Summary
Aortic valve stenosis (AS) shares several similarities with atherosclerosis. Factor
XIII (FXIII) has been detected within atherosclerotic plaques and may contribute to
the development of atherosclerosis via multiple mechanisms. In the current study,
we sought to investigate FXIII expression within human stenotic aortic valves and
its association with severity of the disease. We prospectively enrolled 91 consecutive
patients with AS scheduled for isolated valve replacement. Valvular FXIII subunit
A (FXIII-A), fibrin and macrophages expression was evaluated by immunostaining. FXIII-A
subunit transcripts and FXIII-A Val34Leu polymorphism was determined by real-time
PCR. Plasma FXIII (pFXIII) activity was measured. We demonstrated that the valvular
FXIII-A was predominantly expressed on the aortic side of leaflets, colocalized with
alternatively activated macrophages (AAM). Areas stained for FXIII-A showed positive
correlations with valvular fibrin presence, degree of calcification, pFXIII activity
and the severity of AS, reflected by mean and maximum transvalvular gradients (all,
p<0.001). The FXIII-A mRNA in the stenotic leaflets was significantly elevated compared
to control leaflets. Interestingly, pFXIII activity was also positively correlated
with mean (p<0.001) and maximum (p=0.001) transvalvular gradient. The FXIII-A Val34Leu
polymorphism did not affect FXIII-A and fibrin expression in AS valves. In conclusion,
the study is the first to show abundant expression of FXIII-A at the mRNA and protein
levels within human stenotic aortic valves, which is associated with the severity
of AS. Our findings might suggest that FXIII in the stenotic valves is presented in
AAM and may be involved in the AS progression.
Keywords
Aortic valve stenosis - Calcification - factor XIII - alternatively activated macrophages