation in wild-type mice and in mice lacking a cyclin-dependent kinase inhibitor, p21(WAF1) (p21). Tranilast potently inhibited the proliferation of VSMC cultures derived from wild-type mice, but VSMCs derived from p21-deficient (p21-/-) mice were unaffected by this treatment. In a mouse femoral artery model of vascular injury, tranilast administration to wild-type mice led to an upregulation of p21 expression and a decrease in the number of proliferating VSMCs, as determined by immunostaining for proliferating cell nuclear antigen. In contrast, tranilast had no effect on the number of proliferating cell nuclear antigen-positive cells in the injured arteries of p21-/- mice. Administration of tranilast significantly reduced the neointimal VSMC hyperplasia in wild-type mice at 4 weeks but had no effect on lesion formation in p21-/- mice. CONCLUSIONS: Our findings provide genetic evidence that tranilast inhibits intimal hyperplasia via a p21-dependent pathway, an activity that may contribute to its efficacy in the prophylactic treatment of postangioplasty restenosis.
Animals↗
Disruption of lolCDE, encoding an ATP-binding cassette transporter, is lethal for Escherichia coli and prevents release of lipoproteins from the inner membrane.
ATP-binding cassette transporter LolCDE was previously identified, by using reconstituted proteoliposomes, as an apparatus catalyzing the release of outer membrane-specific lipoproteins from the inner membrane of Escherichia coli. Mutations resulting in defective LolD were previously shown to be lethal for E. coli. The amino acid sequences of LolC and LolE are similar to each other, but the necessity of both proteins for lipoprotein release has not been proved. Moreover, previous reconstitution experiments did not clarify whether or not LolCDE is the sole apparatus for lipoprotein release. To address these issues, a chromosomal lolC-lolD-lolE null mutant harboring a helper plasmid that carries the lolCDE genes and a temperature-sensitive replicon was constructed. The mutant failed to grow at a nonpermissive temperature because of the depletion of LolCDE. In addition to functional LolD, both LolC and LolE were required for growth. At a nonpermissive temperature, the outer membrane lipoproteins were mislocalized in the inner membrane since LolCDE depletion inhibited the release of lipoproteins from the inner membrane. Furthermore, both LolC and LolE were essential for the release of lipoproteins. On the other hand, LolCDE depletion did not affect the translocation of a lipoprotein precursor across the inner membrane and subsequent processing to the mature lipoprotein. From these results, we conclude that the LolCDE complex is an essential ABC transporter for E. coli and the sole apparatus mediating the release of outer membrane lipoproteins from the inner membrane.
ATP-Binding Cassette Transporters↗
Temporal and spatial characterization of cellular constituents during neointimal hyperplasia after vascular injury: Potential contribution of bone-marrow-derived progenitors to arterial remodeling.
BACKGROUND: Exuberant smooth muscle cells (SMCs) hyperplasia is the major cause of postangioplasty restenosis. We suggested that circulating smooth muscle progenitor cells might contribute to lesion formation after vascular injury. METHODS: We extensively investigated the cellular constituents during neointimal formation after mechanical vascular injury. RESULTS: A large wire was inserted into the mouse femoral artery, causing complete endothelial denudation and marked enlargement of the lumen with massive apoptosis of medial SMCs. At 2 h, the injured artery remained dilated with a thin media containing very few cells. A scanning electron microscopy showed fibrin and platelet deposition at the luminal side. One week after the injury, CD45-positive hematopoietic cells accumulated at the luminal side. Those CD45-positive cells gradually disappeared, whereas neointimal hyperplasia was formed with alpha-smooth muscle actin (SMA) positive cells. Bone marrow cells and peripheral mononuclear cells differentiated into alpha-SMA-positive cells in the presence of PDGF and basic FGF. Moreover, in bone marrow chimeric mice, bone-marrow-derived cells substantially contributed to neointimal hyperplasia after wire injury. CONCLUSION: These results suggest that early accumulation of hematopoietic cells may play a role in the pathogenesis of SMC hyperplasia under certain circumstances.
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The role of circulating precursors in vascular repair and lesion formation.
The accumulation of smooth muscle cells (SMCs) plays a principal role in atherogenesis, post-angioplasty restenosis and transplantation-associated vasculopathy. Therefore, much effort has been expended in targeting the migration and proliferation of medial smooth muscle cells to prevent occlusive vascular remodeling. Recent evidence suggests that bone marrow-derived circulating precursors can also give rise to endothelial cells and smooth muscle cells that contribute to vascular repair, remodeling, and lesion formation under physiological and pathological conditions. This article overviews recent findings on circulating vascular progenitor cells and describes potential therapeutic strategies that target these cells to treat occlusive vascular diseases.
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