The immunofluorescence data suggest that the basement membrane may
be lost when débridement wounds take longer than 24 hours to
close. To determine whether this is the case, TEM studies were
conducted. Presented are TEM data from small
(Fig. 5) and large
(Fig. 6) wounds. Data show the BMZ at a region just behind the leading edge but
within the region of active cell movement, the basal surface of a basal
cell migrating at the leading edge of the wound, and the anterior
aspect of the bare stroma at 12 (
Figs. 5A 5B 5C , respectively) and 18
(
Figs. 5D 5E 5F , respectively) hours after the small wound and at 24
(
Figs. 6A 6B 6C , respectively) and 36 (
Figs. 6D 6E and 6F ,
respectively) hours after larger wounds. Higher magnifications of the
bare stroma at 36 hours are presented in 6G and 6H. A continuous,
discrete lamina densa was present behind the leading edge, beneath the
leading edge, and at the denuded anterior stromal surface before
re-epithelialization at 12 and 18 hours after small wounds
(Fig. 5) .
Fragments of basal cell basal membranes can be observed that were left
behind after débridement wounding at 12 hours but not at 18 hours
(Fig. 5C) . Although there are no mature hemidesmosomes apparent at
either time point, a few small hemidesmosomes were found toward the
limbus (not shown). Compared with 12 hours
(Fig. 5C) , at 18 hours
(Fig. 5F) , the exposed lamina densa appeared somewhat thicker but was still
readily apparent. Underneath the cells comprising the leading edge and
behind the leading edge at 12
(Fig. 5A 5B) and 18 hours
(Figs. 5D 5F) an apparent lamina lucida and densa were visible, and epithelial cells
appeared closely associated with the underlying stroma, despite the
absence of mature hemidesmosomes.
At 24 hours after the larger wounds, the lamina densa was still
apparent at the denuded anterior stromal surface
(Fig. 6C) but looked
more disrupted and less discrete than for small wounds at either 12 or
18 hours
(Figs. 5C 5F) . However, by 36 hours the lamina densa was
highly disrupted or completely absent
(Figs. 6F 6G 6H) . The longer
stretches of exposed stroma shown in
Figures 6G and 6H demonstrate that
the disassembly of the BMZ was substantial but partial because remnants
of the lamina densa of the basement membrane could still be observed at
some locations at 36 hours. Underneath the cells comprising the leading
edge and behind the leading edge at both 24 and 36 hours after
wounding, adhesion of the epithelial cells to the stroma appeared to
become progressively less tight, suggested by the increased spacing
between the basal cell membrane and the apparent lamina densa observed
just behind the leading edge at 36 hours
(Fig. 6D) compared with
earlier time points
(Figs. 5A 5D 6A) .