Xiaoyu Yang

Neurofilament proteins in axonal regeneration and neurodegenerative diseases.

Neurofilament protein is a component of the mature neuronal cytoskeleton, and it interacts with the zygosome, which is mediated by neurofilament-related proteins. Neurofilament protein regulates enzyme function and the structure of linker proteins. In addition, neurofilament gene expression plays an important role in nervous system development. Previous studies have shown that neurofilament gene transcriptional regulation is crucial for neurofilament protein expression, especially in axonal regeneration and degenerative diseases. Post-transcriptional regulation increased neurofilament protein gene transcription during axonal regeneration, ultimately resulting in a pattern of neurofilament protein expression. An expression imbalance of post-transcriptional regulatory proteins and other disorders could lead to amyotrophic lateral sclerosis or other neurodegenerative diseases. These findings indicated that after transcription, neurofilament protein regulated expression of related proteins and promoted regeneration of damaged axons, suggesting that regulation disorders could lead to neurodegenerative diseases.

Comparative proteomics analysis of human osteosarcoma by 2D DIGE with MALDI-TOF/TOF MS

Osteosarcoma (OS) is the most common primary malignant tumor of bone and the third most common cancer in childhood and adolescence. However, controversy concerning the ideal combination of chemotherapy agents ensued throughout the last quarter of the 20th century because of conflicting and often nonrandomized data. Collaborative efforts to increase understanding of the biology of osteosarcoma and the use of preclinical models to test novel protein targets will be critical to identify the path toward improving outcomes for patients. We attempted to identify potential protein markers or therapy targets of osteosarcoma and give a glance at tumorigenesis of osteosarcoma. A sensitive and accurate method was employed in comparative proteomic analysis between benign tumor and osteosarcoma. Tumor tissues obtained by open biopsy before induction chemotherapy were investigated With 2D DIGE and MALDI-TOF/TOF MS, 22 differentially expressed proteins were identified after database searching, including 8 up-regulated and 14 down-regulated proteins. We also validated the expression levels of interesting proteins(have higher Ratios(tumor/normal)) by Western blotting assay. Annotating by bioinformatic tools, we found structural and signal transduction associated proteins were in large percentage among altered level proteins. In particular, some low abundant proteins involving translation and transcription, such as EEF2(Elongation Factor 2), LUM Lumican 23 kDa Protein) and GTF2A2(Transcription Initiation Factor Iia Gamma Chain.), were firstly reported by our study comparing to previous observations. Our findings suggest that these differential proteins may be potential biomarkers for diagnosis or molecules for understanding of osteosarcoma tumorigenesis, coming with biologic, preclinical, and clinical trial efforts being described to improve outcomes for patients.

Factors affecting directional migration of bone marrow mesenchymal stem cells to the injured spinal cord

Microtubule-associated protein 1B plays an important role in axon guidance and neuronal migration. In the present study, we sought to discover the mechanisms underlying microtubule-associated protein 1B mediation of axon guidance and neuronal migration. We exposed bone marrow mesenchymal stem cells to okadaic acid or N-acetyl-D-erythro-sphingosine (an inhibitor and stimulator, respectively, of protein phosphatase 2A) for 24 hours. The expression of the phosphorylated form of type I microtubule-associated protein 1B in the cells was greater after exposure to okadaic acid and lower after N-acetyl-D-erythro-sphingosine. We then injected the bone marrow mesenchymal stem cells through the ear vein into rabbit models of spinal cord contusion. The migration of bone marrow mesenchymal stem cells towards the injured spinal cord was poorer in cells exposed to okadaic acid- and N-acetyl-D-erythro-sphingosine than in non-treated bone marrow mesenchymal stem cells. Finally, we blocked phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase 1/2 (ERK1/2) pathways in rabbit bone marrow mesenchymal stem cells using the inhibitors LY294002 and U0126, respectively. LY294002 resulted in an elevated expression of phosphorylated type I microtubule-associated protein 1B, whereas U0126 caused a reduction in expression. The present data indicate that PI3K and ERK1/2 in bone marrow mesenchymal stem cells modulate the phosphorylation of microtubule-associated protein 1B via a cross-signaling network, and affect the migratory efficiency of bone marrow mesenchymal stem cells towards injured spinal cord.

Puerarin accelerates neural regeneration after sciatic nerve injury

Puerarin is a natural isoflavone isolated from plants of the genus Pueraria and functions as a protector against cerebral ischemia. We hypothesized that puerarin can be involved in the repair of peripheral nerve injuries. To test this hypothesis, doses of 10, 5, or 2.5 mg/kg per day puerarin (8-(β-D-Glucopyranosyl-7-hydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) were injected intraperitoneally into mouse models of sciatic nerve injury. Puerarin at the middle and high doses significantly up-regulated the expression of growth-associated protein 43 in the L4–6 segments of the spinal cord from mice at 1, 2, and 4 weeks after modeling, and reduced the atrophy of the triceps surae on the affected side and promoted the regeneration of nerve fibers of the damaged spinal cord at 8 weeks after injury. We conclude that puerarin exerts an ongoing role to activate growth-associated protein 43 in the corresponding segment of the spinal cord after sciatic nerve injury, thus contributing to neural regeneration after sciatic nerve injuries.

Oxidative phosphorylated neurofilament protein M protects spinal cord against ischemia/reperfusion injury

Previous studies have shown that neurofilament protein M expression is upregulated in the early stage of spinal cord ischemia/reperfusion injury, indicating that this protein may play a role in the injury process. In the present study, we compared protein expression in spinal cord tissue of rabbits after 25 minutes of ischemia followed by 0, 12, 24, or 48 hours of reperfusion with that of sham operated rabbits, using proteomic two-dimensional gel electrophoresis and mass spectrometry. In addition, the nerve repair-related neurofilament protein M with the unregulated expression was detected with immunohistochemistry and western blot analysis. Two-dimensional gel electrophoresis and mass spectrometry showed that, compared with the sham group, upregulation of protein expression was most significant in the spinal cords of rabbits that had undergone ischemia and 24 hours of reperfusion. Immunohistochemical analysis revealed that neurofilament protein M was located in the membrane and cytoplasm of neuronal soma and axons at each time point after injury. Western blot analysis showed that neurofilament protein M expression increased with reperfusion time until it peaked at 24 hours and returned to baseline level after 48 hours. Furthermore, neurofilament protein M is phosphorylated under oxidative stress, and expression changes were parallel for the phosphorylated and non-phosphorylated forms. Neurofilament protein M plays an important role in spinal cord ischemia/reperfusion injury, and its functions are achieved through oxidative phosphorylation.

Improving osteogenesis of PLGA/HA porous scaffolds based on dual delivery of BMP-2 and IGF-1 via a polydopamine coating

To engineer bone tissue, an ideal biodegradable implant should be biocompatible, biodegradable, osteoinductive and osteoconductive. However, the lack of bioactivity has seriously restricted the development of biodegradable implants in bone tissue engineering. In this study, we have developed a three-dimensional porous poly(L-lactic-co-glycolic acid)/hydroxyapatite (PLGA/HA) scaffold based on the dual delivery of bone morphogenic protein 2 (BMP-2) and insulin-like growth factor 1 (IGF-1) via polydopamine (PDA) coating. The aim of this study was to improve the osteoinductivity of biodegradable implants for clinical bone repair via a PDA-assisted BMP-2 and IGF-1 surface modification strategy. Our study demonstrated that PDA layer surface modification could more efficiently immobilize BMP-2 and IGF-1 on the scaffold surfaces than physical adsorption, and the immobilized growth factor was released slowly and steadily from the scaffold in a sustained manner. MC3T3-E1 cell attachment and proliferation on IGF-1 and BMP-2-immobilized porous scaffolds were much higher than other groups. According to an in vitro osteogenesis assay, alkaline phosphatase (ALP) activity, the expression of osteogenesis-related genes and the mineralization capacity of MC3T3-E1 cells were increased by the incorporation of BMP-2 and IGF-1. In vivo, digital radiograph evaluation demonstrated that there was the most rapid healing in the defects treated with the IGF-1 and BMP-2 immobilized porous scaffold compared with the other groups eight weeks after implantation. In vitro and in vivo results of this study revealed that the PDA-assisted surface modification method can be a useful tool to graft biomolecules onto biodegradable implants, and the dual release of BMP-2 and IGF-1 could promote cell proliferation and osteogenesis differentiation. Based on the results, the surface modification strategy with growth factors has great potential for the enhancement of osteointegration of biodegradable bone implants.

Key genes expressed in different stages of spinal cord ischemia/reperfusion injury

The temporal expression of microRNA after spinal cord ischemia/reperfusion injury is not yet fully understood. In the present study, we established a model of spinal cord ischemia in Sprague-Dawley rats by clamping the abdominal aorta for 90 minutes, before allowing reperfusion for 24 or 48 hours. A sham-operated group underwent surgery but the aorta was not clamped. The damaged spinal cord was removed for hematoxylin-eosin staining and RNA extraction. Neuronal degeneration and tissue edema were the most severe in the 24-hour reperfusion group, and milder in the 48-hour reperfusion group. RNA amplification, labeling, and hybridization were used to obtain the microRNA expression profiles of each group. Bioinformatics analysis confirmed four differentially expressed microRNAs (miR-22-3p, miR-743b-3p, miR-201-5p and miR-144-5p) and their common target genes (Tmem69 and Cxcl10). Compared with the sham group, miR-22-3p was continuously upregulated in all three ischemia groups but was highest in the group with no reperfusion, whereas miR-743b-3p, miR-201-5p and miR-144-5p were downregulated in the three ischemia groups. We have successfully identified the key genes expressed at different stages of spinal cord ischemia/reperfusion injury, which provide a reference for future investigations into the mechanism of spinal cord injury.

Exercise promotes motor functional recovery in rats with corticospinal tract injury: anti-apoptosis mechanism

Studies have shown that exercise interventions can improve functional recovery after spinal cord injury, but the mechanism of action remains unclear. To investigate the mechanism, we established a unilateral corticospinal tract injury model in rats by pyramidotomy, and used a single pellet reaching task and horizontal ladder walking task as exercise interventions postoperatively. Functional recovery of forelimbs and forepaws in the rat models was noticeably enhanced after the exercises. Furthermore, TUNEL staining revealed significantly fewer apoptotic cells in the spinal cord of exercised rats, and western blot analysis showed that spinal cord expression of the apoptosis-related protein caspase-3 was significantly lower, and the expression of Bcl-2 was significantly higher, while the expression of Bax was not signifiantly changed after exercise, compared with the non-exercised group. Expression of these proteins decreased with time after injury, towards the levels observed in sham-operated rats, however at 4 weeks postoperatively, caspase-3 expression remained significantly greater than in sham-operated rats. The present findings indicate that a reduction in apoptosis is one of the mechanisms underlying the improvement of functional recovery by exercise interventions after corticospinal tract injury.

Neural plasticity after spinal cord injury

Plasticity changes of uninjured nerves can result in a novel neural circuit after spinal cord injury, which can restore sensory and motor functions to different degrees. Although processes of neural plasticity have been studied, the mechanism and treatment to effectively improve neural plasticity changes remain controversial. The present study reviewed studies regarding plasticity of the central nervous system and methods for promoting plasticity to improve repair of injured central nerves. The results showed that synaptic reorganization, axonal sprouting, and neurogenesis are critical factors for neural circuit reconstruction. Directed functional exercise, neurotrophic factor and transplantation of nerve-derived and non-nerve-derived tissues and cells can effectively ameliorate functional disturbances caused by spinal cord injury and improve quality of life for patients.

The role of microtubule-associated protein 1B in axonal growth and neuronal migration in the central nervous system

In this review, we discuss the role of microtubule-associated protein 1B (MAP1B) and its phosphorylation in axonal development and regeneration in the central nervous system. MAP1B exhibits similar functions during axonal development and regeneration. MAP1B and phosphorylated MAP1B in neurons and axons maintain a dynamic balance between cytoskeletal components, and regulate the stability and interaction of microtubules and actin to promote axonal growth, neural connectivity and regeneration in the central nervous system.