Who is who after spinal cord injury and repair? Can the brain stem descending motor pathways take control of skilled hand motor function?

Over the last years,anatomical,electrophysiological and genetic studies have carefully dissected the pathways connecting the brain and the spinal cord.Lawrence and Kuypers（1968）described the organization of the descending motor pathways in the non-human primate spinal cord.Although there are some differences between species regarding the precise anatomical location of each spinal pathway and the selective connectivity onto spinal interneurons and motoneurons, the pattern of organization described is con- served among the mammalian spinal cord （Courtine et al., 2007）. Based on their description, the major descending motor pathways are grouped depending on their anatomical origin and their termi- nal distribution pattern in the spinal grey matter. The motor cortex projects corticospinal axons to the spinal cord, which mostly run in the contralateral cord and innervate the mid and dorsal grey matter neurons.

Engineering of Reversible Luminescent Probes for Real-Time Intravital Imaging of Liver Injury and Repair

As the major organ for drug metabolism and detoxification,the liver is prone to damage and severely impaired functionality.The treatment of liver diseases is based on a clear understanding of the process underlying liver injury and repair.However,intravital real-time imaging of liver injury and repair is still limited due to the lack of in vivo reversible visualization methods.To this end,we proposed a rational design strategy for the development of a reversible upconversion luminescence nanoprobe that allows real-time and in vivo imaging of liver injury and repair processes.As a proof of concept,we first developed a small molecule probe NB3 which can reversibly respond to related analytes of early liver injury[peroxynitrite(ONOO−)]and liver repair[glutathione(GSH)].The small molecule probe was then integrated with a core–shell upconversion nanoparticle to form a sophisticated nanoprobe.Compared with traditional small molecule probes,this nanoprobe exhibited a higher selectivity to ONOO−,longer retention time in liver,and wider dynamic response range to GSH after oxidation by ONOO−.The novel nanoprobe facilitated the successful monitoring and discrimination among the different degrees of liver injury and repair in a mouse model.

Acetyl-11-keto-beta-boswellic acid promotes sciatic nerve repair after injury: molecular mechanism

Previous studies showed that acetyl-11-keto-beta-boswellic acid(AKBA),the active ingredient in the natural Chinese medicine Boswellia,can stimulate sciatic nerve injury repair via promoting Schwann cell proliferation.However,the underlying molecular mechanism remains poorly understood.In this study,we performed genomic sequencing in a rat model of sciatic nerve crush injury after gastric AKBA administration for 30 days.We found that the phagosome pathway was related to AKBA treatment,and brain-derived neurotrophic factor expression in the neurotrophic factor signaling pathway was also highly up-regulated.We further investigated gene and protein expression changes in the phagosome pathway and neurotrophic factor signaling pathway.Myeloperoxidase expression in the phagosome pathway was markedly decreased,and brain-derived neurotrophic factor,nerve growth factor,and nerve growth factor receptor expression levels in the neurotrophic factor signaling pathway were greatly increased.Additionally,expression levels of the inflammatory factors CD68,interleukin-1β,pro-interleukin-1β,and tumor necrosis factor-αwere also decreased.Myelin basic protein-andβ3-tubulin-positive expression as well as the axon diameter-to-total nerve diameter ratio in the injured sciatic nerve were also increased.These findings suggest that,at the molecular level,AKBA can increase neurotrophic factor expression through inhibiting myeloperoxidase expression and reducing inflammatory reactions,which could promote myelin sheath and axon regeneration in the injured sciatic nerve.

The longitudinal epineural incision and complete nerve transection method for modeling sciatic nerve injury

Injury severity, operative technique and nerve regeneration are important factors to consider when constructing a model of peripheral nerve injury. Here, we present a novel peripheral nerve injury model and compare it with the complete sciatic nerve transection method. In the experimental group, under a microscope, a 3-mm longitudinal incision was made in the epineurium of the sciatic nerve to reveal the nerve fibers, which were then transected. The small, longitudinal incision in the epineurium was then sutured closed, requiring no stump anastomosis. In the control group, the sciatic nerve was completely transected, and the epineurium was repaired by anastomosis. At 2 and 4 weeks after surgery, Wallerian degeneration was observed in both groups. In the experimental group, at 8 and 12 weeks after surgery, distinct medullary nerve fibers and axons were observed in the injured sciatic nerve. Regular, dense myelin sheaths were visible, as well as some scarring. By 12 weeks, the myelin sheaths were normal and intact, and a tight lamellar structure was observed. Functionally, limb movement and nerve conduction recovered in the injured region between 4 and 12 weeks. The present results demonstrate that longitudinal epineural incision with nerve transection can stably replicate a model of Sunderland grade IV peripheral nerve injury. Compared with the complete sciatic nerve transection model, our method reduced the difficulties of micromanipulation and surgery time, and resulted in good stump restoration, nerve regeneration, and functional recovery.

Urine-derived stem/progenitor cells:A focus on their characterization and potential

Cell therapy,i.e.,the use of cells to repair an affected tissue or organ,is at the forefront of regenerative and personalized medicine.Among the multiple cell types that have been used for this purpose[including adult stem cells such as mesenchymal stem cells or pluripotent stem cells],urine-derived stem cells(USCs)have aroused interest in the past years.USCs display classical features of mesenchymal stem cells such as differentiation capacity and immunomodulation.Importantly,they have the main advantage of being isolable from one sample of voided urine with a cheap and unpainful procedure,which is broadly applicable,whereas most adult stem cell types require invasive procedure.Moreover,USCs can be differentiated into renal cell types.This is of high interest for renal cell therapy-based regenerative approaches.This review will firstly describe the isolation and characterization of USCs.We will specifically present USC phenotype,which is not an object of consensus in the literature,as well as detail their differentiation capacity.In the second part of this review,we will present and discuss the main applications of USCs.These include use as a substrate to generate human induced pluripotent stem cells,but we will deeply focus on the use of USCs for cell therapy approaches with a detailed analysis depending on the targeted organ or system.Importantly,we will also focus on the applications that rely on the use of USC-derived products such as microvesicles including exosomes,which is a strategy being increasingly employed.In the last section,we will discuss the remaining barriers and challenges in the field of USC-based regenerative medicine.

Biomaterials for spinal cord repair

Spinal cord injury （SCI） results in permanent loss of function leading to often devastating personal, economic and social problems. A contributing factor to the permanence of SCI is that damaged axons do not regenerate, which prevents the re-establishment of axonal circuits involved in function. Many groups are working to develop treatments that address the lack of axon regeneration after SCI. The emergence of biomaterials for regeneration and increased collaboration between engineers, basic and translational scientists, and clinicians hold promise for the development of effective therapies for SCI. A plethora of biomaterials is available and has been tested in various models of SCI. Considering the clinical relevance of contusion injuries, we primarily focus on polymers that meet the specific criteria for addressing this type of injury. Biomaterials may provide structural support and/or serve as a delivery vehicle for factors to arrest growth inhibition and promote axonal growth. Designing materials to address the specific needs of the damaged central nervous system is crucial and possible with current technology. Here, we review the most prominent materials, their optimal characteristics, and their potential roles in repairing and regenerating damaged axons following SCI.