oxalylglycine and Necrosis

The hypoxia-inducible factor (HIF) pathway, regulated by prolyl hydroxylase, is central to tissue adaptation to ischemia. The authors tested whether the prolyl hydroxylase inhibitor dimethyloxalylglycine reduces skin flap necrosis.. Dorsal skin flaps were raised on hairless rats, with dimethyloxalylglycine delivered intraperitoneally and/or topically for 7 days before and after surgery. After 14 treatment days, percentage of flap necrosis was compared grossly and tissue perfusion compared with an in vivo imaging system. Angiogenesis was compared using immunohistochemical CD31 staining and enzyme-linked immunosorbent assay for tissue vascular endothelial growth factor. Expression levels of HIF-1α and terminal deoxynucleotidyl transferase-mediated dUDP end-labeling were compared using immunohistochemical staining. Complete blood counts and gross necropsy specimens were obtained to assess systemic toxicity.. Dimethyloxalylglycine administration significantly improved postoperative flap viability, with combined topical and intraperitoneal dimethyloxalylglycine administration leading to reduced necrosis on postsurgical day 7 at 6 mg/kg/day, 12 mg/kg/day, 24 mg/kg/day, and 48 mg/kg/day versus controls (all p < 0.05). Compared with controls (unperfused, 39.9 ± 3.8 percent), dimethyloxalylglycine treatment led to a dose-dependent decrease in unperfused tissue at 6 mg/kg/day (11.4 ± 1.7 percent), 12 mg/kg/day (9.4 ± 4.2 percent), 24 mg/kg/day (4.7 ± 2.6 percent), and 48 mg/kg/day (1.4 ± 0.9 percent) (all p < 0.001). Topical dimethyloxalylglycine application alone administered at 48 mg/kg/day was sufficient to improve flap viability (p = 0.005). Dimethyloxalylglycine-treated flaps exhibited higher CD31 staining (p = 0.004), tissue vascular endothelial growth factor (p = 0.007), HIF-1α staining (p < 0.001), and reduced terminal deoxynucleotidyl transferase-mediated dUDP end-labeling staining (p = 0.045). There were no differences in hematocrit or macroscopic organ changes on gross necropsy.. Topical and systemic targeting of the HIF-1 pathway may be a promising therapeutic approach to improve flap resistance to ischemia.

Topics: Amino Acids, Dicarboxylic; Animals; Ischemia; Ischemic Preconditioning; Male; Necrosis; Preoperative Period; Prolyl-Hydroxylase Inhibitors; Rats, Hairless; Skin; Skin Transplantation; Surgical Flaps

To observe the effects of pretreatment with dimethyloxalylglycine (DMOG) on the survival of multi-territory perforator flap and the vessels of choke zone (CZ) 2 in rat, and to explore related mechanism.. Sixty adult SD rats were divided into group DMOG and normal saline group (NS) according to the random number table, with 30 rats in each group. Perforator flap with three angiosomes was made on the right dorsal side of rat, including deep iliac circumflex artery perforator, intercostal artery perforator, thoracodorsal artery perforator, as well as CZ 1 and CZ 2. Rats in group DMOG were intraperitoneally injected with 2 mL NS containing DMOG (40 mg/kg) 2 days before operation, 2 hours before operation, and 2 days after operation. Rats in group NS were intraperitoneally injected with equivalent volume of NS at the same time point. On post operation day (POD) 7, gross observation was conducted, and the survival rate of flap was calculated. On POD 7, the vascularity in CZ 2 and potential zone of flap was observed using angiography. On POD 7, new vessel in CZ 2 of flap was observed with HE staining, and the microvessel density (MVD) was calculated. On POD 7, the expression of vascular endothelial growth factor (VEGF) in CZ 2 of flap was detected by immunohistochemistry and Western blotting (respectively denoted as integral absorbance values and ratio of gray value), and blood flow volume of vessel in CZ 2 of flap was examined by laser Doppler perfusion imager. The sample number of each index was 6 in each group. Data were processed with t test.. (1) On POD 7, rats in two groups all survived, and the flaps were not infected. In group DMOG, the necrotic area of flaps of rats with dark yellow crust and soft texture was observed approximately at the distal end of skin entry point of thoracodorsal artery perforator. In group NS, the necrotic area of flaps of rats with brownish black crust and hard texture was observed approximately at the distal end of CZ 2. The survival rate of flap of rats in group DMOG was (88±3) %, which was significantly higher than that in group NS [(82±3) %, t=3.38, P<0.01]. (2) On POD 7, there were clear vascular structure and many new vessels in CZ 2 of flaps of rats in group DMOG, with intact vascular structure in potential zone. On POD 7, there were unclear vascular structure and few new vessels in CZ 2 of flaps of rats in group NS, with disorder vascular structure in potential zone. (3) On POD 7, MVD in CZ 2 of flaps in rats of group DMOG was (29.2±2.2)/mm(2,) which was significantly higher than that of group NS [(20.3±3.6)/mm(2,) t=5.10, P<0.01]. (4) On POD 7, the expressions of VEGF in CZ 2 of flaps in rats of group DMOG detected by immunohistochemistry and Western blotting were 5 060±432 and 0.48±0.04 respectively, which were significantly higher than those of group NS (2 811±382 and 0.26±0.06, with t values respectively 9.54 and 5.67, P values below 0.01). (5) On POD 7, blood flow volume of vessel in CZ 2 of flaps in rats of group DMOG was (58±4) perfusion units (PU), which was significantly more than that of group NS [(46±4) PU, t=5.20, P<0.01].. DMOG can increase the survival rate of multi-territory perforator flap through promoting angiogenesis in CZ 2 of flap on the back of rat and improving blood supply of flap.

Topics: Amino Acids, Dicarboxylic; Angiography; Animals; Arteries; Graft Survival; Male; Necrosis; Neovascularization, Physiologic; Perforator Flap; Rats; Rats, Sprague-Dawley; Skin; Surgical Flaps; Vascular Endothelial Growth Factor A

Local skin flaps often present with flap necrosis caused by critical disruption of the blood supply. Although animal studies demonstrate enhanced angiogenesis in ischemic tissue, no strategy for clinical application of this phenomenon has yet been defined. Hypoxia-inducible factor 1 (HIF-1) plays a pivotal role in ischemic vascular responses, and its expression is induced by the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG). We assessed whether preoperative stabilization of HIF-1 by systemic introduction of DMOG improves skin flap survival.. Mice with ischemic skin flaps on the dorsum were treated intraperitoneally with DMOG 48 hr prior to surgery. The surviving area with neovascularization of the ischemic flaps was significantly greater in the DMOG-treated mice. Significantly fewer apoptotic cells were present in the ischemic flaps of DMOG-treated mice. Interestingly, marked increases in circulating endothelial progenitor cells (EPCs) and bone marrow proliferative progenitor cells were observed within 48 hr after DMOG treatment. Furthermore, heterozygous HIF-1α-deficient mice exhibited smaller surviving flap areas, fewer circulating EPCs, and larger numbers of apoptotic cells than did wild-type mice, while DMOG pretreatment of the mutant mice completely restored these parameters. Finally, reconstitution of wild-type mice with the heterozygous deficient bone marrow cells significantly decreased skin flap survival.. We demonstrated that transient activation of the HIF signaling pathway by a single systemic DMOG treatment upregulates not only anti-apoptotic pathways but also enhances neovascularization with concomitant increase in the numbers of bone marrow-derived progenitor cells.

Topics: Amino Acids, Dicarboxylic; Animals; Apoptosis; Bone Marrow Cells; Bone Marrow Transplantation; Disease Models, Animal; Haploinsufficiency; Hypoxia-Inducible Factor 1, alpha Subunit; Injections, Intraperitoneal; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Necrosis; Neovascularization, Physiologic; Procollagen-Proline Dioxygenase; Protective Agents; Skin; Tissue Survival