The wound healing of deep partial-thickness burn in Bama miniature pigs is accelerated by a higher dose of hUCMSCs

Abstract

Background Deep partial-thickness burns have a significant impact on both the physical and mental health of patients. Our previous study demonstrated human Umbilical Cord Mesenchymal stem cells (hUCMSCs) could enhance the healing of severe burns in small animal burn models, such as rats. Furthermore, our team has developed a deep partial-thickness burn model in Bama miniature pigs, which can be utilized for assessing drug efficacy in preclinical trials for wound healing. Therefore, this study further determine the optimal dosage of hUCMSCs in future clinical practice by comparing the efficacy of low-to-high doses of hUCMSCs on deep partial-thickness burn wounds in Bama miniature pigs. Materials and methods The male Bama miniature pigs (N = 8, weight: 23–28 kg and length: 71–75 cm) were used to establish deep partial-thickness burn models, which were used a continuous pressure of 1 kg and contact times of 35 s by the invented electronic burn instrument at 100℃ to prepare 10 round burn wounds with diameter of 5 cm according to our previous report. And then, 0×10^7, 1×10^7, 2×10^7, 5×10^7 and 1×10^8 doses of hUCMSCs were respectively injected into burn wounds of their corresponding groups. After treatment for 7, 14 and 21 days, the burned wound tissues were obtained for histological evaluation, including Hematoxylin and eosin (HE) for histopathological changes and total inflammatory cells infiltration, immunohistochemistry for neutrophil (MPO+) infiltration and microvessel (CD31+) quantity, and masson staining for collagen deposition. And the levels of lipopolysaccharide (LPS), inflammatory factors TNF-α, IL-1β, IL-10 and angiogenesis factors angiopoietin-2 (Ang-2), vascular endothelial growth factor (VEGF), as well as collagen type-I and type-III of the burned wound tissues were quantified by ELISA. Results All of doses hUCMSCs can significantly increase wound healing rate and shorten healing time of the deep partial-thickness burn pigs in a dose-dependent manner. Furthermore, all of doses hUCMSCs can significantly promote epithelialization and decreased inflammatory reaction of wound, including infiltration of total inflammatory cells and neutrophil, and levels of LPS, and proinflammatory factors TNF- α and IL-1β, while the level of anti-inflammatory factor IL-10 increased compared to the burn group. Meanwhile, the amounts of microvessel, expression of Ang-2 and VEGF were increased in all of doses hUCMSCs group than those in the burn group. Furthermore, the collagen structure was disordered and partially necrotized, and ratios of collagen type-I and type-III were significantly decreased in burn group (4:1 in normal skin tissue), and those of all hUCMSCs groups were significantly improved in a dose-dependent manner. In a word, 1×10^8 dose of hUCMSCs could regenerate the deep partial-thickness burn wounds most efficaciously compared to other dosages and the burn control groups. Conclusion This regenerative cell therapy study using hUCMSCs demonstrates the best efficacy toward a high dose, that is dose of 1×10^8 of hUCMSCs was used as a reference therapeutic dose for treating for 20 cm² deep partial-thickness burns wound in future clinical practice.