GDNF-induced cell signaling and neurite outgrowths are differentially mediated by GFRalpha1 isoforms

Serum Glial Cell Line-Derived Neurotrophic Factor (sGDNF) Is a Novel Biomarker in Predicting Cirrhosis in Patients with Chronic Hepatitis B

OBJECTIVES

We assessed the potential of glial cell line-derived neurotrophic factor (GDNF) as a useful biomarker to predict cirrhosis in chronic hepatitis B (CHB) patients.

METHODS

A total of 735 patients from two medical centers (385 CHB patients and 350 healthy controls) were included to determine the association of serum and tissue GDNF levels with biopsy-proven cirrhosis. The diagnostic accuracy of serum GDNF (sGDNF) was estimated and compared with other indices of cirrhosis.

RESULTS

We showed significantly higher levels of sGDNF in CHB patients with fibrosis (28.4 pg/ml vs. 11.6 pg/ml in patients without) and patients with cirrhosis (33.8 pg/ml vs. 23.5 pg/ml in patients without). The areas under receiver operating curve (AUROCs) of sGDNF were 0.83 (95% confidence interval (CI): 0.80-0.87) for predicting liver fibrosis and 0.84 (95% CI: 0.79-0.89) for cirrhosis. Findings from the serum protein level and hepatic mRNA expression were consistent. Using the best cutoff to predict cirrhosis, we categorized the patients into sGDNF-high and sGDNF-low groups. The sGDNF-high group had significantly larger Masson's trichrome and reticulin staining-positive area, higher Scheuer score, and METAVIR fibrosis stage (all p < 0.001) but not steatosis. On multivariable regression, sGDNF was independently associated with cirrhosis with an odds ratio of 6.98 (95% CI: 1.10-17.94). Finally, we demonstrated that sGDNF outperformed AST to platelet ratio index, FIB-4, fibroscore, forn index, and fibrometer in differentiating F4 vs. F3.

CONCLUSION

Using serum, tissue mRNA, and biopsy data, our study revealed a significant potential of sGDNF as a novel noninvasive biomarker for cirrhosis in CHB patients.

Activation of Three Major Signaling Pathways After Endurance Training and Spinal Cord Injury

We aimed to investigate the effects of endurance training on expression of growth factors (GFs) and stimulation of neurotrophin-dependent signaling pathways (PI3k/Akt, PLCγ/PKC, PLCγ/CAMKII, Ras-Erk1/2 and Rac1-Cdc42) responsible for neuroplasticity, neuroregeneration, survival and growth after spinal cord injury (SCI). Wistar rats were divided into four groups: (i) intact controls; (ii) 6 weeks of endurance training; (iii) SCI; (iv) pre-training + SCI. The animals survived for 6 weeks after SCI. Firstly, endurance training markedly upregulated mRNA expression and protein levels (up to four times) of growth factors (BDNF, GDNF) and their receptors (TrkB, Gfrα) in low thoracic segments (Th8–Th10) compared to levels in untrained animals. Secondly, we found that spontaneous neuroplasticity seen in the SCI alone group was GF-specific and was activated through both PLCγ-PKC and PLC-CAMKII signaling pathways. In addition, training prior to SCI markedly increased the activity of PLCγ-PKC signaling at both transcript and protein levels at and around the lesion site. Similar effects were seen in expression of PI3k/Akt and Ras/Erk1/2 signaling responsible for cell survival and regeneration. Thirdly, rats which underwent physical activity prior to SCI were more active and had significantly better neurological scores at the 14th and 42nd days of survival. These results suggest that regular physical activity could play an important role after SCI, as it maintains increased expression of GFs in spinal cord tissue 6 weeks post-SCI. The BDNF- and/or BDNF + GDNF-dependent signaling pathways were significantly affected in pre-trained SCI animals. In contrast, GDNF-dependent Rac1-Cdc42 signaling was not involved in training-affected SCI response.

Deficiency of GFRα1 promotes hepatocellular carcinoma progression but enhances oxaliplatin-mediated anti-tumor efficacy

Neurotrophic factors and their receptors have been identified to promote tumor progression. GFRα1, the receptor for glial cell line-derived neurotrophic factor (GDNF), has been demonstrated to be predominantly expressed in adult liver tissue. Our preliminary data showed that GFRα1 is significantly downregulated in hepatocellular carcinoma (HCC) tissue, compared to the matched non-neoplastic tissue. However, the role of GFRα1 in HCC progression remains unknown. Here we found that the expression of GFRα1 in HCC tissue is inversely correlated with the poorer prognosis of HCC patients. Silencing of GFRα1 expression markedly enhances HCC cell growth, tumor metastasis, as well as shortens the survival of HCC tumor-bearing mice. Forced expression of GFRα1 in HCC cells significantly reverses the tumor-promoting effects of GFRα1 silencing, and AAV8-mediated GFRα1 transfection in HCC tumor tissues significantly impedes tumor growth and prolongs the survival of HCC tumor-bearing mice. These results are also verified in vivo in GFRα1 knock-out mice model, with increased DEN-induced HCC carcinogenesis. Mechanistically, GFRα1 could inhibit epithelial-to-mesenchymal transition (EMT) of HCC cells, by upregulating expression of Claudin-1 and ZO-1. Of note, silencing of GFRα1 expression promotes oxaliplatin-mediated HCC cell apoptosis resulting in prolonged survival of HCC-bearing mice, and forced expression of GFRα1 markedly increased oxaliplatin resistance of HCC cells. These results demonstrate that deficiency of GFRα1 promotes HCC progression but enhances chemotherapeutic anti-tumor efficacy, suggesting that GFRα1 may be a candidate prognostic biomarker and a potential therapeutic target in HCC.

ZNF281 inhibits neuronal differentiation and is a prognostic marker for neuroblastoma

High-risk neuroblastomas (NBs) show undifferentiated/poorly differentiated morphology as a distinctive feature. We have identified the transcription factor ZNF281 as a factor that can counteract the neuronal differentiation of primary neurons in culture and NB cells. The expression of ZNF281 is inhibited by TAp73 and promoted by MYCN. In turn, ZNF281 inhibits the expression of GDNF and NRP2, two proteins associated with neuronal differentiation. In patients with NB, the expression of ZNF281 is higher in high-risk patients and is associated with worse prognosis. Understanding the molecular mechanisms that regulate neuronal differentiation is relevant for the identification of defects in this process that underlie the development of tumors such as NB, in which an aberrant differentiation arrest has occurred.

Derangement of cellular differentiation because of mutation or inappropriate expression of specific genes is a common feature in tumors. Here, we show that the expression of ZNF281, a zinc finger factor involved in several cellular processes, decreases during terminal differentiation of murine cortical neurons and in retinoic acid-induced differentiation of neuroblastoma (NB) cells. The ectopic expression of ZNF281 inhibits the neuronal differentiation of murine cortical neurons and NB cells, whereas its silencing causes the opposite effect. Furthermore, TAp73 inhibits the expression of ZNF281 through miR34a. Conversely, MYCN promotes the expression of ZNF281 at least in part by inhibiting miR34a. These findings imply a functional network that includes p73, MYCN, and ZNF281 in NB cells, where ZNF281 acts by negatively affecting neuronal differentiation. Array analysis of NB cells silenced for ZNF281 expression identified GDNF and NRP2 as two transcriptional targets inhibited by ZNF281. Binding of ZNF281 to the promoters of these genes suggests a direct mechanism of repression. Bioinformatic analysis of NB datasets indicates that ZNF281 expression is higher in aggressive, undifferentiated stage 4 than in localized stage 1 tumors supporting a central role of ZNF281 in affecting the differentiation of NB. Furthermore, patients with NB with high expression of ZNF281 have a poor clinical outcome compared with low-expressors. These observations suggest that ZNF281 is a controller of neuronal differentiation that should be evaluated as a prognostic marker in NB.

Oxidative stress promotes exit from the stem cell state and spontaneous neuronal differentiation

Reactive oxygen species (ROS) play important roles in fundamental cellular processes such as proliferation and survival. Here we investigated the effect of oxidative stress on stem cell maintenance and neuronal differentiation in a human embryonic stem cell (hESC) model, Ntera2 (NT2). CM-H2DCFDA and DHE assays confirmed that the oxidizing agent paraquat could induce a high level of ROS in NT2 cells. Quantitative PCR, Western blotting and immunocytochemistry showed that paraquat-induced oxidative stress suppressed the expression of stemness markers, including NANOG, OCT4 and TDGF1, whereas it enhanced the spontaneous expression of neuronal differentiation markers such as PAX6, NEUROD1, HOXA1, NCAM, GFRA1 and TUJ1. The treated cells even exhibited a strikingly different morphology from control cells, extending out long neurite-like processes. The neurogenic effect of ROS on stem cell behaviour was confirmed by the observations that the expression of neuronal markers in the paraquat-treated cells was suppressed by an antioxidant while further enhanced by knocking down Nrf2, a key transcription factor associated with antioxidant signaling. Lastly, paraquat dose-dependently activated the neurogenic MAPK-ERK1/2, which can be reversed by the MEK1/2 inhibitor SL327. Our study suggests that excessive intracellular ROS can trigger the exit from stem cell state and promote the neuronal differentiation of hESCs, and that MAPK-ERK1/2 signaling may play a proactive role in the ROS-induced neuronal differentiation of hESCs.

MicroRNA regulation of central glial cell line-derived neurotrophic factor (GDNF) signalling in depression

Although multiple studies have reported that peripheral glial cell line-derived neurotrophic factor (GDNF) is reduced in depression, cerebral GDNF signalling has yet to be examined in this condition. Here, we report an isoform-specific decrease in GDNF family receptor alpha 1 (GFRA1) mRNA expression, resulting in lowered GFRα1a protein levels in basolateral amygdala (BLA) samples from depressed subjects. Downregulation of GFRα1a was associated with increased expression of microRNAs, including miR-511, predicted to bind to long 3' untranslated region (3'-UTR)-containing transcripts (GFRA1-L) coding for GFRα1a. Transfection of human neural progenitor cells (NPCs) with a miR-511 mimic was sufficient to repress GFRA1-L/GFRα1a without altering GFRα1b, and resulted in pathway-specific changes in immediate early gene activity. Unexpectedly, GFRα1a knockdown did not reduce NPC responses to GDNF. Rather, it greatly enhanced mitogen-activated protein kinase signalling. This effect appeared to be mediated by GDNF/soluble GFRα1/neural cell adhesion molecule binding, and substituting the soluble GFRα1a/GFRα1b content of miR-511-transfected NPCs with that of controls rescued signalling. In light of previous reports suggesting that GFRα1b can inhibit GFRα1a-induced neuroplasticity, we also assessed the association between GFRα1 and doublecortin (DCX; a hyperplastic marker) in human BLA. Although controls displayed coordinated expression of GFRα1a and b isoforms and these correlated positively with DCX, the only significant association observed among depressed subjects was a strongly negative correlation between GFRα1b and DCX. Taken together, these results suggest that microRNA-mediated reductions of GFRα1a in depression change the quality, rather than the quantity, of GDNF signalling. They also suggest that central GDNF signalling may represent a novel target for antidepressant treatment.

Prognostic significance of artemin and GFRα1 expression in laryngeal squamous cell carcinoma

Artemin (ARTN) has been implicated in the development and progression of several human malignancies. However, the clinical and prognostic significance of ARTN and its receptors has not yet been investigated in human laryngeal squamous cell carcinoma (LSCC). Therefore, in the present study, the protein expression of ARTN and its receptor, namely GFRα1, was determined in 76 LSCC and 26 laryngeal polyp tissue samples using immunohistochemistry. Furthermore, the clinicopathological and prognostic significance of ARTN and GFRα1 expression was analyzed in patients with LSCC. The results revealed that the expression of ARTN and GFRα1 was significantly increased in LSCC compared with polyp tissue samples. Furthermore, the expression of ARTN and GFRα1 was positively associated with pTNM stage in LSCC. Kaplan-Meier survival analyses revealed a strong association between the expression of ARTN or GFRα1 and the survival of patients with LSCC. Correlation analysis demonstrated that the expression of ARTN was significantly correlated with the expression GFRα1. In conclusion, the results demonstrated that ARTN and GFRα1 may be useful predictors of disease progression and outcome in patients with LSCC.

Comparison of GDF5 and GDNF as neuroprotective factors for postnatal dopamine neurons in ventral mesencephalic cultures

Loss of dopamine neurons is associated with the motor deficits that occur in Parkinson's disease. Although many drugs have proven to be useful in the treatment of the symptoms of this disease, none has been shown to have a significant impact on the development of the disease. However, we believe that several neurotrophic factors have the potential to reduce its progression. Glial cell line-derived neurotrophic factor (GDNF), a member of the transforming growth factor-β superfamily of neurotrophic factors, has been extensively studied in this regard. Less attention has been paid to growth/differentiation factor 5 (GDF5), another member of the same superfamily. This study compares GDNF and GDF5 in dissociated cultures prepared from ventral mesencephalon and in organotypic co-cultures containing substantia nigra, striatum, and neocortex. We report that both GDNF (10-500 ng/ml) and GDF5 (100-500 ng/ml) promoted the survival of dopamine neurons from the substantia nigra of postnatal rats, although GDNF was considerably more potent than GDF5. In contrast, neither factor had any significant effect on the survival of dopamine neurons from the rat ventral tegmental area. Using organotypic co-cultures, we also compared GDF5 with GDNF as chemoattractants for the innervation of the striatum and the neocortex by dopamine neurons from the substantia nigra. The addition of either GDF5 or GDNF (100-500 ng/ml) caused innervation by dopamine neurons into the cortex as well as the striatum, which did not occur in untreated cultures. Our results are consistent with similar findings suggesting that GDF5, like GDNF, deserves attention as a possible therapeutic intervention for Parkinson's disease.

Dynamic changes in dopamine neuron function after DNSP-11 treatment: effects in vivo and increased ERK 1/2 phosphorylation in vitro

Glial cell-line derived neurotrophic factor (GDNF) has demonstrated robust effects on dopamine (DA) neuron function and survival. A post-translational processing model of the human GDNF proprotein theorizes the formation of smaller, amidated peptide(s) from the proregion that exhibit neurobiological function, including an 11-amino-acid peptide named dopamine neuron stimulating peptide-11 (DNSP-11). A single treatment of DNSP-11 was delivered to the substantia nigra in the rat to investigate effects on DA-neuron function. Four weeks after treatment, potassium (K+) and D-amphetamine evoked DA release were studied in the striatum using microdialysis. There were no significant changes in DA-release after DNSP-11 treatment determined by microdialysis. Dopamine release was further examined in discrete regions of the striatum using high-speed chronoamperometry at 1-, 2-, and 4-weeks after DNSP-11 treatment. Two weeks after DNSP-11 treatment, potassium-evoked DA release was increased in specific subregions of the striatum. However, spontaneous locomotor activity was unchanged by DNSP-11 treatment. In addition, we show that a single treatment of DNSP-11 in the MN9D dopaminergic neuronal cell line results in phosphorylation of ERK1/2, which suggests a novel cellular mechanism responsible for increases in DA function.

Concerted interaction of TGF-β and GDNF mediates neuronal differentiation

The glial cell-line derived neurotrophic factor (GDNF) is crucial for ureteric bud morphogenesis, spermatogenesis, and development of the enteric nervous system and is a potent survival factor for various neuronal populations. However, the impact of GDNF, at least on cell survival, was found to depend strongly on the presence of transforming growth factor β (TGF-β). In this study, we investigate the role of TGF-β in GDNF-induced neuronal differentiation. In a cell culture paradigm of N2aGT cells (neuroblastoma cell line), we show that TGF-β signaling localizes the GDNF ligand-binding receptor GFRa1 to the cell surface, which is a known mechanism by which TGF-β is able to facilitate GDNF signaling. TGF-β-mediated GDNF signaling slightly elevated the phosphorylation state of Ret, the canonical coreceptor for the GPI-linked (glycosyl-phosphatidylinositol) GFRa1. On the basis of morphological as well as immunocytological data, we finally show that GDNF-mediated neuronal differentiation is intensified when GDNF and TGF-β act in concert.

High-frequency stimulation of the globus pallidus interna nucleus modulates GFRα1 gene expression in the basal ganglia

Deep brain stimulation (DBS) is an established therapy for movement disorders such as Parkinson's disease (PD). Although the efficacy of DBS is clear, its precise molecular mechanism remains unknown. The glial cell line derived factor (GDNF) family of ligands has been shown to confer neuroprotective effects on dopaminergic neurons, and putaminal infusion of GDNF have been investigated in PD patients with promising results. Despite the potential therapeutic role of GDNF in alleviating motor symptoms, there is no data on the effects of electrical stimulation on GDNF-family receptor (GFR) expression in the basal ganglia structures. Here, we report the effects of electrical stimulation on GFRα1 isoforms, particularly GFRα1a and GFRα1b. Wistar rats underwent 2 hours of high frequency stimulation (HFS) at the globus pallidus interna nucleus. A control group was subjected to a similar procedure but without stimulation. The HFS group, sacrificed 24 hours after treatment, had a threefold decrease in mRNA expression level of GFRα1b (p=0.037), but the expression level reverted to normal 72 hours after stimulation. Our preliminary data reveal the acute effects of HFS on splice isoforms of GFRα1, and suggest that HFS may modulate the splice isoforms of GFRα1a and GFRα1b to varying degrees. Going forward, elucidating the interactions between HFS and GFR may shed new insights into the complexity of GDNF signaling in the nervous system and lead to better design of clinical trials using these signaling pathways to halt disease progression in PD and other neurodegenerative diseases.

Detection of structural and metabolic changes in traumatically injured hippocampus by quantitative differential proteomics

Traumatic brain injury (TBI) is a complex and common problem resulting in the loss of cognitive function. In order to build a comprehensive knowledge base of the proteins that underlie these cognitive deficits, we employed unbiased quantitative mass spectrometry, proteomics, and bioinformatics to identify and quantify dysregulated proteins in the CA3 subregion of the hippocampus in the fluid percussion model of TBI in rats. Using stable isotope 18O-water differential labeling and multidimensional tandem liquid chromatography (LC)-MS/MS with high stringency statistical analyses and filtering, we identified and quantified 1002 common proteins, with 124 increased and 76 decreased. The ingenuity pathway analysis (IPA) bioinformatics tool identified that TBI had profound effects on downregulating global energy metabolism, including glycolysis, the Krebs cycle, and oxidative phosphorylation, as well as cellular structure and function. Widespread upregulation of actin-related cytoskeletal dynamics was also found. IPA indicated a common integrative signaling node, calcineurin B1 (CANB1, CaNBα, or PPP3R1), which was downregulated by TBI. Western blotting confirmed that the calcineurin regulatory subunit, CANB1, and its catalytic binding partner PP2BA, were decreased without changes in other calcineurin subunits. CANB1 plays a critical role in downregulated networks of calcium signaling and homeostasis through calmodulin and calmodulin-dependent kinase II to highly interconnected structural networks dominated by tubulins. This large-scale knowledge base lays the foundation for the identification of novel therapeutic targets for cognitive rescue in TBI.

NTS-Polyplex: a potential nanocarrier for neurotrophic therapy of Parkinson's disease

Nanomedicine has focused on targeted neurotrophic gene delivery to the brain as a strategy to stop and reverse neurodegeneration in Parkinson's disease. Because of improved transfection ability, synthetic nanocarriers have become candidates for neurotrophic therapy. Neurotensin (NTS)-polyplex is a "Trojan horse" synthetic nanocarrier system that enters dopaminergic neurons through NTS receptor internalization to deliver a genetic cargo. The success of preclinical studies with different neurotrophic genes supports the possibility of using NTS-polyplex in nanomedicine. In this review, we describe the mechanism of NTS-polyplex transfection. We discuss the concept that an effective neurotrophic therapy requires a simultaneous effect on the axon terminals and soma of the remaining dopaminergic neurons. We also discuss the future of this strategy for the treatment of Parkinson's disease.

FROM THE CLINICAL EDITOR

This review paper focuses on nanomedicine-based treatment of Parkinson's disease, a neurodegenerative condition with existing symptomatic but no curative treatment. Neurotensin-polyplex is a synthetic nanocarrier system that enables delivery of genetic cargo to dopaminergic neurons via NTS receptor internalization.

Bone mesenchymal stromal cells stimulate neurite outgrowth of spinal neurons by secreting neurotrophic factors

It has been demonstrated that bone mesenchymal stromal cells (BMSCs) stimulate neurite outgrowth from dorsal root ganglion (DRG) neurons. The present in vitro study tested the hypothesis that BMSCs stimulate the neurite outgrowth from spinal neurons by secreting neurotrophic factors. Spinal neurons were cocultured with BMSCs, fibroblasts and control medium in a non-contact system. Neurite outgrowth of spinal neurons cocultured with BMSCs was significantly greater than the neurite outgrowth observed in neurons cultured with control medium or with fibroblasts. In addition, BMSC-conditioned medium increased the length of neurites from spinal neurons compared to those of neurons cultured in the control medium or in the fibroblasts-conditioned medium. BMSCs expressed brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). The concentrations of BDNF and GDNF in BMSC-conditioned medium were 132±12 and 70±6 pg ml(-1), respectively. The addition of anti-BDNF and anti-GDNF antibodies to BMSC-conditioned medium partially blocked the neurite-promoting effect of the BMSC-conditioned medium. In conclusion, our results demonstrate that BMSCs promote neurite outgrowth in spinal neurons by secreting soluble factors. The neurite-promoting effect of BMSCs is partially mediated by BDNF and GDNF.

Molecular mechanisms underlying effects of neural stem cells against traumatic axonal injury

Transplantation of neural stem cells (NSCs) improves functional outcomes following traumatic brain injury (TBI). Previously we demonstrated that human NSCs (hNSCs) via releasing glial cell line-derived neurotrophic factor (GDNF), preserved cognitive function in rats following parasagittal fluid percussion. However, the underlying mechanisms remain elusive. In this study, we report that NSC grafts significantly reduce TBI-induced axonal injury in the fimbria and other brain regions by blocking abnormal accumulation of amyloid precursor protein (APP). A preliminary mass spectrometry proteomics study revealed the opposite effects of TBI and NSCs on many of the cytoskeletal proteins in the CA3 region of the hippocampus, including α-smooth muscle actin (α-SMA), the main stress fiber component. Further, Western blot and immunostaining studies confirmed that TBI significantly increased the expression of α-SMA in hippocampal neurons, whereas NSC grafts counteracted the effect of TBI. In an in vitro model, rapid stretch injury significantly shortened lengths of axons and dendrites, increased the expression of both APP and α-SMA, and induced actin aggregation, effects offset by GDNF treatment. These GDNF protective effects were reversed by a GDNF-neutralizing antibody or a specific calcineurin inhibitor, and were mimicked by a specific Rho inhibitor. In summary, we demonstrate for the first time that hNSC grafts and treatment with GDNF acutely reduce traumatic axonal injury and promote neurite outgrowth. Possible mechanisms underlying GDNF-mediated neurite protection include balancing the activity of calcineurin, whereas GDNF-induced neurite outgrowth may result from the reduction of the abnormal α-SMA expression and actin aggregation via blocking Rho signals. Our study also suggests the necessity of further exploring the roles of α-SMA in the central nervous system (CNS), which may lead to a new avenue to facilitate recovery after TBI and other injuries.

snoU6 and 5S RNAs are not reliable miRNA reference genes in neuronal differentiation

Accurate profiling of microRNAs (miRNAs) is an essential step for understanding the functional significance of these small RNAs in both physiological and pathological processes. Quantitative real-time PCR (qPCR) has gained acceptance as a robust and reliable transcriptomic method to profile subtle changes in miRNA levels and requires reference genes for accurate normalization of gene expression. 5S and snoU6 RNAs are commonly used as reference genes in microRNA quantification. It is currently unknown if these small RNAs are stably expressed during neuronal differentiation. Panels of miRNAs have been suggested as alternative reference genes to 5S and snoU6 in various physiological contexts. To test the hypothesis that miRNAs may serve as stable references during neuronal differentiation, the expressions of eight miRNAs, 5S and snoU6 RNAs in five differentiating neuronal cell types were analyzed using qPCR. The stabilities of the expressions were evaluated using two complementary statistical approaches (geNorm and Normfinder). Expressions of 5S and snoU6 RNAs were stable under some but not all conditions of neuronal differentiation and thus are not suitable reference genes. In contrast, a combination of three miRNAs (miR-103, miR-106b and miR-26b) allowed accurate expression normalization across different models of neuronal differentiation.

Biomaterials coated by dental pulp cells as substrate for neural stem cell differentiation

This study is focused on the development of an in vitro hybrid system, consisting in a polymeric biomaterial covered by a dental pulp cellular stroma that acts as a scaffold offering a neurotrophic support for the subsequent survival and differentiation of neural stem cells. In the first place, the behavior of dental pulp stroma on the polymeric biomaterial based on ethyl acrylate and hydroxy ethyl acrylate copolymer was studied. For this purpose, cells from normal human third molars were grown onto 0.5-mm-diameter biomaterial discs. After cell culture, quantification of neurotrophic factors generated by the stromal cells was performed by means of an ELISA assay. In the second place, survival and differentiation of adult murine neural stem cells on the polymeric biomaterials covered by dental pulp stromal cells was studied. The results show the capacity of dental pulp cells to uniformly coat the majority of the material's surface and to secrete neurotrophic factors that become crucial for a subsequent differentiation of neural stem cells. The use of stromal cells cultured on scaffolding biomaterials provides neurotrophic pumps that may suggest new criteria for the design of cell therapy experiments in animal models to assist the repair of lesions in Central Nervous System.

LIM kinases are attractive targets with many macromolecular partners and only a few small molecule regulators

The LIM kinases 1 and 2 (LIMK1 and LIMK2) are dual specificity (serine/threonine and tyrosine) kinases. Although they show significant structural similarity, LIMK1 and LIMK2 show different expression, subcellular localization, and functions. They are involved in many cellular functions, such as migration, cycle, and neuronal differentiation and also have a role in pathological processes, such as cancer cell invasion and metastatis, as well as in neurodevelopmental disorders (namely, the William's syndrome). LIM kinases have a relevant number of known partners that are able to induce or limit the ability of LIMK1 and LIMK2 to phosphorylate and inactivate their major substrate, cofilin. On the contrary, only a limited number of small molecules that interact with the two proteins to modulate their kinase activity have been identified. In this review, the most important partners of LIM kinases and their modulating activity toward LIMKs are described. The small compounds identified as LIMK1 and LIMK2 modulators are also reported, as well as their role as possible therapeutic agents for LIMK-induced diseases.

A specific isoform of glial cell line-derived neurotrophic factor family receptor alpha 1 regulates RhoA expression and glioma cell migration

Malignant gliomas are highly invasive neuroepithelial tumors where the tendency to invade and migrate away from the primary tumor mass is thought to be a leading cause of tumor recurrence and treatment failures. Autocrine signals produced by secreted factors that signal through receptors on the tumor are known to contribute to the invasiveness. Glial cell line-derived neurotrophic factor and GDNF family receptor alpha 1 (GFRα1) are over-expressed in human gliomas. We have previously reported that human gliomas express high levels of GFRα1b, an alternatively spliced isoform of GFRα1. However, the functional significance of GFRα1b in glioma behaviors is currently unknown. In this study, we have designed isoform-specific small-interfering RNA to knockdown the highly homologous GFRα1a or GFRα1b isoform efficiently in malignant C6 glioma cells. Unexpectedly, the knockdown of GFRα1b but not GFRα1a induced cell elongation and inhibited C6 cell migration and invasion in vitro. In addition, GFRα1b was found to regulate the expression of RhoA small GTPase, which was required for migration of C6 cells. The decreases in RhoA expression and cell migration after GFRα1b knockdown were attenuated by small-interfering RNA -resistant GFRα1b but not GFRα1a, further demonstrating the specific role of GFRα1b in glioma migration. Interestingly, the knockdown of NCAM but not receptor tyrosine kinase Ret resulted in the reduction of RhoA expression and C6 cell migration. Taken together, these unanticipated results indicate that GFRα1b is involved in glioma migration through glial cell line-derived neurotrophic factor -GFRα1b-NCAM signaling complex and modulation of RhoA expression.