[Effects of temperature-sensitive hydroxybutyl chitosan hydrogel on wound healing of full-thickness skin defect in...

Objective: To investigate the effects of temperature-sensitive hydroxybutyl chitosan hydrogel on wound healing of full-thickness skin defect in rats. Methods: The experimental research method was used. Fifty-one no matter male or female Sprague-Dawley rats aged 7-10 weeks were selected, and two round full-thickness skin defect wounds with a diameter of 2 cm were created on the back of each rat at a distance about 1.0 cm to the spine. The rats were divided into temperature-sensitive hydrogel group, gel group, and blank control group according to the random number table, with 17 rats and 34 wounds in each group. Wounds of rats in the first two groups were applied respectively with 0.3 mL temperature-sensitive hydroxybutyl chitosan hydrogel and carboxymethyl chitosan hydrogel immediately after injury, and the wounds of rats in blank control group received no treatment. The wounds of rats in the three groups were all covered with vaseline oil gauze. The states of temperature-sensitive hydroxybutyl chitosan hydrogel in wounds of rats in temperature-sensitive hydrogel group and carboxymethyl chitosan hydrogel in wounds of rats in gel group were observed every day when the dressings were changed, and the difficulty of vaseline oil gauze removal was recorded. On the 3rd, 7th, 10th, 14th, and 21st day after injury, the wound healing of rats in the three groups was observed and the wound healing rates were calculated. On the 3rd, 7th, 10th, 14th, and 21st day after injury, tissue from 4 wounds of 2 rats in each group was collected for the following observation and detection. The infiltration of inflammatory cells, angiogenesis, and re-epithelialization were observed by hematoxylin eosin staining. The regeneration and remodeling of collagen fibers were observed by Masson staining, and the collagen volume fraction was calculated. The expressions of interleukin-6 (IL-6), transforming growth factor β₁ (TGF-β₁), and matrix metalloproteinase-1 (MMP-1) were detected by enzyme-linked immunosorbent assay method. Data were statistically analyzed with analysis of variance for factorial design, one-way analysis of variance, and Bonferroni test. Results: The carboxymethyl chitosan gel in wounds of rats in gel group was liquid gel and could flow with the body position, while the temperature-sensitive hydroxybutyl chitosan hydrogel in wounds of rats in temperature-sensitive hydrogel group was solid gel and could not flow with the body position, and the distribution of the latter was more uniform. The vaseline oil gauzes were easily removed in wounds of rats in temperature-sensitive hydrogel group, while the vaseline oil gauzes were difficult to remove in the other two groups. On the 3rd, 7th, 10th, 14th, and 21st day after injury, the wound granulation tissue of rats grew well in temperature-sensitive hydrogel group and gel group, with no obvious infection, and two rats in blank control group died of wound infection on the 3rd and 5th day after injury. On the 7th, 10th, 14th, and 21st day after injury, the wound healing rates of rats in temperature-sensitive hydrogel group and gel group were significantly higher than that in blank control group (P<0.01). On the 10th day after injury, the wound healing rate of rats in temperature-sensitive hydrogel group was significantly higher than that in gel group (P<0.05). A large number of neutrophils and lymphocytes infiltrated into the wounds of rats in the three groups on the 3rd day after injury. The infiltration of inflammatory cells was gradually reduced and the wound healed gradually in rats of temperature-sensitive hydrogel group and gel group from the 7th to 21st day after injury, and the epidermis and dermis could be seen, without hair follicles and other skin appendages. The wounds of rats in blank control group did not heal completely on 21st day after injury. From the 3rd to 10th day after injury, the newly formed collagen fibers increased gradually in the wounds of rats in the three groups. On the 14th and 21st day after injury, the collagen fibers in the wounds of rats in temperature-sensitive hydrogel group and gel group were denser and more orderly than those in blank control group. On the 10th, 14th, and 21st day after injury, the collagen volume fraction of wounds of rats in temperature-sensitive hydrogel group and gel group was significantly higher than that in blank control group (P<0.01). On the 14th day after injury, the collagen volume fraction of wounds of rats in temperature-sensitive hydrogel group was significantly higher than that in gel group (P<0.01). On the 3rd, 7th, and 10th day after injury, the expressions of IL-6 in wounds of rats in temperature-sensitive hydrogel group were significantly higher than those in gel group and blank control group (P<0.01), and the expressions of IL-6 in wounds of rats in gel group were significantly lower than those in blank control group (P<0.01). On the 3rd, 7th, and 10th day after injury, the expressions of TGF-β₁ in wounds of rats in temperature-sensitive hydrogel group were significantly higher than those in gel group and blank control group (P<0.01). The expressions of TGF-β₁ in wounds of rats in gel group were significantly lower than those in blank control group on the 3rd and 7th day after injury (P<0.01), and the expression of TGF-β₁ in wounds of rats in gel group was significantly higher than that in blank control group on the 10th day after injury (P<0.01). On the 14th day after injury, the expression of TGF-β₁ in wounds of rats in gel group was significantly higher than that in temperature-sensitive hydrogel group and blank control group (P<0.01). On the 21st day after injury, the expression of TGF-β₁ in wounds of rats in temperature-sensitive hydrogel group was significantly lower than that in gel group and blank control group (P<0.01), and the expression of TGF-β₁ in wounds of rats in gel group was significantly lower than that in blank control group (P<0.01). On the 7th day after injury, the expression of MMP-1 in wounds of rats in gel group was significantly higher than that in temperature-sensitive hydrogel group and blank control group (P<0.01). On the 10th, 14th, and 21st day after injury, the expressions of MMP-1 in wounds of rats in temperature-sensitive hydrogel group were significantly higher than those in gel group and blank control group (P<0.01). On the 10th day after injury, the expression of MMP-1 in wounds of rats in gel group was significantly lower than that in blank control group (P<0.01). On the 14th and 21st day after injury, the expressions of MMP-1 in wounds of rats in gel group were significantly higher than those in blank control group (P<0.01). Conclusions: Temperature-sensitive hydroxybutyl chitosan hydrogel can promote the healing of full-thickness skin defect wounds in rats by increasing the expressions of IL-6, TGF-β₁, and MMP-1, regulating the wound healing environment, inhibiting inflammatory reaction, improving the strength of tissue repair, and promoting collagen synthesis or decomposition.