Functional Recellularization of Acellular Rat Liver Scaffold by Induced Pluripotent Stem Cells: Molecular Evidence for Wnt/B-Catenin Upregulation.

BACKGROUND: Liver transplantation remains the only viable therapy for liver failure but has a severely restricted utility. Here, we aimed to decellularize rat livers to form acellular 3D bio-scaffolds suitable for seeding with induced pluripotent cells (iPSCs) as a tool to investigate the role of Wnt/β-catenin signaling in liver development and generation. METHODS: Dissected rat livers were randomly divided into three groups: I (control); II (decellularized scaffolds) and III (recellularized scaffolds). Liver decellularization was established via an adapted perfusion procedure and assessed through the measurement of extracellular matrix (ECM) proteins and DNA content. Liver recellularization was assessed through histological examination and measurement of transcript levels of Wnt/β-catenin pathway, hepatogenesis, liver-specific microRNAs and growth factors essential for liver development. Adult rat liver decellularization was confirmed by the maintenance of ECM proteins and persistence of growth factors essential for liver regeneration. RESULTS: iPSCs seeded rat decellularized livers displayed upregulated transcript expression of Wnt/β-catenin pathway-related, growth factors, and liver specification genes. Further, recellularized livers displayed restored liver-specific functions including albumin secretion and urea synthesis. CONCLUSION: This establishes proof-of-principle for the generation of three-dimensional liver organ scaffolds as grafts and functional re-establishment

Wahrnehmung der Auswirkung der Vertrautheit mit Problemen seitens Studenten auf die Qualität von Gruppendiskussionen in einer problembasierten Lernumgebung

Introduction: Problem-based learning (PBL) is a student-centred approach to learning using health problem scenarios to trigger the learning process. Several factors contribute to the role of the problem scenarios in stimulating student learning. One of those factors is the student's familiarity and knowledge about the problem itself. This may affect the challenge and stimulate the student discussion in the tutorial group. No previous research studied the impact of reusing the case scenarios on the group discussion. This study explored the effect of student familiarity of the problems as a result of reusing the case scenarios on the discussion quality in the tutorial session.Methods: A qualitative study was used primarily to explore an understanding of the underlying opinions of the medical students of first and second academic year in the college of Medicine, University of Sharjah, UAE. Direct-discussion groups were arranged, and an open-ended online questionnaire was provided. Results: The results of the study showed that fore-knowledge about the case scenario had no significant adverse effect on the discussion. Students stated that the facilitators played a vital role in maintaining the excellent quality of the discussion.Discussion: Reuse of problem scenarios in PBL does not hurt the quality of the discussion, provided that the group dynamics are maintained.Einführung: Problembasiertes Lernen (PBL) ist ein auf Studenten bezogener Ansatz, um zu lernen, Gesundheitsproblem-Szenarien für das Auslösen eines Lerneffekts zu nutzen. Mehrere Faktoren tragen zur Rolle von Problemszenarien bei, um Studenten zum Lernen anzuregen. Einer der Faktoren ist die Vertrautheit von Studenten mit einem Problem bzw. deren Kenntnis des Problems selbst. Dies kann einen Einfluss auf die Herausforderung und Stimulierung der Studentendiskussion in einer Lerngruppe haben. Bisherige Forschungen haben nicht den Einfluss auf Gruppendiskussionen untersucht, wenn Fallstudien-Szenarien erneut verwendet werden. Die vorliegende Studie hat die Auswirkungen untersucht, die eine Vertrautheit der Studenten mit den Problemen infolge einer erneuten Verwendung von Fallstudien-Szenarien auf die Diskussionsqualität im Tutoriumskurs hat.Methoden: Eine qualitative Studie wurde vorrangig genutzt, um das Verständnis zugrunde liegender Meinungen von Medizinstudenten des ersten und zweiten akademischen Jahres am College of Medicine, University of Sharjah, VAE, zu untersuchen. Direkte Diskussionsgruppen wurden zusammengestellt und es wurde ein offen endender Online-Fragebogen zur Verfügung gestellt.Ergebnisse: Die Ergebnisse der Studie zeigten, dass Vorkenntnisse von einem Fallstudien-Szenario keine signifikanten nachteiligen Auswirkungen auf die Diskussion hatten. Studenten gaben an, dass die Moderatoren eine wesentliche Rolle dabei spielten, die hohe Qualität der Diskussion beizubehalten.Diskussion: Die erneute Verwendung von Problemszenarien im PBL beeinträchtigt nicht die Qualität der Diskussion, vorausgesetzt, die Gruppendynamik bleibt erhalten

Ultrastructural changes and nestin expression accompanying compensatory renal growth after unilateral nephrectomy in adult rats

Mohamed Ahmed Eladl,1,2 Wael M Elsaed,2,3 Hoda Atef,4 Mohamed El-Sherbiny2 1Department of Basic Medical Sciences, University of Sharjah, Sharjah, United Arab Emirates; 2Anatomy and Embryology Department, Faculty of Medicine, Mansoura University, Mansoura, Egypt; 3Anatomy and Embryology Department, Faculty of Medicine, Taibah University, Madinah, Saudi Arabia; 4Department of Histology, University of Mansoura, Mansoura, Egypt Background: Several renal disorders affect the glomerular podocytes. Compensatory structural and functional changes have been observed in animals that have undergone unilateral renal ablation. These changes occur as a pliant response to quench the increased functional demand to maintain homeostasis of fluid and solutes. Nestin is an intermediate filament protein present in the glomerular podocytes of the adult kidney and is linked with the maintenance of its foot process structure. Structural changes in the podocytes ultimately restructure the filtration barrier. Very few studies related to the ultrastructural and histopathologic changes of the podocytes are documented. The present study aimed to assess the histopathologic changes at the ultrastructural level in the adapted kidney at different time intervals following unilateral renal ablation in adult rats and its relation with nestin.Methods: Forty-eight rats were divided into four groups (n=12 in each group). The animals of Group A were control naïve rats, while the group B, group C and group D animals underwent left unilateral nephrectomy and the remaining right kidney was removed on days 10, 20 and 30, respectively. Each group included four sham-operated rats, which were sacrificed at the same time as the naïve rats. Each nephrectomized sample was weighed and its sections were subjected to hematoxylin and eosin examination, transmission electron microscopic study as well as immunostaining using the intermediate filament protein nestin.Results: No difference was found between the kidney sections from the control group and the sham-operated groups. A significant increase in the weight of the right kidneys was noted in groups B, C and D (P<0.001). The ultrastructural adaptive changes seen in the glomeruli of group B were subsequently reduced in groups C and D. This finding corresponded to a similar pattern of nestin expression in the podocytes, which showed significant increase in group B followed by reduced expression in groups C and D. Histopathologic and transmission electron microscopic evaluation of group B showed signs of kidney injury. On the other hand, group C animals showed markedly reduced renal adaptive changes and similar changes were also noted in group D.Conclusion: Correlation between nestin expression and the ultrastructural changes confirms that nestin has a role in increasing the mechanical stability of the podocytes in order to enhance their morphologic changes in response to the tensile glomerular capillary wall. However, further studies investigating more remote ultrastructural changes and their relation with nestin expression are needed to confirm this relationship. Keywords: glomerular proliferation, podocytes, basement membrane, subpodocytic space, TEM, nestin, nephrectomy, compensator

Transcriptome-wide analysis of Chlorella reveals auxin-induced carotenogenesis pathway in green microalgae

Microalgae are a commercially viable route for the production of carotenoids. Chlorella sp. BR2 was treated with plant hormones indole-3-acetic acid, salicylic acid, abscisic acid and methyl jasmonate and screened for enhanced carotenoid production. Indole-3-acetic acid was the only hormone with an inductive effect on carotenoid accumulation. As such, transcriptome-wide changes following auxin treatment were profiled using RNA-Seq and expressed sequences reconstructed with de novo assembly. This revealed the active pathway components of auxin-induced carotenogenesis. Data analysis specified the differentially expressed genes involved in auxin biosynthesis and signal transduction, which hint at close, yet unique relationship to equivalent pathways in higher plants. Unlike in plants, the ancient ABP1/SCFSKP2A/IBR5-mediated pathways for auxin response likely acted as the primary signaling route in Chlorella. As carotenoids are precursors for abscisic acid and antagonists of reactive oxygen species, the findings suggest a potential link between auxin signaling and abiotic stress tolerance

Blue light enhances astaxanthin biosynthesis metabolism and extraction efficiency in Haematococcus pluvialis by inducing haematocyst germination

Haematococcus pluvialis accumulates large amounts of astaxanthin during its haematocyst stage. Cyst germination is a biological pretreatment method for improved astaxanthin extraction with potential to replace energy-intensive homogenizer-based mechanical cell cracking methods. The present study demonstrates effects of different LED light wavelengths on haematocyst germination and on its astaxanthin biosynthesis pathway. Blue light enhanced the germination efficiency and slowed the nitrogen consumption rate, resulting in significantly higher astaxanthin content and improved extractability compared with white and red lights, that also had lower germination rates. After 5 days, the total astaxanthin extractability under blue light was 4.0 and 6.7 times higher than for white and red lights, respectively. The blue light receptor gene phot was significantly induced which upregulated the biosynthesis pathway genes psy and pds, as well as dgat1 and dgat2d. Hence, blue light triggers germination and astaxanthin biosynthesis, providing a strategy for improved extraction while modulating higher biosynthesis during germination

Gene expression profiling of astaxanthin and fatty acid pathways in Haematococcus pluvialis in response to different LED lighting conditions

Haematococcus pluvialis is a green microalga of major interest to industry based on its ability to produce large amounts of astaxanthin. Biosynthesis of astaxanthin and its mono- and di-esters was significantly stimulated under 150 μmol m s of white LED (W-150) compared with lower light intensities, but the highest astaxanthin amounts were produced under 70 μmol m s of blue LED (B-70). Transcripts of astaxanthin biosynthesis genes psy, crtO, and bkt2 were upregulated under W-150, while psy, lcy, crtO, and crtR-B were upregulated by B-70. Total fatty acid content and biosynthesis genes fata and all dgat genes were induced under W-150, while C18:3n6 biosynthesis and dgat2a expression were specifically stimulated by B-70 which was correlated to astaxanthin ester biosynthesis. Nitrogen starvation, various LEDs and the identified upregulated genes may provide useful tools for future metabolic engineering to significantly increase free astaxanthin, its esters and fatty acid precursors in H. pluvialis