Mammalian Meckel´s cartilage is a temporary structure
associated with mandible development. Notably, its elimination is
not executed by apoptosis, and autophagy was suggested as the
major mechanism. Simultaneous reports point to pro-apoptotic
caspases as novel participants in autophagic pathways in general.
The aim of this research was to find out whether activation of
pro-apoptotic caspases (-2, -3, -6, -7, -8 and -9) was associated
with autophagy of the Meckel´s cartilage chondrocytes. Active
caspases were examined in serial histological sections of mouse
mandible using immunodetection and were correlated with
incidence of autophagy based on Beclin-1 expression. Caspase-2
and caspase-8 were found in Beclin-1 positive regions, whereas
caspase-3, -6, -7 and -9 were not present. Caspase-8 was further
correlated with Fas/FasL and HIF-1α, potential triggers for its
activation. Some Fas and FasL positivity was observed in the
chondrocytes but caspase-8 activation was found also in FasL
deficient cartilage. HIF-1α was abundantly present in the
hypertrophic chondrocytes. Taken together, caspase-8 activation
in the Meckel´s cartilage was demonstrated for the first time.
Caspase-8 and caspase-2 were the only pro-apoptotic caspases
detected in the Beclin-1 positive segment of the cartilage.
Activation of caspase-8 appears FasL/Fas independent but may
be switched on by HIF-1α.