Fibrillin and other matrix proteins in mitral valve prolapse syndrome.
BACKGROUND
Unlike myxomatous degeneration in Marfan syndrome, which has been reported to result from a mutation in the gene that codes for the extracellular structural protein fibrillin, no specific molecular abnormality has been documented to be the underlying cause of myxomatous degeneration in mitral valve prolapse syndrome (MVPS). The present study examined the distribution of fibrillin and other extracellular matrix proteins in patients with isolated MVPS.


METHODS
Mitral valve leaflets from 7 MVPS patients and 5 rheumatic heart disease (RHD) patients were characterized immunohistochemically for fibrillin, elastin, collagen I, and collagen III distribution, and compared with five normal mitral valves.


RESULTS
In normal mitral valve leaflets immunostaining for fibrillin, elastin, collagen I, and collagen III revealed a fibrillary and laminar pattern in the atrialis and the spongiosa. In addition, both the collagens were present in the ventricularis, and the coarse bundles in the fibrosa exhibited alternating bandlike collagen I immunoreactivity. The staining patterns of fibrillin, elastin, and collagens I and III revealed distinctly different distribution in MVPS relative to the normal and RHD leaflets. MVPS leaflets in areas of myxoid degeneration displayed a more diffuse, weaker, and nonlaminar pattern of staining for fibrillin. Similar, but less severe abnormality of elastin, collagen I, and collagen III was also observed. Unlike diffuse abnormality in MVPS, the disruption of extracellular proteins in RHD only occurred at the site of the inflammatory damage, but the overall architecture was preserved.


CONCLUSIONS
The results of the current study suggest a primary role for abnormal fibrillin and other matrix proteins in producing myxoid degeneration of mitral valve leaflets in MVPS.
Nasuti
Joseph F
JF
Hospital of University of Pennsylvania, Philadelphia, PA, USA.
Zhang
Paul J
PJ
Feldman
Michael D
MD
Pasha
Terri
T
Khurana
Jasvir S
JS
Gorman
Joseph H
JH
Gorman
Robert C
RC
Narula
Jagat
J
Narula
Navneet
N
D000328:Adult; D000368:Aged; D024042:Collagen Type I / Q000032:analysis; D024061:Collagen Type III / Q000032:analysis; D004549:Elastin / Q000032:analysis; D005109:Extracellular Matrix / Q000473:pathology; D016326:Extracellular Matrix Proteins / Q000032:analysis*; D005260:Female; D000071837:Fibrillins; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008840:Microfilament Proteins / Q000032:analysis*; D008875:Middle Aged; D008943:Mitral Valve / Q000473:pathology; D008945:Mitral Valve Prolapse / Q000473:pathology*; D012016:Reference Values; D012214:Rheumatic Heart Disease / Q000473:pathology
D024042:Collagen Type I; D024061:Collagen Type III; D016326:Extracellular Matrix Proteins; D000071837:Fibrillins; D008840:Microfilament Proteins; D004549:Elastin