Both Wnt/ß-catenin and ERK5 signaling pathways are involved in BDNF-induced differentiation of pluripotent stem cells into neural stem cells.

Although brain-derived neurotrophic factor (BDNF) induces the differentiation of induced pluripotent stem cells (iPSCs) into neural stem cells (NSCs), its exact mechanism remains unelucidated. Wnt/ß-catenin and ERK5 are two important signalling pathways of the Wnt and MAPK signalling cascades and are speculated to be closely related to the differentiation of cells. In this study, we reported the role of the Wnt/ß-catenin and ERK5 signalling pathways on the BDNF-induced differentiation of iPSCs into NSCs. We examined the expression of ß-catenin and p-ERK5 using small interfering RNA (siRNA)-induced silencing of ß-catenin and ERK genes. We found that BDNF significantly improved the efficiency of iPSC differentiation and that the expression of ß-catenin and p-ERK5 in the BDNF culture medium was significantly upregulated. Furthermore, we found that the expression of the ß-catenin component was downregulated by siRNA-ß-catenin, and the expression of the p-ERK5 component was downregulated by siRNA-ERK5. Flow cytometry showed that the differentiation rate of iPSCs was also significantly decreased by RNA interference. The results suggested that the Wnt/ß-catenin and ERK5 signalling pathways are activated in the process of BDNF-induced iPSC differentiation. Interestingly, our study showed that siRNA-ERK5 not only inhibits the activity of the ERK5 signalling pathway but also partially controls the activity of the Wnt/ß-catenin signalling pathway. The results suggested that the Wnt/ß-catenin and ERK5 signalling pathways are not independently involved in the process of BDNF-induced iPSC differentiation. Our study showed that BDNF promotes the differentiation of iPSCs into NSCs by activating the Wnt/ß-catenin and ERK5 signalling pathways, and an interconnected relationship may exist between the Wnt/ß-catenin and ERK5 signalling pathways.

7.0 tesla high resolution MRI study on intracerebral migration of magnet-labeled neural stem cells in a mouse model of Alzheimer's disease.

OBJECTIVE: To observe the migration characteristics of neural stem cells (NSCs) labeled with the MRI contrast agent superparamagnetic iron oxide (SPIO) in the brain of APP/PS1 transgenic mice with Alzheimer's disease (AD) by 7.0 T high resolution MRI. METHODS: C57BL/6 mouse NSCs were cultured, amplified, labeled with Feridex and Poly-l-lysine (FE-PLL) and evaluated by transmission electron microscopy (TEM). Using the random number table method, 24 APP/PS1 transgenic AD mice aged 12 months were equally assigned to two groups: animals in group A were transplanted with FE-PLL labeled NSCs and those in group B were transplanted with non-labeled NSCs in the right hippocampus. Twelve wild-type mice of the same age and born from the same litter were used as the control group (group C) and transplanted with FE-PLL labeled NSCs. Using the 7.0 T high resolution MR scanner, the transplanted NSCs were traced in vivo at 1 day, 1 and 2 weeks after cell transplantation. The MRI findings were compared with the histopathological findings. RESULTS: C57BL/6 mouse NSCs were cultured and amplified successfully. TEM showed large amounts of iron-containing particles in the cytoplasm of transplanted cells. MRI in group A showed the presence of spheroid low signals at the injection point of the hippocampus on T2*WI one day after transplantation; one weeks later, the low signals were seen diffusing to the surroundings along the injection point, and covering almost the whole hippocampal area but the intensity of the low signals became weaker gradually; two weeks after transplantation, almost all low signals disappeared. In group B, no significant change in low signals was observed in the transplantation area at all designated time points. Although low signals were also observed in the hippocampus after transplantation of FE-PLL labeled NSCs in group C, their size and location remained almost unchanged. Prussian blue staining showed that migration of the FE-PLL labeled NSCs in the hippocampus of the AD mice was consistent with the MRI findings at all designated time points. CONCLUSION: NSCs underwent diffuse and non-directional migration to the surroundings after they were transplanted to the hippocampus of APP/PS1 transgenic AD mice, and this migration pattern could be traced in vivo by MRI when they were labeled with magnet.

[3.0 T magnetic resonance imaging of pancreatic cancer in an orthotopic nude murine model].

OBJECTIVE: To assess the methods of establishing an orthotopic nude murine model of human pancreatic cancer and explore the manifestations of MRI (magnetic resonance imaging) and its pathological fundamentals so as to provide research rationales for human pancreatic cancer. METHODS: The BXPC-3 cell of human pancreatic cancer was orthotopically planted in nude mice. And the animals were examined by a clinical 3.0 T magnetic resonance imager. The MRI examinations were analyzed along with their pathological findings. RESULTS: Among 18 mice, 15 of them grew tumors with a success ratio of 83.3%. The pathological findings conformed to those of high differentiation pancreatic parenchyma cancer. Comparing with the neighbor muscles, the tumors were homogeneous (66.7%, 10/15) or heterogeneous (33.3%, 5/15) of hypointense on T1-weighted images while homogeneous (26.7%, 4/15) or heterogeneous (73.3%, 11/15) hyperintense on T2-weighted images with heterogeneous enhancement. The border became obviously enhanced and there was mild central enhancement while the necrotic part showed no enhancement. CONCLUSION: 3.0T MRI can detect pancreatic neoplasms ≥ 2 mm and visualize clearly their locations, shapes, dimensions and internal structures in an orthotopic nude murine model. Thus it provides a visible framework for further studies of human pancreatic cancer.