Wounds are defined as the disruption or interruption of the normal anatomical structure and functional continuity of tissue (Farahani and Shafiee, 2021). Wound healing is an important physiological process of self-repair and regeneration after injury, which includes three consecutive and overlapping stages: hemostasis/inflammation, proliferation, and remodeling (Kim and Nair, 2019). The destruction of normal wound healing will lead to the formation of refractory ulcer, whereas excessive healing will lead to the formation of keloid, which seriously damages the appearance and normal function of the human body and increases the economic and medical burden of the society and country (Wang et al., 2018; Subramaniam et al., 2021). Therefore, effective wound management and treatment are important. Vitamin K, a fat-soluble vitamin, is an essential cofactor of γ-glutamyl carboxylase, which is involved in the catalytic carboxylation of specific glutamic acid residues. Vitamin K primarily includes vitamin K1 (phylloquinone), vitamin K2 (menaquinones), vitamin K3 (menadione), and other forms, among which the former two are natural forms, whereas the latter is synthetic (Halder et al., 2019). Vitamin K is commonly used in the treatment of various diseases, including vascular calcification, osteoporosis, diabetes, and liver cancer, because of its pro-coagulant, anti-inflammatory, antioxidant, and other pharmacological effects (Anwar et al., 2019; Fusaro et al., 2020; Shioi et al., 2020; Popa et al., 2021). In addition, vitamin K plays an important role in wound healing (Pazyar et al., 2019). Considering the lack of comprehensive quantitative analyses of the effect of vitamin K on wound healing, we reviewed relevant in vivo and in vitro studies to evaluate the effect of vitamin K on wound healing and provide insights into clinical treatment and new drug development.

We used PRISMA 2020 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and AMSTAR 2 as guidelines for selecting relevant studies and assessing the methodological quality of systematic reviews (Page et al., 2021).

This study is a systematic compilation of the existing literature on the efficacy of vitamin K for wound healing. Through comprehensive and systematic search of literature and strict screening, we obtained six articles (16 qualified studies) in total. We divided these studies into the animal group, cell group, and clinical group. The animal group includes rat and mouse models. Only one article is found in mouse model and clinical test; thus, comprehensive quantitative analysis cannot be carried out. This study only summarizes the research results of the rat model and cell test. The intervention method used vitamin K to cure wound, and it was compared with PBS, conventional medicine, or blank group. The meta-analysis results of the animal model group suggested that vitamin K may improve the wound healing rate. However, the cell group showed opposite summary analysis results, which may be due to the small number of included studies, the quality of the literature, and the high heterogeneity. The heterogeneity of rat models is significant, with I² of 98% (p < 0.00001), probably because only six studies were included in this group. Four studies conducted by Hemmati et al. (2014) explored the effect of Eucerin ointment containing 1% vitamin K1 or 2% vitamin K1 on wound contraction rate relative to Eucerin ointment or Eucerin ointment containing 1% phenytoin. The difference in vitamin K concentration and control group may also be the source of high heterogeneity. In addition, the different forms and adjuvants of vitamin K will cause high heterogeneity. In the two studies conducted by Kandhasamy et al. (2021), vitamin K was brought into silk fibroin electrospun fibers and compared with silk fibroin electrospun fibers and PBS. In these studies, the strain and body weight of rats may also cause heterogeneity. However, regardless of the study excluded, the overall results have not changed in direction, which shows that the summarized results are reliable. In view of the high heterogeneity of the rat model, we conducted a subgroup analysis. Among the four studies conducted by Hemmati et al. (2014), 1% vitamin K studies has the most significant effect. In order to compare the effect of vitamin K on wound healing, an common drug is better to use as an control group, the study of Hemmati et al. (2014) 3) with Euserine ointment containing 1% phenytoin and Kandhasamy et al. (2021) 1) with silk fibroin electrospun fiber are selected to subgroup analysis. The result indicates that, vitamin K treatment was associated with an increased wound healing rate [WMD = 20.11 (95% CI: 16.71, 23.52)]. The heterogeneity of the combined results was very low (I² = 0%, p = 0.69). The overall effect test (Z) was 11.58 (p < 0.00001). This suggests that vitamin K may be related to promoting wound healing rate, and the concentration of vitamin K and control group’s differences may be the main cause of heterogeneity. The heterogeneity of cell experiments is also significant (I² = 99%, p < 0.00001). After removing each study in turn, significant heterogeneity is still observed, which may be related to the types of cells, different control groups, vitamin K concentrations, and forms. The limited number of included studies is also the main source of heterogeneity. The two studies conducted by Rush et al. (2016) selected human telomerase-immortalized corneal epithelial cells. The intervention group used different concentrations of vitamins and receptor tyrosine kinase inhibitors, and the receptor tyrosine kinase inhibitor group was set as the control, the treatment time of vitamin K is 4.5 h. However, the four studies conducted by Pinilla et al. (2014) selected human connective fibroblasts to explore the effect of different concentrations of vitamin K on wound healing, the treatment time of vitamin K is 18 h. The results showed no difference between the 1 mg/L vitamin K3 group and the control group, whereas vitamin K3 significantly reduced the speed of wound healing at 2, 4, and 6 mg/L. Excluding two studies of Rush et al. (2016), the result still showed that vitamin K significantly decelerates the process of wound healing; Excluding Pinilla et al.’s four studies (Pinilla et al., 2014), the result shows that vitamin K significantly improves wound healing rate. This suggests that the concentration of vitamin K may have a great impact on the results. In addition, the difference of cell type and treatment time may also be an important reason for different results. Therefore, the opposite summary results of animal models and cell experiments may be due to the difference in vitamin K concentration. The safe dose and concentration of vitamin K is a problem worthy of our attention, which needs more large-scale and high-quality randomized trials for further research. The reasons lead to different results of animal models and cell experiments may be as follows: in fact, there are some unavoidable factors to add the drug consumption in animal models, such as waste during exercises. So, it is very hard to measure the effective doses. While in cell experiments vitamin K is added into the culture and could interact with cells directly. In cell models, although the researchers use the dose of vitamin K which is calculated based on animal experiments, it may be not suitable for cells. In that, the concentration and bioavailability of drugs will be relatively high, which may be harmful to wound healing; the intervention measures of these animal experimental studies are vitamin K, some of them contain adjuncts, such as silk fibroin. The treatment for animal is the drug laid on the surface of wound, but the vitamin K is used as an addition in cultures in cell experiments; There are also some differences between animal experiments models and cell experiments models. Animal experiments used full-thickness skin wound models. The process of wound healing includes hemostasis, inflammation, proliferation and remodeling, which is a complex process requiring coordination of multiple factors (Wilkinson and Hardman, 2020). Vitamin K plays an important role in wound healing in animal models because of its pharmacological effects such as promoting hemostasis, anti-inflammatory, antioxidant, and promoting cell proliferation and differentiation (Simes et al., 2020). The cell experiments modeling method is to use physical methods to create a cell-free area, mainly to explore the role of vitamin K in promoting cell proliferation and migration, which may also be an important reason for the opposite combined results of animal models and cell experiments. The quality of evidence assessed by GRADE approach are not very satisfactory, because there are few studies on this field at present. However, it provides us a potential method to promote wound healing, and we hope that more relevant studies can be published in the future.

The study of Hemmati et al. (2014) and Amaral et al. (2014) reported the wound tensile strength. The combined results suggested that there was no significant difference in wound tensile strength between vitamin K group and control group. These studies also showed high heterogeneity, which may be related to different wound types and control groups. Of course, the small number of included studies is also a very important reason.

Wounds are common worldwide, and its incidence is also increasing rapidly, which causes a heavy burden on medical care and economy. Based on the survey, about 6.5 million chronic wound patients are reported every year in the United States, and the annual cost of chronic wound treatment is more than 25 billion dollars. Post-traumatic repair is complex, and it is affected by many factors, which is also a great challenge for medical workers. At present, antibiotics are primarily used to treat wounds because of the antibacterial and bactericidal properties, but the abuse of antibiotics will also lead to certain side effects and lose good efficacy. Wound healing therapies can be broadly divided into traditional therapies and modern therapies. Traditional therapies include aloe vera, calendula officinalis, honey, propolis, traditional dressings, silver, phenytoin, etc; Modern therapies include modern dressings, bioengineered skin substitutes, grafts, cell/growth factor therapies etc, (Pereira and Bártolo, 2016; Doshi et al., 2021). In recent years, people have found that vitamin K has certain advantages in wound treatment. Hemmati et al. (2014) studied the application of 1% vitamin K1, 2% vitamin K1 and 1% phenytoin in the treatment of wound healing. The results showed that 1% vitamin K1 and 2% vitamin K1 were more effective than 1% phenytoin. In addition, the results of this meta-analysis of animal models also suggest that vitamin K has a certain effect on wound healing. The combination of vitamin K with these traditional and modern therapies may have a greater effect on wound healing, which also gives us an idea to develop a new drug in the future. In addition, the different bioavailability, therapeutic dose and duration of drugs may also have a great impact on the therapeutic effect (Dludla et al., 2022). Relevant studies have shown that MK7, a subtype of vitamin K2, is the most effective in terms of bioavailability and biological effects (Cirilli et al., 2020; Cirilli et al., 2022). Trans MK7 shows a higher ability to carboxylate Gla protein than cis MK7 (Cirilli et al., 2022). This suggests that the type and chemical structure of vitamins are also very important factors. Therefore, more in-depth research is needed to decode the effect of vitamins on wound healing.

The mechanism of vitamin K in the treatment of wound healing can be attributed to a variety of reasons can be attributed to a variety of reasons (Figure 5): vitamin K often exists in the form of vitamin K quinone, which is converted into vitamin K hydroquinone under the action of vitamin K oxidoreductase. Under the action of γ-glutamic acid carboxylase, vitamin K hydroquinone is converted into vitamin K epoxide, and at the same time, inactive glutamic acid residues of coagulation factors (II, VII, IX, X), protein S, and Gas6 is converted into active γ-carboxyglutamic acid. Under the action of vitamin K oxidoreductase, vitamin K epoxide is converted into vitamin K quinone, thereby forming the vitamin K cycle (Schurgers and Spronk, 2014). 1) Activated coagulation factors II, VII, IX, and X provide effective chelating sites for calcium ions, and they can easily combine with negatively charged phospholipid membrane to promote hemostasis (Kaesler et al., 2021). In addition, Gas6 can activate Tyro3, Axl, and Mer (TAM) receptors, which is conducive to platelet aggregation and stability, thereby promoting hemostasis (van der Meer et al., 2014). 2) Protein S and Gas6 can activate TAM receptors to promote cell proliferation, thereby accelerating wound healing (Hafizi and Dahlbäck, 2006; van der Meer et al., 2014). 3) Vitamin K hydroquinone can be used as an effective antioxidant to remove excess active oxygen from damaged parts (Vervoort et al., 1997). 4) Vitamin K can inhibit inhibitor of kappa-B kinase (IKK) α/β phosphorylation to inhibit nuclear factor kappa-B (NF-κB) activation, thereby reducing the expression of IL-6, IL-1β, TNF-α, and other inflammatory factors, which play a role in inhibiting inflammatory response (Li et al., 2018). Vitamin K can also inhibit the expression of IL-1β and IL-18 by inhibiting the assembly and activation of NLRP3 inflammasome, which plays a role in inhibiting inflammatory response (Huang et al., 2020; Zheng et al., 2021). The research of Osman et al. (Osman and Amin, 2020) showed that the combination of vitamin K and Mebootment may promote wound healing by promoting the expression of transforming growth factor β (TGF-β) and platelet-derived growth factor (PDGF). The results of the corneal epithelial injury mouse model test of Rush et al. (2016) show that vitamin K3 can promote corneal epithelial wound healing in vivo. A randomized controlled clinical trial of Pazyar et al. (2019) showed that the wound area of the vitamin K group was significantly reduced on the 4th day after injury compared with the control group, but no significant difference was observed on the 7th day. Furthermore, no significant difference in healing time was found between the two groups.

In this study, we also found that some studies reported other indicators that were not included in the meta-analysis, such as epithelialization time, hydroproline content, growth factors and cell proliferation efficiency, to indicate the effect of vitamin K on wound healing (Table 4). These studies used rats and cells as research objects to test the effect of vitamin K. The research of Ambrożewicz et al. (2019) showed that vitamin K could reduce the adverse effects of hydroxyapatite-based biomaterials and promote the repair of bone damage because of its evident bone-inducing, antioxidant, and anti-inflammatory properties. Another study showed that the increase in wound severity was associated with a decrease in the intake of nutrients such as vitamin K (Wojcik et al., 2011).

This study has also some limitations. First, the number of studies included in this meta-analysis and the number of literatures included in each group are limited. In addition, the heterogeneity is significant, which may have some effects on our results. Second, given the small number of literatures included in each group, we did not conduct a publication bias assessment. Moreover, the form and composition of vitamin K in these study intervention groups are quite different, such as the use of different concentrations of vitamin K and the introduction of biomaterials. Different control groups and treatment time may also affect the results. The current research in this field is preliminary, and it is difficult to draw any conclusion about the use of vitamin K in wound healing. It is hoped that more domestic and foreign scholars can invest more samples in research to explore the effect of vitamin K on wound healing and its safe dose and concentration. With the publication of more studies in this area, more definite results can be provided.

In this meta-analysis, we found that vitamin K may increase wound healing rate in animal models, but opposite results were obtained in cell tests. Therefore, vitamin K has a certain effect on wound healing, but its role remains unknown, which needs to be studied on a larger scale. In addition, the concentration, safe dose, treatment time, type and chemical structure of vitamin K deserve further study.