Impaired wound healing is a well-documented phenomenon in experimental and clinical diabetes. Experimental evidence suggests that a defect in vascular endothelial growth factor (VEGF) regulation might be associated with wound-healing disorders. We studied the involvement of lipid peroxidation in the pathogenesis of altered VEGF expression in diabetes-related healing deficit by using an incisional skin-wound model produced on the back of female diabetic C57BL/KsJ db؉/ db؉ mice and their normal (db؉/؉m) littermates. Animals were then randomized to the following treatment: raxofelast (15 mg ⅐ kg -1 ⅐ day -1 i.p.), an inhibitor of lipid peroxidation, or its vehicle (DMSO/NaCl 0.9%, 1:1 vol: vol). The animals were killed on different days (3, 6, and 12 days after skin injury), and the wounded skin tissues were used for histological evaluation, for analysis of conjugated dienes (CDs), as an index of lipid peroxidation and wound breaking strength. Furthermore, we studied the time course of VEGF mRNA expression throughout the skin-repair process (3, 6, and 12 days after skin injury), by means of reverse transcriptasepolymerase chain reaction, as well as the mature protein in the wounds. Diabetic mice showed impaired wound healing with delayed angiogenesis, low breaking strength, and increased wound CD content when compared with their normal littermates. In healthy control mice, a strong induction of VEGF mRNA was found between day 3 and day 6 after injury, while no significant VEGF mRNA expression was observed at day 12 after injury. In contrast, VEGF mRNA levels, after an initial increase (day 3), were significantly lower in diabetic mice than in normal littermates, and light induction of VEGF mRNA expression was also present at day 12 after injury. Similarly, the wound content of the angiogenic factor was markedly changed in diabetic mice. Administration of raxofelast did not modify the process of wound repair in normal mice, but significantly improved the impaired wound healing in diabetic mice through the stimulation of angiogenesis, re-epithelization, and synthesis and maturation of extracellular matrix. Moreover, raxofelast treatment significantly reduced wound CD levels and increased the breaking strength of the wound. Lastly, the inhibition of lipid peroxidation restored the defect in VEGF expression during the process of skin repair in diabetic mice and normalized the VEGF wound content. The current study provides evidence that lipid peroxidation inhibition restores wound healing to nearly normal levels in experimental diabetes-impaired wounds and normalizes the defect in VEGF regulation associated with diabetes-induced skin-repair disorders. Diabetes 50:667-674, 2001

Healing of diabetic wounds still remains a critical medical problem. Polydeoxyribonucleotide (PDRN), a compound having a mixture of deoxyribonucleotide polymers, stimulates the A2 purinergic receptor with no toxic or adverse effect. We studied the effects of PDRN in diabetes-related healing defect using an incisional skin-wound model produced on the back of female diabetic mice (db1/ db1) and their normal littermates (db1/1m). Animals were treated daily for 12 days with PDRN (8 mg/kg/ip) or its vehicle (100 mL 0.9%NaCl). Mice were killed 3, 6, and 12 days after skin injury to measure vascular endothelial growth factor (VEGF) mRNA expression and protein synthesis, to assay angiogenesis and tissue remodeling through histological evaluation, and to study CD31, Angiopoietin-1 and Transglutaminase-II. Furthermore, we measured wound breaking strength at day 12. PDRN injection in diabetic mice resulted in an increased VEGF message (vehicle51.0 AE 0.2 n-fold vs. b-actin; PDRN51.5 AE 0.09 n-fold vs. b-actin) and protein wound content on day 6 (vehicle50.3 AE 0.07 pg/wound; PDRN50.9 AE 0.1 pg/wound). PDRN injection improved the impaired wound healing and increased the wound-breaking strength in diabetic mice. PDRN also caused a marked increase in CD31 immunostaining and induced Transglutaminase-II and Angiopoietin-1 expression. Furthermore, the concomitant administration of 3,7-dimethyl-1-propargilxanthine, a selective adenosine A2A receptor antagonist, abolished PDRN positive effects on healing. However, 3,7-dimethyl-1-propargilxanthine alone did not affect wound healing in both diabetic mice and normal littermates. These results suggest that PDRN might be useful in wound disorders associated with diabetes.

The effects of recombinant human erythropoietin (rHuEPO) in diabetes-related healing defects were investigated by using an incisional skin-wound model produced on the back of female diabetic C57BL/KsJm ؉/؉ Lept db mice (db ϩ /db ϩ ) and their normoglycemic littermates (db ϩ/ϩ m). Animals were treated with rHuEPO (400 units/kg in 100 l s.c.) or its vehicle alone (100 l). Mice were killed on different days (3, 6, and 12 days after skin injury) for measurement of vascular endothelial growth factor (VEGF) mRNA expression and protein synthesis, for monitoring angiogenesis by CD31 expression, and for evaluating histological changes. Furthermore, we evaluated wound-breaking strength at day 12. At day 6, rHuEPO injection in diabetic mice resulted in an increase in VEGF mRNA expression (vehicle ‫؍‬ 0.33 ؎ 0.1 relative amount of mRNA; rHuEPO ‫؍‬ 0.9 ؎ 0.09 relative amount of mRNA; P < 0.05) and protein wound content (vehicle ‫؍‬ 23 ؎ 5 pg/wound; rHuEPO ‫؍‬ 92 ؎ 12 pg/wound; P < 0.05) and caused a marked increase in CD31 gene expression (vehicle ‫؍‬ 0.18 ؎ 0.05 relative amount of mRNA; rHuEPO ‫؍‬ 0.98 ؎ 0.21 relative amount of mRNA; P < 0.05) and protein synthesis. Furthermore, rHuEPO injection improved the impaired wound healing and, at day 12, increased the wound-breaking strength in diabetic mice (vehicle ‫؍‬ 12 ؎ 2 g/mm; rHuEPO 21 ؎ 5 g/mm; P < 0.05). Erythropoietin may have a potential application in diabetes-related wound disorders.

Our study suggests that rHuEPO may be an effective therapeutic approach to improve clinical outcomes after thermal injury.