Study on the preservation effects of the amputated forelimb by machine perfusion at physiological temperature.

PURPOSE: Ischemia and hypoxia are the main factors limiting limb replantation and transplantation. Static cold storage (SCS), a common preservation method for tissues and organs, can only prolong limb ischemia time to 4 - 6 h. The normothermic machine perfusion (NMP) is a promising method for the preservation of tissues and organs, which can extend the preservation time in vitro by providing continuous oxygen and nutrients. This study aimed to evaluate the difference in the efficacy of the 2 limb preservation methods. METHODS: The 6 forelimbs from beagle dogs were divided into 2 groups. In the SCS group (n = 3), the limbs were preserved in a sterile refrigerator at 4 °C for 24 h, and in the NMP group (n = 3), the perfusate prepared with autologous blood was used for the oxygenated machine perfusion at physiological temperature for 24 h, and the solution was changed every 6 h. The effects of limb storage were evaluated by weight gain, perfusate biochemical analysis, enzyme-linked immunosorbent assay, and histological analysis. All statistical analyses and graphs were performed using GraphPad Prism 9.0 one-way or two-way analysis of variance. The p value of less than 0.05 was considered to indicate statistical significance. RESULTS: In the NMP group, the weight gained percentage was 11.72% ± 4.06%; the hypoxia-inducible factor-1α contents showed no significant changes; the shape of muscle fibers was normal; the gap between muscle fibers slightly increased, showing the intercellular distance of (30.19 ± 2.83) µm; and the vascular α-smooth muscle actin (α-SMA) contents were lower than those in the normal blood vessels. The creatine kinase level in the perfusate of the NMP group increased from the beginning of perfusion, decreased after each perfusate change, and remained stable at the end of perfusion showing a peak level of 4097.6 U/L. The lactate dehydrogenase level of the NMP group increased near the end of perfusion and reached the peak level of 374.4 U/L. In the SCS group, the percentage of weight gain was 0.18% ± 0.10%, and the contents of hypoxia-inducible factor-1α increased gradually and reached the maximum level of (164.85 ± 20.75) pg/mL at the end of the experiment. The muscle fibers lost their normal shape and the gap between muscle fibers increased, showing an intercellular distance of (41.66 ± 5.38) µm. The contents of vascular α-SMA were much lower in the SCS group as compared to normal blood vessels. CONCLUSIONS: NMP caused lesser muscle damage and contained more vascular α-SMA as compared to SCS. This study demonstrated that NMP of the amputated limb with perfusate solution based on autologous blood could maintain the physiological activities of the limb for at least 24 h.

Induced pluripotent stem cell-derived mesenchymal stem cells enhance acellular nerve allografts to promote peripheral nerve regeneration by facilitating angiogenesis.

Previous research has demonstrated the feasibility of repairing nerve defects through acellular allogeneic nerve grafting with bone marrow mesenchymal stem cells. However, adult tissue-derived mesenchymal stem cells encounter various obstacles, including limited tissue sources, invasive acquisition methods, cellular heterogeneity, purification challenges, cellular senescence, and diminished pluripotency and proliferation over successive passages. In this study, we used induced pluripotent stem cell-derived mesenchymal stem cells, known for their self-renewal capacity, multilineage differentiation potential, and immunomodulatory characteristics. We used induced pluripotent stem cell-derived mesenchymal stem cells in conjunction with acellular nerve allografts to address a 10 mm-long defect in a rat model of sciatic nerve injury. Our findings reveal that induced pluripotent stem cell-derived mesenchymal stem cells exhibit survival for up to 17 days in a rat model of peripheral nerve injury with acellular nerve allograft transplantation. Furthermore, the combination of acellular nerve allograft and induced pluripotent stem cell-derived mesenchymal stem cells significantly accelerates the regeneration of injured axons and improves behavioral function recovery in rats. Additionally, our in vivo and in vitro experiments indicate that induced pluripotent stem cell-derived mesenchymal stem cells play a pivotal role in promoting neovascularization. Collectively, our results suggest the potential of acellular nerve allografts with induced pluripotent stem cell-derived mesenchymal stem cells to augment nerve regeneration in rats, offering promising therapeutic strategies for clinical translation.