Vascular Calcification
Kristina Boström, MD, PhD
Cardiology, UCLA
Case Presentation
74 y o Caucasian female, with hypertension and critical
aortic stenosis.
One year prior to presentation, aortic valve replacement
had been attempted but was aborted due to severe
aortic calcification, so called “porcelain aorta”.
Now increasing symptoms of shortness of breath with
exertion and chest pain, with recurrent hospital
admissions for congestive heart failure.
Echocardiogram:
LVEF >60% with concentric left ventricular hypertrophy and
diastolic dysfunction.
Mild mitral regurgitation.
Moderate tricuspid regurgitation.
Cardiac Catheterization:
Normal systolic function. Non-obstructive coronary disease.
CT Chest:
“Uniform, smooth calcification of the ascending aorta
extending from the root to the origin of great vessels, with
trivial atherosclerotic calcifications of the descending
aorta. The appearance of the ascending aorta is
reminiscent of aortic graft.”
Extensive aortic valve calcification and moderate mitral
valve calcification.
Circumferential Calcification in the Ascending Aorta
Left Ventricular Apical Conduit to Descending Thoracic Aorta
This Case Illustrates ….
• Calcification can be characterized by the
anatomical location.
• There are more than one type of vascular
calcification.
• We are unable to efficiently treat vascular
calcification.
• Vascular calcification may cause clinical
complications.
Vascular Calcification Differs in:
Anatomical location
Aortic
Coronary
Peripheral arteries
Heart valve
Vascular layer
Intima
Media
Adventitia
Heart valve
Association with disease
Atherosclerosis
Mönckeberg’s (Media Sclerosis)
Diabetes
Renal Failure
Vascular Calcification Is Associated with Vascular Disease:
Intima
Atherosclerosis
Renal Failure
Diabetes
Media
Mönckeberg’s (Media sclerosis)
Renal Failure
Diabetes
Adventitia
Diabetes
Heart valves
Atherosclerosis
Intimal Calcification - Atherosclerosis
Sangiorgi et al. JACC 1998
CLINICAL IMPLICATIONS OF INTIMAL CALCIFICATION
Coronary Arteries
• Correlated with Coronary Artery Disease and
atherosclerotic plaque burden.
• Associated with Sudden Cardiac Death
• Promotes dissection following angioplasty
Media
Calcified, Atherosclerotic
Coronary Artery
Intima
Calcification
Webpath
Rupture at Edge of Calcified Lesion
In Vitro
In Vivo - after angioplasty
Mechanical stress analysis of a rigid inclusion in distensible material: a model of
atherosclerotic calcification and plaque vulnerability. Hoshino et al. Am J Physiol 2009
Coronary Calcification
Detected by Electron Beam CT (EBCT) - “Heart Scans”
Coronary Calcification - EBCT
A negative EBCT test is associated with a low risk of a
cardiovascular event in the next 2 to 5 years.
A positive EBCT confirms the presence of a coronary
atherosclerotic plaque.
The greater the amount of calcium, the greater the
likelihood of occlusive CAD, but there is not a 1-to-1
relationship, and findings may not be site specific.
The total amount of calcium correlates best with the
total amount of atherosclerotic plaque, although the
true "plaque burden" is underestimated
Atherosclerotic
Plaques
Medial
Calcification
VASCULAR MEDIAL CALCIFICATION
(Mönckeberg’s media sclerosis, elastocalcinosis)
Arteriosclerosis associated
with aging, diabetes, and end
stage renal disease
Webpath
Price et al. ATVB 2000
CLINICAL IMPLICATIONS OF VASCULAR MEDIAL CALCIFICATION
Aorta
• Correlates with increased ischemic episodes in peripheral
vascular disease (PVD)
Peripheral Arteries
• Strong marker for future cardiac events, PVD, and lower
extremity amputations in diabetics
• Prognostic marker for all-cause and cardiovascular mortality in
dialysis patients
Causes increased aortic stiffness, pulse pressure, left
ventricular hypertrophy and cardiovascular mortality
Medial Calcification in Arteries of Dialysis Patients
30-700 fold increase in cardiovascular mortality risk in
dialysis patients compared to the general population.
Decreased survival in end stage renal disease patient with
intimal and medial vascular calcification
Moe et al. Kidney Int. 2002
Heart Valve Calcification
Normal Aortic Valve
Senile Aortic Stenosis
Calcified
Bioprosthetic Valve
CLINICAL IMPLICATIONS OF VALVE CALCIFICATION
• Major cause of failure in native valves
• Major cause of failure in bioprosthetic valves
• Highly prevalent in patients with end stage renal failure
Mechanisms of
Vascular Calcification
Normal Vessels Don’t Mineralize
Active
Inducers
Active
Inhibitors
Both Inhibitors and Promotors of Calcification
in Atherosclerotic Plaques
Inhibitors
Promotors
Dhore et al. ATVB 2001
Major Theories of Vascular Calcification
DISTURBED Ca/Pi BALANCE
Hyperphosphatemia
Hypercalcemia
LOSS OF INHIBITION
Pyrophosphate
MGP
OPN
Fetuin/alpha2-HS glycoprotein
Others
Ca x Pi
VASCULAR CALCIFICATION
CIRCULATING
NUCLEATIONAL
COMPLEXES
INDUCING FACTORS
Pi
Lipids
Inflammatory cytokines
Others
INDUCTION OF
BONE FORMATION
Vascular bone and
cartilage-like cells
Matrix Vesicles
Apoptotic bodies
Bisphosphonates
OPG
Bone Remodeling
CELL DEATH
Adapted from Speer & Giachelli, Cardiovasc Path 2004
Major Theories of Vascular Calcification
DISTURBED Ca/Pi BALANCE
Hyperphosphatemia
Hypercalcemia
LOSS OF INHIBITION
Pyrophosphate
MGP
OPN
Fetuin/alpha2-HS glycoprotein
Others
Ca x Pi
VASCULAR CALCIFICATION
CIRCULATING
NUCLEATIONAL
COMPLEXES
INDUCING FACTORS
Pi
Lipids
Inflammatory cytokines
Others
INDUCTION OF
BONE FORMATION
Vascular bone and
cartilage-like cells
Matrix Vesicles
Apoptotic bodies
Bisphosphonates
OPG
Bone Remodeling
CELL DEATH
Adapted from Speer & Giachelli, Cardiovasc Path 2004
GENERALIZED INFANTILE ARTERIAL CALCIFICATION
• Rare human genetic disorder; early lethal
• Vascular medial calcification leading to a stenosing,
fibroproliferative arterial process
• Characterized by deficiency in extracellular pyrophosphate (PPi),
due to a deficiency in PPi-generating nucleoside triphosphate
pyrophosphohydrolase plasma membrane 1 enzyme (PC-1,
ENPP1).
Long-axis image of
aorta and aortic arch
Levine et al. Circulation 2001
Matrix Gla Protein (MGP)
Inhibitor of Bone Morphogenetic Proteins (BMP)
(Zebboudj 2002, Yao 2006)
Dependent on Vitamin K for correct gamma-carboxylation
of glutamates (Gla-modifications) and anti-calcific activity
(Murshed 2004)
Dependent on specific proline and Gla-residues for BMP
binding
(Yao 2008)
MGP loss of function mutations in humans cause Keutel
syndrome
(Keutel 1971, Munroe 1999)
Vascular Calcification in MGP Null Mice
MGP null
Aortic
media
Wild type
Aortic
media
Luo et al. Science 1997
BONE MORPHOGENETIC PROTEINS (BMP)
• Potent inducers of bone formation
• Inflammatory mediators induced in vascular endothelium by
abnormal oscillatory flow
(Sorescu et al. 2004)
• Promotes hypertension and atherogenesis in mice
(Miriyala et al. 2006, Jo et al. - in prep.)
• MGP reduces formation of atherosclerotic plaques and lesions
calcification
(Yao et al. - in revision)
Warfarin / Coumadin Use:
• Inhibits MGP gamma-carboxylation, induces vascular
calcification in growing rats
(Price 1998, Essalihi 2003, Schurgers 2007)
• Correlated with increased coronary and valve calcification
(Schurgers 2004, Koos 2005)
• Associated with calcific uremic arteriolopathy in dialysis
patients
(Coates 1998, Piccoli 2002)
Fetuin, 2 Hermann-Schmid Glycoprotein (AHSG)
• Made in the liver
• Inhibitor of spontaneous hydroxyapatite (HA) formation
from supersaturated calcium- and phosphate containing
solutions
• Fetuin null mice have decreased serum HA
inhibitory activity and increased soft tissue calcification
(Jahnen-Dechent 1997, Schafer 2003)
Normal mouse after
phosphate challenge
Fetuin-deficient mouse
after phosphate challenge
Westenfeld et al. Trends Cardiovasc Med 2007
OSTEOPONTIN
• Acidic phosphoprotein found in bone and teeth
• Inhibitor of apatite crystal growth
• Promotes osteoclast function
Osteopontin Deficiency Worsens Calcification
in MGP Null Mice
Speer MY et al. 2002
Major Theories of Vascular Calcification
DISTURBED Ca/Pi BALANCE
Hyperphosphatemia
Hypercalcemia
LOSS OF INHIBITION
MGP
OPN
Fetuin/alpha2-HS glycoprotein
Pyrophosphate
Others
Ca x Pi
VASCULAR CALCIFICATION
CIRCULATING
NUCLEATIONAL
COMPLEXES
INDUCING FACTORS
Pi
Lipids
Inflammatory cytokines
Others
INDUCTION OF
BONE FORMATION
Vascular bone and
cartilage-like cells
Matrix Vesicles
Apoptotic bodies
Bisphosphonates
OPG
Bone Remodeling
CELL DEATH
Adapted from Speer & Giachelli, Cardiovasc Path 2004
Ectopic Calcification in Atherosclerotic Plaqes
Chondrocytes in Mouse Atherosclerotic Lesions
Rattazzi et al. ATVB 2005
Mineral Precipitation
Ca2+
Cell Differentiation
osteoblast-like cell
PO42-
matrix
vesicles
CaPO4 mineral
precipitation
“Active” inhibitor
Ca2+
PO42-
CaPO4 mineral
precipitation
osteoid
(matrix)
hydroxyapatite
Potential Origins of Osteoblast-like Cells in the Artery Wall
• Pericytes
• Mesenchymal stem cells
• Multipotent cells from the adventitia
• Resident cells in the media or intima
• Trans-differentiated SMC
(Synthetic vs contractile phenotype)
Calcifying Vascular Cells (CVC)
UNDIFFERENTIATED
CONDENSATION
CALCIFIED
NODULES
Bone Related Factors in Calcified Artery Wall
BMP-2 and -4
Cbfa1
Osterix
Collagen I
Alkaline Phosphatase
Osteocalcin
Hydroxyapatite
Osteopontin
Matrix GLA protein (MGP)
Osteoprotegerin
… and others …..
Both Inhibitors and Promotors of Calcification in Plaques
Dhore et al. ATVB 2001
Major Theories of Vascular Calcification
DISTURBED Ca/Pi BALANCE
Hyperphosphatemia
Hypercalcemia
LOSS OF INHIBITION
MGP
OPN
Fetuin/alpha2-HS glycoprotein
Pyrophosphate
Others
Ca x Pi
VASCULAR CALCIFICATION
CIRCULATING
NUCLEATIONAL
COMPLEXES
INDUCING FACTORS
Pi
Lipids
Inflammatory cytokines
Others
INDUCTION OF
BONE FORMATION
Vascular bone and
cartilage-like cells
Matrix Vesicles
Apoptotic bodies
Bisphosphonates
OPG
Bone Remodeling
CELL DEATH
Adapted from Speer & Giachelli, Cardiovasc Path 2004
Normal Vessels Don’t Mineralize
(Despite serum Ca x P at or near solubility product)
Active
Inducers
Active
Inhibitors
Intima
Atherosclerosis
Renal Failure
Diabetes
Media
Mönckeberg’s (Media sclerosis)
Renal Failure
Diabetes
Adventitia
Diabetes
Heart valves
Atherosclerosis
Calcium x Phosphate Product
Already above precipitation point at certain places
Renal failure may increase Ca x P product further
Hyperphosphatemia:
Major independent risk factor for vascular calcification and
cardiovascular mortality in dialysis patients
(Block 1998, 2004, Goodman 2000,
Shigematsu 2003, Young 2005)
Phosphate-Induced Changes in SMC Differentiation
Pi/Ca
Contractile SMC
SM-MHC
SM22alpha
SM-alpha actin
Desmin
Osteochondrogenic cell
Cbfa1
OPN
Osteocalcin
Alk Phos
Type III sodium-dependent phosphate co-transporters (Pit-1, Pit-2)
Blockage of these transporters leads to phosphate induced SMC mineralization
Pit-1 can be induced by BMP-2
Calcified Vascular Smooth Muscle Cells
Wada et al. Circ Res 1999
Major Theories of Vascular Calcification
DISTURBED Ca/Pi BALANCE
Hyperphosphatemia
Hypercalcemia
LOSS OF INHIBITION
MGP
OPN
Fetuin/alpha2-HS glycoprotein
Pyrophosphate
Others
Ca x Pi
VASCULAR CALCIFICATION
CIRCULATING
NUCLEATIONAL
COMPLEXES
INDUCTION OF
BONE FORMATION
Vascular bone and
cartilage-like cells
Matrix Vesicles
Apoptotic bodies
Bisphosphonates
OPG
Bone Remodeling
INDUCING FACTORS
Pi
Lipids
Inflammatory cytokines
Others
CELL DEATH
Degenerative
Joint Diseases
Connection
between are
“Crystal
diseases”
Vascular
Calcification and Bone
where synovial fibroblasts have an
inflammatory response to the crystals.
Aortic Calcification and Osteoporosis Frequently Coexist
Similarities to Bone:
Bone Proteins
Osteoblast-like Cells
Osteoclast-like Cells
“The paradox of arterial calcification in osteoporotic patients”
Parhami et al. ATVB 1997
Oxidized lipids or other agents may be mediating the effect.
Mody et al. J Nucl Card 2003
Resorptive osteoclast-like cells are found in calcified
atherosclerotic lesions.
(Tintut et al. 2002)
Maybe derived from blood monocytes
Osteoclast-like cell with multiple nuclei
Osteoprotegerin (OPG)
OPG is a secreted protein that inhibits osteoclast formation
OPG deficient mice have osteoporosis and arterial (medial)
calcification
OPG Null Mouse
Bucay et al. Genes & Development 1998
Bone Resorption in the Skeleton Often Coexists with Bone
Formation in the Vasculature
Panizo et al., Circ Res 2009
Alexander, Circ Res 2009
VASCULAR CALCIFICATION
AND INFLAMMATION
The Size of Vascular Calcification
May Matter!
Large Chunks
Dhore et al. ATVB 2001
Small BCP Crystals
Engelse et al.2001
BCP = Basic calcium phosphate
Degenerative Joint Diseases are
“Crystal diseases”
where synovial fibroblasts have an
inflammatory response to the crystals.
Nadra et al. Circ Res 2005
The ingestion of BCP crystals by human
monocyte-derived macrophages generates a
pro-inflammatory response.
BCP Crystals Induces Pro-Inflammatory Factors in Macrophages
TNF-alpha
TNF-alpha Increases Calcification in Calcifying Vascular Cells (CVC)
Nadra et al. Circ Res 2005
Tintut et al. Circ 2000
Large calcified areas may be less pro-inflammatory.
How dangerous is the calcification we find on EBCT?
Mouse models for vascular calcification
Genes Associated with Ectopic Calcification in Mice
MUTATION
PHENOTYPE
Matrix Gla Protein
Arterial, valve and cartilage calcification
Fetuin
Decreased serum HA inhibitory activity
Osteopontin
Increased calcification of implanted bioprosthetic valves
Fibrillin
Vascular calcification, aortic stenosis
Osteoprotegerin
Osteoporosis, vascular calcification
FGF23
Hyperphosphatemia, vascular calcification
PC-1/Enpp1/NPP1
(nucleotide pyrophosphatase)
Vascular and articular cartilage calcification
Ank (pyrophosphate transporter)
Articular cartilage calcification, soft tissue calcification
ß-glucosidase (klotho)
Vascular calcification, rapid aging
Carbonic Anhydrase II
Calcification of small arteries
Smad6
Valve calcification
Desmin
Neonatal cardiomyopahty with calcificationAriall
Mouse Models Illustrate the Diversity of Vascular Calcification
MGP knockout
Fibrillin-1 deficient
Fat-fed ApoE (or
LDLR) knockout mice
Carbonic anhydrase II deficient
OPG knockout
Warfarin treated rat
VitD/Ca
Smad6 knockout
Vascular calcification is
heterogeneous and is
triggered through multiple
mechanisms