G. Filippatos et al., Expression of FAS adjacent to fibrotic foci in the failing human heart is not associated with increased apoptosis, AM J P-HEAR, 46(2), 1999, pp. H445-H451
Citations number
35
Categorie Soggetti
Cardiovascular & Hematology Research
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Fibrosis in the heart may result from loss of myocytes, which are replaced
by collagens. Apoptosis is now known to contribute to myocyte loss in the f
ailing human heart. The mechanisms underlying the induction of cardiomyocyt
e apoptosis, and thus the expansion of fibrotic foci in the failing heart,
are poorly understood. We hypothesized that viable heart cells adjacent to
fibrotic foci might become "predisposed" to apoptosis by expression of the
receptor FAS (APO1, CD95). We therefore studied the spatial relationship of
FAS expression and fibrosis in patients with heart failure. Left ventricul
ar biopsies were obtained from seven patients undergoing coronary artery by
pass grafting. All patients had reduced ejection fraction but varied in New
York Heart Association class score at the time of surgery. Heart cell apop
tosis, fibrosis, and FAS expression were studied by propidium iodide and in
situ end labeling (ISEL) of DNA, Picrosirius red staining, and immunohisto
chemistry. All patient samples exhibited, albeit to varying degrees, apopto
sis detected by ISEL, chromatin condensation, and nuclear fragmentation. In
all samples, fibrosis (collagen) was evident both perivascular and in isol
ated regions of scarring. Regardless of the extent of fibrosis or detectabl
e apoptosis, FAS expression was observed in regions immediately adjacent to
the fibrosis, but not in regions distal to fibrosis, nor in fibrotic areas
devoid of nuclei. Expression of FAS was found adjacent to both perivascula
r and diffuse fibrosis, and ISEL-positive nuclei were found within cells re
acting positively with anti-FAS antibodies. However, ISEL-positive nuclei w
ere no more abundant in FAS-positive regions (67.6 +/- 5.8% of total nuclei
) than in FAS-negative ar eas (69.5 +/- 9.8%). We conclude that expression
of FAS occurs in remaining heart cells adjacent to fibrosis of either periv
ascular or presumed reparative origin. Although this phenomenon could contr
ibute to the expansion of fibrotic foci, FAS-induced apoptosis in the faili
ng heart may not be more prevalent than apoptosis initiated by other signal
ing mechanisms.