Abstract: BACKGROUND: Mesenchymal stem cells-derived exosome and curcumin can enhance the diabetic wound healing. However, the yield of exosome is low, while curcumin has relatively unstable structure and poor solubility, which affects the repair effect. 
OBJECTIVE: To observe the therapeutic effect of the nanocellular vesicles loaded with curcumin for the refractory wounds in diabetic mice. 
METHODS: Primary bone marrow mesenchymal stem cells were harvested from limbs of C57BL/6J suckling mice. Nanocellular vesicles loaded with curcumin were prepared via micro-extrusion mechanism. Encapsulation efficiency and drug loading of vesicles were detected. (1) In vitro, the effect of nanocellular vesicles on fibroblast NIH-3T3 proliferation at different mass concentrations (0, 10, 20, 40, and 80 mg/L) was detected by cell counting method. The effect of nanocellular vesicles (40 mg/L) on fibroblast migration was detected by Transwell assay. The effect of curcumin on tumor necrosis factor α and interleukin-6 mRNA expression were detected in RAW 264.7 macrophages induced by lipopolysaccharide. (2) In vivo, twenty-four adult C57BL/6J mice were taken and injected intraperitoneally with streptozotocin to establish diabetic models. Skin wounds with two 6 mm diameter wounds were produced on the backs of diabetic mice after modeling. Group A was injected with PBS; group B was injected with nanocellular vesicles; and group C was injected with curcumin solution; group D was injected with curcumin-loaded nanocellular vesicles (n=6 per group). The wound healing and histomorphological changes were observed.  
RESULTS AND CONCLUSION: (1) The encapsulation rate of vesicles was 42%, and the drug loading rate was 2.3%. Nanocellular vesicles with different mass concentrations could promote the proliferation of fibroblasts. Of them, the concentration of 40 mg/L had the best proliferation effect. Nanocellular vesicles 40 mg/L promoted the migration of fibroblasts. Curcumin decreased the LPS-stimulated inflammatory response in macrophages. (2) After 14 days of wound modeling, the wounds in groups B, C, and D were significantly reduced, and the wound area in group D was the smallest. Hematoxylin-eosin staining and Masson staining showed that there was a large amount of granulation tissue formation and collagen fiber deposition in groups B, C, and D after 7 days, among which group D had the most. At 14 days after the wound modeling, the granulation tissue formation and collagen fiber deposition in groups B, C, and D further increased, and the changes were most remarkable in group D. (3) These results suggested that the nanocellular vesicles loaded with curcumin showed their synergistic role in promoting diabetic wound healing.

Key words: nanocellular vesicles, curcumin, bone marrow mesenchymal stem cells, synergistic effect, diabetic animal model, fibroblast, wound healing