Vitamin D and Vitamin A Receptor Expression and the Proliferative Effects of Ligand Activation of These Receptors on the Development of Pancreatic Progenitor Cells Derived from Human Fetal Pancreas
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China. Stem cell reviews
(Impact Factor: 2.77).
03/2010; 7(1):53-63. DOI: 10.1007/s12015-010-9146-1
The growth and development of pancreatic islet cells are regulated by various morphogens. Vitamin A modulates in vitro differentiation of islet cells and vitamin D affects beta-cell insulin secretion, while both vitamin ligands act through heterodimerization with the retinoid X receptor (RXR). However, their effects in modulating pancreatic development have not been determined. In this study, cultured human pancreatic progenitor cells (PPCs) isolated from human fetal pancreas were stimulated to differentiate into islet-like cell clusters (ICCs). RT-PCR, Western blotting and immunocytochemistry were used to examine the expression and localization of vitamin D receptor (VDR), retinoic acid receptor (RAR), and RXR in PPCs. The effects of added all-trans retinoic acid (atRA, a form of vitamin A), calcitriol (activated vitamin D) and of these ligands together on PPC cell viability, proliferation and apoptosis were assessed by MTT, BrdU and ELISA assays, respectively. Post-treatment neurogenin-3 (NGN3) expression, necessary for islet-cell lineage development, was examined by real-time RT-PCR. Results showed that RAR, RXR and VDR were expressed in PPCs. RAR and RXR were localized in nuclei, and the VDR in nuclei, cytoplasm and plasma membrane. atRA and calcitriol each increased PPC viability and proliferation; atRA additionally decreased PPC apoptosis. Co-addition of atRA and calcitriol had no additive effects on cell viability but did increase ngn3 responses. In conclusion, RAR, RXR and VDR are expressed in human fetal PPCs and PPC proliferation can be promoted by calcitriol, atRA or both together, data valuable for elucidating mechanisms underlying islet development and for developing clinical islet transplantation.
Available from: Philipp Gut
- "This role in pancreatic induction has also been examined during mouse and human ES cell differentiation in vitro, and has been shown to be relevant for the induction of the pancreatic endoderm marker, PDX1 –. Although little is known about the proliferation effect of retinoic acid, recent studies have shown that retinoic acid can increase the proliferation of cultured human pancreatic progenitor cells  and the number of pancreatic beta-cells in zebrafish . "
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ABSTRACT: Inducing beta-cell mass expansion in diabetic patients with the aim to restore glucose homeostasis is a promising therapeutic strategy. Although several in vitro studies have been carried out to identify modulators of beta-cell mass expansion, restoring endogenous beta-cell mass in vivo has yet to be achieved. To identify potential stimulators of beta-cell replication in vivo, we established transgenic zebrafish lines that monitor and allow the quantification of cell proliferation by using the fluorescent ubiquitylation-based cell cycle indicator (FUCCI) technology. Using these new reagents, we performed an unbiased chemical screen, and identified 20 small molecules that markedly increased beta-cell proliferation in vivo. Importantly, these structurally distinct molecules, which include clinically-approved drugs, modulate three specific signaling pathways: serotonin, retinoic acid and glucocorticoids, showing the high sensitivity and robustness of our screen. Notably, two drug classes, retinoic acid and glucocorticoids, also promoted beta-cell regeneration after beta-cell ablation. Thus, this study establishes a proof of principle for a high-throughput small molecule-screen for beta-cell proliferation in vivo, and identified compounds that stimulate beta-cell proliferation and regeneration.
Available from: Jose M González-Sancho
- "Titration out of common co-activators, but not of RXR, may be the mechanism by which ligand-bound VDR represses retinoic acid receptor (RAR) transactivation in GH4C1 pituitary cells (Jiménez-Lara and Aranda, 1999). The relation between 1α,25(OH) 2 D 3 and retinoic acid is however complex, as cooperative effects on target genes and cellular outcome (proliferation inhibition and differentiation) have been described in other systems (Tavera-Mendoza et al., 2006; Anand et al., 2008; Ng et al., 2010). As for estrogen receptor (ER), D. Feldman's group has shown that 1α,25(OH) 2 D 3 exerts a multilevel protective effect against breast cancer that includes the inhibition of estrogen synthesis through the direct and indirect repression of aromatase (CYP19) and the downregulation of ER-α expression through two VDREs in its promoter region (Krishnan et al., 2010; Swami et al., 2013). "
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ABSTRACT: Many studies in different biological systems have revealed that 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) modulates signaling pathways triggered at the plasma membrane by agents such as Wnt, transforming growth factor (TGF)-β, epidermal growth factor (EGF), and others. In addition, 1α,25(OH)2D3 may affect gene expression by paracrine mechanisms that involve the regulation of cytokine or growth factor secretion by neighboring cells. Moreover, post-transcriptional and post-translational effects of 1α,25(OH)2D3 add to or overlap with its classical modulation of gene transcription rate. Together, these findings show that vitamin D receptor (VDR) cannot be considered only as a nuclear-acting, ligand-modulated transcription factor that binds to and controls the transcription of target genes. Instead, available data support the view that much of the complex biological activity of 1α,25(OH)2D3 resides in its capacity to interact with membrane-based signaling pathways and to modulate the expression and secretion of paracrine factors. Therefore, we propose that future research in the vitamin D field should focus on the interplay between 1α,25(OH)2D3 and agents that act at the plasma membrane, and on the analysis of intercellular communication. Global analyses such as RNA-Seq, transcriptomic arrays, and genome-wide ChIP are expected to dissect the interactions at the gene and molecular levels.
Available from: Leonardo J. Solmesky
- "The molecule chosen to prove this principle was Retinoic acid (RA), which is known by its ability to induce many cellular changes in diverse cell types in vivo and in vitro –. RA is the oxidized form of Vitamin A that determines anterior/posterior patterning in chordates at early developmental stages . "
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ABSTRACT: Human mesenchymal stem cells (hMSC) are easily isolated from the bone marrow by adherence to plastic surfaces. These cells show self-renewal capacity and multipotency. A unique feature of hMSC is their capacity to survive without serum. Under this condition hMSC neither proliferate nor differentiate but maintain their biological properties unaffected. Therefore, this should be a perfect platform to study the biological effects of defined molecules on these human stem cells. We show that hMSC treated for five days with retinoic acid (RA) in the absence of serum undergo several transcriptional changes causing an inhibition of ERK related pathways. We found that RA induces the loss of hMSC properties such as differentiation potential to either osteoblasts or adipocytes. We also found that RA inhibits cell cycle progression in the presence of proliferating signals such as epidermal growth factor (EGF) combined with basic fibroblast growth factor (bFGF). In the same manner, RA showed to cause a reduction in cell adhesion and cell migration. In contrast to these results, the addition of EGF+bFGF to serum free cultures was enough to upregulate ERK activity and induce hMSC proliferation and cell migration. Furthermore, the addition of these factors to differentiation specific media instead of serum was enough to induce either osteogenesis or adipogenesis. Altogether, our results show that hMSC's ability to survive without serum enables the identification of signaling factors and pathways that are involved in their stem cell biological characteristics without possible serum interferences.
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