Wound healing, cell communication, and DNA synthesis during imaginal disc regeneration in Drosophila

Wound healing, gap-junctional cell communication, and DNA synthesis were studied in 3/4 fragments of the imaginal wing disc of Drosophila melanogaster cultured in the female adult abdomen. Such fragments regenerate the missing sector by cell proliferation over a period of several days. Individual cells were marked in the starting fragment by intracellular injection of high-molecular-weight lysinated rhodamine dextran, and the positions of the marked cells were determined by fluorescence microscopy before and after various culture times. These experiments showed that cells along the two wound edges were brought together by wound healing during the first day of the culture period. The marked cells then gradually moved apart over the next 3 days as new cells were added between them by intercalary regeneration. Gap-junctional cell communication across the healed wound, assessed by the movement of intracellularly injected small fluorescent dye molecules, was not detectable after 1 day of culture. After 2 days there was some dye transfer into the growth zone but not as much as in other directions. After 3 days there was significant dye transfer into the growth zone. DNA synthesis, detected by immunolocalization of incorporated bromodeoxyuridine, was first apparent at 18 hr after the beginning of the culture period; at this time as well as at later times it occurred only in the immediate vicinity of the healed wound. DNA synthesis was stimulated over a distance of several cell diameters from the wound, and for one of the cuts it was much more prevalent on one side of the wound than on the other. The results indicate that wound healing brings together cells from distant positions in the disc, and that the response to this is local DNA synthesis and cell proliferation. Gap-junctional communication across the wound does not appear to be necessary for stimulating this cell proliferation, although the timing of the reappearance of gap-junctional communication suggests that it may be involved in terminating proliferation.