Protective Effect of Mild Hypothermia on Spinal Cord Ischemia-Induced Delayed Paralysis and Spinal Cord Injury

The future of artificial hibernation medicine: protection of nerves and organs after spinal cord injury

Spinal cord injury is a serious disease of the central nervous system involving irreversible nerve injury and various organ system injuries. At present, no effective clinical treatment exists. As one of the artificial hibernation techniques, mild hypothermia has preliminarily confirmed its clinical effect on spinal cord injury. However, its technical defects and barriers, along with serious clinical side effects, restrict its clinical application for spinal cord injury. Artificial hibernation is a future-oriented disruptive technology for human life support. It involves endogenous hibernation inducers and hibernation-related central neuromodulation that activate particular neurons, reduce the central constant temperature setting point, disrupt the normal constant body temperature, make the body "adapt" to the external cold environment, and reduce the physiological resistance to cold stimulation. Thus, studying the artificial hibernation mechanism may help develop new treatment strategies more suitable for clinical use than the cooling method of mild hypothermia technology. This review introduces artificial hibernation technologies, including mild hypothermia technology, hibernation inducers, and hibernation-related central neuromodulation technology. It summarizes the relevant research on hypothermia and hibernation for organ and nerve protection. These studies show that artificial hibernation technologies have therapeutic significance on nerve injury after spinal cord injury through inflammatory inhibition, immunosuppression, oxidative defense, and possible central protection. It also promotes the repair and protection of respiratory and digestive, cardiovascular, locomotor, urinary, and endocrine systems. This review provides new insights for the clinical treatment of nerve and multiple organ protection after spinal cord injury thanks to artificial hibernation. At present, artificial hibernation technology is not mature, and research faces various challenges. Nevertheless, the effort is worthwhile for the future development of medicine.

Early outcome of simplified total arch reconstruction under mild hypothermia (30-32 °C) with distal aortic perfusion

OBJECTIVE

We designed a simplified total arch reconstruction (s-TAR) technique which could be performed under mild hypothermia (30-32 °C) with distal aortic perfusion. This study aimed to compare its efficacy of organ protection with the conventional total arch reconstruction (c-TAR).

METHODS

We reviewed the clinical data of 195 patients who had ascending aortic aneurysm with extended aortic arch dilation and underwent simultaneous ascending aorta replacement and TAR procedure between January 2018 and December 2022 in our center. 105 received c-TAR under moderate hypothermia (25-28 °C) with circulatory arrest (c-TAR group); rest 90 received s-TAR under mild hypothermia (30-32 °C) with distal aortic perfusion (s-TAR group).

RESULTS

The s-TAR group demonstrated shorter CPB time, cross-clamp time and lower body circulatory arrest time compared with the c-TAR group. The 30-day mortality was 2.9% for the c-TAR group and 1.1% for the s-TAR group (P = 0.043). The mean duration of mechanical ventilation was shorter in the s-TAR group. Paraplegia was observed in 4 of 105 patients (3.8%) in the c-TAR group, while no such events were observed in the s-TAR group. The incidence of temporary neurologic dysfunction was significantly higher in the c-TAR group. The incidence of permanent neurologic dysfunction also showed a tendency to be higher in the c-TAR group, without statistical significance. Furthermore, the incidence of reoperation for bleeding were significantly lower in the s-TAR group. The rate of postoperative hepatic dysfunction and all grades of AKI was remarkably lower in the s-TAR group. The 3-year survival rate was 95.6% in the s-TAR group and 91.4% in the c-TAR group.

CONCLUSIONS

s-TAR under mild hypothermia (30-32℃) with distal aortic perfusion is associated with lower mortality and morbidity, offering better neurological and visceral organ protection compared with c-TAR.

Clemastine in remyelination and protection of neurons and skeletal muscle after spinal cord injury

Spinal cord injuries affect nearly five to ten individuals per million every year. Spinal cord injury causes damage to the nerves, muscles, and the tissue surrounding the spinal cord. Depending on the severity, spinal injuries are linked to degeneration of axons and myelin, resulting in neuronal impairment and skeletal muscle weakness and atrophy. The protection of neurons and promotion of myelin regeneration during spinal cord injury is important for recovery of function following spinal cord injury. Current treatments have little to no effect on spinal cord injury and neurogenic muscle loss. Clemastine, an Food and Drug Administration-approved antihistamine drug, reduces inflammation, protects cells, promotes remyelination, and preserves myelin integrity. Recent clinical evidence suggests that clemastine can decrease the loss of axons after spinal cord injury, stimulating the differentiation of oligodendrocyte progenitor cells into mature oligodendrocytes that are capable of myelination. While clemastine can aid not only in the remyelination and preservation of myelin sheath integrity, it also protects neurons. However, its role in neurogenic muscle loss remains unclear. This review discusses the pathophysiology of spinal cord injury, and the role of clemastine in the protection of neurons, myelin, and axons as well as attenuation of skeletal muscle loss following spinal cord injury.

TAZ Induces Migration of Microglia and Promotes Neurological Recovery After Spinal Cord Injury

Following spinal cord injury (SCI), microglia gradually migrate to the edge of the lesion, interweaving around the border of the lesion to form the microglial scar, which performs inflammatory limiting and neuroprotective functions. Recent reports showed that Yes-associated protein (YAP) was expressed in astrocytes and promoted the formation of astrocytic scars, while YAP was not expressed in microglia after SCI. YAP and its paralogue transcriptional coactivator with PDZ-binding motif (TAZ) are transcriptional coactivators, which have a similar functional role as both are negatively regulated by the Hippo signalling pathway. However, the expression and function of TAZ after SCI are unclear. Our research group previously found that Fascin-1 was highly expressed in microglia and promoted migration of microglia after SCI, and that, there was a close regulatory relationship between Fascin-1 and YAP/TAZ. In this study, we demonstrated that TAZ was significantly upregulated and mainly expressed in microglia after SCI, and accumulated in the nuclei of microglia in the spinal cord at 14 days post-SCI. Moreover, TAZ was upregulated and accumulated in the nuclei of anti-inflammatory M2-like (M2-L) polarized or myelin-treated microglia. Additionally, XMU-MP-1 (an inhibitor of the Hippo kinase MST1/2 to active TAZ) promoted the aggregation of microglia around the lesion core, resulting in the formation of microglial scars and the functional recovery of mice after SCI. Our findings also indicated that TAZ promoted microglial migration in vitro. Mechanistically, Fascin-1 interacted with TAZ, which upregulated TAZ expression and induced TAZ nuclear accumulation in microglia to promote microglial migration. These findings revealed that TAZ mediated microglial migration to the edge of the lesion core, promoting the formation of microglial scars and functional recovery after SCI. Moreover, TAZ was downstream of Fascin-1, which positively regulated microglial migration after SCI.