Elsevier

Surgery

Volume 132, Issue 5, November 2002, Pages 866-876
Surgery

Original Communications
Characterization of incisional wound healing in inducible nitric oxide synthase knockout mice*,**

https://doi.org/10.1067/msy.2002.127422Get rights and content

Abstract

Background. Excisional wound healing in inducible nitric oxide synthase knockout (iNOS-KO) mice has been previously shown to be impaired compared with their background strain controls. Incisional wounds were created in this experiment in both types of animals and paradoxically were found to heal with the same rapidity and breaking strength in both groups. Methods. Dorsal 2.5 cm incisional wounds were created in iNOS-KO mice, as well as their parental strain controls (C57BL/6J). Standardized polyvinyl alcohol sponges were implanted in the wounds to allow for measurement of collagen deposition. Animals were harvested on postoperative days (PODs) 3, 5, 7, 10, 14, and 28, and their wounds subjected to tensiometric breaking strength analysis. Nonisotopic in situ hybridization quantitative analysis for iNOS, endothelial NOS (eNOS), basic fibroblast growth factor (bFGF), transforming growth factor-β1 (TGF-β1), vascular endothelial growth factor (VEGF), and interleukin-4 (IL-4) expression in the wounds was performed. Hydroxyproline levels were quantitated in the harvested polyvinyl alcohol sponges. Data were analyzed with the Students t test. Results. No significant differences were found in breaking strengths or levels of hydroxyproline (and thus collagen) in iNOS-KO versus wild-type wounds at all tested time points. Flawed iNOS expression levels in iNOS-KO animals were similar to (functional) iNOS expression in wild-types. eNOS and bFGF expression nearly doubled on POD 7 in iNOS-KO incisions (P =.002, and.002), respectively and remained 200% to 300% elevated thereafter. TGF-β1 expression was increased approximately 50% to 100% in iNOS-KO wounds on PODs 5 and 7 (P =.006 and.01, respectively). VEGF and IL-4 expression was elevated by 25% to 100% in wild-type compared with iNOS-KO animals at all time points (P <.01). Conclusions. The overexpression of TGF-β1 and eNOS may represent mechanisms in iNOS-KO mice to compensate for their loss of functional iNOS, resulting in incisional wound healing equivalent to controls. Their impaired expression of VEGF and IL-4, on the other hand, may partially explain the delayed excisional wound healing noted in these animals. (Surgery 2002;132:866-76.)

Section snippets

Animals

Male, 8- to 10-week-old C57BL/6J mice (the parental background strain) were obtained from a commercial breeder (Jackson Labs, Bar Harbor, Me). Inducible nitric oxide synthase knockout (iNOS-KO) mice were obtained from an established breeding colony at the Surgical Research Laboratory of the Sinai Hospital of Baltimore. The original breeding pairs (homozygous for the iNOS-KO trait, background strain C57BL/6J) were obtained commercially (Jackson Labs) and were of the same background strain as the

Wound breaking strength

Early in the wound healing process (post-wounding day 7), breaking strengths for iNOS-KO wounds were not statistically significantly different from wild-type wounds (78.6 ± 9.2 g vs 80.7 ± 5.1 g, respectively; P =.844; Fig 1).

. Wound breaking strengths. The x-axis represents experimental groups. The y-axis represents grams of force needed to rupture the wound segment. Data are denoted as means ± standard errors of the means (SEM).

Similarly, middle-stage wounds demonstrated no statistically

Discussion

Incisional wounds undergo a more rapid epithelialization than excisional wounds, due to the much smaller surface area of the former. Injured dermis in the adult organism does not regenerate, but is instead replaced by scar tissue. Again, due to the smaller surface area of incisional wounds, a smaller volume of scar tissue is produced in response to incising rather than excising skin.19

Incisional wound healing in iNOS-KO mice, as measured by breaking strength, was not significantly different

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    *

    Supported by grant # GM54566 (A.B.) from the National Institutes of Health.

    **

    Reprint requests: A.B. Surgeon-in-Chief, Department of Surgery, The Sinai Hospital of Baltimore, 2401 W Belvedere Ave, Baltimore, MD 21215.

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