Vascular Calcification Kristina Boström, MD, PhD Cardiology, UCLA

Vascular Calcification

Kristina Boström, MD, PhDCardiology, 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

• 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.

This Case Illustrates ….

Anatomical location AorticCoronaryPeripheral arteriesHeart valve

Vascular layer Intima Media Adventitia Heart valve

Association with disease AtherosclerosisMönckeberg’s (Media Sclerosis)DiabetesRenal Failure

Vascular Calcification Differs in:

Intima

Media

Adventitia

Heart valves

AtherosclerosisRenal FailureDiabetes

Mönckeberg’s (Media sclerosis)Renal FailureDiabetes

Atherosclerosis

Diabetes

Vascular Calcification Is Associated with Vascular Disease:

Sangiorgi et al. JACC 1998

Intimal Calcification - Atherosclerosis

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

Calcified, Atherosclerotic Coronary Artery

Calcification

Intima

Media

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

Medial Calcification

Atherosclerotic Plaques

(Mönckeberg’s media sclerosis, elastocalcinosis)

WebpathPrice et al. ATVB 2000

VASCULAR MEDIAL CALCIFICATION

Arteriosclerosis associated with aging, diabetes, and end stage renal disease

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

Senile Aortic Stenosis CalcifiedBioprosthetic Valve

Normal Aortic 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

ActiveInducers

ActiveInhibitors

Dhore et al. ATVB 2001

Inhibitors

Promotors

Both Inhibitors and Promotors of Calcification in Atherosclerotic Plaques

VASCULAR CALCIFICATION

DISTURBED Ca/Pi BALANCEHyperphosphatemiaHypercalcemia

Ca x Pi

INDUCING FACTORSPiLipidsInflammatory cytokinesOthers

INDUCTION OF BONE FORMATIONVascular bone and cartilage-like cells

Apoptotic bodies

CELL DEATH

LOSS OF INHIBITIONPyrophosphateMGPOPNFetuin/alpha2-HS glycoproteinOthers

CIRCULATING NUCLEATIONAL COMPLEXES

BisphosphonatesOPG

Bone Remodeling

Matrix Vesicles

Major Theories of Vascular Calcification

Adapted from Speer & Giachelli, Cardiovasc Path 2004



Ca x Pi



Apoptotic bodies

CELL DEATH

LOSS OF INHIBITIONPyrophosphateMGPOPNFetuin/alpha2-HS glycoproteinOthers


BisphosphonatesOPG

Bone Remodeling

Matrix Vesicles



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).

Levine et al. Circulation 2001

Long-axis image of aorta and aortic arch

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)

Matrix Gla Protein (MGP)

Vascular Calcification in MGP Null Mice

Luo et al. Science 1997

Aortic media

Wild type

Aortic media

MGP null

• 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)

BONE MORPHOGENETIC PROTEINS (BMP)

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)

Westenfeld et al. Trends Cardiovasc Med 2007

Normal mouse after phosphate challenge

Fetuin-deficient mouse after phosphate challenge

• Acidic phosphoprotein found in bone and teeth

• Inhibitor of apatite crystal growth

• Promotes osteoclast function

OSTEOPONTIN

Osteopontin Deficiency Worsens Calcification in MGP Null Mice

Speer MY et al. 2002



Ca x Pi



Apoptotic bodies

CELL DEATH

LOSS OF INHIBITIONMGPOPNFetuin/alpha2-HS glycoproteinPyrophosphateOthers


BisphosphonatesOPG

Bone Remodeling

Matrix Vesicles



Ectopic Calcification in Atherosclerotic Plaqes

Rattazzi et al. ATVB 2005

Chondrocytes in Mouse Atherosclerotic Lesions

Mineral Precipitation Cell Differentiation

Ca2+ PO42-

CaPO4 mineral precipitation

osteoid(matrix)

matrix vesicles

hydroxyapatite

Ca2+ PO42-

CaPO4 mineral precipitation

“Active” inhibitor

osteoblast-like cell

• Pericytes

• Mesenchymal stem cells

• Multipotent cells from the adventitia

• Resident cells in the media or intima

• Trans-differentiated SMC(Synthetic vs contractile phenotype)

Potential Origins of Osteoblast-like Cells in the Artery Wall

Calcifying Vascular Cells (CVC)

CONDENSATION CALCIFIEDNODULES

UNDIFFERENTIATED

Bone Related Factors in Calcified Artery Wall

BMP-2 and -4Cbfa1OsterixCollagen IAlkaline PhosphataseOsteocalcinHydroxyapatite

OsteopontinMatrix GLA protein (MGP)Osteoprotegerin… and others …..

Dhore et al. ATVB 2001

Both Inhibitors and Promotors of Calcification in Plaques



Ca x Pi



Apoptotic bodies

CELL DEATH



BisphosphonatesOPG

Bone Remodeling

Matrix Vesicles



(Despite serum Ca x P at or near solubility product)Normal Vessels Don’t Mineralize

ActiveInducers

ActiveInhibitors

Intima

Media

Adventitia

Heart valves

AtherosclerosisRenal FailureDiabetes

Mönckeberg’s (Media sclerosis)Renal FailureDiabetes

Atherosclerosis

Diabetes

Already above precipitation point at certain placesRenal 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)

Calcium x Phosphate Product

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

Pi/Ca

Contractile SMC

Osteochondrogenic cellSM-MHCSM22alphaSM-alpha actinDesmin

Cbfa1OPNOsteocalcinAlk Phos

Phosphate-Induced Changes in SMC Differentiation

Wada et al. Circ Res 1999

Calcified Vascular Smooth Muscle Cells



Ca x Pi



Apoptotic bodies

CELL DEATH



BisphosphonatesOPG

Bone Remodeling

Matrix Vesicles


Degenerative Joint Diseases are “Crystal diseases”where synovial fibroblasts have an inflammatory response to the crystals.

Connection between Vascular Calcification and Bone

Aortic Calcification and Osteoporosis Frequently Coexist

Similarities to Bone:Bone ProteinsOsteoblast-like CellsOsteoclast-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

OPG is a secreted protein that inhibits osteoclast formationOPG deficient mice have osteoporosis and arterial (medial) calcification

OPG Null Mouse

Bucay et al. Genes & Development 1998

Osteoprotegerin (OPG)

Bone Resorption in the Skeleton Often Coexists with Bone Formation in the Vasculature

Panizo et al., Circ Res 2009Alexander, Circ Res 2009

The Size of Vascular Calcification May Matter!

VASCULAR CALCIFICATION AND INFLAMMATION

Dhore et al. ATVB 2001 Engelse et al.2001

Large Chunks Small BCP Crystals

BCP = Basic calcium phosphate

Degenerative Joint Diseases are “Crystal diseases”where synovial fibroblasts have an inflammatory response to the crystals.

The ingestion of BCP crystals by human monocyte-derived macrophages generates a pro-inflammatory response.

Nadra et al. Circ Res 2005

BCP Crystals Induces Pro-Inflammatory Factors in Macrophages

TNF-alpha

Nadra et al. Circ Res 2005

TNF-alpha Increases Calcification in Calcifying Vascular Cells (CVC)

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 Vascular and articular cartilage calcification(nucleotide pyrophosphatase)

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 CalcificationMGP knockout

OPG knockout

Smad6 knockout

Carbonic anhydrase II deficient

Fibrillin-1 deficient

Fat-fed ApoE (or LDLR) knockout mice

Warfarin treated ratVitD/Ca

Vascular calcification is heterogeneous and is

triggered through multiple mechanisms

Documents

Vascular Calcification Kristina Boström, MD, PhD Cardiology, UCLA