[show abstract][hide abstract] ABSTRACT: RATIONALE: Hematopoietic stem/progenitor cells (HSPC) are responsible for maintaining the blood system as a result of their self-renewal and multilineage differentiation capacity. Recently, studies have suggested that HDL cholesterol may inhibit and impaired cholesterol efflux may increase HSPC proliferation and differentiation. OBJECTIVES: We hypothesized that LDL may enhance HSPC proliferation and differentiation while HDL might have the opposing effect which might influence the size of the pool of inflammatory cells. METHODS AND RESULTS: HSPC number and function were studied in hypercholesterolemic LDL receptor knockout (LDLr(-/-)) mice on high fat diet. Hypercholesterolemia was associated with increased frequency of HSPC, monocytes and granulocytes in the peripheral blood (PB). In addition, an increased proportion of BM HSPC was in G(2)M of the cell cycle, and the percentage of HSPC and granulocyte-macrophage progenitors (GMP) increased in BM of LDLr(-/-) mice. When BM Lin-Sca-1+cKit+ (i.e. "LSK") cells were cultured in the presence of LDL in vitro we also found enhanced differentiation towards monocytes and granulocytes. Furthermore, LDL promoted lineage negative (Lin-) cells motility. The modulation by LDL on HSPC differentiation into granulocytes and motility was inhibited by inhibiting ERK phosphorylation. By contrast, when mice were infused with human apoA-I (the major apolipoprotein of HDL) or reconstituted HDL (rHDL), the frequency and proliferation of HSPC was reduced in BM in vivo. HDL also reversed the LDL-induced monocyte and granulocyte differentiation in vitro. CONCLUSION: Our data suggest that LDL and HDL have opposing effects on HSPC proliferation and differentiation. It will be of interest to determine if breakdown of HSPC homeostasis by hypercholesterolemia contributes to inflammation and atherosclerosis progression.
PLoS ONE 01/2012; 7(11):e47286. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: A key problem in solid tumor therapy is tumor regrowth from a residual viable rim after treatment with a vascular disrupting agent (VDA). As a potential solution, we studied a combined treatment of a VDA and antiangiogenic. This study was approved by the institutional ethical committee for the use and care of laboratory animals. Rats with implanted liver tumors were randomized into four treatment groups: 1) Zd6126 (Zd); 2) Thalidomide (Tha); 3) Zd in combination with Tha (ZdTha); and 4) controls. Multiparametric MRIs were performed and quantified before and after treatment. Circulating endothelial progenitor cells (EPCs) and plasma stromal cell-derived factor-1α (SDF-1α) were monitored. Tumor apoptosis, necrosis, and microvessels were verified by histopathology. A single use of Zd or Tha did not significantly delay tumor growth. The combined ZdTha showed enhanced antitumor efficacy due to synergistic effects; it induced a cumulative tumor apoptosis or necrosis, which resulted in significant delay in tumor growth and reduction in the viable tumor rim; it also reduced tumor vessel permeability; and it improved tumor hemodynamic indexes, most likely via a transient normalization of tumor vasculature induced by Tha. A stepwise linear regression analysis showed that the apparent diffusion coefficient was an independent predictor of tumor growth. We found no significant increases in Zd-induced circulating EPCs or plasma SDF-1α. ZdTha showed improved therapeutic efficacy in solid tumors compared to either agent alone. The therapeutic effects were successfully tracked in vivo with multiparametric MRI.
PLoS ONE 01/2012; 7(7):e41140. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: The ATP-binding cassette transporter A1 (ABCA1) lipidates apolipoprotein (apo) A-I. The hypothesis that hepatocyte-specific ABCA1 overexpression results in high-density lipoprotein (HDL) dysfunction was evaluated by comparing the effects of murine ABCA1 (AdABCA1) and human apo A-I (AdA-I) transfer on lipoprotein profile, HDL function, and progression of atherosclerosis.
Gene transfer in male and female C57BL/6 apo E(-/-) mice was performed at the age of 3 months with E1E3E4-deleted adenoviral vectors containing hepatocyte-specific expression cassettes. Atherosclerosis was quantified at baseline and 56 days later in AdABCA1, AdA-I, and control mice. HDL cholesterol after AdA-I transfer was 1.7-fold (P < 0.001) and 1.8-fold (P < 0.001) higher in male and female mice, respectively, and potently inhibited atherosclerosis progression compared with respective controls. Notwithstanding a 1.4-fold (P < 0.01) and a 1.7-fold (P < 0.01) increase of HDL cholesterol in male and female mice, respectively, after AdABCA1 transfer, the intima was 2.2-fold (P < 0.001) larger in male and 1.3-fold (P = NS) larger in female mice compared with respective controls. HDL isolated from control and AdA-I mice but not from AdABCA1 mice enhanced endothelial progenitor cell (EPC) migration in vitro and reduced endothelial cell death in vitro after serum and growth factor withdrawal. Scavenger receptor class B type I (SR-BI) protein level in the liver was significantly lower in AdABCA1 mice than in control and AdA-I mice.
Hepatocyte-specific ABCA1 transfer decreases SR-BI protein level in the liver and abrogates beneficial effects of HDL on EPCs and endothelial cells. Decreased HDL function may underlie accelerated atherosclerosis in AdABCA1 apo E(-/-)mice.
Cardiovascular research 11/2010; 88(2):376-85. · 5.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Use of autologous vein grafts for surgical revascularisation is limited by vein graft failure. Topical high-density lipoprotein (HDL) administration on the adventitial side of vein grafts was evaluated as a new therapeutic modality to improve vein graft patency and function.
Caval veins of C57BL/6 apo E(-/-) mice were grafted to the right carotid arteries of recipient 3 month-old C57BL/6 TIE2-LacZ/apo E(-/-) mice. HDL (200 μg/ml; 50 μl) in 20% pluronic F-127 gel was applied on the adventitial side of vein grafts.
Topical HDL application reduced intimal area by 55% (p < 0.001) at day 28 compared to control mice. Blood flow quantified by micro magnetic resonance imaging at day 28 was 2.8-fold (p < 0.0001) higher in grafts of topical HDL treated mice than in control mice. Topical HDL potently reduced intimal inflammation and resulted in enhanced endothelial regeneration as evidenced by a 1.9-fold (p < 0.05) increase in the number of CD31 positive endothelial cells. HDL potently enhanced migration and adhesion of endothelial colony-forming cells (ECFCs) in vitro, and these effects were dependent on signaling via scavenger receptor-BI, extracellular signal-regulated kinases, and NO, and on increased β1 integrin expression. Correspondingly, the number of CD31 β-galactosidase double positive cells, reflecting incorporated circulating progenitor cells, was 3.9-fold (p < 0.01) higher in grafts of HDL treated mice than in control grafts.
Topical HDL administration on the adventitial side of vein grafts attenuates vein graft atherosclerosis via increased incorporation of circulating progenitor cells in the endothelium, enhanced endothelial regeneration, and reduced intimal inflammation.
[show abstract][hide abstract] ABSTRACT: To evaluate whether the relative atherogenicity of VLDL and LDL is dependent on the topographic site, atherosclerosis was compared at four topographic sites in homozygous LDL receptor (LDLr)-deficient rabbits fed normal chow and in heterozygous LDLr-deficient rabbits with the same genetic background fed a 0.15% cholesterol diet to match cholesterol levels. VLDL cholesterol was significantly higher and LDL cholesterol significantly lower in LDLr(+/-) diet rabbits compared with LDLr(-/-) rabbits. Intimal area in the ascending thoracic aorta and in the abdominal aorta at the level of the renal arteries was 1.4-fold (P < 0.05) and 1.5-fold (P < 0.05) higher, respectively, in LDLr(-/-) rabbits than in LDLr(+/-) diet rabbits, whereas no significant difference occurred in the descending thoracic aorta and in the abdominal aorta just above the bifurcation. Differences remained statistically significant after adjustment for plasma cholesterol, triglycerides, and sex. Compared with LDLr(+/-) diet rabbits, higher intimal lipoprotein lipase (LPL) and apolipoprotein (apo) B levels were observed in LDLr(-/-) rabbits only at the level of the descending thoracic aorta. Intimal apo E levels in LDLr(-/-) rabbits were significantly lower in sites with a larger intima than in LDLr(+/-) diet rabbits. In conclusion, the relative atherogenicity of VLDL and LDL is dependent on the topographic site.
The Journal of Lipid Research 06/2010; 51(6):1478-85. · 4.39 Impact Factor
[show abstract][hide abstract] ABSTRACT: The objective of the current study was to investigate the hypothesis that high-density lipoprotein (HDL) influences adipocyte metabolism and adiponectin expression. Therefore, HDL was increased in vivo via apolipoprotein (apo) A-I gene transfer and in vitro via supplementation of HDL to partly differentiated adipocytes, in the presence or absence of lipopolysaccharide (LPS), known to decrease HDL cholesterol and adiponectin levels in vivo.
Apo A-I transfer resulted in a significant increase of HDL cholesterol in control and LPS-injected C57BL/6 mice, which was paralleled by an increase in plasma adiponectin levels and adiponectin expression in abdominal fat. Triglyceride and free fatty acids levels after LPS administration were 2.2-fold (p<0.05) and 1.3-fold (p<0.05) lower, respectively, in Ad.hapoA-I-LPS than in Ad.Null-LPS mice. In parallel, the LPS-induced mRNA expression of hormone sensitive lipase was 3.5-fold (p=0.05) decreased in the Ad.hapoA-I-LPS group. On the other hand, apo A-I transfer abrogated the LPS-mediated reduction in lipin-1 and CD36 mRNA expression by 8.2-fold (p<0.05) and 18-fold (p<0.05), respectively. Concomitantly, the phosphorylation state of Akt was 2.0-fold (p<0.05) increased in the Ad.hapoA-I-LPS compared to the Ad.Null-LPS group. Pre-incubation of partly differentiated adipocytes with HDL (50 microg protein/ml) increased adiponectin expression by 1.5-fold under basal conditions (p<0.05) and could abrogate LPS-induced down-regulation of adiponectin, both in a phosphatidylinositol-3-kinase-dependent manner.
HDL affects adipocyte metabolism and adiponectin expression.
[show abstract][hide abstract] ABSTRACT: The liver is a key organ in lipid and lipoprotein metabolism. It has been postulated that a small diameter of sinusoidal fenestrae retards clearance of chylomicron remnants, resulting in hypercholesterolemia and atherosclerosis. However, this hypothesis has not been rigorously tested hitherto.
In the current study, we compared plasma levels of proatherogenic lipoproteins and assessed the development of atherosclerosis at distinct locations throughout the arterial tree in heterozygous New Zealand White and Dutch Belt rabbits that are deficient in low-density lipoprotein receptor and with an average fenestrae size of 103 and 124 nm, respectively.
Feeding of a 0.15% cholesterol diet for 4 months resulted in similar total plasma cholesterol levels in New Zealand White (420±20 mg/dl) and Dutch Belt (380±30 mg/dl) rabbits. Following isolation of lipoproteins by ultracentrifugation, no biologically significant differences in very-low-density lipoprotein, intermediate-density lipoprotein, and low-density lipoprotein cholesterol levels were observed between cholesterol-fed New Zealand White and Dutch Belt rabbits. Furthermore, the relative amount of intestinally derived apolipoprotein-B48-containing lipoproteins did not differ significantly between both strains (7.3±0.42% vs. 8.0±0.54%). Atherosclerosis was more pronounced in the thoracic aorta in New Zealand White rabbits than in Dutch Belt rabbits, but the reverse was observed with the abdominal aorta. These topographic differences cannot be explained by circulating lipoprotein levels.
The data presented in this study do not support the hypothesis that the diameter of fenestrae is an important determinant of chylomicron remnant levels, diet-induced hypercholesterolemia, and atherosclerosis in cholesterol-fed rabbits.
Cardiovascular pathology: the official journal of the Society for Cardiovascular Pathology 11/2009; 20(1):44-50. · 1.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: The liver is a key organ in numerous metabolic pathways, in cholesterol metabolism, and in production of coagulation factors. Therefore, gene transfer to hepatocytes has been extensively pursued. There are numerous biological parameters that may affect the outcome of hepatocyte-directed gene transfer. Species or strain variation of any of these multiple determinants hinders the process of clinical translation. This review specifically focuses on functional aspects of liver histology that are pertinent for gene transfer to parenchymal liver cells. We discuss the reticulo-endothelial cells of the liver and the spleen, and their impact on innate immune responses after adenoviral transfer and on vector clearance. Liver sinusoidal endothelial cells contain pores, called fenestrae, and have no basal lamina. Fenestrae are clustered in sieve plates and may provide direct access for circulating gene transfer vectors to the space of Disse, in which microvilli of parenchymal liver cells protrude. We present multiple lines of evidence that the species differences in the diameter of sinusoidal fenestrae are a critical determinant of transgene expression after adenoviral transfer. The small diameter of fenestrae in humans should be considered in any rational design of gene transfer technologies for hepatocyte-directed transfer. Hydrodynamic gene transfer is highly successful in rodents. The significantly lower efficacy in higher species may also partially be due to species differences in liver architecture. Finally, we discuss species differences in adaptive immune responses against the transgene product that may constitute one of the most significant hurdles for clinical translation.
Current Gene Therapy 05/2009; 9(2):83-90. · 5.32 Impact Factor
[show abstract][hide abstract] ABSTRACT: Apolipoprotein (apo) A-I(Milano) is an apo A-I mutant characterized by a cysteine for arginine substitution at position 173. Apo A-I(Milano) carriers have much less atherosclerosis than expected from their low plasma high-density lipoprotein cholesterol levels, suggesting that this mutant may have superior atheroprotective properties. Here, we compare the effect of hepatocyte-directed gene transfer of wild-type human apo A-I and human apo A-I(Milano) on endothelial progenitor cell (EPC) biology and on the progression of native atherosclerosis and allograft vasculopathy in C57BL/6 apo E(-/-) mice. Human apo A-I and apo A-I(Milano) transfer resulted in an equivalent increase of EPC number and function as well as EPC incorporation and endothelial regeneration in allografts and inhibited the progression of native atherosclerosis and allograft vasculopathy to a similar extent. In conclusion, the current head-to-head comparison indicates that human apo A-I(Milano) transfer is not superior compared to wild-type human apo A-I transfer.
Journal of Molecular Medicine 01/2009; 87(3):287-97. · 4.77 Impact Factor
[show abstract][hide abstract] ABSTRACT: Allograft vasculopathy is the leading cause of death in patients with heart transplantation. Accelerated endothelial regeneration mediated by enhanced endothelial progenitor cell (EPC) incorporation may attenuate the development of allograft vasculopathy. We investigated the hypothesis that modulation of EPC biology and attenuation of allograft vasculopathy by increased high-density lipoprotein cholesterol after human apo A-I (AdA-I) transfer requires scavenger receptor (SR)-BI expression in bone marrow-derived EPCs. After AdA-I transfer, the number of circulating EPCs increased 2.0-fold (P < .001) at different time points in C57BL/6 mice transplanted with SR-BI(+/+) bone marrow but remained unaltered in mice with SR-BI(-/-) bone marrow. The effect of high-density lipoprotein on EPC migration in vitro requires signaling via SR-BI and extracellular signal-regulated kinases and is dependent on increased nitric oxide (NO) production in EPCs. Human apo A-I transfer 2 weeks before paratopic artery transplantation reduced intimal area at day 21 3.7-fold (P < .001) in mice with SR-BI(+/+) bone marrow but had no effect in mice with SR-BI(-/-) bone marrow. AdA-I transfer potently stimulated EPC incorporation and accelerated endothelial regeneration in chimeric SR-BI(+/+) mice but not in chimeric SR-BI(-/-) mice. In conclusion, human apo A-I transfer accelerates endothelial regeneration mediated via SR-BI expressing bone marrow-derived EPCs, thereby preventing allograft vasculopathy.
[show abstract][hide abstract] ABSTRACT: Familial hypercholesterolemia is an autosomal codominant disease characterized by high concentrations of pro-atherogenic lipoproteins and premature atherosclerosis secondary to low density lipoprotein receptor (LDLr) deficiency. In the current study, the effects of gene transfer with 5 x 10(10) particles of E1E3E4-deleted adenoviral vectors expressing the LDLr (AdLDLr) or VLDLr (AdVLDLr) under control of the hepatocyte-specific human alpha(1)-antitrypsin promoter and 4 copies of the human apo E enhancer in C57BL/6 LDLr(-/-) mice were investigated. Evaluation was performed in both sexes and in mice fed either standard chow or an atherogenic diet containing 0.2% cholesterol and 10% coconut oil. Compared to control mice, AdLDLr and AdVLDLr persistently decreased plasma non-HDL cholesterol in both sexes and on both diets. Six months after LDLr gene transfer in mice fed the atherogenic diet, average intimal area was 2.5-fold (p<0.01) and 3.2-fold (p<0.001) lower in male and female mice, respectively, compared to controls. In mice fed standard chow, intimal area was reduced 22-fold (p<0.001) and 21-fold (p<0.001) after LDLr gene transfer in male and female mice, respectively. We show that non-HDL lipoproteins are more atherogenic in female mice, independent of sex differences of plasma HDL cholesterol levels, and that saturated fat does not have an effect on atherosclerosis independent of plasma cholesterol levels. Finally, quantification of tissue cholesterol levels indicates that AdLDLr does not induce cholesterol accumulation in the liver and reduces cholesterol content in the myocardium, quadriceps muscle and kidney. In conclusion, hepatocyte-specific LDLr gene transfer significantly improves cholesterol homeostasis in LDLr(-/-) mice.
[show abstract][hide abstract] ABSTRACT: Transplant arteriosclerosis is the leading cause of graft failure and death in patients with heart transplantation. Endothelial progenitor cells (EPCs) contribute to endothelial regeneration in allografts. We investigated whether increased HDL cholesterol induced by adenoviral human apoA-I (AdA-I) transfer increases number and function of EPCs, promotes incorporation of EPCs in Balb/c allografts transplanted paratopically in C57BL/6 ApoE-/- mice, and attenuates transplant arteriosclerosis.
EPC number in ApoE-/- mice was increased after AdA-I transfer as evidenced by 1.5-fold (P<0.01) higher Flk-1 Sca-1-positive cells and 1.4-fold (P<0.01) higher DiI-acLDL isolectin-positive spleen cells. In addition, HDL enhanced EPC function in vitro. Incorporation of bone marrow-derived EPCs was 5.8-fold (P<0.01) higher at day 21 after transplantation in AdA-I-treated apoE-/- mice compared with control mice. Enhanced endothelial regeneration in AdA-I-treated apoE-/- mice as evidenced by a 2.6-fold (P<0.01) increase of CD31-positive endothelial cells resulted in a 1.4-fold (P=0.059) reduction of neointima and a 3.9-fold (P<0.01) increase of luminal area.
Human apoA-I transfer increases the number of circulating EPCs, enhances their incorporation into allografts, promotes endothelial regeneration, and attenuates neointima formation in a murine model of transplant arteriosclerosis.
[show abstract][hide abstract] ABSTRACT: Background: We have previously shown that the size of sinusoidal fenestrae is a critical determinant of hepatocyte transduction after adenoviral transfer (Lievens et al. Gene Therapy 2004; 11: 1523-1531). Previous in vitro studies have demonstrated that ethanol increases the size of fenestrae. The diameter of fenestrae in New Zealand White (NZW) rabbits is approximately 1.7-fold smaller than in C57BL/6 mice. Therefore, the hypothesis of this study was that intravenous administration of ethanol before transfer may increase transgene expression in NZW rabbits but not in C57BL/6 mice.Methods: Gene transfer of an E1E3E4-deleted vector containing the hepatocyte-specific 1.5 kb human α1-antitrypsin promoter upstream of the genomic human apo A-I sequence and 4 copies of the human apo E enhancer (AdA-I) was performed by marginal ear vein and tail vein injection in NZW rabbits and C57BL/6 mice, respectively. Isolation of parenchymal (PC) and non-parenchymal (NPC) liver cells was performed by collagenase perfusion and Nycodenz centrifugation. Transgene DNA levels were determined by real time PCR. The size of sinusoidal fenestrae was determined by transmission electron microscopy (TEM) on plastic embedded specimens.Results: Injection of 0.75 g/kg of ethanol 10 minutes before transfer with 4×1012 particles/kg of AdA-I in NZW rabbits increased human apo A-I plasma levels 22-fold (22±5.8 mg/dl; p
[show abstract][hide abstract] ABSTRACT: Background: High density lipoprotein (HDL) cholesterol is the most powerful predictor of ischemic cardiovascular diseases in humans. Dyslipidemic rabbits are a more appropriate model of human dyslipidemia and atherosclerosis than mice. In contrast to mice and similar as humans, rabbits express cholesteryl ester transfer protein and rabbit liver does not edit apolipoprotein (apo) B mRNA. The purpose of this study was to evaluate the effect of rabbit apo A-I and rabbit lecithin:cholesterol acyltransferase (LCAT) transfer on the lipoprotein profile and on atherosclerosis in rabbits.Methods: Hyperlipidemia was induced by feeding 0.15 % cholesterol to heterozygous LDL receptor deficient rabbits (n=46) for 14 months starting from the age of 5 months. Gene transfer was performed with 4 × 1012 particles/kg of E1E3E4-deleted adenoviral vectors. Rabbits were randomized into 4 different groups: (1) a baseline group (n=14) sacrificed at 14 months, (2) a progression group (n=10) treated with the control vector Adnul, (3) an intervention group (n=10) treated with the rabbit apo A-I expressing vector AdrA-I and (4) an intervention group (n=14) treated with the rabbit LCAT expressing vector AdrLCAT. Very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), low density lipoproteins (LDL), HDL and very high density lipoproteins (VHDL) were isolated by ultracentrifugation. Rabbits were sacrificed 4 months after transfer.Results: Cholesterol feeding increased plasma cholesterol level from 84 ± 7.2 mg/dl before diet to 550 ± 35 mg/dl at day 56, 450 ± 28 mg/dl at day 120 and 430 ± 17 mg/dl at day 420 after the start of the diet. VLDL cholesterol and IDL cholesterol comprised more than 80 % of lipoprotein cholesterol. Together, HDL and VHDL contained less than 4% of lipoprotein cholesterol. Gene transfer with Adnul was associated with a transient decrease of HDL cholesterol in the first two weeks (1.5-fold (p=0.0002) at day 7 and 1.2-fold (p
[show abstract][hide abstract] ABSTRACT: Background: High density lipoprotein (HDL) cholesterol levels are negatively correlated with ischemic cardiovascular diseases in humans. Apolipoprotein (apo) A-I is the principal apolipoprotein of HDL and a strong correlation exists between apo A-I and HDL cholesterol levels. The ATP binding cassette transporter I (ABCA1) is defective in patients with Tangier disease and familial HDL deficiency. Indirect evidence suggests that ABCA1 expression in the liver is an important determinant of HDL cholesterol levels. Therefore, the effect of adenoviral human apo A-I (AdA-I), murine ABCA1 (AdABCA1) and combined AdA-I and AdABCA1 transfer on the lipoprotein profile and on progression of atherosclerosis in C57BL/6 apo E deficient mice was evaluated.Methods: Forty-four apo E deficient mice were randomized to 5 different groups: a baseline reference group, an Adnul control progression group, an AdABCA1 intervention group, an AdA-I intervention group and a combined AdA-I and AdABCA1 intervention group. Gene transfer was performed at the age of 3 months with 5 × 1010 particles of E1E3E4-deleted adenoviral vectors expressing the transgenes under control of a hepatocyte-specific promoter. Lipoprotein profiles were determined by gel filtration on a Superdex HR column. The baseline reference group was sacrificed at the age of 3 months for histological analysis, whereas gene transfer mice were sacrificed 56 days after transfer.Results: Non-HDL and HDL cholesterol levels at baseline in apo E deficient mice were 290 ± 37 mg/dl and 25 ± 1.4 mg/dl, respectively. The lipoprotein profile was unaltered after transfer with Adnul. Human apo A-I levels were stable for the entire duration of the experiment and were 96 ± 12 mg/dl and 120 ± 5.4 mg/dl after AdA-I and combined AdA-I and AdABCA1 transfer, respectively. Transfer with AdA-I resulted in a 1.8-fold (p