Response of chemokine receptors CXCR2 and integrin β2 after Streptococcus agalactiae and Aeromonas hydrophila challenge in GIFT strain of Nile tilapia Oreochromis niloticus

CXCR2 is a G-protein-coupled cell surface chemokine receptor, and integrins are heterodimeric transmembrane (TM) glycoproteins. These proteins work together to activate neutrophils in the immune defense, but knowledge of their function in tilapia is limited. RACE technology was used to clone the full length of the Nile tilapia Oreochromis niloticus Cxcr2 gene, which included a 954 bp open reading frame encoding 318 amino acids, and the integrin β2 gene, with a 2373 bp open reading frame and 791 amino acids. Sequence analyses showed that Cxcr2 and integrin β2 are conserved among species. Expression profile was performed using qRT-PCR and indicated that Cxcr2 and integrin β2 were distributed throughout the examined organ tissues, with highest expression observed in the immune tissues. Expression of Cxcr2 and integrin β2 were increased after challenged with Streptococcus agalactiae or Aeromonas hydrophila. Results suggest that Cxcr2 and integrin β2 genes play a role in immune response in Nile tilapia and provide basic data for molecular-assistant selection of disease-resistant bloodstock to improve the production.

Genome-Wide DNA Methylation and RNA Analysis Reveal Potential Mechanism of Resistance to Streptococcus agalactiae in GIFT Strain of Nile Tilapia (Oreochromis niloticus )

Streptococcus agalactiae is an important pathogenic bacterium causing great economic loss in Nile tilapia (Oreochromis niloticus) culture. Resistant and susceptible groups sharing the same genome showed significantly different resistance to S. agalactiae in the genetically improved farmed tilapia strain of Nile tilapia. The resistance mechanism is unclear. We determined genome-wide DNA methylation profiles in spleen of resistant and susceptible O. niloticus at 5 h postinfection with S. agalactiae using whole-genome bisulfite sequencing. The methylation status was higher in the spleen samples from resistant fish than in the susceptible group. A total of 10,177 differentially methylated regions were identified in the two groups, including 3725 differentially methylated genes (DMGs) (3129 hyper-DMGs and 596 hypo-DMGs). The RNA sequencing showed 2374 differentially expressed genes (DEGs), including 1483 upregulated and 891 downregulated. Integrated analysis showed 337 overlapping DEGs and DMGs and 82 overlapping DEGs and differentially methylated region promoters. By integrating promoter DNA methylation with gene expression, we revealed four immune-related genes (Arnt2, Nhr38, Pcdh10, and Ccdc158) as key factors in epigenetic mechanisms contributing to pathogen resistance. Our study provided systematic methylome maps to explore the epigenetic mechanism and reveal the methylation loci of pathogen resistance and identified methylation-regulated genes that are potentially involved in defense against pathogens.

Characterization and expression of galectin-3 after Streptococcus agalactiae and Aeromonas hydrophila challenge in GIFT strain Nile tilapia (Oreochromis niloticus)

In mammals, Galectin-3 has been revealed to be widely expressed in immune cells and played important role in immune reactions. However, Galectin-3 is frequently less reported in teleost. In the present study, a molecular characterization and expression analysis of galectin-3 were conducted in GIFT strain Nile tilapia. The full-length cDNA is 1034 bp with 690 bp of protein coding sequences. The result of qRT-PCR showed that the mRNA of galectin-3 was widely expressed in various tissues (heart, liver, spleen, gill, kidney, brain, intestine, skin, muscle, and ovary), and the higher expression was observed in immune-related tissues (liver and spleen). The time-course expression analysis revealed that galectin-3 was significantly up-regulated in intestine (5 h, 50 h, and 7 d), liver (5 h, 50 h, and 7 d), spleen (5 and 50 h), head-kidney (5 and 50 h), gill (5 h and 7 d) after Streptococcus agalactiae challenge, and significantly up-regulated in intestine (18, 24, 36, 72, and 96 h), liver (6, 18, 24, 96 h, and 6 d), spleen (18, 24, 36, 72, and 96 h), head-kidney (6, 12, 18, 24, 36, 72, and 96 h), and gill (12, 18, 24, and 36 h) after Aeromonas hydrophila challenge. Taken together, these data suggest that galectin-3 plays a role in immune responses in Nile tilapia after bacterial challenge.

Basal polarization of the immune responses to Streptococcus agalactiae susceptible and resistant tilapia (Oreochromis niloticus)

One of the highest priority areas for improvement is the development of effective strategies for decreasing disease mortality levels in aquaculture production, a better understanding of the components of the fish immune system and their functions in the context of pathogen invasion is needed. Tilapia is the most common fish in South China, and Streptococcus agalactiae has become the most serious disease problem for tilapia industry in China. Here, we profiled gene expression differences between tilapia differing in their susceptibility to S. agalactiae both basally (before infection) and at three early timepoints post-infection (5 h, 50 h, and 7 d). Between group comparisons revealed 5756 unique genes differentially expressed greater than 2-fold at one or more timepoints. And the resistant fish showed much more strong ability in pathogen recognition, antigen presentation, immune activation, while the susceptible fish showed fast activation of apoptosis. Taken together, the immune profiles expand our knowledge for molecular mechanisms for disease resistance, as well as provide solid molecular resources for further identification of the candidate markers for disease-resistant selection and evaluation of disease prevention and treatment options for tilapia industry.

Transcriptomic profiling analysis of tilapia (Oreochromis niloticus) following Streptococcus agalactiae challenge

Innate immune system is the primary defense mechanism against pathogen infection in teleost, which are living in pathogen-rich aquatic environment. It has been long hypothesized that the disease resistance in teleost are strongly correlated to the activities of innate immune genes. Tilapia is an important economical fish around the world, especially in China, where the production accounts for nearly half of the global production. Recently, S. agalactiae has become one of the most serious bacterial diseases in southern China, resulted in high cumulative mortality and economic loss to tilapia industry. Therefore, we sought here to characterize the expression profiles of tilapia against S. agalactiae infection at whole transcriptome level by RNA-seq technology. A total of 2822 genes were revealed significantly expressed in tilapia spleen with a general trend of induction. Notably, most of the genes were rapidly the most induced at the early timepoint. The significantly changed genes highlighted the function of pathogen attachment and recognition, antioxidant/apoptosis, cytoskeletal rearrangement, and immune activation. Collectively, the induced expression patterns suggested the strong ability of tilapia to rapidly recognize the invasive bacteria, and activation of downstream immune signaling pathways to clear the bacteria and prevent the tissue damage and bacteria triggered cell apoptosis. Our results heighted important roles of novel candidate genes which were often missed in previous tilapia studies. Further studies are needed to characterize the molecular relationships between key immune genes and disease resistance, and to identify the candidate genes for molecular-assistant selection of disease-resistant broodstock and evaluation of disease prevention and treatment measures.

Trancriptomic profiling revealed the signatures of acute immune response in tilapia (Oreochromis niloticus) following Streptococcus iniae challenge

Streptococcus iniae is the most significant bacterial disease of tilapia throughout the world, and commonly leads to tremendous economic losses. In contrast to other important fish species, our knowledge about the molecular mechanisms of tilapia in response to bacterial infection is still limited. Here, therefore, we utilized RNA-seq to first profiling of host responses in tilapia spleen following S. iniae infection at transcriptome level. A total of 223 million reads were obtained and assembled into 192,884 contigs with average length 844 bp. Gene expression analysis between control and infected samples at 5 h, 50 h, and 7 d revealed 1475 differentially expressed genes. In particular, the differentially expressed gene set was dramatically induced as early as 5 h, and rapidly declined to basal levels at 50 h. Enrichment and pathway analysis of the differentially expressed genes revealed the centrality of the pathogen attachment and recognition, cytoskeletal rearrangement and immune activation/inflammation in the pathogen entry and host inflammatory responses. Understanding of these responses can highlight mechanisms of tilapia host defense, and expand our knowledge of teleost immunology. Our findings will set a foundation of valuable biomarkers for future individual, strain, and family-level studies to evaluate immune effect of vaccine and individual response in host defense mechanisms to S. iniae infection, to select disease resistant families and strains.

Schwann-like cell differentiation of rat adipose-derived stem cells by indirect co-culture with Schwann cells in vitro

OBJECTIVES

Schwann cell (SC) transplantation is a promising therapy for peripheral nerve transaction, however, clinical use of SCs is limited due to their very limited availability. Adipose-derived stem cells (ADSCs) have been identified as an alternative source of adult stem cells in recent years. The aim of this study was to evaluate the feasibility of using ADSCs as a source of stem cells for differentiation into Schwann-like cells by an indirect co-culture approach, in vitro.

MATERIALS AND METHODS

Multilineage differentiation potential of the obtained ADSCs was assayed by testing their ability to differentiate into osteoblasts and adipocytes. The ADSCs were co-cultured with SCs to be induced into Schwann-like cells through proximity, using a Millicell system. Expression of typical SC markers S-100, GFAP and P75NTR of the treated ADSCs was determined by immunocytochemical staining, western blotting and RT-PCR. Myelination capacity of the differentiated ADSCs (dADSCs) was evaluated in dADSC/dorsal root ganglia neuron (DRGN) co-cultures.

RESULTS

The treated ADSCs adopted a spindle shaped-like morphology after co-cultured with SCs for 6 days. All results of immunocytochemical staining, western blotting and RT-PCR showed that the treated cells expressed S-100, GFAP and P75NTR, indications of differentiation. dADSCs could form Schwann-like cell myelin in co-culture with DRGNs. Undifferentiated ADSCs (uADSCs) did not form myelin compared to DRGNs cultured alone, but could produce neurite extension.

CONCLUSIONS

These results demonstrate that this indirect co-culture microenvironment could induce ADSCs to differentiate into Schwann-like cells in vitro, which may be beneficial for treatment of peripheral nerve injuries in the near future.

Protective role of tretinoin and N-acetyl-L-cysteine from antiproliferative action of cigarette smoke extract on alveolar epithelial cells

To investigate the mechanisms by which tretinoin and N-acetyl-L-cysteine (NAC) reverse the growth inhibition of alveolar epithelial cells induced by cigarette smoke extract (CSE), MTT assay was used to evaluate cell viability. It was observed that both tretinoin and NAC could restore the viability of CSE-inhibited A549 cells. By incubation with fluorescent indicator H2DCFDA, it was documented that CSE-stimulated accumulation of intracellular reactive oxygen species (ROS) was obviously decreased by tretinoin or NAC. Furthermore, using semi-quantitative and real-time quantitative RT-PCR as well as western blot methods, high expression of insulin-like growth factor binding protein-2 (IGFBP-2) in A549 cells treated with CSE was found at both transcriptional and protein levels, and concomitant with the restoration of cell growth after treatment with tretinoin or NAC, down regulation of IGFBP-2 was observed. From the present study, it is concluded that both RA and NAC can antagonize CSE-induced growth arrest of alveolar epithelial cells and that down regulation of IGFBP-2 may play an important role in the process.

Combined transplantation of neural stem cells and olfactory ensheathing cells for the repair of spinal cord injuries

Spinal cord repair is a problem that has long puzzled neuroscientists. The failure of the spinal cord to regenerate and undergo reconstruction after spinal cord injury (SCI) can be attributed to secondary axonal demyelination and neuronal death followed by cyst formation and infarction as well as to the nature of the injury environment, which promotes glial scar formation. Cellular replacement and axon guidance are both necessary for SCI repair. Multipotent neural stem cells (NSCs) have the potential to differentiate into both neuronal and glial cells and are, therefore, likely candidates for cell replacement therapy following SCI. However, NSC transplantation alone is not sufficient for spinal cord repair because the majority of the NSCs engrafted into the spinal cord have been shown to differentiate with a phenotype which is restricted to glial lineages, further promoting glial scaring. Olfactory ensheathing cells (OECs) are a unique type of glial cell that occur both peripherally and centrally along the olfactory nerve. The ability of olfactory neurons to grow axons in the mature central nervous system (CNS) milieu has been attributed to the presence of OECs. It has been shown that transplanted OECs are capable of migrating into and through astrocytic scars and thereby facilitating axonal regrowth through an injury barrier. Given the complementary properties of NSCs and OECs, we predict that the co-transplantation of NSCs and OECs into an injured spinal cord would have a synergistic effect, promoting neural regeneration and functional reconstruction. The lost neurocytes would be replaced by NSCs, while the OECs would build "bridges" crossing the glial scaring that conduct axon elongation and promote myelinization simultaneously. Furthermore, the two types of cells could first be seeded into a bioactive scaffold and then the cell seeded construct could be implanted into the defect site. We believe that this type of treatment would lead to improved neural regeneration and functional reconstruction after SCI.

Protective effects of extract of Ginkgo biloba (EGb 761) on nerve cells after spinal cord injury in rats

STUDY DESIGN

An experimental animal model was used to assess spinal cord injury following lateral hemitransection at thoracic spinal cord level.

OBJECTIVE

To determine whether extract of Ginkgo biloba (EGb) could have a neuroprotective effect in spinal cord injury (SCI) in rats.

SETTING

Department of Biological Sciences and Biotechnology, Tsinghua University, China.

METHODS

A total of 72 adult rats were divided randomly into three groups: the EGb group, normal saline (NS) group, and sham operation group (sham group). After thoracic spinal cord hemitransection was performed at the level of the 9th thoracic vertebra (T9), rats in the EGb group were given 100 mg/kg EGb 761 daily, while rats in the NS group received NS. The rats in the sham group only underwent laminectomy without spinal cord hemitransection. At various time points after surgery, thoracic spinal cords were sampled and sliced for histochemistry, immunohistochemistry of inducible nitric oxide synthase (iNOS), and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) of apoptotic cells.

RESULTS

Myelin staining showed that the area of cavities was small and the demyelinated zones were limited at and around the injury site of the spinal cord in the EGb group, while the area of cavities was large and the demyelinated zones were serious in the NS group. Nissl staining showed that the ratio of bilateral ventral horn neurons (transection side/uninjured side) in the EGb group was higher than that in the NS group (P<0.05). The apoptotic index and the percentage of iNOS-positive cells were lower in the EGb group than in the NS group. Furthermore, the percentage of iNOS-positive cells positively correlated with the apoptotic index (r( 2)=0.729, P<0.01) after SCI.

CONCLUSION

This study demonstrated that EGb 761 could inhibit iNOS expression and have neuroprotective effect by preventing nerve cells from apoptosis after SCI in rats.

Development of the specific purpose Monte Carlo code CEARXRF for the design and use of in vivo X-ray fluorescence analysis systems for lead in bone

X-ray fluorescence (XRF) systems have been increasingly used for in vivo toxic trace-element analysis in the human body, such as lead in the tibia. Monte Carlo simulation can provide an efficient and flexible method for designing and using in vivo XRF systems. The Monte Carlo code CEARXRF has been developed specifically to simulate the complete pulse height spectrum of energy-dispersive XRF systems. This code is capable of tracking photons in a general geometry and modelling all of the physics of photon interactions in the energy range 1-150 keV for elements Z = 1-94, including primary and higher degree excitations of K and L XRF, the Doppler broadening of Compton-scattered photon energies, and the polarization effects in low-energy photon scatterings. The scattering background for minimum detectable concentration (MDC) analysis may be simulated more accurately by taking into account Doppler broadening in the distribution of the Compton-scattered photon energy due to electron-binding effects. The use of polarized excitation photons has been shown to be important in producing a low scattering background and good measurement sensitivity. The code has two very unique and important features: (1) complete composition and density correlated sampling that is extremely useful for studying measurement sensitivity to small changes in sample composition and density; and (2) Monte Carlo library spectra calculation for the determination of elemental amounts by the Monte Carlo-Library Least-Squares (MCLLS) method. The capability of CEARXRF to aid the design and optimization of in vivo XRF analysis has been verified by modelling hypothesized lead K and L XRF measurement systems.

Optimization of in vivo X-ray fluorescence analysis methods for bone lead by simulation with the Monte Carlo code CEARXRF

In the design of X-ray fluorescence (XRF) systems for in vivo measurements of lead in human bone, the most important considerations are the minimum detectable concentration (MDC), and accuracy and precision. Possible design optimizations can be investigated much more easily and economically by Monte Carlo simulation than by experiment. The specific purpose Monte Carlo code CEARXRF has been used in the present study for: (1) improving the MDC of a hypothesized in vivo 109Cd source-based KXRF system and a 109Cd source or X-ray tube source-based LXRF system by investigating the effects of source polarization and source-bone-detector geometry modification on reducing the scattering background, and (2) investigating the effects of sample variables, such as overlying skin thickness on the MDC and the lead XRF intensity precision. In addition, the feasibility of the Monte Carlo-Library Least-Squares (MCLLS) approach has been investigated in a preliminary fashion for 109Cd-based KXRF spectroscopy analysis.

Black box radiation gauges and analyzers: dream or reality?

This paper describes our attempts to make radiation gauges and analyzers operate in more of a 'black box' manner-being more independent of or at least more insensitive to changes in such things as sample composition and position. Our overall approach relies heavily on Monte Carlo simulation and that is discussed first in relation to radiation gauge and analyzer design and usage. Then the principles and applications of radiation gauges and analyzers including the Measurement Chi-Square and Monte Carlo Library Least-Squares, respectively, are treated. Finally, future work in this area is discussed.