The Effect of Spirulina Extract on the Healing of Skin Wounds in Adult Albino Rats: A Light and Scanning Electron Microscopic Study

Abstract

Aim of the Work: Wounds are common in clinical practice. Spirulina is analga, consumed as a dietary supplement and it is well known as apotent antioxidant. Therefore, the aim of this study was to determine the effect of topical application of spirulina extract on the healing process in a rat model of excisional skin wound. Material and Methods: Seventy two adult male albino rats weighing 180200-g were used. An excisional skin wound of 2 cm diameter was performed on their mid-back. The animals were divided into four groups (18 rats per group): group I (untreated control group), group II (xanthan gum treated group); this gum was used as vehicle for spirulina.Group III(carboxymethyl cellulose (CMC) treated group) which was the reference group and group IV (spirulina treated group). In II, III and IVgroups the material (0.2ml) was topically applied twice daily. The rats of all groups were sacrificed on day 3, 7 and 12 post-wounding (6 rats per day). Specimens from the site of the wound and 2 mm of adjacent normal skin were collected. Some of them werefixed in 10% neutral formalin for preparation of paraffin sectionswhich were stained with hematoxylin and eosin and Mallory's trichrome. Other specimens were fixed immediately in 2.5% glutaraldehyde and processed for scanning electron microscopic examination (SEM). Morphometric study was performed using image analyzer for the following parameters: counting the number of newly formed blood vessels, macrophages and fibroblasts and also calculating area % of collagen fibers deposition. Statistical analysis was done using ANOVA test. Results: Thehistological findings of xanthan gum group were similar to those of the control group on day 3, 7 and 12 post-wounding.On day 3 post-wounding the epidermis at the wound area was absent in all groups, but spirulina treated group showed beginning of re-epithelialization.Few inflammatory cells were detectedin the granulation tissuein the spirulina treated group while heavy inflammatory infiltrate was observed in control and CMC treated groups. On day 7 post-wounding the epidermis of the spirulina treated group showed mature differentiation and was regularly arranged in four layers unlike the immature differentiation of other groups. On day 12 post-woundingthe spirulina treatedgroup showed that the wound area was bridged by the newly formed thick epidermis with complete re-epithelializationand appearance of skin appendages (hair follicles) in contrary to other groups. In the granulation tissue the image analysis for the spirulina treated group showed a highly statisticalsignificant increase in the number of newly formed blood vessels, and fibroblastson day 3 and 7post-wounding and decrease on day 12 post-wounding. The macrophages count showed highly statistical significant increase in spirulina treated group only on day 3 post-wounding .In spirulina treated group, Mallory's trichrome stained sections on day7 and 12 post-wounding revealedregular collagen fibers aligned horizontally with high statistically significant increase in area % of collagen fibers deposition. SEM revealed thatthe collagen fibers were discriminated as three zones (sub-epithelial, middle and deep) in spirulina treated group on day 7 and12 post-wounding. These zones were only observed on day12 post-wounding in control and CMC treated groups. Conclusion: Spirulina extract significantly promoted the rate of skin wound closure. It enhanced re-epithelialization and improved the neovascularization process at the wound site. It also augmented fibroblast proliferation and collagen synthesis as well as proliferation of hair follicles; in contrast to CMC treated group and the control group.