Rt. Allen et al., Morphologic and temporal analysis of vascular smooth muscle cell apoptosisinduced by c-myc and E1A, SCANNING, 20(8), 1998, pp. 577-586
Apoptosis is a physiologic form of cell death present in many disease condi
tions. When the balance of mitosis versus apoptosis is altered, tumor-like
growth or degeneration of tissues may ensue. This appears to occur in sever
al diseases, including those of the cardiovascular system, where apoptosis
plays a key role in atherosclerosis and restenosis following angioplasty. S
ince c-myc is upregulated in the pathogenesis of these diseases, we chose t
o study the sequential morphologic features of programmed cell death in vas
cular smooth muscle cells induced by c-myc and by the adenovirus early gene
E1A. Morphology and timed events in apoptotic cell cultures were analyzed
by scanning electron microscopy, transmission electron microscopy, and time
-lapse videomicroscopy. We observed that both c-myc and E1A-induced apoptos
is (in serum-free medium) resulted in numerous, tightly packed clusters of
apoptotic blebs, as well as in one or two asymmetrically larger blebs. Tran
smission electron microscopy analysis revealed the larger blebs contained m
ostly nuclear chromatin, whereas the many smaller fragments often had littl
e or no chromatin. Time-lapse studies showed that apoptosis was induced at
a slower rate in cells stably transfected with c-myc versus those stably tr
ansfected with E1A. The early changes of apoptosis, including cell shrinkag
e and intense blebbing, occurred in under 5 min in both cells. Slight alter
ations such as cell size and further rounding occurred up to 8 h following
the initial changes of apoptosis. Rather than being a part of the apoptotic
response, release from the culture floor almost entirely resulted from mov
ement of the culture flask. These studies provide a framework of timed morp
hologic events for future mechanistic investigation into the key aspects of
myc- and E1A-induced apoptosis in vascular smooth muscle.