Incision Wound Healing Models Research Articles

Sex Dimorphism in Wound Healing: The Roles of Sex Steroids and Macrophage Migration Inhibitory Factor

That endogenous sex steroid hormones profoundly influence the response to cutaneous injury is well established. How they and other factors combine to direct repair in male and female animals is much less well understood. Using a murine incisional wound-healing model, we investigated the roles of circulating sex steroids, macrophage migration inhibitory factor (MIF) (the mediator of delayed healing in ovariectomized animals), and hormone- and MIF-independent factors in controlling repair. We report that d 3 wounds, of comparable size in intact male and female mice, are significantly larger in ovariectomized female animals than in castrated males, suggesting that native sex hormones mask inherent underlying differences in the ways in which males and females respond to wounding. Wound MIF levels were comparable in intact male and female mice but greater in ovariectomized females than castrated males. Furthermore, wound levels of Jun activation domain-binding protein 1 (JAB1), a key factor by which MIF activates intracellular responses, were increased through ovariectomy and greater in ovariectomized females than castrated males. This difference in wound JAB1 levels may underscore the marked sex difference we observed in the responses of MIF knockout mice to the local application of MIF: healing was impaired in ovariectomized females but not castrated males. Separately, systemic treatment with androgens and estrogens yielded contrasting effects on repair in male and female animals. Collectively, the presented data indicate sex divergence in wound healing to be multifaceted, being strongly influenced by MIF and seemingly limited by the combined actions of gonadal steroids.

Effect of a Low Molecular Weight Heparin Molecule, Dalteparin, on Cellular Apoptosis and Inflammatory Process in an Incisional Wound-Healing Model

In this study we aimed to test the effect of a low molecular weight heparin molecule, namely dalteparin, on the inflammation and cellular apoptosis in an incisional wound-healing model in rats. Eighteen male Sprague-Dawley rats were randomly assigned to three groups (n = 6 for each group). Two full-thickness skin incisions were made over cervical and lumbar regions of all rats. Group 1 (sham group) received no treatment, group 2 (control group) received 0.01 ml/g saline subcutaneously 12 h two times daily from 0 to 10th postoperative day, and group 3 (dalteparin group): received 1 IU/g dalteparin subcutaneously two times daily from 0 to 10th postoperative day. A histological evaluation was done by light microscopy. Apoptosis was detected immunohistochemically by anti-poly (ADP-ribose) polymerase p85 fragment pAb. The early inflammatory response and related tissue edema were depressed on day 3 in the dalteparin group when compared with those in the other groups (P < 0.05). Fibroblast proliferation was also depressed on day 10 in the dalteparin group compared to the others (P < 0.05). Furthermore, increased apoptosis was detected in the dalteparin group both on day 3 and day 10. Our results showed that dalteparin may adversely affect the incisional wound healing by suppressing the early inflammatory process and increasing cellular apoptosis; however, further studies are warranted to confirm the results.

Green Tea Extract and (−)-Epigallocatechin-3-Gallate Inhibit Mast Cell-Stimulated Type I Collagen Expression in Keloid Fibroblasts via Blocking PI-3K/Akt Signaling Pathways

Keloid, a chronic fibro-proliferative disease, exhibits distinctive histological features characterized by an abundant extracellular matrix stroma, a local infiltration of inflammatory cells including mast cells (MCs), and a milieu of enriched cytokines. Previous studies have demonstrated that co-culture with MCs stimulate type I collagen synthesis in fibroblasts, but the signaling mechanisms remain largely unknown. In this study, we investigated the signaling pathways involved in MC-stimulated type I collagen synthesis and the effects of green tea extract (GTE) and its major catechin, (-)-epigallocatechin-3-gallate (EGCG), on collagen homeostasis in keloid fibroblasts. Our results showed that MCs significantly stimulated type I collagen expression in keloid fibroblasts, and the upregulation of type I collagen was significantly attenuated by blockade of phosphatidylinositol-3-kinase (PI-3K), mammalian target of rapamycin (mTOR), and p38 MAPK signaling pathways, but not by blockade of ERK1/2 pathway. Furthermore, GTE and EGCG dramatically inhibited type I collagen production possibly by interfering with the PI-3K/Akt/mTOR signaling pathway. Our findings suggest that interaction between MCs and keloid fibroblasts may contribute to excessive collagen accumulation in keloids and imply a therapeutic potential of green tea for the intervention and prevention of keloids and other fibrotic diseases.

Effects of Epicatechin Gallate on Wound Healing and Scar Formation in a Full Thickness Incisional Wound Healing Model in Rats

Catechins are naturally occurring polyphenolic compounds with putative anti-inflammatory, antioxidant and free radical scavenging effects in vitro. However, their potential effects in vivo have not been established. Therefore we have investigated the effects of the catechin epicatechin gallate (ECG), on scar formation in a full thickness incisional model of wound healing in rats. ECG showed a significant improvement in the quality of scar formation both in terms of maturity and orientation of the collagen fibers. An increase in inducible nitric oxide synthase and cyclooxygenase-2 and a decrease in arginase-I activity and protein levels were observed at earlier time points. In addition, an increase in the number of new blood vessels was observed in the ECG-treated group. This correlated with the protein levels of vascular endothelial growth factor, the most potent angiogenic protein known. This study has therefore demonstrated, for the first time, that catechins, namely ECG, can significantly improve the quality of wound healing and scar formation. These effects may in part be due to an acceleration of the angiogenic response and an up-regulation of the enzymes nitric oxide synthase and cyclooxygenase.

Effects of CO2 insufflation and laparotomy on wound healing in mice.

The aim of the present study was to evaluate the effects of laparotomy and CO2 insufflation on wound healing in a murine incisional wound healing model. Seventy-two male Swiss Albino mice were randomly allocated into three groups of control, laparotomy and CO2 insufflation. A transverse skin incision of 15 mm was made in the dorsum of each mouse, and four interrupted mattress sutures with 4.0 polypropylene thread were laid for wound closure. A median laparotomy was performed in the laparotomy group. CO2 insufflation was performed with an intra-abdominal pressure of 9 mmHg. The retained gas was evacuated from the abdominal cavity at the end of a 60-min period. Mice were killed on the 3rd, 7th and 15th postoperative days. The wound tensile strength and 5-hydroxyproline concentration in the wound tissue were measured. Tensile strength of the incised skin increased as the post-incision period progressed. There was no significant difference between the tensile strengths of the incised skin of control, laparotomy and CO2 insufflation groups throughout the observation period. The skin 5-hydroxyproline concentrations of all groups were not significantly different at the 3rd postoperative day. But laparotomy and CO2 insufflation groups had lower 5-hydroxyproline concentrations at the 7th and 15th postoperative days, when compared to controls (P < 0.02 for 7th and 15th days). CO2 insufflation and laparotomy reduce the 5-hydroxyproline concentration of the wound, suggesting a diminished wound healing capacity.

Keratinocyte Growth Factor-2 Accelerates Wound Healing in Incisional Wounds

Background.Keratinocyte growth factor-2 (KGF-2) also described as fibroblast growth factor-10 (FGF-10) is a newly identified member of the fibroblast growth factor family. KGF-2 is 96% identical to the recently identified rat FGF-10 and specifically stimulates growth of normal human epidermal keratinocytes. The present study was undertaken to examine the effects of topically applied KGF-2 in an incisional wound healing model. KGF-2 treatment resulted in an improvement in incisional wound healing as characterized by an increase in breaking strength, collagen content, and epidermal thickness.Methods.KGF-2 was topically applied to linear incisions made in the dorsal skin of Sprague-Dawley rats. Biomechanical testing was done using an Instron tensiometer for breaking and tensile strength determinations. Wound collagen content was determined using the Sircol collagen assay. Epidermal thickness measurements were conducted using Masson's trichrome-stained sections of the wound.Results.A single topical application of KGF-2 at the time of wounding resulted in an increase in wound breaking and tensile strength at Day 5 after wounding. Breaking strength of KGF-2-treated wounds was significantly higher compared with the buffer control (1 μg, 222.1 ± 13.5 g,P= 0.0007; 4 μg, 248.7 ± 15.4 g,P= 0.0001; 10 μg, 247.2 ± 21.9 g,P= 0.001; buffer, 141.0 ± 9.7 g). Epidermal thickness and wound collagen content were significantly increased following treatment with KGF-2.Conclusions.Based on our findings, KGF-2 is a potent stimulator of wound healing as demonstrated by increased mechanical strength accompanied by an increase in wound collagen content. KGF-2 could be an important cellular mediator responsible for the initiation and acceleration of wound healing and may enhance the healing of surgical wounds.

Aging Is Associated with Reduced Deposition of Specific Extracellular Matrix Components, an Upregulation of Angiogenesis, and an Altered Inflammatory Response in a Murine Incisional Wound Healing Model

The concept that aging impairs wound healing is largely unsubstantiated, the literature being contradictory because of poor experimental design and a failure to adequately characterize animal models. This study tested the hypothesis that aging retards the rate of wound repair using standardized cutaneous incisional wounds in a well-characterized aging mouse colony. Against the background of age-related changes in normal dermal composition, marked differences in healing were observed. Immunostaining for fibronectin was decreased in the wounds of the old mice, with a delay in the inflammatory response, re-epithelialization, and the appearance of extracellular matrix components. Heparan sulfate and blood vessel staining were both unexpectedly increased in the wounds of the old animals at late time points. Despite an overall decrease in collagen I and III deposition in the wounds of old mice, the dermal organization was surprisingly similar to that of normal dermal basket-weave collagen architecture. By contrast, young animals developed abnormal, dense scars. Intriguingly, some of these age-related changes in scar quality and inflammatory cell profile are similar to those seen in fetal wound healing. The rate of healing in young animals appears to be increased at the expense of the scar quality, perhaps resulting from an altered inflammatory response.