Increased thrombospondin-2 in human fibrosclerotic and stenotic aortic valves.
BACKGROUND
Active involvement of extracellular matrix (ECM) and its composition regulating factors may have a central role in the pathogenesis of calcific aortic valve disease (CAVD). Thrombospondins (TSPs) are highly conserved matricellular proteins regulating inflammation, angiogenesis and ECM remodeling. These processes are strongly associated with progression of aortic valve stenosis (AS). However, the expression of TSPs in CAVD is not known.


METHODS
We characterized the expression of TSPs 1-4 in human aortic valves by real-time quantitative reverse transcriptase polymerase chain reaction and immunohistochemistry. Control valves (n=8), thickened and stiffened fibro(sclero)tic valves (n=8), and calcified AS valves (n=24) were compared. Furthermore, potential factors regulating TSP-2 expression was studied by western blotting and gel mobility shift assay in another set of control (n=10) and AS (n=20) valves.


RESULTS
TSP-2 mRNA levels were increased 4.9-fold (P=0.037) and 4.8-fold (P=0.001) in fibro(sclero)tic and stenotic valves, respectively, whereas the expression of other TSPs did not change significantly. All TSPs 1-4 were detected from aortic valves by immunohistochemistry. Positive TSP-2 immunostaining was seen in the valvular myofibroblasts and patchily in endothelial cells. Semiquantitative analysis of TSP-2 staining indicated increased immunoreactivity for TSP-2 in neo vessels of fibro(sclero)tic and calcified aortic valves. Finally, when compared to controls, AS was associated with significant down regulation of Akt-pathway and diminished binding activity of nuclear factor-κB (NF-κB).


CONCLUSIONS
We report for the first time that TSPs 1-4 are expressed in human aortic valves. CAVD is characterized by myofibroblastic proliferation and neovascularization associated upregulation of TSP-2 expression, as well as inactivation of Akt and NF-κB.
Department of Pharmacology and Toxicology, Institute of Biomedicine, University of Oulu, Biocenter Oulu, Oulu, Finland.
Virva
V
Pohjolainen
Erja
E
Mustonen
Panu
P
Taskinen
Juha
J
Näpänkangas
Hanna
H
Leskinen
Pauli
P
Ohukainen
Tuomas
T
Peltonen
Jani
J
Aro
Tatu
T
Juvonen
Jari
J
Satta
Heikki
H
Ruskoaho
Jaana
J
Rysä
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001021:Aortic Valve / Q000737:chemistry* / Q000473:pathology; D001024:Aortic Valve Stenosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015153:Blotting, Western; D002114:Calcinosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016022:Case-Control Studies; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D005355:Fibrosis; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D016328:NF-kappa B / Q000032:analysis; D051057:Proto-Oncogene Proteins c-akt / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012598:Sclerosis; D019700:Thrombospondin 1 / Q000032:analysis; D019699:Thrombospondins / Q000032:analysis* / Q000235:genetics; D015854:Up-Regulation; D000099262:Thrombospondin 2
D016328:NF-kappa B; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D019700:Thrombospondin 1; D019699:Thrombospondins; D000099262:Thrombospondin 2; C101863:thrombospondin 3; C101864:thrombospondin 4