Secretomes from various cell sources exert strong regenerative activities on numerous organs, including the skin. Although secretomes consist of many diverse components, a growing body of evidence suggests that small extracellular vesicles (EVs) account for their regenerative capacity. We previously demonstrated that the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCs) exhibits wound healing capacity. Therefore, we sought to dissect the molecular composition of EVs present in the secretome and compared wound healing-related activities of these EVs to other subfractions of the secretome and the fully supplemented secretome (MNCaposec). Compared to EVs derived from non-irradiated PBMCs, γ-irradiation significantly increased the size and number and changed the composition of released EVs. Detailed characterization of the molecular components of EVs, i.e. miRNA, proteins, and lipids, derived from irradiated PBMCs revealed a strong association with regenerative processes. Reporter gene assays and aortic ring sprouting assays revealed diminished activity of the subfractions compared to MNCaposec. In addition, we showed that MNCaposec accelerated wound closure in a diabetic mouse model. Taken together, our results suggest that secretome-based wound healing represents a promising new therapeutic avenue, and strongly recommend using the complete secretome instead of purified subfractions, such as EVs, to exploit its full regenerative capacity.

Burn wounds pose a serious threat to patients and often require surgical treatment. Skin grafting aims to achieve wound closure but requires a well-vascularized wound bed. The secretome of peripheral blood mononuclear cells (PBMCs) has been shown to improve wound healing and angiogenesis. We hypothesized that topical application of the PBMC secretome would improve the quality of regenerating skin, increase angiogenesis, and reduce scar formation after burn injury and skin grafting in a porcine model. Full-thickness burn injuries were created on the back of female pigs. Necrotic areas were excised and the wounds were covered with split-thickness mesh skin grafts. Wounds were treated repeatedly with either the secretome of cultured PBMCs (SecPBMC), apoptotic PBMCs (Apo-SecPBMC), or controls. The wounds treated with Apo-SecPBMC had an increased epidermal thickness, higher number of rete ridges, and more advanced epidermal differentiation than controls. The samples treated with Apo-SecPBMC had a two-fold increase in CD31+ cells, indicating more angiogenesis. These data suggest that the repeated application of Apo-SecPBMC significantly improves epidermal thickness, angiogenesis, and skin quality in a porcine model of burn injury and skin grafting.

Based on the results of the present study we suggest that mild hypothermia can be safely performed after stabilization following major trauma. Mild hypothermia has effects on the coagulation system but does not aggravate trauma-induced coagulopathy in our model. Before hypothermic treatment can be performed in the clinical setting, additional experiments with prolonged and deeper hypothermia to exclude detrimental effects are required.

Computerized gait analysis is a common evaluation method in rat models of hind limb nerve injuries, but its use remains unpublished in models of segmental nerve injury of the forelimb. It was the aim of this work to investigate if computerized gait analysis is a feasible evaluation method in a rat model of segmental median nerve injury and autograft repair. Ten male Lewis rats underwent 7-mm resection of the right median nerve with immediate autograft repair. The left median nerve was resected without repair and served as an internal control. Animals were assessed for 12 weeks after surgery via CatWalk (CW) gait analysis every 2 weeks. Evaluation of motor recovery by means of the grasping test was performed weekly while electrophysiological measurements were performed at the end of the observation period. CW data were correlated with grasping strength at each post-operative time point. CW data were also correlated with electrophysiology using linear regression analysis. Principal component analysis was performed to identify clusters of outcome metrics. Recovery of motor function was observable 4 weeks after surgery, but grasping strength was significantly reduced (p < 0.01) compared to baseline values until post-operative week 6. In terms of sensory recovery, the pain-related parameter Duty Cycle showed significant (p < 0.05) recovery starting from post-operative week 8. The Print Area of the right paw was significantly (p < 0.05) increased compared to the left side starting from post-operative week 10. Various parameters of gait correlated significantly (p < 0.05) with mean and maximum grasping strength. However, only Stand Index showed a significant correlation with compound muscle action potential (CMAP) amplitude (p < 0.05). With this work, we prove that computerized gait analysis is a valid and feasible method to evaluate functional recovery after autograft repair of the rat median nerve. We were able to identify parameters such as Print Area, Duty Cycle, and Stand Index, which allow assessment of nerve regeneration. The course of these parameters following nerve resection without repair was also assessed. Additionally, external paw rotation was identified as a valid parameter to evaluate motor reinnervation. In summary, computerized gait analysis is a valuable additional tool to study nerve regeneration in rats with median nerve injury.

Despite the high incidence and prognostic relevance of hemorrhagic shock and abdominal and blunt chest trauma in multiply injured patients, there are no animal models combining these injuries. Therefore, we established a new porcine multiple trauma model consisting of blunt chest trauma, penetrating abdominal trauma (two incisions in the right upper liver lobe using a four-edged scalpel and subsequent liver packing), and pressure-controlled hemorrhagic shock with a mean arterial pressure of 30 ± 5 mmHg (a maximum of 45% of the total blood volume). The combined traumatic insult led to severe signs of hemorrhagic shock and impaired pulmonary function. In conclusion, a consistent, reproducible, and clinically relevant porcine model of multisystem injury with controlled (pressure-controlled blood withdrawal) and uncontrolled components of hemorrhage (liver laceration) with the potential for rebleeding was established.