Figure 5.

Necrosis of ischemic skin flaps correlates with Ankrd1 zygosity. Diagram depicts the sectioning pattern of the ischemic dorsal skin flap. After euthanasia at 12 days, the flaps were excised, cut horizontally into four 4-mm strips (dashed lines) to represent the tissue response as a function of distance from the (cranial) base of the flap, and embedded with the caudal edge of each segment at the paraffin block face. Histological sections, 4× objective: The base of flaps, irrespective of genotype, shows an intact epidermis, a pale green dermis penetrated by numerous hair follicles, s.c. fat, and a deep red panniculus carnosus. At 50% of flap length, hemizygous flaps show a hypertrophic epidermis, immature follicular structures, and a granular dermal response, suggesting incomplete repair. Knockout (KO) flaps show a transition from intact, condensed dermal collagen to frank necrosis (bright red with trichrome staining). By 75% of the flap length, FLOX tissues also undergo signs of deterioration, whereas hemizygous and KO tissues are highly necrotic. Frank necrosis is present at the tip of the flaps, although tissue disintegration is more prominent in the KO animals. Necrosis at the distal end of the ischemic dorsal skin flaps of FLOX mice is minimal, <10% of flap length. WT/⁻ mice showed approximately 25% to 50% necrosis, whereas 50% to 75% of the flap on KO mice became necrotic. Similar results were obtained in three separate experiments.