Aging Is Associated With Organ-Specific Alterations in the Level and Expression Pattern of von Willebrand Factor

BACKGROUND

VWF (von Willebrand factor) is an endothelial-specific procoagulant protein with a major role in thrombosis. Aging is associated with increased circulating levels of VWF, which presents a risk factor for thrombus formation.

METHODS

Circulating plasma, cellular protein, and mRNA levels of VWF were determined and compared in young and aged mice. Major organs were subjected to immunofluorescence analyses to determine the vascular pattern of VWF expression and the presence of platelet aggregates. An in vitro model of aging, using extended culture time of endothelial cells, was used to explore the mechanism of age-associated increased VWF levels.

RESULTS

Increased circulating plasma levels of VWF with elevated levels of larger multimers, indicative of VWF functional activity, were observed in aged mice. VWF mRNA and cellular protein levels were significantly increased in the brains, lungs, and livers but not in the kidneys and hearts of aged mice. Higher proportion of small vessels in brains, lungs, and livers of aged mice exhibited VWF expression compared with young, and this was concomitant with increased platelet aggregate formation. Prolonged culture of endothelial cells resulted in increased cell senescence that correlated with increased VWF expression; VWF expression was specifically detected in senescent cultured endothelial cells and abolished in response to p53 knockdown. A significantly higher proportion of VWF expressing endothelial cells in vivo exhibited senescence markers SA-β-Gal (senescence-associated β-galactosidase) and p53 in aged mouse brains compared with that of the young.

CONCLUSIONS

Aging elicits a heterogenic response in endothelial cells with regard to VWF expression, leading to organ-specific increase in VWF levels and alterations in vascular tree pattern of expression. This is concomitant with increased platelet aggregate formation. The age-associated increase in VWF expression may be modulated through the process of cell senescence, and p53 transcription factor contributes to its regulation.

Disrupted Stiffness Ratio Alters Nuclear Mechanosensing

The ability of endothelial cells to sense and respond to dynamic changes in blood flow is critical for vascular homeostasis and cardiovascular health. The mechanical and geometric properties of the nuclear and cytoplasmic compartments affect mechanotransduction. We hypothesized that alterations to these parameters have resulting mechanosensory consequences. Using atomic force microscopy and mathematical modeling, we assessed how the nuclear and cytoplasmic compartment stiffnesses modulate shear stress transfer to the nucleus within aging endothelial cells. Our computational studies revealed that the critical parameter controlling shear transfer is not the individual mechanics of these compartments, but the stiffness ratio between them. Replicatively aged cells had a reduced stiffness ratio, attenuating shear transfer, while the ratio was not altered in a genetic model of accelerated aging. We provide a theoretical framework suggesting that dysregulation of the shear stress response can be uniquely imparted by relative mechanical changes in subcellular compartments.

Maximizing the recovery of the native p28 bacterial peptide with improved activity and maintained solubility and stability in Escherichia coli BL21 (DE3)

p28 is a natural bacterial product, which recently has attracted much attention as an efficient cell penetrating peptide (CPP) and a promising anticancer agent. Considering the interesting biological qualities of p28, maximizing its expression appears to be a prominent priority. The optimization of such bioprocesses might be facilitated by utilizing statistical approaches such as Design of Experiment (DoE). In this study, we aimed to maximize the expression of "biologically active" p28 in Escherichia coli BL21 (DE3) host by harnessing statistical tools and experimental methods. Using Minitab, Plackett-Burman and Box-Behnken Response Surface Methodology (RSM) designs were generated to optimize the conditions for the expression of p28. Each condition was experimentally investigated by assessing the biological activity of the purified p28 in the MCF-7 breast cancer cell line. Seven independent variables were investigated, and three of them including ethanol concentration, OD₆₀₀ of the culture at the time of induction, and the post-induction temperature were demonstrated to significantly affect the p28 expression in E. coli. The cytotoxicity, penetration efficiency, and total process time were measured as dependent variables. The optimized expression conditions were validated experimentally, and the final products were investigated in terms of expression yield, solubility, and stability in vitro. Following the optimization, an 8-fold increase of the concentration of p28 expression was observed. In this study, we suggest an optimized combination of effective factors to produce soluble p28 in the E. coli host, a protocol that results in the production of a significantly high amount of the biologically active peptide with retained solubility and stability.

Vascular senescence in progeria: role of endothelial dysfunction

Aims

Hutchinson-Gilford progeria syndrome (HGPS) is a pre-mature aging disorder caused by the mutation of the LMNA gene leading to an irreversibly farnesylated lamin A protein: progerin. The major causes of death in HGPS are coronary and arterial occlusive disease. In the murine model of HGPS, vascular smooth muscle cell (VSMC) loss is the primary vascular manifestation, which is different from the arterial occlusive disease seen in older patients.

Methods and results

To identify the mechanisms of HGPS vascular disease in humans, we differentiated isogenic endothelial cells (ECs) and VSMCs from HGPS-induced pluripotent stem cells (iPSCs) and control-iPSCs. Both HGPS-ECs and HGPS-VSMCs manifested cellular hallmarks of aging, including dysmorphic nuclei, impaired proliferation, increased β-galactosidase staining, shortened telomeres, up-regulated secretion of inflammatory cytokines, increased DNA damage, loss of heterochromatin, and altered shelterin protein complex (SPC) expression. However, at similar days after differentiation, even with lower levels of progerin, HGPS-ECs manifested more severe signs of senescence, as indicated in part by a higher percentage of β-galactosidase positive cells, shorter telomere length, and more DNA damage signals. We observed increased γH2A.X binding to RAP1 and reduced TRF2 binding to lamin A in HGPS-ECs but not in HGPS-VSMCs. The expression of γH2A.X was greater in HGPS-ECs than in HGPS-VSMCs and is associated with greater telomere shortening, impaired SPC interactions, and loss of heterochromatin.

Conclusion

Although progerin expression has a deleterious effect on both ECs and VSMCs, the dysfunction is greater in HGPS-ECs compared with HGPS-VSMCs. This study suggests that an endothelial-targeted therapy may be useful for HGPS patients.

Telomerase therapy reverses vascular senescence and extends lifespan in progeria mice

AIMS

Hutchinson-Gilford progeria syndrome (HGPS) is an accelerated ageing syndrome associated with premature vascular disease and death due to heart attack and stroke. In HGPS a mutation in lamin A (progerin) alters nuclear morphology and gene expression. Current therapy increases the lifespan of these children only modestly. Thus, greater understanding of the underlying mechanisms of HGPS is required to improve therapy. Endothelial cells (ECs) differentiated from induced pluripotent stem cells (iPSCs) derived from these patients exhibit hallmarks of senescence including replication arrest, increased expression of inflammatory markers, DNA damage, and telomere erosion. We hypothesized that correction of shortened telomeres may reverse these measures of vascular ageing.

METHODS AND RESULTS

We generated ECs from iPSCs belonging to children with HGPS and their unaffected parents. Telomerase mRNA (hTERT) was used to treat HGPS ECs. Endothelial morphology and functions were assessed, as well as proteomic and transcriptional profiles with attention to inflammatory markers, DNA damage, and EC identity genes. In a mouse model of HGPS, we assessed the effects of lentiviral transfection of mTERT on measures of senescence, focusing on the EC phenotype in various organs. hTERT treatment of human HGPS ECs improved replicative capacity; restored endothelial functions such as nitric oxide generation, acetylated low-density lipoprotein uptake and angiogenesis; and reduced the elaboration of inflammatory cytokines. In addition, hTERT treatment improved cellular and nuclear morphology, in association with a normalization of the transcriptional profile, effects that may be mediated in part by a reduction in progerin expression and an increase in sirtuin 1 (SIRT1). Progeria mice treated with mTERT lentivirus manifested similar improvements, with a reduction in inflammatory and DNA damage markers and increased SIRT1 in their vasculature and other organs. Furthermore, mTERT therapy increased the lifespan of HGPS mice.

CONCLUSION

Vascular rejuvenation using telomerase mRNA is a promising approach for progeria and other age-related diseases.

Dysfunction of iPSC-derived endothelial cells in human Hutchinson-Gilford progeria syndrome

Children with Hutchinson-Gilford progeria syndrome (HGPS) succumb to myocardial infarction and stroke in their teen years. Endothelial dysfunction is an early event in more common forms of atherosclerosis. Endothelial pathobiology may contribute to HGPS, but a comprehensive characterization of endothelial function in HGPS has not been performed. iPSCs derived from fibroblasts of HGPS patients or unaffected relatives were differentiated into endothelial cells (ECs). Immunofluorescent signal of the pluripotent stem cell markers SSEA4, Oct4, Sox2 and TRAI-60 was similar in HGPS or control iPSCs. Following the differentiation, FACS analysis and immunocytochemistry for CD31 and CD144 revealed a smaller percentage of ECs from HGPS iPSCs. Immunostaining for Lamin A revealed nuclear dysmorphology in HGPS iPSC-ECs. Furthermore, these cells were significantly larger and rounded, and they proliferated less, features which are typical of senescent endothelial cells. HGPS iPSC-ECs manifested less Dil-Ac-LDL uptake; less DAF-2DA staining for nitric oxide generation and formed fewer networks in matrigel in vitro. In immunodeficient mice injected with iPSC-ECs, HGPS iPSC-ECs generated a sparser vascular network compared to the control, with reduced capillary number. Telomere length (T/S ratio) of HGPS iPSC-EC was reduced as assessed by mmqPCR. iPSC-ECs derived from HGPS patients have dysmorphic appearance, abnormal nuclear morphology, shortened telomeres, reduced replicative capacity and impaired functions in vitro and in vivo. Targeting the endothelial abnormality in patients with HGPS may provide a new therapeutic avenue for the treatment of this condition. Abbreviations: HGPS: Hutchinson-Gilford progeria syndrome; ZMPSTE24: Zinc metallopeptidase STE24; FTI: Farnesyltransferase inhibitors; VSMCs: Vascular smooth muscle cells; iPSC: Induced pluripotent stem cells; EC: Endothelial cells; hTERT: Human telomerase reverse transcriptase; VEGF: vascular endothelial growth factor; DAF-FM DA: 3-Amino, 4-aminomethyl-2',7'-difluorofluorescein diacetate; BMP4: Bone Morphogenetic Protein 4; mmqPCR: mono chrome multiplex PCR; SCG: single-copy gene; CSI: Cell shape index.

Endothelial cells of different organs exhibit heterogeneity in von Willebrand factor expression in response to hypoxia

BACKGROUND AND AIMS

We have previously demonstrated that in response to hypoxia, von Willebrand factor (VWF) expression is upregulated in lung and heart endothelial cells both in vitro and in vivo, but not in kidney endothelial cells. The aim of our current study was to determine whether endothelial cells of different organs employ distinct molecular mechanisms to mediate VWF response to hypoxia.

METHODS

We used cultured human primary lung, heart and kidney endothelial cells to determine the activation of endogenous VWF as well as exogenously expressed VWF promoter in response to hypoxia. Chromatin immunoprecipitation and siRNA knockdown analyses were used to determine the roles of VWF promoter associated transacting factors in mediating its hypoxia response. Platelet aggregates formations in vascular beds of mice were used as a marker for potential functional consequences of hypoxia-induced VWF upregulation in vivo.

RESULTS

Our analyses demonstrated that while Yin Yang 1 (YY1) and specificity protein 1 (Sp1) participate in the hypoxia-induced upregulation of VWF specifically in lung endothelial cells, GATA6 mediates this process specifically in heart endothelial cells. In both cell types, the response to hypoxia involves the decreased association of the NFIB repressor with the VWF promoter, and the increased acetylation of the promoter-associated histone H4. In mice exposed to hypoxia, the upregulation of VWF expression was concomitant with the presence of thrombi in heart and lung, but not kidney vascular beds.

CONCLUSIONS

Heart and lung endothelial cells demonstrated VWF upregulation in response to hypoxia, using distinct mechanisms, while this response was lacking in kidney endothelial cells.

Regulation of von Willebrand Factor Gene in Endothelial Cells That Are Programmed to Pluripotency and Differentiated Back to Endothelial Cells

Endothelial cells play a central role in physiological function and pathophysiology of blood vessels in health and disease. However, the molecular mechanism that establishes the endothelial phenotype, and contributes to its signature cell type-specific gene expression, is not yet understood. We studied the regulation of a highly endothelial-specific gene, von Willebrand factor (VWF), in induced pluripotent stem cells generated from primary endothelial cells (human umbilical vein endothelial cells [HUVEC] into a pluripotent state [HiPS]) and subsequently differentiated back into endothelial cells. This allowed us to explore how VWF expression is regulated when the endothelial phenotype is revoked (endothelial cells to HiPS), and re-established (HiPS back to endothelial cells [EC-Diff]). HiPS were generated from HUVECs, their pluripotency established, and then differentiated back to endothelial cells. We established phenotypic characteristics and robust angiogenic function of EC-Diff. Gene array analyses, VWF chromatin modifications, and transacting factors binding assays were performed on the three cell types (HUVEC, HiPS, and EC-Diff). The results demonstrated that generally cohorts of transacting factors that function as transcriptional activators, and those that contribute to histone acetylation and DNA demethylation, were significantly decreased in HiPS compared with HUVECs and EC-Diff. In contrast, there were significant increases in the gene expression levels of epigenetic modifiers that function as methyl transferases in HiPS compared with endothelial cells. The results demonstrated that alterations in chromatin modifications of the VWF gene, in addition to expression and binding of transacting factors that specifically function as activators, are responsible for establishing endothelial specific regulation of the VWF gene. Stem Cells 2019;37:542-554.

Von Willebrand factor contribution to pathophysiology outside of von Willebrand disease

VWF is a procoagulant protein that plays a central role in the initiation of platelets aggregate formation and thrombosis. While von Willebrand disease has long been known to result from qualitative and quantitative deficiencies of VWF, it is recently that contribution of elevated levels of VWF to various pathological conditions including thrombosis, inflammation, angiogenesis, and cancer metastasis has been appreciated. Here, we discuss contribution of elevated levels of VWF to various thrombotic and nonthrombotic pathological conditions.

The stationary regions for the parameter space of unilateral second-order spatial AR model

The analysis of spatial models has received much attention in the last three decades. It involves methods which take into account the data location for exploring and modelling spatial data. Spatial modelling has its applications in many fields like geology, geography, agriculture, meteorology, economics etc. In this paper, the unilateral second-order spatial autoregressive model, denoted as {\operatorname{SAR}(2,1)} model, is introduced. Then the necessary conditions for casual solutions of this model will be given. Since each casual model is a stationary model, these conditions will be stationary regions for the parameter space of the {\operatorname{SAR}(2,1)} model. Under the stationary conditions, we can estimate the model parameters.

Functional assessment of von Willebrand factor expression by cancer cells of non-endothelial origin

Von Willebrand factor (VWF) is a highly adhesive procoagulant molecule that mediates platelet adhesion to endothelial and subendothelial surfaces. Normally it is expressed exclusively in endothelial cells (ECs) and megakaryocytes. However, a few studies have reported VWF detection in cancer cells of non-endothelial origin, including osteosarcoma. A role for VWF in cancer metastasis has long been postulated but evidence supporting both pro- and anti-metastatic roles for VWF has been presented. We hypothesized that the role of VWF in cancer metastasis is influenced by its cellular origin and that cancer cell acquisition of VWF expression may contribute to enhanced metastatic potential. We demonstrated de novo expression of VWF in glioma as well as osteosarcoma cells. Endothelial monolayer adhesion, transmigration and extravasation capacities of VWF expressing cancer cells were shown to be enhanced compared to non-VWF expressing cells, and were significantly reduced as a result of VWF knock down. VWF expressing cancer cells were also detected in patient tumor samples of varying histologies. Analyses of the mechanism of transcriptional activation of the VWF in cancer cells demonstrated a pattern of trans-activating factor binding and epigenetic modifications consistent overall with that observed in ECs. These results demonstrate that cancer cells of non-endothelial origin can acquire de novo expression of VWF, which can enhance processes, including endothelial and platelet adhesion and extravasation, that contribute to cancer metastasis.

A role of stochastic phenotype switching in generating mosaic endothelial cell heterogeneity

Previous studies have shown that biological noise may drive dynamic phenotypic mosaicism in isogenic unicellular organisms. However, there is no evidence for a similar mechanism operating in metazoans. Here we show that the endothelial-restricted gene, von Willebrand factor (VWF), is expressed in a mosaic pattern in the capillaries of many vascular beds and in the aorta. In capillaries, the mosaicism is dynamically regulated, with VWF switching between ON and OFF states during the lifetime of the animal. Clonal analysis of cultured endothelial cells reveals that dynamic mosaic heterogeneity is controlled by a low-barrier, noise-sensitive bistable switch that involves random transitions in the DNA methylation status of the VWF promoter. Finally, the hearts of VWF-null mice demonstrate an abnormal endothelial phenotype as well as cardiac dysfunction. Together, these findings suggest a novel stochastic phenotype switching strategy for adaptive homoeostasis in the adult vasculature.

Modeling reflection loss from an evacuated tube inside a compound parabolic concentrator with a cylindrical receiver

Linear compound parabolic concentrators with cylindrical receivers are often combined with evacuated tubes along their focal length to suppress convective heat loss for use as thermal collectors. When investigating the optical efficiency of such collectors it is important to consider the reflection loss introduced by the evacuated tube particularly at large angles of incidence of light onto the CPC aperture. In this paper reflection losses are determined using ray-tracing as a function of the angle of incidence in both the longitudinal and transversal planes of a CPC. The reflection losses are found to be approximately constant except close to the maximum acceptance angle.

Abstract 44: Organ-specific Stochastic Phenotype Switching is Required for Endothelial Health

Among unicellular organisms, stochastic phenotype switching is a documented strategy for survival. These populations "hedge their bets": while the majority of their cells are adapted to their present environment, a minority remains poised to thrive under drastically different conditions. Bet hedging has also been described in metazoan cells, primarily in vitro. However, its role in tissue homeostasis has yet to be established. Here, we show that von Willebrand factor (vWF) is expressed in a spatially heterogeneous manner in a small fraction of capillary endothelial cells in the heart, skeletal muscle, lung and brain. Moreover, these mosaic patterns are dynamic, in that vWF expression stochastically toggles ON/OFF over time. By contrast, expression of vWF in the aorta and liver is static in time. In cultured primary endothelial cells, biological noise resulted in mosaic vWF heterogeneity through a promoter-level DNA methylation switch. Finally, vWF-/- mice demonstrated extensive endothelial cell damage in capillaries of the heart and impaired cardiac function, but not kidney or aorta. Taken together, these findings suggest that dynamic mosaicism of vWF expression is functionally relevant and that bet hedging represents a previously unrecognized strategy for adaptive, organ-specific homeostasis.

Hypoxia results in upregulation and de novo activation of von Willebrand factor expression in lung endothelial cells

OBJECTIVE

Increased von Willebrand factor (VWF) levels in lungs are associated with diseases such as pulmonary hypertension. The objective of our study was to determine the mechanism of increased VWF levels in conditions, such as hypoxia, which contribute to pulmonary hypertension.

APPROACH AND RESULTS

We have previously reported generation of transgenic mice that express LacZ transgene under the regulation of lung- and brain-specific transcriptional regulatory elements of the VWF gene. Hypoxia exposure of these transgenic mice resulted in increased VWF and LacZ mRNA levels as well as redistribution of their expression from primarily larger vessels in the lungs to microvessels. Exposure of cultured lung microvascular endothelial cells to hypoxia demonstrated that VWF upregulation was accompanied by increased platelet binding. Transcription upregulation was mediated through inhibition of the repressor nuclear factor-IB association with the VWF promoter, and increased nuclear translocation of the transcription factor YY1 and association with its cognate binding site on the VWF gene. Knockdown of YY1 expression abolished the hypoxia-induced upregulation and reduced basal level of VWF.

CONCLUSIONS

These analyses demonstrate that hypoxia induces a phenotypic shift, accompanied by modulation of nuclear factor-IB and YY1 activities, in microvascular endothelial cells of the lungs to support VWF promoter activation.

Hepatitis B virus genotypes in southwest Iran: Molecular, serological and clinical outcomes

AIM: To investigate the associations of hepatitis B virus (HBV) genotype with HBeAg and anti-HBe status, alanine aminotransferase (ALT) levels and HBV-DNA detection in different groups of HBV-infected patients in southwest Iran.

METHODS: A total of 89 HBsAg-positive serum samples were collected from the same number of patients. All sera were then investigated to determine HBV DNA and serological markers. For all the polymerase chain reaction (PCR)-positive samples, biochemical, histopathological assays and genotyping were also performed.

RESULTS: Genotype D was the only type of HBV found in different clinical forms of acute and chronic infections. There was a high prevalence of HBeAg-negative HBV-infected patients with chronic hepatitis (52.7%). Out of 55 patients with chronic hepatitis, seven (12.7%) were diagnosed with cirrhosis. A significant association between the presence of anti-HBe antibody and an increase in ALT level, among either HBeAg-negative (P = 0.01) or HBeAg-positive (P = 0.026) patients, was demonstrated. No significant differences were observed between the clinical outcomes of HBeAg-positive and -negative individuals (P = 0.24).

CONCLUSION: Genotype D has been recognized as the only type of HBV found in different clinical forms of HBV infections, including cirrhosis, among the residents of southwest Iran. Anti-HBe possibly plays a role in disease progression in some patients with chronic hepatitis, at least for a period of disease.

Risk of Viral Transmission Via Bone Marrow Progenitor Cells Versus Umbilical Cord Blood Hematopoietic Stem Cells in Bone Marrow Transplantation

Hematopoietic stem cell transplantation (HSCT) is the treatment of choice for children and certain adults with malignant and nonmalignant hematologic disease. Since viral infections are the major problem, this study examined those that might potentially be transmitted to HSCT recipients via bone marrow (BM) versus umbilical cord blood (UCB). BM progenitor cells, peripheral blood leukocytes, and plasma samples were collected from 30 allogenic BM donors. Umbilical cord blood hematopoietic stem cells and plasma samples were also collected from 34 UCB donors. Viral DNA extracted and purified from collected specimens was processed using nested polymerase chain reactions (PCR) to detect human parvovirus B19 (HPV B19), human herpesvirus-6 (HHV-6), varicella-zoster virus (VZV), human cytomegalovirus (HCMV), and Epstein-Barr virus (EBV). The prevalences of HCMV DNA in collected BM progenitor cells versus UCB hematopoietic stem cells were 73% versus 23%, respectively. Conversely, HHV-6 DNA was not detected in any collected specimen by simple PCR. Distribution of the other investigated virus DNAs except EBV DNA was similar in specimens collected from both groups. EBV DNA was not determined in UCB hematopoietic stem cells. The results indicate that the risk of viral transmission to BM transplant recipients via UCB hematopoietic stem cells is less than that with BM progenitor cells.

Outcome of Hepatitis B and C Virus Infection on Graft Function After Renal Transplantation

INTRODUCTION

Chronic liver disease resulting from hepatitis B virus (HBV) and hepatitis C virus (HCV) infections is still a major concern in kidney recipients. It is unclear whether HCV antibody status and markers of HBV infection are associated with renal dysfunction. Thus, we designed a study to investigate the incidence of HBV and HCV infection after renal transplantation and whether these infections alter graft function.

METHODS

Fifty-eight patients who underwent renal transplantation participated in the study. Serum creatinine and aminotransferase levels were measured with standard automated analyzers. Anti-HCV antibodies were detected with an enzyme immunoassay, and a reverse transcriptase-polymerase chain reaction (RT-PCR) technique was used to test for HCV-RNA. Serological markers for HBV (HBsAg and anti-HBc antibody) were detected by enzyme immunoassay. All samples from patients who were seropositive for HBsAg or anti-HBc antibody were PCR-tested for HBV-DNA. A serum sample collected from living donors was tested for anti-HCV antibodies and serological markers for HBV. Serum creatinine and aminotransferase levels were also measured in living donors.

RESULTS

Anti-HCV was not detected in serum samples of any cases before transplantation. However, 10 (17.2%) tested positive after transplantation. HCV-RNA was detected in 2 of the 10 patients (3.4% of all patients). None of the pretransplantation serum samples tested positive for HBsAg. However, anti-HBc antibody was identified in 8 (13.8%) of the 58 patients.. No HBV DNA was detected in serum samples of the patients with anti-HBc or HBsAg-positive. HBsAg was only detected in 1 (1.7%) recipient after transplantation. None of the 58 patients showed clinical signs or symptoms of renal dysfunction during the study period.

CONCLUSION

Our data suggest that, neither HBV nor HCV infection appears to cause or contribute to renal dysfunction in the early period (1 year) after renal transplantation. Nevertheless, a long-term consequence of chronic HBV or HCV liver disease or graft loss is not impossible in renal transplant recipients.