Objective: To study the effect of various doses of estrogen on tissue injury, blood supply and survival area of skin flap and to investigate its mechanism.
Methods: Thirty New Zealand white rabbits aged 3-4 months old and weighing 1.5-2.2 kg (male or female) were used. Random pattern skin flap (12 cm x 3 cm in size) taking the central line of the rabbit dorsum as axis and with the pedicle attached at the proximal end was prepared, and the flap pedicle division was performed 7 days after operation. The rabbits were divided randomly into three groups (n = 10 rabbits per group). At 2, 4, and 6 days after operation, the proximal edge of flap in group A and B received 100 microg/kg and 50 microg/kg subcutaneous injection of estradiol benzoate, respectively, while group C received no further treatment serving as control group. General condition of the rabbits was observed after injection, gross observation was performed 3 and 7 days after injection, survival area of the skin flap was measured 7 days after injection, contents of malondialdehyde (MDA) and nitric oxide (NO) were tested 5 days after injection, and the flaps were harvested 4 and 7 days after injection to receive histology and immunohistochemistry observation, neutrophil (NEU) counting and VEGF scoring.
Results: All rabbits survived to the end of the experiment except 3 rabbits (1 rabbit per group) dying from anesthesia overdose. After operation the distal edge of flap in each group all demonstrated different degrees of darkening and hardening, especially group C, and no exudation was observed. Skin temperature of the flaps was close to that of normal skin 3 days after injection. The survival area of the skin flap 7 days after injection was (13.71 +/- 2.91) cm in group A, (12.80 +/- 1.99) cm2 in group B, and (10.12 +/- 1.43) cm2 in group C; at 5 days after injection, the MDA content was (4.02 +/- 0.85) nmol/mL in group A, (3.99 +/- 0.77) nmol/mL in group B, and (4.89 +/- 0.75) nmol/mL in group C, and the NO content was (89.36 +/- 14.82) micromol/L in group A, (88.37 +/- 24.81) micromol/L in group B, and (65.78 +/- 19.04) micromol/L in group C. Significant difference was evident when comparing group A or B with group C in terms of the above parameters (P < 0.05), and no significant difference was noted between group A and group B (P > 0.05). The NEU counts 4 days after injection were (18.20 +/- 6.24) cells/HP in group A, (21.27 +/- 5.34) cells/HP in group B, and (28.78 +/- 7.92) cells/HP in group C, and at 7 days after injection, there were (15.16 +/- 7.02) cells/HP in group A, (18.12 +/- 6.44) cells/HP in group B, and (29.67 +/- 9.12) cells/HP in group C. The VEGF score 4 days after injection was (4.02 +/- 0.48) points in group A, (4.19 +/- 0.66) points in group B and (3.67 +/- 0.49) points in group C, and at 7 day after injection, it was (4.96 +/- 0.69) points in group A, (5.12 +/- 0.77) points in group B, and (3.81 +/- 0.54) points in group C. Significant difference was evident between 4 days and 7 days after injection in group A or B in terms of NEU counts and VEGF score (P < 0.05), and difference between 4 days and 7 days after injection in group C was not significant (P > 0.05), and the differences among 3 groups were significant (P < 0.05).
Conclusion: Estrogen injection can increase VEGF expression and NO content of flap, decrease MDA content and NEU infiltration of flat, and improve survival area of flap.