Therapeutic Potential of Mesenchymal Stem Cells for Cancer Therapy

Mesenchymal stem cells (MSCs) are among the most frequently used cell type for regenerative medicine. A large number of studies have shown the beneficial effects of MSC-based therapies to treat different pathologies, including neurological disorders, cardiac ischemia, diabetes, and bone and cartilage diseases. However, the therapeutic potential of MSCs in cancer is still controversial. While some studies indicate that MSCs may contribute to cancer pathogenesis, emerging data reported the suppressive effects of MSCs on cancer cells. Because of this reality, a sustained effort to understand when MSCs promote or suppress tumor development is needed before planning a MSC-based therapy for cancer. Herein, we provide an overview on the therapeutic application of MSCs for regenerative medicine and the processes that orchestrates tissue repair, with a special emphasis placed on cancer, including central nervous system tumors. Furthermore, we will discuss the current evidence regarding the double-edged sword of MSCs in oncological treatment and the latest advances in MSC-based anti-cancer agent delivery systems.Junta de Andalucía PI-0272-2017Ministerio de Ciencia, Innovación y Universdad CD16/00118, CP19/00046, PI16/00259, BFU2017-83588-P, CP14/00105, PI18/01590, PI17/02104, PIC18/0010, IC19/0052Juvenile Diabetes Research Foundation (USA) 2-SRA-2019-837-S-BFundación Española para la Ciencia y la Tecnología 2018-00023

Magnetic structure of the antiferromagnetic half-Heusler compound NdBiPt

We present results of single crystal neutron diffraction experiments on the rare-earth, half-Heusler antiferromagnet (AFM) NdBiPt. This compound exhibits an AFM phase transition at $T_{\mathrm N}=2.18$~K with an ordered moment of $1.78(9)$~$\mu_{\mathrm B}$ per Nd atom. The magnetic moments are aligned along the $[001]$-direction, arranged in a type-I AFM structure with ferromagnetic planes, alternating antiferromagnetically along a propagation vector $\tau$ of $(100)$. The $R$BiPt ($R$= Ce-Lu) family of materials has been proposed as candidates of a new family of antiferromagnetic topological insulators (AFTI) with magnetic space group that corresponds to a type-II AFM structure where ferromagnetic sheets are stacked along the space diagonal. The resolved structure makes it unlikely, that NdBiPt qualifies as an AFTI.Comment: As resubmitted to PRB, corrected typos and changed symbols in Fig.

The diabetes-linked transcription factor Pax4 is expressed in human pancreatic islets and is activated by mitogens and GLP-1

We previously demonstrated that the transcription factor Pax4 is important for β-cell replication and survival in rat islets. Herein, we investigate Pax4 expression in islets of non-diabetic and diabetic donors, its regulation by mitogens, glucose and the incretin GLP-1 and evaluate its effect on human islet proliferation. Pax4 expression was increased in islets derived from Type 2 diabetic donors correlating with hyperglycaemia. In vitro studies on non diabetic islets demonstrated that glucose, betacellulin, activin A, GLP-1 and insulin increased Pax4 mRNA levels. Glucose-induced Pax4 expression was abolished by the inhibitors LY294002, PD98050 or H89. Surprisingly, increases in Pax4 expression did not prompt a surge in human islet cell replication. Furthermore, expression of the proliferation marker gene Id2 remained unaltered. Adenoviral-mediated expression of human Pax4 resulted in a small increase in Bcl-xL expression while Id2 transcript levels and cell replication were unchanged in human islets. In contrast, overexpression of mouse Pax4 induced human islet cell proliferation. Treatment of islets with 5-Aza-2′-deoxycytidine induced Pax4 without stimulating Bcl-xL and Id2 expression. Human Pax4 DNA binding activity was found to be lower than that of the mouse homologue. Thus, human pax4 gene expression is epigenetically regulated and induced by physiological stimuli through the concerted action of multiple signalling pathways. However, it is unable to initiate the transcriptional replication program likely due to post-translational modifications of the protein. The latter highlights fundamental differences between human and rodent islet physiology and emphasizes the importance of validating results obtained with animal models in human tissue

PAX4 preserves endoplasmic reticulum integrity preventing beta cell degeneration in a mouse model of type 1 diabetes mellitus

[Aims/hypothesis]: A strategy to enhance pancreatic islet functional beta cell mass (BCM) while restraining inflammation, through the manipulation of molecular and cellular targets, would provide a means to counteract the deteriorating glycaemic control associated with diabetes mellitus. The aims of the current study were to investigate the therapeutic potential of such a target, the islet-enriched and diabetes-linked transcription factor paired box 4 (PAX4), to restrain experimental autoimmune diabetes (EAD) in the RIP-B7.1 mouse model background and to characterise putative cellular mechanisms associated with preserved BCM. [Methods]: Two groups of RIP-B7.1 mice were genetically engineered to: (1) conditionally express either PAX4 (BPTL) or its diabetes-linked mutant variant R129W (mutBPTL) using doxycycline (DOX); and (2) constitutively express luciferase in beta cells through the use of RIP. Mice were treated or not with DOX, and EAD was induced by immunisation with a murine preproinsulin II cDNA expression plasmid. The development of hyperglycaemia was monitored for up to 4 weeks following immunisation and alterations in the BCM were assessed weekly by non-invasive in vivo bioluminescence intensity (BLI). In parallel, BCM, islet cell proliferation and apoptosis were evaluated by immunocytochemistry. Alterations in PAX4- and PAX4R129W-mediated islet gene expression were investigated by microarray profiling. PAX4 preservation of endoplasmic reticulum (ER) homeostasis was assessed using thapsigargin, electron microscopy and intracellular calcium measurements. [Results]: PAX4 overexpression blunted EAD, whereas the diabetes-linked mutant variant PAX4R129W did not convey protection. PAX4-expressing islets exhibited reduced insulitis and decreased beta cell apoptosis, correlating with diminished DNA damage and increased islet cell proliferation. Microarray profiling revealed that PAX4 but not PAX4R129W targeted expression of genes implicated in cell cycle and ER homeostasis. Consistent with the latter, islets overexpressing PAX4 were protected against thapsigargin-mediated ER-stress-related apoptosis. Luminal swelling associated with ER stress induced by thapsigargin was rescued in PAX4-overexpressing beta cells, correlating with preserved cytosolic calcium oscillations in response to glucose. In contrast, RNA interference mediated repression of PAX4-sensitised MIN6 cells to thapsigargin cell death. [Conclusions/interpretation]: The coordinated regulation of distinct cellular pathways particularly related to ER homeostasis by PAX4 not achieved by the mutant variant PAX4R129W alleviates beta cell degeneration and protects against diabetes mellitus. The raw data for the RNA microarray described herein are accessible in the Gene Expression Omnibus database under accession number GSE62846

Cx36 makes channels coupling human pancreatic β-cells, and correlates with insulin expression

Previous studies have documented that the insulin-producing β-cells of laboratory rodents are coupled by gap junction channels made solely of the connexin36 (Cx36) protein, and have shown that loss of this protein desynchronizes β-cells, leading to secretory defects reminiscent of those observed in type 2 diabetes. Since human islets differ in several respects from those of laboratory rodents, we have now screened human pancreas, and islets isolated thereof, for expression of a variety of connexin genes, tested whether the cognate proteins form functional channels for islet cell exchanges, and assessed whether this expression changes with β-cell function in islets of control and type 2 diabetics. Here, we show that (i) different connexin isoforms are differentially distributed in the exocrine and endocrine parts of the human pancreas; (ii) human islets express at the transcript level different connexin isoforms; (iii) the membrane of β-cells harbors detectable levels of gap junctions made of Cx36; (iv) this protein is concentrated in lipid raft domains of the β-cell membrane where it forms gap junctions; (v) Cx36 channels allow for the preferential exchange of cationic molecules between human β-cells; (vi) the levels of Cx36 mRNA correlated with the expression of the insulin gene in the islets of both control and type 2 diabetics. The data show that Cx36 is a native protein of human pancreatic islets, which mediates the coupling of the insulin-producing β-cells, and contributes to control β-cell function by modulating gene expressio

Transcriptional response of pancreatic beta cells to metabolic stimulation: large scale identification of immediate-early and secondary response genes

<p>Abstract</p> <p>Background</p> <p>Physiological long term adaptation of pancreatic beta cells is driven by stimuli such as glucose and incretin hormones acting via cAMP (e.g. GLP-1) and involves regulated gene expression. Several rapidly inducible immediate-early genes (IEGs) have been identified in beta cells. Many of these IEGs code for transcription factors and have the potential to control the transcription of downstream <it>target </it>genes likely involved in long term cellular adaptation. The identity of these <it>target </it>genes has not been determined, and the sequence of events occurring during beta cell adaptation is still unclear.</p> <p>Results</p> <p>We have developed a microarray-based strategy for the systematic search of <it>targets</it>. In Min6 insulin-secreting cells, we identified 592 <it>targets </it>and 1278 IEGs responding to a co-stimulation with glucose and cAMP. Both IEGs and <it>targets </it>were involved in a large panel of functions, including those important to beta cell physiology (metabolism, secretion). Nearly 200 IEGs were involved in signaling and transcriptional regulation. To find specific examples of the regulatory link between IEGs and <it>targets</it>, <it>target </it>promoter sequences were analyzed <it>in silico</it>. Statistically significant over-representation of AP-1 response elements notably suggested an important role for this transcription factor, which was experimentally verified. Indeed, cell stimulation altered expression of IEG-encoded components of the AP-1 complex, activating AP-1-dependent transcription. Loss and gain-of-function experiments furthermore allowed to validate a new AP-1 regulated gene (<it>sulfiredoxin</it>) among the <it>targets</it>. AP-1 and <it>sulfiredoxin </it>are sequentially induced also in primary cells from rat islets of Langerhans.</p> <p>Conclusion</p> <p>By identifying IEGs and their downstream <it>targets</it>, this study brings a comprehensive description of the transcriptional response occurring after beta cell stimulation, as well as new mechanistic insights concerning the AP-1 transcription factor.</p

The liver receptor homolog-1 (LRH-1) is expressed in human islets and protects β-cells against stress-induced apoptosis

Liver receptor homolog (LRH-1) is an orphan nuclear receptor (NR5A2) that regulates cholesterol homeostasis and cell plasticity in endodermal-derived tissues. Estrogen increases LRH-1 expression conveying cell protection and proliferation. Independently, estrogen also protects isolated human islets against cytokine-induced apoptosis. Herein, we demonstrate that LRH-1 is expressed in islets, including β-cells, and that transcript levels are modulated by 17β-estradiol through the estrogen receptor (ER)α but not ERβ signaling pathway. Repression of LRH-1 by siRNA abrogated the protective effect conveyed by estrogen on rat islets against cytokines. Adenoviral-mediated overexpression of LRH-1 in human islets did not alter proliferation but conferred protection against cytokines and streptozotocin-induced apoptosis. Expression levels of the cell cycle genes cyclin D1 and cyclin E1 as well as the antiapoptotic gene bcl-xl were unaltered in LRH-1 expressing islets. In contrast, the steroidogenic enzymes CYP11A1 and CYP11B1 involved in glucocorticoid biosynthesis were both stimulated in transduced islets. In parallel, graded overexpression of LRH-1 dose-dependently impaired glucose-induced insulin secretion. Our results demonstrate the crucial role of the estrogen target gene nr5a2 in protecting human islets against-stressed-induced apoptosis. We postulate that this effect is mediated through increased glucocorticoid production that blunts the pro-inflammatory response of islet

Characterization of the "diabesity" gene HMG20A in pancreatic islets

Motivation: Type 2 Diabetes (T2D) accounts for 90-95% of diagnosed diabetic patients, which tendency in the next years is also expected to increase. Recent genomic wide association studies showed a correlation of an allelic variation of HMG20A with T2D in some ethnic groups. Up to date, there is no scientific evidence of the role of this gene in pancreatic tissue. But, in central nervous system, HMG20A regulates the expression of NeuroD, common in pancreas and nervous system morphogenesis. Here, our group makes an approach to characterize HMG20A in pancreatic islets, focusing on its involvement in glucose-stimulated insulin secretion (GSIS) and pancreatic islets development. We want to demonstrate that: 1) HMG20A is expressed in endocrine pancreas 2) HMG20A modifies expression of genes involved in pancreas development 3) silencing HMG20A affects expression levels of insulin secretion related genes and functionality.Methods: Qualitative expression of HMG20A is tested out in slides of pancreatic sections obtained from control mice. Co-localization with α or β cells is analyzed by immunofluorescence using anti-HMG20A, anti-insulin/glucagon antibodies and Dapi for nuclei. INS-1E cells are cultured and treated with a specific siRNA against HMG20A or a non-specific siRNA control during 72h. Genes involved in insulin secretion and endocrine pancreas development are assayed via qRT-PCR in INS1-E cells after siRNA treatment. Pdx1, Pax4, MafA and HMG20A expression levels are assessed following 2-ΔΔCt method. Finally, HMG20A silenced mouse islets and INS-1E are cultured at low glucose (2.8 mM) and high glucose medium (22 mM) following quantification of insulin secretion by ELISA.Results: Immunofluorescence confirmed co-localization of HMG20A with insulin (β-cell) and with glucagon (α-cells) producing cells in mouse pancreas. HMG20A expression diminished a 60% after treating INS1-E cells with a specific siRNA for HMG20A. Insulin secretion regulator gene, MafA, is downregulated significantly (50-60%) after HMG20A silencing. Pax4 expression significantly increased meanwhile Pdx1 showed a tendency to decrease. A 40% drop in insulin secretion is obtained in siHMG20A treated mouse islets compared to control.Conclusions: This data confirms HMG20A expression in pancreatic islets and impairment of insulin secretion when it is knocked down. Hence, concluding that HMG20A plays an important role in physiological GSIS and regulating pancreatic development related genes