[Effects of pretreatment with dimethyloxalylglycine on the survival of multi-territory perforator flap in rat and related mechanism].

OBJECTIVE

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.

METHODS

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.

RESULTS

(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].

CONCLUSIONS

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.