Ma. Wride et Ej. Sanders, NUCLEAR DEGENERATION IN THE DEVELOPING LENS AND ITS REGULATION BY TNF-ALPHA, Experimental Eye Research, 66(3), 1998, pp. 371-383
DNA fragmentation in lens fibre cell nuclei undergoing programmed dege
neration was identified by terminal deoxynucleotidyl transferase (TdT)
-mediated biotin-dUTP nick end labelling (TUNEL). Lens epithelial cell
s in culture were induced to differentiate into lens fibre-like clumps
of cells (lentoids) by insulin and it was shown that the TUNEL method
was also an effective means of labelling degenerating nuclei in lento
id cells in lens epithelial cell cultures. Using immuno-fluorescence a
nd confocal microscopy, it was shown that TNF alpha and TNF receptor (
TNFR1, and TNFR2) immunoreactivity was present in sections of chick em
bryo lenses. TNF alpha immunoreactivity was associated with the lens e
pithelium and lens fibres. TNFR1 immunoreactivity was present in lens
epithelial cells, cortical lens fibres, and lens fibre cell nuclei, wh
ile TNFR2 immunoreactivity had a similar distribution to that of TNFR1
, but was not associated with nuclei. Similar patterns of TNF alpha, T
NFR1, and TNFR2 immunoreactivity were observed in lens epithelial cell
cultures. When added to lens epithelial cell cultures, TNF alpha, at
concentrations of 50 to 100 ng ml(-1), and agonistic antibodies to bot
h TNFR1 and TNFR2 significantly (P < 0.05) enhanced the number of dege
nerating (TUNEL-positive) nuclei. On the other hand, a neutralising an
tibody to TNF alpha significantly (P < 0.05) reduced the number of TUN
EL-positive nuclei. These results demonstrate that TUNEL is an effecti
ve means of labelling degenerating lens fibre nuclei during lens fibre
and lentoid differentiation, and suggest a potential role for TNF alp
ha-like factors and their receptors in the degeneration of lens fibre
cell nuclei during lens differentiation. We further suggest that the n
uclear degeneration of lens fibre cells is analogous to the nuclear ev
ents that occur during apoptosis, and that in lens cells the nuclear d
egeneration is uncoupled from the plasma membrane events of apoptosis
that normally lead to cell death. (C) 1998 Academic Press Limited.