Atorvastatin inhibits hypercholesterolemia-induced cellular proliferation and bone matrix production in the rabbit aortic valve.
BACKGROUND
Despite the common occurrence of aortic stenosis, the cellular causes of the disorder are unknown, in part because of the absence of experimental models. We hypothesized that atherosclerosis and early bone matrix expression in the aortic valve occurs secondary to experimental hypercholesterolemia and that treatment with atorvastatin modifies this transformation.


RESULTS
To test this hypothesis, we developed an experimental hypercholesterolemic rabbit model. New Zealand White rabbits (n=48) were studied: group 1 (n=16), normal diet; group 2 (n=16), 1% (wt/wt) cholesterol diet; and group 3 (n=16), 1% (wt/wt) cholesterol diet plus atorvastatin (3 mg/kg per day). The aortic valves were examined with hematoxylin and eosin stain, Masson trichrome, macrophage (RAM 11), proliferation cell nuclear antigen (PCNA), and osteopontin immunostains. Cholesterol and highly sensitive C-reactive protein (hsCRP) serum levels were obtained by standard assays. Computerized morphometry and digital image analysis were performed for quantifying PCNA (% area). Electron microscopy and immunogold labeling were performed for osteopontin. Semiquantitative RT-PCR was performed for the osteoblast bone markers [alkaline phosphatase, osteopontin, and osteoblast lineage-specific transcription factor (Cbfa-1)]. There was an increase in cholesterol, hsCRP, PCNA, RAM 11, and osteopontin and osteoblast gene markers (alkaline phosphatase, osteopontin, and Cbfa-1) in the cholesterol-fed rabbits compared with control rabbits. All markers except hsCRP were reduced by atorvastatin.


CONCLUSIONS
These findings of increased macrophages, PCNA levels, and bone matrix proteins in the aortic valve during experimental hypercholesterolemia provide evidence of a proliferative atherosclerosis-like process in the aortic valve associated with the transformation to an osteoblast-like phenotype that is inhibited by atorvastatin.
Rajamannan
Nalini M
NM
Division of Cardiology, Department of Medicine, Northwestern University Medical School, Chicago, Ill 60611, USA. n.rajamannan@northwestern.edu
Subramaniam
Malayannan
M
Springett
Margaret
M
Sebo
Thomas C
TC
Niekrasz
Marek
M
McConnell
Joseph P
JP
Singh
Ravinder J
RJ
Stone
Neil J
NJ
Bonow
Robert O
RO
Spelsberg
Thomas C
TC
D000469:Alkaline Phosphatase / Q000032:analysis / Q000096:biosynthesis; D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D001021:Aortic Valve / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000069059:Atorvastatin; D015415:Biomarkers / Q000032:analysis; D002097:C-Reactive Protein / Q000032:analysis; D002114:Calcinosis / Q000150:complications / Q000473:pathology / Q000517:prevention & control*; D002455:Cell Division / Q000187:drug effects; D002784:Cholesterol / Q000097:blood; D002791:Cholesterol, Dietary; D004195:Disease Models, Animal; D006349:Heart Valve Diseases / Q000150:complications / Q000473:pathology / Q000517:prevention & control*; D006538:Heptanoic Acids / Q000494:pharmacology*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D006937:Hypercholesterolemia / Q000150:complications / Q000188:drug therapy* / Q000473:pathology; D007150:Immunohistochemistry; D008264:Macrophages / Q000473:pathology; D008297:Male; D016253:Microscopy, Immunoelectron; D010006:Osteoblasts / Q000378:metabolism / Q000473:pathology; D053495:Osteopontin; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012795:Sialoglycoproteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics
D000924:Anticholesteremic Agents; D015415:Biomarkers; D002791:Cholesterol, Dietary; D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D018809:Proliferating Cell Nuclear Antigen; D011758:Pyrroles; D012333:RNA, Messenger; D012795:Sialoglycoproteins; D053495:Osteopontin; D002097:C-Reactive Protein; D002784:Cholesterol; D000069059:Atorvastatin; D000469:Alkaline Phosphatase