The effect of intravitreal bevacizumab and ranibizumab on cutaneous tensile strength during wound healing

Abstract

Purpose: To investigate the effect of intravitreal bevacizumab and ranibizumab on wound tension and by histopathology during cutaneous wound healing in a rabbit model and to compare this effect to placebo intravitreal saline controls 1 and 2 weeks following intravitreal injection.

Methods: A total of 120 New Zealand white rabbits were randomly assigned to one of three treatment groups each consisting of 40 rabbits. Each group received intravitreal injections of bevacizumab, ranibizumab, or normal saline. Immediately afterwards, each rabbit underwent four 6 mm full-thickness dermatologic punch biopsies. Twenty rabbits from each agent group underwent wound harvesting on day 7 or day 14. The skin samples were stained for CD34 for vascular endothelial cells on day 7, and maximal wound tensile load was measured on days 7 and 14. Quantitative assessment of mean neovascularization (MNV) scores was obtained from 10 contiguous biopsy margin 400× fields of CD34-stained sections by two independent observers.

Results: Wound tension reading means (N) with standard error and adjusted P-values on day 7 were: saline placebos, 7.46 ± 0.87; bevacizumab, 4.50 ± 0.88 (P = 0.041); and ranibizumab, 4.67 ± 0.84 (P = 0.025). On day 14 these were: saline placebos, 7.34 ± 0.55; bevacizumab, 6.05 ± 0.54 (P = 0.18); and ranibizumab 7.99 ± 0.54 (P = 0.40). MNV scores in CD34 stained sections were: saline controls, 18.31 ± 0.43; bevacizumab, 11.02 ± 0.45 (P < 0.0001); and ranibizumab, 13.55 ± 0.43 (P < 0.0001). The interobserver correlation coefficient was 0.928.

Conclusion: At day 7, both anti-vascular endothelial growth factor (anti-VEGF) agents had significantly suppressed MNV scores and exerted a significant reduction of cutaneous wound tensile strength compared with saline controls. At day 14, neither agent produced a significant effect on tensile wound strength. Since angiogenesis is an integral component of the proliferative phase of wound healing, we encourage clinicians to be aware of their patients' recent surgical history during intravitreal anti-VEGF therapy and to consider refraining from their use during the perioperative period.

Keywords: bevacizumab; ranibizumab; tensile strength; wound healing.

Figure 1

To assess the strength of the healing wounds, skin biopsies (30 mm × 80 mm) were harvested from the flanks of the bevacizumab-, ranibizumab-, and saline-treated rabbits 7 or 14 days post wounding (A). Following wound harvesting, the anesthetized rabbits were euthanized by intravenous injection of 3 mL of saturated potassium chloride. Each rectangular-shaped skin biopsy was stored in a 50 mL polypropylene conical tube containing normal saline solution and placed in ice for 2–4 hours until they were cut into dog bone–shaped specimens (gauge length of 2 mm and gauge width of 4 mm) for tensile testing (B). The harvested skin was placed in a position such that the biopsied site was in the center of the gauge length and width. The muscle fascia was removed from each dog bone specimen with a scalpel. Each specimen was then mounted into the grips of a TestResources mechanical tester model 1000R12 (TestResources, Shakopee, MN, USA) with a 50 lbf load cell (C).

Figure 2

Wound tension maximal load means with 95% confidence intervals and treatment group P-values for each group at days 7 and 14. Note: The adjusted P-values are in relation to saline control at each time point. Abbreviations: Bevac, bevacizumab-treated group; Ranib, ranibizumab-treated group; Saline, saline-treated group.

Figure 3

Representative CD34 histological figures of cutaneous wounds 1 week after wounding. At 20×, wound margins are demonstrated (A, C and E). At 400×, note increased numbers of endothelial cells counts in the placebo (about 17) (B) versus bevacizumab (about 11) (D) and ranibizumab (about 12) (F).

Figure 4

CD34 endothelial cell cluster per high power field means with 95% confidence intervals and treatment group P-values for each group at day 7. Abbreviations: NV, neovascularization; Bevac, bevacizumab-treated group; Ranib, ranibizumab-treated group; Saline, saline-treated group.