Atherosclerotic-like process in aortic stenosis: activation of the tissue factor-thrombin pathway and potential role through osteopontin alteration.
BACKGROUND
We recently demonstrated in an experimental model the expression of tissue factor (TF) in aortic valves. Thrombin, generated at the end of the TF-initiated coagulation cascade, has been shown to cleave the anti-calcific osteopontin (OSP) liberating the pro-inflammatory OSP N-half.


OBJECTIVE
We hypothesized that TF might play an important role in calcific aortic valve stenosis (AS) through thrombin generation and hence evaluated the valvular expression of TF and its inhibitor (TF pathway inhibitor), α-thrombin, OSP and its thrombin-cleaved form (OSP N-half).


METHODS
Calcified aortic valves were obtained from patients undergoing valve replacement. Protein expression was evaluated by immunostaining and measured using ELISA kits. Transcripts were analyzed by RT-PCR.


RESULTS
We included 52 patients (31 men; age 70 ± 10 years; aortic valve area index 0.35 ± 0.13 cm(2)/m(2)). Immunohistochemistry revealed that TF, OSP and α-thrombin expressions were associated with calcifications at the aortic side of the leaflets. There was an overexpression in calcified regions as compared to non-calcified zones of TF (733.3 ± 70.5 pg/mg vs. 429.4 ± 73.2 pg/mg; p<0.0001), OSP (88.9 ± 12.7 ng/mg vs. 15.0 ± 3.3 ng/mg; p<0.0001) and OSP N-half (0.41 ± 0.06 pmol/mg vs. 0.056 ± 0.011 pmol/mg; p<0.0001). Additionally, both TF and α-thrombin expressions were associated with OSP N-half (r=0.52; p<0.0001 and r=0.33; p=0.019, respectively).


CONCLUSIONS
Aortic leaflet TF and α-thrombin expressions and their association with the thrombin-cleaved form of OSP, are a new and important feature of AS. We hypothesize that TF may be involved in the mineralization process of aortic valves by enhancing the generation of the pro-inflammatory OSP N-half through thrombin induction. This pathway deserves further studies to address its implication in the aortic valve calcification process.
Breyne
Joke
J
Univ Lille Nord de France, IFR 114, EA 2693, F-59000 Lille, France. joke.breyne@gmail.com
Juthier
Francis
F
Corseaux
Delphine
D
Marechaux
Sylvestre
S
Zawadzki
Christophe
C
Jeanpierre
Emmanuelle
E
Ung
Alexandre
A
Ennezat
Pierre-Vladimir
PV
Susen
Sophie
S
Van Belle
Eric
E
Le Marec
Hervé
H
Vincentelli
André
A
Le Tourneau
Thierry
T
Jude
Brigitte
B
D000368:Aged; D000369:Aged, 80 and over; D001021:Aortic Valve / Q000378:metabolism; D001024:Aortic Valve Stenosis / Q000503:physiopathology*; D050197:Atherosclerosis / Q000378:metabolism*; D002114:Calcinosis / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D008297:Male; D008875:Middle Aged; D053495:Osteopontin / Q000378:metabolism*; D013917:Thrombin / Q000096:biosynthesis / Q000502:physiology*; D013925:Thromboplastin / Q000502:physiology*
D053495:Osteopontin; D013925:Thromboplastin; D013917:Thrombin