Objective

2

To establish a rat model of diabetic wound by feeding on a high-fat and high-sugar diet combined with intraperitoneal injection of streptozotocin （STZ） and surgical preparation of full-thickness skin defects， observe the effect of cinnamaldehyde on the wound healing of diabetes rats， and explore the therapeutic mechanism of cinnamaldehyde in improving wound healing of diabetes rats based on the PTEN-induced putative kinase （PINK1）/Parkin pathway-mediated mitochondrial autophagy.

Method

2

Forty-eight male SD rats were randomly divided into blank group （

n

=12） and diabetes group （

n

=36）. The diabetes group was further randomly divided into model group， cinnamaldehyde group， and Beifuxin group， with 12 rats in each group. The blank group and the model group received routine disinfection with physiological saline after creating the wounds， while the cinnamaldehyde group received topical application of polyethylene glycol 400 （PEG 400） gel containing 4 μmol·L

-1

cinnamaldehyde， and the Beifuxin group received topical application of Beifuxin gel. Dressings were changed once daily. The wound healing rate of each group was observed. On the 7th and 14th days after intervention， the wound tissues of the rats were collected. Hematoxylin and eosin （HE） staining was performed to observe the pathological changes in the local tissues. Immunohistochemistry （IHC） was used to detect the expression of interleukin-6 （IL-6）， tumor necrosis factor-

α

（TNF-

α

）， vascular endothelial growth factor （VEGF）， and collagen fibers. Immunofluorescence （IF） and Real-time polymerase chain reaction （Real-time PCR） were used to detect the protein， and mRNA expression of PINK1， Parkin， microtubule-associated protein 1 light chain 3 Ⅱ （LC3 Ⅱ）.

Result

2

After intraperitoneal injection of STZ， compared with the blank group， the random blood glucose values of rats in the diabetic group increased significantly （

P

<

0.01）， all higher than 16.7 mmol·L

-1

， and persistently hyperglycemic for some time after modeling. Compared with the blank group， the model group showed poor growth and healing of granulation tissue in the wounds， and the wound healing rate decreased （

P

<

0.01）. On the 7

th

day after intervention， the blank group had squamous epithelial coverage on the wounds. Compared with the blank group， the model group only had a small amount of scab at the wound edges， with a large number of infiltrating inflammatory cells in the wounds. The protein expression levels of IL-6 and TNF-

α

in the tissues increased （

P

<

0.01）， and the protein and mRNA levels of PINK1， Parkin， and LC3Ⅱ decreased （

P

<

0.01）. On the 14

th

day after the intervention， the granulation tissue in the wounds of the blank group was mature and well-healed. Compared with the blank group， the model group still had infiltrating inflammatory cells and red blood cell exudation. The protein expression levels of VEGF and collagen fibers in the tissues decreased （

P

<

0.01）， and the protein and mRNA expression levels of PINK1， Parkin， and LC3Ⅱ increased （

P

<

0.01）. Compared with the model group， the cinnamaldehyde group and the Beifuxin group showed better wound healing， with increased wound healing rates （

P

<

0.01）. On the 7th day after intervention， the protein expression levels of IL-6 and TNF-

α

in the tissues decreased （

P

<

0.01）， and the protein and mRNA expression levels of PINK1， Parkin， and LC3Ⅱ increased （

P

<

0.01）. On the 14th day after intervention， the protein expression levels of VEGF and collagen fibers in the tissues increased （

P

<

0.01）， and the protein and mRNA expression levels of PINK1， Parkin， and LC3Ⅱ decreased （

P

<

0.01）.

Conclusion

2

Cinnamaldehyde can promote the wound healing of diabetes rats by increasing the wound healing rate， reducing the levels of inflammatory factors IL-6 and TNF-

α

， and increasing the levels of VEGF and collagen fibers. Its mechanism may be related to the regulation of the PINK1/Parkin signaling pathway， activation of mitochondrial autophagy， inhibition of inflammatory responses， and promotion of angiogenesis and collagen synthesis， thereby promoting the wound healing of diabetes rats.