The retinoic acid response is a minor component of the cardiac phenotype in H9c2 myoblast differentiation.

The H9c2 myoblast cell line, isolated from the left ventricular tissue of rat, is currently used in vitro as a mimetic for skeletal and cardiac muscle due to its biochemical, morphological, and electrical/hormonal signaling properties. During culture, H9c2 cells acquire a myotube phenotype, where a critical component is the inclusion of retinoic acid (RA). The results from some authors on H9c2 suggested that thousands of genes respond to RA stimuli, while others report hundreds of genes responding to RA over different cell types. In this article, using a more appropriate experimental design, we first confirm the H9c2 cardiac phenotype with and without RA and report transcriptomic and physiological changes regarding calcium handling, bioenergetics, and other biological concepts. Interestingly, of the 2360 genes showing a transcriptional change, 622 genes were statistically associated with the RA response. Of these genes, only 305 were RA-specific, and the rest also showed a culture-time component. Thus, the major expression changes (from 74 to 87%) were indeed due to culture conditions over time. Unexpectedly, only a few components of the retinol pathway in KEGG responded to RA. Our results show the role of RA in the H9c2 cultures impacting the interpretation using H9c2 as an in vitro model.

Neuroprotective Effect of Luteolin-7-O-Glucoside against 6-OHDA-Induced Damage in Undifferentiated and RA-Differentiated SH-SY5Y Cells.

Luteolin is one of the most common flavonoids present in edible plants and its potential benefits to the central nervous system include decrease of microglia activation, neuronal damage and high antioxidant properties. The aim of this research was to evaluate the neuroprotective, antioxidant and anti-inflammatory activities of luteolin-7-O-glucoside (Lut7). Undifferentiated and retinoic acid (RA)-differentiated SH-SY5Y cells were pretreated with Lut7 and incubated with 6-hydroxydopamine (6-OHDA). Cytotoxic and neuroprotective effects were determined by MTT assay. Antioxidant capacity was determined by DPPH, FRAP, and ORAC assays. ROS production, mitochondrial membrane potential (ΔΨm), Caspase-3 activity, acetylcholinesterase inhibition (AChEI) and nuclear damage were also determined in SH-SY5Y cells. TNF-α, IL-6 and IL-10 release were evaluated in LPS-induced RAW264.7 cells by ELISA. In undifferentiated SH-SY5Y cells, Lut7 increased cell viability after 24 h, while in RA-differentiated SH-SY5Y cells, Lut7 increased cell viability after 24 and 48 h. Lut7 showed a high antioxidant activity when compared with synthetic antioxidants. In undifferentiated cells, Lut7 prevented mitochondrial membrane depolarization induced by 6-OHDA treatment, decreased Caspase-3 and AChE activity, and inhibited nuclear condensation and fragmentation. In LPS-stimulated RAW264.7 cells, Lut7 treatment reduced TNF-α levels and increased IL-10 levels after 3 and 24 h, respectively. In summary, the results suggest that Lut7 has neuroprotective effects, thus, further studies should be considered to validate its pharmacological potential in more complex models, aiming the treatment of neurodegenerative diseases.

Crosstalk between hnRNP K and SET in ATRA-induced differentiation in acute promyelocytic leukemia.

HnRNP K protein is a heterogeneous nuclear ribonucleoprotein which has been proposed to be involved in the leukemogenesis of acute promyelocytic leukemia (APL), as well as in differentiation induced by all-trans retinoic acid (ATRA). We previously demonstrated a connection between SET and hnRNP K function in head and neck squamous cell carcinoma (HNSCC) cells related to splicing processing. The objective of this study was to characterize the participation of hnRNP K and SET proteins in ATRA-induced differentiation in APL. We observed higher (5- to 40-fold) levels of hnRNP K and SET mRNA in APL patients at the diagnosis phase compared with induction and maintenance phases. hnRNP K knockdown using short-hairpin RNA led to cell death in ATRA-sensitive NB4 and resistant NB4-R2 cells by apoptosis with SET cleavage. In addition, hnRNP K knockdown increased granulocytic differentiation in APL cells, mainly in NB4-R2 with ATRA. hnRNP K knockdown had an effect similar to that of treatment with U0126 (an meiosis-specific serine/threonine protein kinase/ERK inhibitor), mainly in NB4-R2 cells. SET knockdown in APL cells revealed that apoptosis induction in cells with hnRNP K knockdown occurred by SET cleavage rather than by reduction in SET protein. Transplantation of NB4-R2 cells into nude mice confirmed that arsenic trioxide (ATO) combined with U0126 has higher potential against tumor progression when compared to ATO. Therefore, hnRNP K/SET and ERK are potential therapeutic targets for both antineoplastic leukemia therapy and relapsed APL patients with ATRA resistance.

Mating induces early transcriptional response in the rat endosalpinx: the role of TNF and RA.

During mating, males provide not only the spermatozoa to fertilize the oocyte but also other stimuli that are essential for initiating and maintaining the reproductive programme in females. In the mammalian oviduct, mating regulates sperm storage, egg transport, fertilization, early embryonic development, and oestradiol metabolism. However, the main molecules underlying these processes are poorly understood. Using microarray analyses, we identified 58 genes that were either induced or repressed by mating in the endosalpinx at 3 h post-stimulus. RT-qPCR confirmed that mating downregulated the expression of the Oas1h and Prim1 genes and upregulated the expression of the Ceacam1, Chad, Chst10, Slc5a3 and Slc26a4 genes. The functional category 'cell-to-cell signalling and interaction' was over-represented in this gene list. Network modelling identified TNF and all-trans retinoic acid (RA) as upstream regulators of the mating-induced transcriptional response, which was confirmed by intraoviductal injection of TNF or RA in unmated rats. It partially mimicked the transcriptional effect of mating in the rat endosalpinx. Furthermore, mating decreased RA levels in oviductal fluid, and RA-receptor-gamma (RARG) exhibited a nuclear location in oviductal epithelium in both unmated and mated rats, indicating RA-RARG transcriptional activity. In conclusion, the early transcriptional response regulated by mating in the rat endosalpinx is mediated by TNF and RA. These signalling molecules regulate a cohort of genes involved in 'cell-to-cell signalling and interactions' and merit further studies to understand the specific processes activated in the endosalpinx to sustain the events that occur in the mammalian oviduct early after mating.

Caudal Regression Syndrome-A Review Focusing on Genetic Associations.

Caudal regression syndrome (CRS) represents a spectrum of clinical phenotypes with varying degrees of malformation of the lower body with involvement of structures deriving from all 3 layers of the trilaminar embryo. We review areas of active investigation in the diagnosis, etiology, epidemiology, and treatment of the disease with a focus on underlying genetics. CRS pathobiology is complex and multifactorial with a significant contribution from environmental factors as evidenced in twin studies. Contemporary genomic and genetic investigations in both human primary tissue and murine in vitro and in vivo models implicate various genes associated with caudal differentiation and neural cell migration in embryogenesis. A large number of identified targets center around the metabolic regulation of retinoic acid and its derivatives. Dysregulation of retinoic acid homeostasis has been associated with abnormal embryonic cell migration, differentiation, and organogenesis with resulting malformations and agenesis in both a laboratory and a clinical setting. There appears to be a significant overlap in potential genetic targets with CRS and other developmental syndromes with similar presentations, such as VACTERL (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities) association. CRS represents a spectrum of caudal developmental abnormalities with treatment options limited to mild and moderate expressions of disease. Continued research is necessary to further clarify mechanisms of disease pathobiology and complex polygenetic and environmental interaction. Despite this, progress has been made in identifying genetic targets and downstream effectors contributing to preclinical and clinical progression.

CYP26B1 declines postnatally in Sertoli cells independently of androgen action in the mouse testis.

Meiosis begins at puberty and relies on several factors, including androgens and retinoic acid in the mouse testis. CYP26B1 degrades retinoic acid in the testis during prenatal development preventing meiosis initiation. Given the concurrence of meiotic entry and completion of Sertoli cell maturation in response to androgens at puberty in the mouse, we proposed that CYP26B1 is downregulated by androgens in the Sertoli cell during this period. By immunohistochemistry, we showed that CYP26B1 declines in Sertoli cells after birth. However, luciferase reporter assays and quantitative reverse transcription-polymerase chain reaction performed in the prepubertal mouse Sertoli cell line SMAT1 revealed no changes in Cyp26b1 expression in response to androgen treatment. Furthermore, studies carried out using primary Sertoli cells of 10-day-old mice showed no changes in either Cyp26b1 or CYP26B1 expression in response to androgen treatment. In summary, the hereby reported decline in CYP26B1 expression in Sertoli cells towards pubertal onset does not appear to be caused by a direct inhibitory effect of androgens on Sertoli cells in the mouse.

Retinoic Acid Binding Leads to CRABP2 Rigidification and Dimerization.

Cellular retinoic acid-binding protein 2 (CRABP2) delivers all-trans retinoic acid (atRA) to retinoic acid receptors (RARs), allowing for the activation of specific gene transcription. The structural similarities between free and atRA-bound CRABP2 raise the questions of how atRA binding occurs and how the atRA:CRABP2 complex is recognized by downstream binding partners. Thus, to gain insights into these questions, we conducted a detailed atRA-CRABP2 interaction study using nuclear magnetic resonance spectroscopy. The data showed that free CRABP2 displays widespread intermediate-time scale dynamics that is effectively suppressed upon atRA binding. This effect is mirrored by the fast-time scale dynamics of CRABP2. Unexpectedly, CRABP2 rigidification in response to atRA binding leads to the stabilization of a homodimerization interface, which encompasses residues located on helix α2 and the ßC-ßD loop as well as residues on strands ßI-ßA and the ßH-ßI loop. Critically, this rigidification also affects CRABP2's nuclear localization signal and RAR-binding motif, suggesting that the loss of conformational entropy upon atRA binding may be the key for the diverse cellular functions of CRABP2.

Crosstalk of BMP-4 and RA signaling pathways on Pomc gene regulation in corticotrophs.

Retinoic acid (RA), an active metabolite of Vitamin A, and bone morphogenetic protein 4 (BMP-4) pathways control the transcription of pro-opiomelanocortin (Pomc), the precursor of ACTH. We describe a novel mechanism by which RA and BMP-4 act together in the context of pituitary corticotroph tumoral cells to regulate Pomc transcription. BMP-4 and RA exert a potentiated inhibition on Pomc gene expression. This potentiation of the inhibitory action on Pomc transcription was blocked by the inhibitory SMADs of the BMP-4 pathway (SMAD6 and SMAD7), a negative regulator of BMP-4 signaling (TOB1) and a blocker of RA pathway (COUP-TFI). AtT-20 corticotrophinoma cells express RA receptors (RARB, RXRA and RXRG) which associate with factors of BMP-4 (SMAD4 and SMAD1) signaling cascade in transcriptional complexes that block Pomc transcription. COUP-TFI and TOB1 disrupt these complexes. Deletions and mutations of the Pomc promoter and a specific DNA-binding assay show that the complexes bind to the RARE site in the Pomc promoter. The enhanced inhibitory interaction between RA and BMP-4 pathways occurs also in another relevant corticotroph gene promoter, the corticotropin-releasing hormone receptor 1 (Crh-r1). The understanding of the molecules that participate in the control of corticotroph gene expression contribute to define more precise targets for the treatment of corticotrophinomas.

FGF, BMP, and RA signaling are sufficient for the induction of complete limb regeneration from non-regenerating wounds on Ambystoma mexicanum limbs.

Some organisms, such as the Mexican axolotl, have the capacity to regenerate complicated biological structures throughout their lives. Which molecular pathways are sufficient to induce a complete endogenous regenerative response in injured tissue is an important question that remains unanswered. Using a gain-of-function regeneration assay, known as the Accessory Limb Model (ALM), we and others have begun to identify the molecular underpinnings of the three essential requirements for limb regeneration; wounding, neurotrophic signaling, and the induction of pattern from cells that retain positional memory. We have previously shown that treatment of Mexican axolotls with exogenous retinoic acid (RA) is sufficient to induce the formation of complete limb structures from blastemas that were generated by deviating a nerve bundle into an anterior-located wound site on the limb. Here we show that these ectopic structures are capable of regenerating and inducing new pattern to form when grafted into new anterior-located wounds. We additionally found that the expression of Alx4 decreases, and Shh expression increases in these anterior located blastemas, but not in the mature anterior tissues, supporting the hypothesis that RA treatment posteriorizes blastema tissue. Based on these and previous observations, we used the ALM assay to test the hypothesis that a complete regenerative response can be generated by treating anterior-located superficial limb wounds with a specific combination of growth factors at defined developmental stages. Our data shows that limb wounds that are first treated with a combination of FGF-2, FGF-8, and BMP-2, followed by RA treatment of the resultant mid-bud stage blastema, will result in the generation of limbs with complete proximal/distal and anterior/posterior limb axes. Thus, the minimal signaling requirements from the nerve and a positional disparity are achieved with the application of this specific combination of signaling molecules.

KDM2B regulates choline kinase expression and neuronal differentiation of neuroblastoma cells.

The process of neuronal differentiation is associated with neurite elongation and membrane biogenesis, and phosphatidylcholine (PtdCho) is the major membrane phospholipid in mammalian cells. During neuroblast differentiation, the transcription of two genes involved in PtdCho biosynthesis are stimulated: Chka gene for choline kinase (CK) alpha isoform and Pcyt1a gene for CTP:phosphocholine cytidylyltransferase (CCT) alpha isoform. Here we show that CKα is essential for neuronal differentiation. In addition, we demonstrated that KDM2B regulates CKα expression and, as a consequence, neuronal differentiation. This factor is up-regulated in the course of the neuroblasts proliferative and undifferentiated state and down-regulated during differentiation induced by retinoic acid (RA). During proliferation, KDM2B binds to the Box2 located in the Chka promoter repressing its transcription. Interestingly, KDM2B knockdown enhances the levels of CKα expression in neuroblast cells and induces neuronal differentiation even in the absence of RA. These results suggest that KDM2B is required for the appropriate regulation of CKα during neuronal differentiation and to the maintaining of the undifferentiated stage of neuroblast cells.

Transcriptional regulation of genes involved in retinoic acid metabolism in Senegalese sole larvae.

The aim of this study was the characterization of transcriptional regulatory pathways mediated by retinoic acid (RA) in Senegalese sole larvae. For this purpose, pre-metamorphic larvae were treated with a low concentration of DEAB, an inhibitor of RALDH enzyme, until the end of metamorphosis. No differences in growth, eye migration or survival were observed. Nevertheless, gene expression analysis revealed a total of 20 transcripts differentially expressed during larval development and only six related with DEAB treatments directly involved in RA metabolism and actions (rdh10a, aldh1a2, crbp1, igf2r, rarg and cyp26a1) to adapt to a low-RA environment. In a second experiment, post-metamorphic larvae were exposed to the all-trans RA (atRA) observing an opposite regulation for those genes involved in RA synthesis and degradation (rdh10a, aldh1a2, crbp1 and cyp26a1) as well as other related with thyroid- (dio2) and IGF-axes (igfbp1, igf2r and igfbp5) to balance RA levels. In a third experiment, DEAB-pretreated post-metamorphic larvae were exposed to atRA and TTNPB (a specific RAR agonist). Both drugs down-regulated rdh10a and aldh1a2 and up-regulated cyp26a1 expression demonstrating their important role in RA homeostasis. Moreover, five retinoic receptors that mediate RA actions, the thyroid receptor thrb, and five IGF binding proteins changed differentially their expression. Overall, this study demonstrates that exogenous RA modulates the expression of some genes involved in the RA synthesis, degradation and cellular transport through RAR-mediated regulatory pathways establishing a negative feedback regulatory mechanism necessary to balance endogenous RA levels and gradients.

IL-33 enhances retinoic acid signaling on CD4+ T cells.

Several molecules have been described as CD4+ T cells differentiation modulators and among them retinoic acid (RA) and more recently, IL-33, have been studied. Due to the similarities in T helper cell skewing properties between RA and IL-33, we asked whether IL-33 intersects, directly or indirectly, the RA signaling pathway. Total CD4+ T cells from DR5-luciferase mice were activated in the presence of RA with or without IL-33, and RA signaling was visualized using ex vivo imaging. Our results demonstrate that IL-33 itself is able to trigger RA signaling on CD4+ T cells, which is highly increased when IL-33 is added in conjunction with RA. This study presents IL-33 as a potential player that may synergize with RA in controlling T cell differentiation, and suggests that IL-33 may be an attractive target in controlling T cell differentiation in vivo.

Whole-Exome Sequencing in a South American Cohort Links ALDH1A3, FOXN1 and Retinoic Acid Regulation Pathways to Autism Spectrum Disorders.

Autism spectrum disorders (ASDs) are a range of complex neurodevelopmental conditions principally characterized by dysfunctions linked to mental development. Previous studies have shown that there are more than 1000 genes likely involved in ASD, expressed mainly in brain and highly interconnected among them. We applied whole exome sequencing in Colombian-South American trios. Two missense novel SNVs were found in the same child: ALDH1A3 (RefSeq NM_000693: c.1514T>C (p.I505T)) and FOXN1 (RefSeq NM_003593: c.146C>T (p.S49L)). Gene expression studies reveal that Aldh1a3 and Foxn1 are expressed in ~E13.5 mouse embryonic brain, as well as in adult piriform cortex (PC; ~P30). Conserved Retinoic Acid Response Elements (RAREs) upstream of human ALDH1A3 and FOXN1 and in mouse Aldh1a3 and Foxn1 genes were revealed using bioinformatic approximation. Chromatin immunoprecipitation (ChIP) assay using Retinoid Acid Receptor B (Rarb) as the immunoprecipitation target suggests RA regulation of Aldh1a3 and Foxn1 in mice. Our results frame a possible link of RA regulation in brain to ASD etiology, and a feasible non-additive effect of two apparently unrelated variants in ALDH1A3 and FOXN1 recognizing that every result given by next generation sequencing should be cautiously analyzed, as it might be an incidental finding.

Expression profiles of retinoic acid synthetases ALDH1As and metabolic enzymes CYP26s in adult and embryonic zebrafish (Danio rerio).

Retinoic acid (RA) plays a crucial role in cellular proliferation, differentiation, and apoptosis. The physiological activity of RA begins early in development and continues throughout an organism's life. RA distribution is tightly controlled by the RA synthetases ALDH1As and the metabolic enzymes CYP26s. We analyzed the expressions of ALDH1As and CYP26s in whole embryos during zebrafish (Danio rerio) development and in adult zebrafish organs, by quantitative reverse transcriptase polymerase chain reaction analysis. All the ALDH1A and CYP26 genes exhibited similar pulse expression patterns, with peak expressions at different developmental stages. ALDH1A2 exhibited an earlier and sharper expression peak [12 hours post-fertilization (hpf)] than ALDH1A3 (24 hpf). CYP26A1 transcription peaked earlier (8 hpf) than CYP26B1 and CYP26C1 (12 hpf), while CYP26C1 expression dropped to basal levels later (48 hpf) than that of CYP26A1 and CYP26B1 (18 hpf). ALDH1A2 and CYP26A1 exhibited the highest mRNA peak level and seem to be the dominant isoenzymes in their families during zebrafish development. Expression patterns of ALDH1As and CYP26s in most adult zebrafish tissues were similar to those in humans. Nevertheless, three CYP26s were more vigorously expressed in the zebrafish brain than in human organs, whereas much weaker ALDH1A and CYP26 transcription was found in the zebrafish liver and intestine. This suggests that RA metabolic rates differ between zebrafish and humans or that other enzymes are responsible for RA homeostasis in the zebrafish liver and intestine. All the ALDH1A and CYP26 genes exhibited distinct expression patterns during zebrafish development and in adult zebrafish tissues.

Dual embryonic origin and patterning of the pharyngeal skeleton in the axolotl (Ambystoma mexicanum).

The impressive morphological diversification of vertebrates was achieved in part by innovation and modification of the pharyngeal skeleton. Extensive fate mapping in amniote models has revealed a primarily cranial neural crest derivation of the pharyngeal skeleton. Although comparable fate maps of amphibians produced over several decades have failed to document a neural crest derivation of ventromedial elements in these vertebrates, a recent report provides evidence of a mesodermal origin of one of these elements, basibranchial 2, in the axolotl. We used a transgenic labeling protocol and grafts of labeled cells between GFP+ and white embryos to derive a fate map that describes contributions of both cranial neural crest and mesoderm to the axolotl pharyngeal skeleton, and we conducted additional experiments that probe the mechanisms that underlie mesodermal patterning. Our fate map confirms a dual embryonic origin of the pharyngeal skeleton in urodeles, including derivation of basibranchial 2 from mesoderm closely associated with the second heart field. Additionally, heterotopic transplantation experiments reveal lineage restriction of mesodermal cells that contribute to pharyngeal cartilage. The mesoderm-derived component of the pharyngeal skeleton appears to be particularly sensitive to retinoic acid (RA): administration of exogenous RA leads to loss of the second basibranchial, but not the first. Neural crest was undoubtedly critical in the evolution of the vertebrate pharyngeal skeleton, but mesoderm may have played a central role in forming ventromedial elements, in particular. When and how many times during vertebrate phylogeny a mesodermal contribution to the pharyngeal skeleton evolved remain to be resolved.

Retinaldehyde dehydrogenase activity is triggered during allograft rejection and it drives Th1/Th17 cytokine production.

Retinoic acid (RA), a vitamin A metabolite, has been attributed to relevant functions in adaptive immunity. On T cells, the disruption on RA signaling alters both CD4+ and CD8+ T cells effector function. In this study, we evaluated the contribution of RA synthesis during the immune response using an in vivo skin transplantation model. Our data indicates that the frequency and number of cells containing an active retinaldehyde dehydrogenase (RALDH), a key enzyme for RA synthesis, is increased during skin transplant rejection. In addition, we found that the expression of the mRNA coding for the isoform RALDH2 is up-regulated on graft rejecting draining lymph nodes (dLNs) cells. Lastly, we observed that IFN-γ and IL-17 production by ex vivo re-stimulated dLNs cells is greatly increased during rejection, which it turns depends on RA synthesis, as shown in experiments using a specific RALDH inhibitor. Altogether, our data demonstrate that RA synthesis is incremented during the immune response against an allograft, and also indicates that the synthesis of RA is required for cytokine production by dLNs resident T cells.

Involvement of protein kinase C α and δ activities on the induction of the retinoic acid system in mammary cancer cells.

It has been established that retinoids exert some of their effects on cell differentiation and malignant phenotype reversion through the interaction with different members of the protein kinase C (PKC) family. Till nowadays the nature and extension of this interaction is not well understood. Due to the cytostatic and differentiating effects of retinoids, in the present study we propose to evaluate whether the crosstalk between the retinoid system and the PKC pathway could become a possible target for breast cancer treatment. We could determine that ATRA (all-trans retinoic) treatment showed a significant growth inhibition due to (G1 or G2) cell cycle arrest both in LM3 and SKBR3, a murine and human mammary cell line respectively. ATRA also induced a remarkable increase in PKCα and PKCδ expression and activity. Interestingly, the pharmacological inhibition of these two PKC isoforms prevented the activation of retinoic acid receptors (RARs) by ATRA, indicating that both PKC isoforms are required for RARs activation. Moreover, PKCδ inhibition also impaired ATRA-induced RARα translocation to the nucleus. In vivo assays revealed that a combined treatment using ATRA and PKCα inhibitors prevented lung metastatic dissemination in an additive way. Our results clearly indicate that ATRA modulates the expression and activity of different PKCs. Besides inducing cell arrest, the activity of both PKC is necessary for the induction of the retinoic acid system. The combined ATRA and PKCα inhibitors could be an option for the hormone-independent breast cancer treatment.

Parasite infections in multiple sclerosis modulate immune responses through a retinoic acid-dependent pathway.

We recently demonstrated better outcomes in helminth-infected multiple sclerosis (MS) patients, compared with uninfected ones. The present study evaluates the role of TLR2 and retinoic acid (RA) in parasite-driven protection in MS patients. RA serum levels were significantly higher in helminth-infected MS patients than in uninfected MS subjects or healthy controls. Genes involved in RA biosynthesis and metabolism, such as Adh1 and Raldh2, as well as RA receptors and IL-10, were induced in dendritic cells (DCs) via TLR2-dependent ERK signaling. This programmed DCs to induce FOXP3(+) T regulatory cells and suppressed production of proinflammatory cytokines (IL-6, IL-12, IL-23, and TNF-α) via induction of suppressor of cytokine signaling 3 (SOCS3), an effect mediated by soluble egg Ag (SEA) obtained from Schistosoma mansoni, and by RA. SEA-activated DCs also inhibited IL-17 and IFN-γ production through autoreactive T cells. These inhibitory effects were abrogated when SOCS3 gene expression was silenced, indicating that SEA-mediated signaling inhibited production of these cytokines by T cells, through a SOCS3-dependent pathway. Overall, helminth-related immunomodulation observed in MS patients was mediated by TLR2- and RA-dependent pathways, through two different mechanisms, as follows: 1) induction of IL-10 and FOXP3(+) T regulatory cells, and 2) suppression of proinflammatory cytokine production mediated by SOCS3.

Full regeneration of the tribasal Polypterus fin.

Full limb regeneration is a property that seems to be restricted to urodele amphibians. Here we found that Polypterus, the most basal living ray-finned fish, regenerates its pectoral lobed fins with a remarkable accuracy. Pectoral Polypterus fins are complex, formed by a well-organized endoskeleton to which the exoskeleton rays are connected. Regeneration initiates with the formation of a blastema similar to that observed in regenerating amphibian limbs. Retinoic acid induces dose-dependent phenotypes ranging from inhibition of regeneration to apparent anterior-posterior duplications. As in all developing tetrapod limbs and regenerating amphibian blastema, Sonic hedgehog is expressed in the posterior mesenchyme during fin regeneration. Hedgehog signaling plays a role in the regeneration and patterning processes: an increase or reduction of fin bony elements results when this signaling is activated or disrupted, respectively. The tail fin also regenerates but, in contrast with pectoral fins, regeneration can resume after release from the arrest caused by hedgehog inhibition. A comparative analysis of fin phenotypes obtained after retinoic acid treatment or altering the hedgehog signaling levels during regeneration allowed us to assign a limb tetrapod equivalent segment to Polypterus fin skeletal structures, thus providing clues to the origin of the autopod. We propose that appendage regeneration was a common property of vertebrates during the fin to limb transition.

Neural differentiation of rat aorta pericyte cells.

Pericyte perivascular cells, believed to originate mesenchymal stem cells (MSC), are characterized by their capability to differentiate into various phenotypes and participate in tissue reconstruction of different organs, including the brain. We show that these cells can be induced to differentiation into neural-like phenotypes. For these studies, pericytes were obtained from aorta ex-plants of Sprague-Dawley rats and differentiated into neural cells following induction with trans retinoic acid (RA) in serum-free defined media or differentiation media containing nerve growth and brain-derived neuronal factor, B27, N2, and IBMX. When induced to differentiation with RA, cells express the pluripotency marker protein stage-specific embryonic antigen-1, neural-specific proteins ß3-tubulin, neurofilament-200, and glial fibrillary acidic protein, suggesting that pericytes undergo differentiation, similar to that of neuroectodermal cells. Differentiated cells respond with intracellular calcium transients to membrane depolarization by KCl indicating the presence of voltage-gated ion channels and express functional N-methyl-D-aspartate receptors, characteristic for functional neurons. The study of neural differentiation of pericytes contributes to the understanding of induction of neuroectodermal differentiation as well as providing a new possible stem-cell source for cell regeneration therapy in the brain.