Enhanced arsenic tolerance of transgenic eastern cottonwood plants expressing gamma-glutamylcysteine synthetase

Arsenic is a metalloid that occurs naturally at parts per million (ppm) levels in the earth's crust. Natural and human activities have contributed to arsenic mobilization and increased concentration in the environment, such that World Health Organization guidelines for arsenic levels in drinking water are exceeded at many locations, worldwide. This translates into an increased risk of arsenic-related illnesses for millions of people. Recent studies demonstrate that increasing thiol-sinks in transgenic plants by overexpressing the bacterial gamma-glutamylcysteine synthetase (ECS) gene results in a higher tolerance and accumulation of metals and metalloids such as cadmium, mercury, and arsenic. We used Agrobacterium-mediated transformation to genetically engineer eastern cottonwood with a bacterial ECS gene. Eastern cottonwood plants expressing ECS had elevated thiol group levels, consistent with increased ECS activity. In addition, these ECS-expressing plants had enhanced growth on levels of arsenate toxic to control plants in vitro. Furthermore, roots of ECS-expressing plants accumulated significantly more arsenic than control roots (approximately twice as much), while shoots accumulated significantly less arsenic than control shoots (approximately two-thirds as much). We discuss potential mechanisms for shifting the balance of plant arsenic distribution from root accumulation to shoot accumulation, as it pertains to arsenic phytoremediation.

314 ADIPOSE- AND BONE MARROW-DERIVED MESENCHYMAL STEM CELLS PRESENT LARGE SIMILARITIES IN TRANSCRIPTOME PRIOR TO AND DURING ADIPOGENIC AND OSTEOGENIC DIFFERENTIATION

Previous data support adipose-derived stem cells as an alternative to bone marrow as a source of adult stem cells for therapeutic purposes. The aim of the present study was to directly compare the transcriptome of adipose-derived (ADSC) and bone marrow-derived (BMSC) mesenchymal stem cells prior to differentiation and during in vitro osteogenic and adipogenic differentiation. The ADSC and BMSC were harvested from 3 adult pigs and differentiated in vitro into adipocytes and osteocytes for up to 4 weeks. Prior to differentiation and at differentiation day 2, 7, and 21, cells were harvested and RNA extracted for transcriptomics analysis by a 13 263 oligo 70-mers array (Sus scrofa AROS V1.0 with extension; Operon). Data were normalized by Lowess and statistical analysis was run using ANOVA with Benjamini-Hochberg false discovery rate (FDR) correction. Data mining was carried out using Ingenuity Pathway Analysis and David. Using an FDR of <0.05 for overall tissue effect and a post-hoc correction of P < 0.001, we observed 65 differentially expressed genes (DEG) between ADSC and BMSC before starting differentiation (0.66% of unique genes in the array). Functional analysis uncovered significant enrichment of extracellular matrix genes with direct roles in cell adhesion, migration, movement, and morphology. When the interaction cell type × differentiation × time was assessed, we observed >2 000 DEG with an FDR <0.05. This large number was mostly due to time effects. When pair-wise comparisons between cell types for each time point during the same differentiation were performed (post-hoc P < 0.001), we observed a strikingly low number of DEG. The number of DEG was lower between cell types in osteogenic (<100 DEG) compared with adipogenic (<200 DEG) differentiation. We observed significant enrichment (FDR-corrected P-value cut-off <0.05) of functions related to metabolism, antigen presentation, angiogenesis, and cell cycle in both differentiation conditions. We also observed an overall greater induction of the enriched functions in ADSC and a decrease in BMSC during adipogenic differentiation and the opposite during osteogenic differentiation except for metabolism, which appeared to be larger in ADSC in all cases. Among the significant enriched functions of DEG between the 2 differentiations, we observed enrichment of genes involved in metabolism, cell death, cell-to-cell signalling, and antigen presentation in ADSC during adipogenic compared with osteogenic differentiation. In BMSC we observed enrichment of functions related to cell death, antigen presentation, and lipid metabolism in osteogenic v. adipogenic differentiation. Overall data uncovered a high similarity at the transcriptional level between ADSC and BMSC both prior to differentiation and during differentiation. Those data support ADSC being particularly similar to BMSC. This work was support by the Illinois Regenerative Medicine Institute (IDPH # 63080017).

Involvement of brain-derived neurotrophic factor and neurogenesis in oestradiol neuroprotection of the hippocampus of hypertensive rats

The hippocampus of spontaneously hypertensive rats (SHR) and deoxycorticosterone (DOCA)-salt hypertensive rats shows decreased cell proliferation and astrogliosis as well as a reduced number of hilar cells. These defects are corrected after administration of 17β-oestradiol (E(2) ) for 2 weeks. The present work investigated whether E(2) treatment of SHR and of hypertensive DOCA-salt male rats modulated the expression of brain-derived neurotrophic factor (BDNF), a neurotrophin involved in hippocampal neurogenesis. The neurogenic response to E(2) was simultaneously determined by counting the number of doublecortin-immunopositive immature neurones in the subgranular zone of the dentate gyrus. Both hypertensive models showed decreased expression of BDNF mRNA in the granular zone of the dentate gyrus, without changes in CA1 or CA3 pyramidal cell layers, decreased BDNF protein levels in whole hippocampal tissue, low density of doublecortin (DCX)-positive immature neurones in the subgranule zone and decreased length of DCX+ neurites in the dentate gyrus. After s.c. implantation of a single E(2) pellet for 2 weeks, BDNF mRNA in the dentate gyrus, BDNF protein in whole hippocampus, DCX immunopositive cells and the length of DCX+ neurites were significantly raised in both SHR and DOCA-salt-treated rats. These results indicate that: (i) low BDNF expression and deficient neurogenesis distinguished the hippocampus of SHR and DOCA-salt hypertensive rats and (ii) E(2) was able to normalise these biologically important functions in the hippocampus of hypertensive animals.

Very-long-chain fatty acids are involved in polar auxin transport and developmental patterning in Arabidopsis

Very-long-chain fatty acids (VLCFAs) are essential for many aspects of plant development and necessary for the synthesis of seed storage triacylglycerols, epicuticular waxes, and sphingolipids. Identification of the acetyl-CoA carboxylase PASTICCINO3 and the 3-hydroxy acyl-CoA dehydratase PASTICCINO2 revealed that VLCFAs are important for cell proliferation and tissue patterning. Here, we show that the immunophilin PASTICCINO1 (PAS1) is also required for VLCFA synthesis. Impairment of PAS1 function results in reduction of VLCFA levels that particularly affects the composition of sphingolipids, known to be important for cell polarity in animals. Moreover, PAS1 associates with several enzymes of the VLCFA elongase complex in the endoplasmic reticulum. The pas1 mutants are deficient in lateral root formation and are characterized by an abnormal patterning of the embryo apex, which leads to defective cotyledon organogenesis. Our data indicate that in both tissues, defective organogenesis is associated with the mistargeting of the auxin efflux carrier PIN FORMED1 in specific cells, resulting in local alteration of polar auxin distribution. Furthermore, we show that exogenous VLCFAs rescue lateral root organogenesis and polar auxin distribution, indicating their direct involvement in these processes. Based on these data, we propose that PAS1 acts as a molecular scaffold for the fatty acid elongase complex in the endoplasmic reticulum and that the resulting VLCFAs are required for polar auxin transport and tissue patterning during plant development.

Very-long-chain fatty acids are involved in polar auxin transport and developmental patterning in Arabidopsis

Very-long-chain fatty acids (VLCFAs) are essential for many aspects of plant development and necessary for the synthesis of seed storage triacylglycerols, epicuticular waxes, and sphingolipids. Identification of the acetyl-CoA carboxylase PASTICCINO3 and the 3-hydroxy acyl-CoA dehydratase PASTICCINO2 revealed that VLCFAs are important for cell proliferation and tissue patterning. Here, we show that the immunophilin PASTICCINO1 (PAS1) is also required for VLCFA synthesis. Impairment of PAS1 function results in reduction of VLCFA levels that particularly affects the composition of sphingolipids, known to be important for cell polarity in animals. Moreover, PAS1 associates with several enzymes of the VLCFA elongase complex in the endoplasmic reticulum. The pas1 mutants are deficient in lateral root formation and are characterized by an abnormal patterning of the embryo apex, which leads to defective cotyledon organogenesis. Our data indicate that in both tissues, defective organogenesis is associated with the mistargeting of the auxin efflux carrier PIN FORMED1 in specific cells, resulting in local alteration of polar auxin distribution. Furthermore, we show that exogenous VLCFAs rescue lateral root organogenesis and polar auxin distribution, indicating their direct involvement in these processes. Based on these data, we propose that PAS1 acts as a molecular scaffold for the fatty acid elongase complex in the endoplasmic reticulum and that the resulting VLCFAs are required for polar auxin transport and tissue patterning during plant development.

OXIDATIVE STRESS 3 is a chromatin-associated factor involved in tolerance to heavy metals and oxidative stress

A cDNA expression library from Brassica juncea was introduced into the fission yeast Schizosaccharomyces pombe to select for transformants tolerant to cadmium. Transformants expressing OXIDATIVE STRESS 3 (OXS3) or OXS3-Like cDNA exhibited enhanced tolerance to a range of metals and oxidizing chemicals. OXS3 belongs to a family of proteins that share a highly conserved domain corresponding to a putative N-acetyltransferase or thioltransferase catalytic site. Mutations within this conserved domain abolished the ability of Arabidopsis thaliana OXS3 to enhance stress tolerance in S. pombe, indicating a role in stress tolerance for the presumptive catalytic domain. A stress-sensitive mutant of AtOXS3 and enhanced tolerance of overexpression lines support the role of OXS3 in stress tolerance. The expression of tagged B. juncea and A. thaliana OXS3 proteins in plant cells revealed a subnuclear speckling pattern related to the nucleosome in discrete parts of the chromatin. It is possible that OXS3 might act as a chromatin remodeling factor for the stress response.

179 INTERNAL CONTROL GENES FOR QUANTITATIVE PCR OF PORCINE MESENCHYMAL STEM CELLS DURING ADIPOGENIC AND OSTEOGENIC DIFFERENTIATION IN VITRO

Uncovering transcriptomic adaptation of porcine adult stem cells during differentiation in vitro towards a target tissue can provide important information for human adult stem cell therapeutic applications. High-throughput microarrays allow the parallel analysis of thousands of genes simultaneously. However, quantitative RT-PCR (qPCR) remains the chosen method for high-precision mRNA abundance analysis and microarray data verification. Essential for qPCR reliability is data normalization using appropriate internal control genes (ICG). The objective of this study was to find reliable ICG for normalization of qPCR data for porcine adult mesenchymal stem cells induced to differentiate toward adipogenic and osteogenic lineages. Mesenchymal stem cells were harvested from porcine adipose tissue and bone marrow and cultured in vitro with specific differentiation media for up to 3 weeks. The experiment was analyzed by a porcine 13 000-oligo microarray, and data were mined to uncover highly stable genes. Statistical analysis was performed using PROC MIXED of SAS (SAS Institute Inc., Cary, NC, USA). The model included fixed effect of time, cell type, differentiation, and all interaction between them. Pig (n = 3) was considered a random variable. Initial microarray analysis revealed 27 genes with high stability across all samples (sample/reference = 1 ± 0.2). Gene network analysis identified 20 genes without known co-regulation (i.e. common up-stream regulators). Among those genes, we could design high-quality primers (i.e. absence of primer-dimer, single amplicon) only for 10 of them (BANF1, DAK, DPH3, GTF2H3, PRR3, NSUN5, NUBP, SSU72, TIMM17B, and VPS4A), and qPCR using a standard curve was run. Stability of those genes was assessed using pairwise comparison of expression ratios. All genes examined were highly stable with TIMM17B, NSUN5, and VPS4A as the most stable. All the potential ICG tested had significant time, tissue × differentiation, and tissue × time effects. For the 3 most stable genes, we did not observe additional effects, while other ICG were significantly affected by differentiation. The analysis also indicated calculation of the normalization factor using the 3 most stable genes (NF3) as highly reliable; however, the use of 7 genes (NF7) would provide the best reliability. To assess the effect of normalization, we ran qPCR for DBI and COL1A1, genes specific of adipogenic and osteogenic differentiation, respectively. The effect on qPCR data normalization was highly apparent for the adipogenic differentiation and less apparent for the osteogenic differentiation. No differences were observed when qPCR data were normalized by NF3 or NF7. The combination of microarray data and pairwise analysis uncovered novel and high reliable ICG for qPCR normalization in adult porcine stem cells induced into adipogenic and osteogenic lineages. This work was supported by the Illinois Regenerative Medicine Institute.

282 ADIPOGENIC DIFFERENTIATION IN VITRO OF PORCINE ADULT MESENCHYMAL STEM CELLS

The quantity and accessibility of subcutaneous adipose tissue in humans make it an attractive alternative to bone marrow as a source of adult stem cells for therapeutic purposes. However, before such a cell source substitution can be proposed, the properties of stem cells derived from adipose tissue (ADSC) and bone marrow (BMSC), and their differentiated progeny must be compared in an animal model, such as swine, that adequately simulates the structure and physiology of humans. The objective of this work was to induce adult porcine stem cells isolated from subcutaneous adipose tissue and bone marrow to differentiate in vitro along the adipogenic lineage and to compare their transcript profile properties. ADSC and BMSC were isolated from subcutaneous adipose tissue and femurs of adult pigs, respectively, and differentiated along the adipogenic lineage using specific inducing medium. Cells were incubated up to 4 weeks with medium replaced every 3 days. Histological staining with Oil Red O was performed at 0, 2, 4, 7, 14, 21, 28 days of differentiation (dd) to confirm the adipogenic differentiation. RNA was also extracted at these time points. qPCR was performed on PPARG, DBI, ACSL1, CD36, CEBPA, DGAT2, ADFP, ADIPOQ, SCD. The geometrical mean of GTF2H3, NUBP, and PPP2CB was used as an internal control. Gene expression was analyzed using a mixed model of SAS with repeated time. The adipogenic differentiation of both ADSC and BMSC was confirmed by the Oil Red O positive staining. The relative mRNA abundance of all the genes at dd0 was similar between the ADSC and BMSC. The relative mRNA abundance of most of the genes was also similar between ADSC and BMSC throughout the adipogenic differentiation. ACSL1 and ADIPOQ had analogous expression patterns among the cell types. ACSL1 had relatively large mRNA abundance before differentiation, but ADIPOQ was barely detectable. As a consequence of differentiation, ACSL1 increased in relative mRNA abundance about 10-fold, whereas ADIPOQ mRNA increased about 1000-fold. Temporal expression patterns of SCD, DGAT2, and ADFP were similar. The increase in gene expression was >800% for SCD, >500% for ADFP, and >50 000% for DGAT2 after 7dd. ADSC had significantly higher expression of those genes compared to BMSC at 14 and 28dd. Both ADIPOQ and DGAT2 were almost undetectable prior to differentiation. mRNA expression of CD36 and DBI was similar with a significantly larger increase in expression of ADSC compared with BMSC. Relative mRNA abundance of CEBPA and PPARG was also larger in ADSC compared with BMSC; however, BMSC had a remarkable increase in temporal expression of those genes throughout adipogenic differentiation. These results suggest both cell types can differentiate towards the adipogenic lineage but with quantitatively different gene expression patterns. More investigation is needed before the ADSC can be considered a practical alternative source for stem cells in future human clinical applications. This research was supported by the Illinois Regenerative Medicine Institute.

182 OSTEOPONTIN GENE EXPRESSION IN IMMATURE AND MATURE SWINE CUMULUS CELLS AND OOCYTES

Osteopontin (OPN) is an acidic single-chain phosphorylated glycoprotein found in both the female and the male reproductive tract that is believed to facilitate reproduction. It was recently reported in swine that OPN improves in vitro fertilization (Hao et al. 2006 Biol. Reprod. 75, 726–733). In bovine, OPN improves the efficiency of in vitro embryo production, and it has been detected on the zona pellucida (ZP) of immature and mature oocytes (Monaco et al. 2007 J. Anim. Sci. 85, 529 abst). This study was designed to evaluate the gene expression of OPN (SPP1) in immature and mature swine cumulus cells and oocytes. Ovaries from a local slaughterhouse were collected on three different days. Half of the immature cumulus–oocyte complexes (COCs) from each day were vortexed in 1 mL TCM-199 HEPES containing 10 mg mL–1 hyaluronidase to separate immature cumulus cells, while the other half of the COCs were maturated for 40-42 h and then the cumulus cells were separated. RNA from cumulus cells and oocytes was extracted and genomic DNA was removed by DNase treatment. cDNA was synthesized using 100 ng of RNA and diluted 50% with DNase–RNase-free water. The RT-PCR product from cumulus cells and oocytes was run in a 2% agarose gel stained with ethidium bromide to verify the presence of SPP1. Relative mRNA abundance between immature and mature cumulus cells was assessed by SYBR green real-time RT–PCR run in triplicate using a 6-point twofold dilution standard curve. GAPDH was used as internal control. Primers for SPP1 and GAPDH were designed spanning an exon/exon junction. The presence of a single and specific PCR product was assessed by gel electrophoresis (a single band was expected at 100 and 90 bp, respectively, for SPP1 and GAPDH), dissociation curve, and sequencing. A t-test was used to assess differences between immature (n = 3) and mature (n = 3) cumulus cells. SPP1 was detected in agarose gel in both immature and mature oocytes and cumulus cells. Cumulus cells presented a Ct for SPP1 ranging from 20 (immature) to 29 (mature). Immature cumulus cells showed a 32-fold larger mRNA abundance compared to the mature cumulus cells (P < 0.05) when data were transformed using a standard curve. Results showed expression of SPP1 in porcine oocytes and cumulus cells. However, maturation significantly decreased the expression of SPP1 in cumulus cells. The presence of SPP1 mRNA in oocytes and cumulus cells and the larger mRNA abundance before maturation may suggest a role of this protein prior to maturation of oocytes. Additional studies will be required to determine the specific role of SPP1 in oocyte maturation in the pig.

284 HIGH-THROUGHPUT MICROFLUIDIC TECHNOLOGIES FOR STEM CELL RESEARCH

One of the major issues in stem cell biology is to determine the conditions that enable stem cell culture, which has been slow and laborious due to the present nature of culture systems. Our current research is designed to leverage existing robotic and fluid handling technologies with the unique fluid control and microenvironment properties of the microscale, along with the extensive expertise in stem cell research. One key advantage of microfluidic systems for stem cell research is the ability to ultra-miniaturize the cell-based assays. Swine adipose-derived stem cells (ADSCs) were cultured and differentiated into adipogenic and osteogenic cells. A fluid handling robot was used to implement the passive pumping in the microdevices, which did not require any fluid connectors. A 192-channel micro-conduit polydimethylsiloxane (PDMS) array was made using soft lithography and bonded onto a standard microplate. The fluid handling robot was programmed to load cells and change medium. The total time to change medium for 192 channels was 30 min. Swine adipose-derived stem cells were cultured using DMEM + 10% fetal bovine serum (FBS) for six days in a 100% humidified 5% CO2 atmosphere. Two different cell concentrations were compared (1 � 106 cells and 2 � 106). The ADSCs were differentiated into adipogenic and osteogenic cells using specific differentiation media for the following ten days. The medium was changed every 24 h by the fluid handling robot. To assess for the differentiation, the adipogenic and osteogenic cells were stained using oil red O and alizarin red S to verify fat and calcium formation, respectively. Fatty acid accumulation was confirmed by red-stained lipid vesicles inside the adipogenic cells, and calcium formation was observed as red-stained calcium deposits around the osteogenic cells. We also determined that the concentration of 1 � 106 cells (equivalent to 1500 cells per channel) gave better results than the concentration of 2 � 106 cells (equivalent to 3000 cells per channel) in terms of cell morphology and differentiation parameters. The use of multifactorial directed differentiation using high-speed robotic systems, as employed in our research, will enable the examination of large matrices of culture and differentiation conditions for stem cells. Furthermore, our approach enables the use of gene expression analysis and other analytical methodologies to study the differentiation and cell function of cells cultured under essentially unlimited conditions. Using the automated microscale system in large factorial experiments allows analysis of the basic mechanisms underlying stem cell development in vitro, and ultimately in vivo. This research was supported by the Illinois Regenerative Medicine Institute (IRMI).