Peijun Wang

Bioreducible polyethylenimine-delivered siRNA targeting human telomerase reverse transcriptase inhibits HepG2 cell growth in vitro and in vivo

One new siRNA sequence was found efficient for human telomerase reverse transcriptase (hTERT) gene silencing in vitro in five types of human cancer cells. Then, a biodegradable polyethylenimine containing multiple disulfide bonds (SS-PEI) was successfully applied as a potent non-viral carrier for intracellular delivery of the hTERT siRNA in vitro and in vivo. The SS-PEI could strongly bind siRNA to form nano-sized and positively-charged complexes, but which were readily destabilized to sufficiently release siRNA in a reducing environment. Transfection experiments showed that the complexes of SS-PEI/hTERT siRNA were able to transfect HepG2 cells in vitro, inducing reduced levels of hTERT mRNA and hTERT protein, decreased telomerase activity, cell growth inhibition and significant cell apoptosis. Besides, treatment with the complexes of SS-PEI/hTERT siRNA could inhibit HepG2 tumor growth in a xenograft mouse model. Importantly, the SS-PEI revealed relatively low cytotoxicity in vitro and at an appropriate dose had no adverse effect on liver and kidney functions in vivo. The results of this study indicate that SS-PEI/siRNA-induced hTERT gene silencing provides a promising method for human cancer gene therapy.

Neural Stem Cell Transplants Improve Cognitive Function Without Altering Amyloid Pathology in an APP/PS1 Double Transgenic Model of Alzheimer’s Disease

Neural stem cells (NSCs) are capable of self-renewal and are multipotent. Transplantation of NSCs may represent a promising approach for treating neurodegenerative disorders associated with cognitive decline, such as Alzheimer disease (AD) characterized by extensive loss of neurons. In this study, we investigated the effect of NSC transplantation on cognitive function in the amyloid precursor protein/presenilin-1 (APP/PS1) transgenic mouse, an AD mouse model with age-dependent cognitive deficits. We found that NSCs bilaterally transplanted into hippocampal regions improved spatial learning and memory function in these mice, but did not alter Aβ pathology. Immunohistochemical analyses determined that NSCs proliferated, migrated, and differentiated into three neuronal cell types. The improvement in cognitive function was correlated with enhanced long-term potentiation (LTP) and an increase in the neuron expression of proteins related to cognitive function: N-methyl-d-aspartate (NMDA) 2B unit, synaptophysin (SYP), protein kinase C ζ subtypes (PKCζ), tyrosine receptor kinase B (TrkB), and brain-derived neurotrophic factor (BDNF). Taken together, our data indicated that injected NSCs can rescue cognitive deficits in APP/PS1 transgenic mice by replacing neuronal cell types expressing multiple cognition-related proteins that enhance LTP.

Age-related changes in brain metabolites and cognitive function in APP/PS1 transgenic mice.

Proton magnetic resonance spectroscopy ((1)H-MRS) and the Morris water maze (MWM) have played an important role in Alzheimers disease (AD) research. The aim of this study was to determine whether (1)H-MRS and the MWM can detect for early AD in APP/PS1 transgenic (tg) mice. (1)H-MRS was performed in 20 tg mice and 15 wild-type mice at 3, 5 and 8 months of age. The concentration of N-acetylaspartate (NAA), glutamate (Glu), myo-inositol (mI), choline (Cho) and creatine (Cr) in the hippocampus were measured, and the NAA/Cr, Glu/Cr, mI/Cr and Cho/Cr ratios were quantified. Additionally, the spatial learning and memory of the mice were evaluated by MWM. The (1)H-MRS revealed that mI levels in tg mice were significantly higher at 3 months of age compared to wt mice, while the NAA and Glu levels in 5- and 8-month-old tg mice were significantly decreased (p<0.05). Additionally, significant cognitive changes only occurred at 8 months of age in APP/PS1 tg mice. These results indicated that metabolic changes preceded overt cognitive dysfunctions in early-stage AD, suggesting that (1)H-MRS is a more sensitive biomarker for assessing early AD.

Effects of neural stem cells on synaptic proteins and memory in a mouse model of Alzheimer's disease

Transplanting neural stem cells (NSC) to the damaged brain has been regarded as a potential treatment for neurodegenerative diseases such as Alzheimers disease (AD), a condition characterized by memory loss. We hypothesized that transplantation of NSC into the hippocampal regions of APP + PS1 transgenic (Tg) mice, a well‐established model of AD, would enhance the expression of synaptic proteins, which may be helpful for improving cognitive function. Our results showed that NSC transplantation significantly improved spatial learning and memory function in Tg mice. The results obtained by real‐time RT‐PCR, immunofluorescence, and Western blot analyses demonstrated that the expression of synaptophysin (SYN) and that of growth‐associated protein‐43 (GAP‐43) in Tg‐NSC mice, 8 weeks after transplantation, were significantly improved compared with what was observed in Tg‐Veh (control) mice. This finding was confirmed by the increase in the number of synapses in Tg‐NSC mice as observed via electron microscopy. Our results suggest that NSC‐induced changes can recover memory loss in APP + PS1 transgenic mice, possibly by establishing new neural circuits resulting from the engrafted NSC.

Neural stem cell transplantation enhances mitochondrial biogenesis in a transgenic mouse model of Alzheimer's disease–like pathology

Mitochondrial dysfunction, especially a defect in mitochondrial biogenesis, is an early and prominent feature of Alzheimers disease (AD). Previous studies demonstrated that the number of mitochondria is significantly reduced in susceptible hippocampal neurons from AD patients. Neural stem cell (NSC) transplantation in AD-like mice can compensate for the neuronal loss resulting from amyloid-beta protein deposition. The effects of NSC transplantation on mitochondrial biogenesis and cognitive function in AD-like mice, however, are poorly understood. In this study, we injected NSCs or vehicle into 12-month-old amyloid precursor protein (APP)/PS1 transgenic mice, a mouse model of AD-like pathology. The effects of NSC transplantation on cognitive function, the amount of mitochondrial DNA, the expression of mitochondrial biogenesis factors and mitochondria-related proteins, and mitochondrial morphology were investigated. Our results show that in NSC-injected APP/PS1 (Tg-NSC) mice, the cognitive function, number of mitochondria, and expression of mitochondria-related proteins, specifically the mitochondrial fission factors (dynamin-related protein 1 [Drp1] and fission 1 [Fis1]) and the mitochondrial fusion factor optic atrophy 1 (OPA1), were significantly increased compared with those in age-matched vehicle-injected APP/PS1 (Tg-Veh) mice, whereas the expression of mitochondrial fusion factors mitofusion 1 (Mfn1) and Mfn2 was significantly decreased. These data indicate that NSC transplantation may enhance mitochondria biogenesis and further rescue cognitive deficits in AD-like mice.

1H-MRS Evaluation of Therapeutic Effect of Neural Stem Cell Transplantation on Alzheimer's disease in AβPP/PS1 Double Transgenic Mice

The aim of this work was to explore the applicable value of (1)H-MRS evaluation on the treatment of Alzheimers disease (AD) with neural stem cell (NSC) transplantation by quantitative analysis of metabolite changes in the hippocampal area in AβPP/PS1 transgenic (tg) mice. The tg mice (n = 30) aged 12 months were randomized into two subgroups: One receiving NSCs and the other receiving PBS transplantation in the bilateral hippocampal CA1 region. The wild-type mice (n = 15) were used as the control group. (1)H-MRS was performed before transplantation and 6 weeks after transplantation to measure the change of N-acetylaspartate (NAA), myo-inositol (mI), glutamate (Glu), choline (Cho), and creatine (Cr) in the hippocampus. Results showed NAA and Glu levels were increased and mI level was decreased in NSC group compared with the PBS group at six weeks after transplantation (p < 0.05). There was no significant difference in NAA and Glu (p > 0.05), and there was significant difference in mI (p < 0.05) between NSC and control groups. However, there was no significant difference in Cho before and after transplantation among the three groups (p > 0.05). Histology showed the number of neurons in the hippocampal CA1 region increased significantly in the NSC group than those in the PBS group (p < 0.05), and the number of astrocytes significantly decreased in the NSC group compared with the PBS group. Ultrastructure showed that the neurons in the NSC group were morphologically normal. In conclusion, (1)H-MRS can display intracranial metabolite changes before and after NSC transplantation in tg mice and has a applicable value in evaluating the therapeutic effect of NSCs on AD.

Dynamic contrast-enhanced MRI of gastric cancer: Correlations of the pharmacokinetic parameters with histological type, Lauren classification, and angiogenesis

PURPOSE To compare the pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in gastric cancers of different histological type and Lauren classification, and to investigate whether DCE-MRI parameters correlate with vascular endothelial growth factor (VEGF) expression levels in gastric cancer. METHODS Included were 32 patients with gastric cancer who underwent DCE-MRI of the upper abdomen before tumor resection. DCE-MRI parameters including the volume transfer coefficient (Ktrans), reverse reflux rate constant (Kep), and extracellular extravascular volume fraction (Ve) were calculated from the tumor region. Post-operative specimens were used for determination of histological differentiation (i.e., non-mucinous, mucinous, or signet-ring-cell adenocarcinoma) as well as Lauren classification (intestinal type or diffuse type). VEGF expression was examined for assessing angiogenesis. DCE-MRI parameters with different histological type and Lauren classification were compared using independent samples t-test and analysis of variance, respectively. Correlations between DCE-MRI parameters and VEGF expression grades were tested using Spearman correlation analysis. RESULTS Among gastric adenocarcinomas of three different histological types, mucinous adenocarcinomas showed a higher Ve and lower Ktrans than the others (P<0.01). Between the two Lauren classifications, the diffuse type showed a higher Ve than the intestinal type (P<0.001). The mean Ktrans showed a significantly positive correlation with VEGF (r=0.762, P<0.001). CONCLUSION DCE-MRI permits noninvasive prediction of tumor histological type and Lauren classification and estimation of tumor angiogenesis in gastric cancer. DCE-MRI parameters can be used as imaging biomarkers to predict the biologic aggressiveness of a tumor as well as patient prognosis.

CT presentations of colorectal cancer with chronic schistosomiasis: A comparative study with pathological findings

OBJECTIVE To clarify pathological basis of computed tomography (CT) presentations of colorectal cancer (CRC) with schistosomiasis for the purpose of improving the accuracy of CT diagnosis and differential diagnosis of the condition. MATERIALS AND METHODS 130 patients (87 male and 43 female; age range 49-86 years, mean 71.1) were selected whose diagnoses were pathologically confirmed as CRC with schistosomiasis. All the patients underwent abdominal plain CT and contrast enhanced scanning. The location, morphology, size, calcification features and enhancement modalities (patterns) were evaluated and compared with the pathological findings by two radiologists in a blind way. RESULTS CT showed that in 130 patients, the tumors occurred in the large intestine, among which 109 (83.9%) were solitary and 21 (16.1%) were multifocal. The intestinal wall was irregularly thickened in 123 patients, with soft tissue masses in 7 patients. Linear, spotty and small patchy calcifications were seen in 104 (80.0%) patients, with unclear margins in 96 patients. The tumors were markedly unevenly enhanced in 92 patients. Pathological examination revealed adenocarcinoma in 114 patients and in 104 patients, calcified Shistosoma japonicum (S. japonicum) ova inside the tumors, 15 patients were mucinous adenocarcinoma, and one patient was that of adenosquamous carcinoma. CONCLUSION Irregular thickening of the intestinal wall, soft tissue masses, multiple S. japonicum ova calcifications inside the tumor with obscured margins and multiple intestinal masses in some patients are important CT features of CRC with schistosomiasis.

Enhanced Synergism of Thermo-chemotherapy For Liver Cancer with Magnetothermally Responsive Nanocarriers

A combination of magnetic hyperthermia and magnetothermally-facilitated drug release system was developed as a promising strategy for liver cancer therapy. The thermosensitive copolymer, 6sPCL-b-P(MEO2MA-co-OEGMA) shows a good temperature-controlled drug release response. Mn-Zn ferrite magnetic nanoparticles (MZF-MNPs) exhibit a strong magnetic thermal effect with an alternating magnetic field (AMF). Owing to its high magnetic sensitivity, the magnetothermally-responsive nanocarrier/doxorubicin (MTRN/DOX) can be concentrated in the tumor site efficiently through magnetic targeting. Given this information, we synthesized MTRN/DOX which was composed of MZF-MNPs, thermosensitive copolymer drug carriers, and the chemotherapeutic drug---DOX, to study its anticancer effects both in vitro and in vivo. METHODS: MTRN/DOX was designed and prepared. Firstly, we investigated the accumulation effects of MTRN/DOX by Prussian blue staining, transmission electron microscopy (TEM), laser scanning confocal microscopy (LSCM) and conducted 7.0 T MRI. Following this, the magnetothermal effects of MTRN/DOX were studied using an infrared thermal camera. DOX uptake, distribution, and retention in tumor cells and the distribution of MTRN/DOX in vivo were then analyzed via LSCM, flow cytometry and live fluorescence imaging. Lastly, its anticancer effects were evaluated by MTT, AM/PI staining, Annexin-VFITC/PI staining and comparison of relative tumor volume. RESULTS: We found that MTRN/DOX can be efficiently concentrated in the tumor site through magnetic targeting, increasing the uptake of DOX by tumor cells, and prolonging the retention time of the drug within the tumors. MTRN/DOX showed good magnetothermal effects both in vitro and in vivo. Based on the above results, MTRN/DOX had significant anticancer effects. CONCLUSIONS: MTRN/DOX causes temporal-spatial synchronism of thermo-chemotherapy and together with chemotherapeutic drugs, produces a synergistic effect, which enhances the sensitivity of tumor cells to DOX and reduces their side effects.

Prenatal Exposure to Ultrasound Affects Learning and Memory in Young Rats

Prenatal exposure to ultrasound may cause cognitive impairments in experimental animals; however, the exact mechanisms remain unknown. In this study, we exposed pregnant rats (or sham-exposed controls) to different intensities of ultrasound repeatedly on days 6, 12 and 18 of pregnancy for 4 min (3.5 MHz, spatial peak time average intensity = 7.6 mW/cm(2), mechanical index = 0.1, thermal index bone = 0.1: 4-min group) or 20 min (3.5 MHz, spatial peak time average intensity = 106 mW/cm(2), mechanical index = 1.4, thermal index bone = 1.0: 20-min group). The Morris water maze was used to assess learning and memory function in pups at 2 mo of age. Noticeable deficits in behavior occurred in the group exposed to ultrasound for 20 min. Using real-time polymerase chain reaction and Western blot, we also determined that both the mRNA and protein expression levels of hippocampal N-methyl-D-aspartate (NMDA) receptor units 1 (NR1) and 2B (NR2B) and brain-derived neurotrophic factor (BDNF) were significantly lower in pups exposed to ultrasound for 20 min than in controls. Furthermore, the morphology of the synapses in the hippocampus was partially damaged. Compared with the control group, the 4-min group had better spatial learning and memory abilities, as well as higher mRNA and protein levels of NR1, NR2B and BDNF. Our study suggests that high-intensity ultrasound irradiation can decrease learning and memory abilities by reducing the expression of NR1, NR2B and BDNF in the hippocampal regions and damaging the structure of synapses. In contrast, low-intensity ultrasound irradiation can enhance the learning and memory abilities of the offspring rats by increasing the expression of NR1, NR2B and BDNF receptor in the hippocampal regions.