2000 — 2004 |
Bostrom, Kristina I |
K08Activity Code Description: To provide the opportunity for promising medical scientists with demonstrated aptitude to develop into independent investigators, or for faculty members to pursue research aspects of categorical areas applicable to the awarding unit, and aid in filling the academic faculty gap in these shortage areas within health profession's institutions of the country. |
Molecular Mechanisms of Matrix Gla Protein @ University of California Los Angeles
Calcification of vessels and cardiac valves causes a multitude of clinical problems including congestive heart failure, cardiomyopathy, angina, and complications during interventional and surgical procedures. Currently, there are no medical therapies able to prevent or reverse calcification. An understanding of the underlying mechanisms would identify new targets for developments of such therapies. Mice deficient in Matrix GLA Protein (MGP) develop extensive vascular calcification with replacement of the vascular wall by typical cartilage cells. This suggests that MGP plays a role in vascular cell differentiation. We hypothesize that the function of MGP is to act as an inhibitor of bone morphogenetic protein 2 (BMP-2), a potent inducer of calcified tissues. In absence of MGP, vascular cells may be induced by BMP-2, and differentiate into cartilage and bone cells instead of vascular smooth muscle cells. We hypothesize that this effect of MGP occurs early in vessel formation. The proposal has four aims. The first is to study the effect of increased levels of MGP on cell differentiation induced by BMP-2 in tissue culture, and then use this system to identify key sequences in MGP by altering the MGP protein. The second aim is to characterize the putative binding between MGP and BMP-2 by using cross-linking and binding studies. The third aim is to identify when in the development of MGP deficient mice, vascular cells lose their normal characteristics and differentiate into cartilage cells, using specific markers for smooth muscle and cartilage cells. Finally, we will generate transgenic mice deficient in normal MGP but expressing selected key sequences of MGP identified in previous aims to affect cell differentiation, and to study the effect of these sequences on in vascular calcification in vivo. Understanding the molecular mechanisms of MGP will provide information that is widely applicable to the development of vascular disease.
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2003 — 2006 |
Bostrom, Kristina I |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Cellular /Molecular Mechanisms of Vascular Calcification @ University of California Los Angeles
This Project is focused on understanding the molecular mechanisms involved in vascular calcification and osteoporosis. Matrix GLA protein (MGP) was strongly implicated in the pathogenesis of vascular calcification when an MGP knockout mouse was found to have extensive vascular calcification. Based on this mouse model, MGP might be thought to be an inhibitory factor in vascular calcification. However, in calcified lesions of mice that have a normal MGP gene and in human lesions, MGP expression is postively correlated with the degree of lesion calcification. During the current grant period we demonstrated that MGP regulates bone morphogenetic protein (BMP-2), During the next grant period we will determine the molecular basis for the regulatory role of MGP in the artery wall and its interaction with BMP-2. Other work from this Project during the current grant period provided important clues as to why many patients with progressive vascular calcification also have progressive osteoporosis. Oxidized lipids were shown to promote calcification of calcifying vascular cells (CVC) but inhibited the osteoblastic differentiation and mineralization of marrow stromal cells that are the precursors to mature bone osteoblasts. This was true whether the oxidized lipids were added in vitro or were produced by feeding atherosclerosis suceptible C57BL/6J (BL6) mice an atherogenic diet. These oxidized lipids were also shown to promote osteoclastogenesis and osteoclast activation in vitro. In vivo, feeding an atherogenic diet to atherosclerosis susceptible BL6 mice produced a dramatic reduction in bone mineral density and bone mineral content. Feeding an atherogenic diet to atherosclerosis resistant C3H/HeJ mice causes the same degree of hyperlipidemia as in BL6 mice, but there was no significant reduction in either bone mineral density or bone mineral content in the C3H/HeJ mice. In the next grant period we propose to determine the molecular mechanisms for these observations and we will determine if high density lipoproteins (HDL), components of HDL, and mimetics of HDL will protect against bone loss in mouse models of atherosclerosis. These studies may identify potential new therapeutic targets in vascular calcification and osteoporosis.
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2006 — 2010 |
Bostrom, Kristina I |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Molecular Mechanism of Matrix Gla Protein (Mgp) @ University of California Los Angeles
Calcification is ubiquitous in vascular disease, and contributes significantly to morbidity and mortality. Matrix GLA protein (MGP) is an alleged calcification inhibitor that is up-regulated in atherosclerotic lesions. Deletion of the MGP gene results in arterial calcification and in morphological abnormalities in mice and humans. MGP is a secreted protein that is modified by vitamin K-dependent g-carboxylation. When isolated from bone, it is processed and lacks seven C-terminal amino acids. The mechanism of MGP is poorly understood. However, our experimental data points to a role in transforming growth factor-fi (TGF-fi) and bone morphogenetic protein (BMP) signaling. The data suggest a potential link between BMP and TGF-li in that BMP2 and BMP-4 induce expression of the TGF-R, receptor Activin-like Kinase receptor 1 (ALK1). Signaling through ALK1 induces MGP, which provides negative feedback regulation for BMP. Interactions between MGP and specific receptors were also observed. Three hypotheses will be tested in this grant. The first hypothesis is that MGP regulates TGF-fi and BMP signaling at the receptor level, resulting in altered SMAD signaling and gene expression. We will characterize activation of SMAD signaling and relevant reporter genes induced by TGF-li1, BMP-2 and BMP-4 in presence of MGP, and identify the TGF-li / BMP receptors that are regulated by MGP. The second hypothesis is that MGP participates in specific protein-protein interactions that may be altered by C-terminal processing. We will characterize the interactions, which include the TGF-ft receptors, using specific immunoprecipitations in combination with a general proteomic approach. The third hypothesis is that MGP functions as a BMP inhibitor in developing arteries and in atherosclerotic lesions. We will generate a transgenic mouse for targeted, conditional expression of the BMP-inhibitor Noggin. Noggin expression will be induced in MGP null mice in attempt to replace MGP and abolish calcification. The effect of Noggin will also be determined in atherosclerotic lesions in LDL-receptor null mice. Our results will add insight to calcification of vessels and heart valves, a common problem in heart disease. In addition, it may provide information on how to design new treatments for unwanted calcification.
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2007 |
Bostrom, Kristina I |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Cellular /Molecular Mechanisms of Vascular Calcification and Osteoporosis @ University of California Los Angeles
This Project is focused on understanding the molecular mechanisms involved in vascular calcification and osteoporosis. Matrix GLA protein (MGP) was strongly implicated in the pathogenesis of vascular calcification when an MGP knockout mouse was found to have extensive vascular calcification. Based on this mouse model, MGP might be thought to be an inhibitory factor in vascular calcification. However, in calcified lesions of mice that have a normal MGP gene and in human lesions, MGP expression is postively correlated with the degree of lesion calcification. During the current grant period we demonstrated that MGP regulates bone morphogenetic protein (BMP-2), During the next grant period we will determine the molecular basis for the regulatory role of MGP in the artery wall and its interaction with BMP-2. Other work from this Project during the current grant period provided important clues as to why many patients with progressive vascular calcification also have progressive osteoporosis. Oxidized lipids were shown to promote calcification of calcifying vascular cells (CVC) but inhibited the osteoblastic differentiation and mineralization of marrow stromal cells that are the precursors to mature bone osteoblasts. This was true whether the oxidized lipids were added in vitro or were produced by feeding atherosclerosis suceptible C57BL/6J (BL6) mice an atherogenic diet. These oxidized lipids were also shown to promote osteoclastogenesis and osteoclast activation in vitro. In vivo, feeding an atherogenic diet to atherosclerosis susceptible BL6 mice produced a dramatic reduction in bone mineral density and bone mineral content. Feeding an atherogenic diet to atherosclerosis resistant C3H/HeJ mice causes the same degree of hyperlipidemia as in BL6 mice, but there was no significant reduction in either bone mineral density or bone mineral content in the C3H/HeJ mice. In the next grant period we propose to determine the molecular mechanisms for these observations and we will determine if high density lipoproteins (HDL), components of HDL, and mimetics of HDL will protect against bone loss in mouse models of atherosclerosis. These studies may identify potential new therapeutic targets in vascular calcification and osteoporosis.
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2009 — 2013 |
Bostrom, Kristina I |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Molecular Mechanisms of Vascular Calcification @ University of California Los Angeles
Prevention of vascular calcification is mediated in part by Matrix Gla Protein (MGP) and the hepatic ABC transporter C6 (AbccG). MGP is a secreted matrix protein and may affect vascular calcification in vivo by binding bone morphogenetic proteins (BMP) and/or calcium through gamma-carboxylated glutamates. Our data show that in vascular cells BMP-2/4 induce expression of the activin-like kinase receptor 1 (ALK1), an essential TGF-3 receptor in vascular development. ALK1 is also expressed in atherosclerotic lesions and promotes aggregation and proliferation of cultured lesion cells. Induction of the ALK1 receptor allows BMP- 2/4 to regulate expression of vascular endothelial growth factor and MGP, which provides a feed back loop to limit BMP-activity. The importance of this pathway in atherogenesis is unknown. Abcc6 is a membrane transporter that is mainly expressed in the liver. AbccG was identified in our previous studies using an integrative genomics approach, and was shown to protect against vascular calcification. Abcc6 deficiency has been associated with pseudoxanthoma elasticum that is characterized by progressive calcification and accelerated atherosclerosis. The site and the mechanism of action of Abcc6 are not understood. This application focuses on the mechanisms by which MGP and Abcc6 prevent vascular calcification, and the effect of ALK1 and Abcc6 on atherogenesis. Four specific aims will be addressed. In Specific Aim 1; we will determine the importance of BMP-binding versus calcium-binding for the ability of MGP to inhibit vascular calcification in vivo using homologous recombination in mice. In Specific Aim 2, we will identify the receptor(s) and signaling pathway(s) that are required for BMP-2/4 to induce expression of the ALK1- receptor using siRNA, dominant negative receptors and molecular inhibitors in vitro. Specific Aim 3 will address Abcc6 and Abcc6 related pathways and determine the site and the molecular basis of its inhibitory effect on vascular calcification using both in vitro and in vivo techniques. Finally, in Specific Aim 4, we will address the effects of modulating expression of ALK1 and Abcc6 on lesion development in established mouse models of atherosclerosis.
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2012 — 2016 |
Bostrom, Kristina I |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Molecular Mechanisms of Matrix Gla Protein (Mgp) @ University of California Los Angeles
DESCRIPTION (provided by applicant): Therapeutic advances in cardiovascular disease may have far-reaching public benefits. Bone morphogenetic proteins (BMPs) are emerging as essential regulators of the vasculature, important in disorders such as arteriovenous malformations (AVMs) and diabetic vasculopathy. Our data show that endothelial BMP4 activity causes a sequential induction of two BMP inhibitors, Matrix Gla Protein (MGP) and Crossveinless-2 (Cv2). MGP inhibits BMP4, and when deficient, allows the emergence of stem cell markers in the endothelium, vascular calcification, and AVMs. Deficiency of Cv2 leads to an abnormal and thickened endothelium, without the increase in stem cell markers. Our data suggest a 2-step model where MGP regulates proliferation and stem cell characteristics in vascular progenitor cells, and Cv2 regulates proliferation and maturation of committed ECs. In this 2-step model, we hypothesize that BMP4 and MGP regulate the size of the vascular progenitor pool, whereas BMP9 and Cv2 regulate the size of the committed EC pool. Thus, enhanced BMP4 activity or decreased MGP would allow for osteogenesis in the multipotent progenitor cells leading to vascular calcification. Both MGP and Cv2 may play important roles in the regulation of diabetic microvascular abnormalities and AVMs. We hypothesize that by manipulating MGP and Cv2, we will be able to inhibit the vascular abnormalities in which these inhibitors play a role. Specific Aim 1 will test the validity of a 2-step model of EC lineage differentiation in vitro and in vivo. The model predicts that elevating the level of MGP will limit excessive endothelial growth resulting from Cv2 deficiency. Specific Aim 2 will determine the contribution of MGP and Cv2 to the formation of AVMs in a mouse model of hereditary hemorrhagic telangiectasia (HHT). Our model predicts that increasing BMP inhibition through MGP or Cv2 will limit the signs of HHT. Specific Aim 3 will determine the mechanism by which BMP inhibition could regulate diabetic vasculopathy. MGP and Cv2 are predicted to be stage-specific BMP inhibitors, and inadequate BMP inhibition would allow for vascular pathology in the aorta and the microvasculature as modeled by the diabetic Ins2Akita/+ mouse. If successful, the obtained information may translate into strategies for using BMP inhibitors in treating vascular disease.
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2013 — 2016 |
Bostrom, Kristina I |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Role of the Endothelium in Vascular Calcification @ University of California Los Angeles
DESCRIPTION (provided by applicant): Vascular calcification is a frequent complication of vascular disease associated with increased morbidity and mortality. It is recognized to be an active process involving osteochondrogenic differentiation in multipotent cells. Previous reports have suggested that endothelial cells (ECs) contribute calcifying cells in congenital disorders with soft tissue calcification, triggered by abnormal bone morphogenetic protein (BMP) signaling. Matrix Gla protein (MGP) is an inhibitor of vascular calcification, and an antagonist to BMP2/4. MGP null mice show strong activation of vascular BMP signaling and extensive aortic calcification. Ins2-Akita/+ mice, a model of type 1 diabetes, exhibit similar findings due to induction of BMPs and BMP receptors. Preliminary data show that BMP activation causes stem cell characteristics to emerge in normal ECs. Indeed, EC lineage markers co- stain with osteogenic and pluripotent stem cell markers in MGP null aortas, and MGP-depletion in human aortic ECs in vitro causes the cells to undergo osteogenic differentiation in response to osteoinductive factors. In addition, Ins2-Akita/+ mice exhibit increased aortic expression of multiple pluripotency-associated markers. Thus, normal ECs may contribute osteoprogenitor cells to vascular calcification when subjected to increased BMP activity. The scientific purpose of this proposal is to define the role of the endothelium in vascular calcification in MGP deficiency and diabetes. We hypothesize that normal endothelium contributes multipotent cells to vascular calcification due to the capacity of abnormal BMP activity to induce stem cell characteristics and subsequent osteogenesis. Specific Aim 1 will define multipotency and osteochondrogenic potential in ECs in the setting of MGP deficiency or hyperglycemia in vitro and in vivo. Specific Aim 2 will determine if ECs contribute cells to calcific lesions using lineag tracing in two models of vascular calcification, the MGP-/- mouse and the diabetic Ins2Akita/+ mouse. For lineage tracing, the currently available Tie2-GFP or Tie2- Cre;R262R-eGFP transgenic mice will be used. Specific Aim 3 will determine the relative contributions of EC- and SMC-specific loss of MGP in the development of vascular calcification using EC- and SMC-specific MGP knockout mice. If successful, the endothelium may emerge an important target to treat calcification in acquired vascular disease.
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2015 — 2019 |
Bostrom, Kristina I |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Role of Bmp Signaling in Tissue Composition @ University of California Los Angeles
PROJECT SUMMARY/ABSTRACT Alterations in tissue composition are fundamental in atherogenesis, and may be detected as bone-like calcification in aorta or changes in vascularity and adipogenic phenotype in adipose tissue, both affecting cardiovascular disease. In this proposal, we will investigate the importance of the Bone Morphogenetic Proteins (BMPs) and their inhibitors in regulating adipose vascularity and composition, and how proatherogenic factors influence BMP activity. Recent discoveries have shown that BMP4 and 7 influence the development of adipose tissue. In addition, the balance between BMP4 activation and inhibition determines the extent of vascular calcification through cell differentiation. New data also suggest that the BMP balance orchestrates vascular growth and adipogenic differentiation in adipose tissue, and is therefore a likely determinant of tissue perfusion and hypoxia leading to inflammation. Aim 1 will test the hypothesis that the BMP balance orchestrates angiogenesis and adipogenesis in adipose tissue. New findings in null mice for Matrix Gla Protein (MGP), a BMP inhibitor, suggest an inverse relationship between endothelial and adipogenic differentiation regulated by BMP4, BMP7 and MGP. We will (a) determine how the BMPs and BMP inhibitors regulate endothelial and adipogenic phenotype in progenitor cells, (b) investigate how BMP and BMP inhibitors regulate angiogenesis and adipogenesis using genetically altered mice, and (c) examine if high BMP activity stimulates the endothelium to contribute adipogenic cells. Aim 2 will test the hypothesis that delivery of glucose or lipids to adipose tissue and genetic variations act on the BMP balance in adipose tissue to regulate tissue composition. We will take advantage of (a) diabetic Ins2-Akita/+ mice with normal and enhanced MGP expression, (b) fat-fed Ldlr-/- mice, and (c) adipocyte-specific Idol transgenic mice developed with Project 5 to investigate how these conditions influence adipose BMP signaling, vascularity and cell differentiation. We will also use the Hybrid Mouse Diversity Panel developed in Project 4 to examine variations in BMP, Notch (together with Project 1) and related gene expression in aorta and adipose tissue. Understanding BMP signaling in the adipose and vascular tissues may lead to new treatments aimed at cardiovascular disease.
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2018 — 2020 |
Bostrom, Kristina I |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Molecular Mechanisms of Mgp; Role in Avms @ University of California Los Angeles
PROJECT SUMMARY: The vascular system consists of elaborate networks that develop in combination with close regulation of endothelial cells (ECs). An understanding of such regulation is essential for the development of new treatment strategies aimed at vascular malformations, such as arteriovenous malformations (AVMs) and hereditary hemorrhagic telangiectasia (HHT), caused by mutations in activin receptor-like kinase 1 (ALK1). We previously showed that gene deletion in mice of matrix Gla protein (MGP), an inhibitor of bone morphogenetic proteins (BMPs), causes AVMs in multiple organs similar to HHT. We showed that BMP9/ALK1 signaling induces MGP expression in ECs, where MGP plays an important role in differentiation. BMP9/ALK1 signaling also induces Crossveinless-2 (CV2) with a different induction delay, thereby creating two negative feedback loops. Together, MGP and CV2 regulate BMP9 signaling by a previously unknown mechanism. In cultured ECs, we found oscillations of MGP and CV2 expression that temporally coordinated transition to EC stalk cell phenotype in ECs. This also caused markers of stalk cells to oscillate, whereas tip cell markers were suppressed. Deletion of Mgp abolished the oscillatory behavior. In vivo, MGP and CV2 were seen as ?shaping waves? or stripes in the growing retina, and lack of MGP perturbed the vascular networks. Our hypothesis is that MGP and CV2 are regulators of BMP9 signaling and vascular morphogenesis through generation of oscillations or waves of expression. In Aim 1, we will characterize how MGP and CV2 orchestrate EC differentiation in response to BMP9 using oscillations of gene expression. We will relate BMP9-induced stalk cell phenotype to the oscillations, and explore expression profiles of ECs capable of this behavior. We will disrupt the system by deleting the Mgp gene in vitro using established techniques of shRNA, and determine the effect on the waves of inhibitors and stalk cell markers. We will also investigate whether waves of MGP and CV2 can be detected in normal vasculature, with focus on the retina. In Aim 2, we will obtain key information about the role of MGP in retinal vascular networks and AVMs by deleting Mgp, impairing MGP protein function, and modulating the cellular origin. We will modulate potential targets for AVM treatments using the Mgp-/- mice as an AVM model. We will start with modulation of CV2 and use approaches that include crossbreeding with genetically altered mice and transmammary immunoblocking, and subsequently screen other factors in the BMP9 response. Our studies will help identify targets in the BMP9 response system that might be used in designing treatments for AVMs.
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