Effects on neurite outgrowth and cell survival of a secreted fibroblast growth factor binding protein upregulated during spinal cord injury

A Comparative Analysis of Multipotent Mesenchymal Stromal Cells derived from Different Sources, with a Focus on Neuroregenerative Potential

Multipotent mesenchymal stromal cells (MSCs) can be considered an accessible therapeutic tool for regenerative medicine. Here, we compared the growth kinetics, immunophenotypic and immunomodulatory properties, gene expression and secretome profile of MSCs derived from human adult bone marrow (BM-MSCs), adipose tissue (AT-MSCs) and Wharton’s jelly (WJ-MSCs) cultured in clinically-relevant conditions, with the focus on the neuroregenerative potential. All the cell types were positive for CD10/CD29/CD44/CD73/CD90/CD105/HLA-ABC and negative for CD14/CD45/CD235a/CD271/HLA-DR/VEGFR2 markers, but they differed in the expression of CD34/CD133/CD146/SSEA-4/MSCA-1/CD271/HLA-DR markers. BM-MSCs displayed the highest immunomodulatory activity compared to AT- and WJ-MSCs. On the other hand, BM-MSCs secreted the lower content and had the lower gene expression of neurotrophic growth factors compared to other cell lines, which may be caused by the higher sensitivity of BM-MSCs to nutrient limitations. Despite the differences in growth factor secretion, the MSC secretome derived from all cell sources had a pronounced neurotrophic potential to stimulate the neurite outgrowth of DRG-neurons and reduce the cell death of neural stem/progenitor cells after H₂O₂ treatment. Overall, our study provides important information for the transfer of basic MSC research towards clinical-grade manufacturing and therapeutic applications.

Fibroblast Growth Factor Binding Protein 3 (FGFBP3) impacts carbohydrate and lipid metabolism

Secreted FGF binding proteins (FGFBP) mobilize locally-acting paracrine FGFs from their extracellular storage. Here, we report that FGFBP3 (BP3) modulates fat and glucose metabolism in mouse models of metabolic syndrome. BP3 knockout mice exhibited altered lipid metabolism pathways with reduced hepatic and serum triglycerides. In obese mice the expression of exogenous BP3 reduced hyperglycemia, hepatosteatosis and weight gain, blunted de novo lipogenesis in liver and adipose tissues, increased circulating adiponectin and decreased NEFA. The BP3 protein interacts with endocrine FGFs through its C-terminus and thus enhances their signaling. We propose that BP3 may constitute a new therapeutic to reverse the pathology associated with metabolic syndrome that includes nonalcoholic fatty liver disease and type 2 diabetes mellitus.

Ghrelin Ameliorates Traumatic Brain Injury by Down-Regulating bFGF and FGF-BP

Traumatic brain injury (TBI) is a primary cause of disability and mortality. Ghrelin, a gastrointestinal hormone, has been found to have protective effects for the brain, but the molecular mechanism of these neuroprotective effects of ghrelin remains unclear. In this study, an electronic cortical contusion impactor was used to establish a rat TBI model and we investigated the effect of ghrelin on brain repair by neurological severity score and histological examination. An antibody array was employed to uncover the molecular mechanism of ghrelin’s neuroprotective effects by determining the alterations of multiple proteins in the brain cortex. As a result, ghrelin attenuated brain injury and promoted brain functional recovery. After TBI, 13 proteins were up-regulated in the brain cortex, while basic fibroblast growth factor (bFGF) and fibroblast growth factor-binding protein (FGF-BP) were down-regulated after ghrelin treatment. It is known that bFGF can induce angiogenesis in the brain and accelerate wound healing, which can be further enhanced by FGF-BP. Based on the previous studies, it is hypothesized that the exogenous ghrelin curing TBI might cause the closure of bFGF and FGF-BP functions on wound healing, or ghrelin might exert the neuroprotective effects by competitively inhibiting bFGF/FGF-BP-induced neovascularization. Whether the combinational administration of ghrelin and bFGF/FGF-BP can enhance or weaken the therapeutic effect on TBI requires further research.

FGF binding proteins (FGFBPs): Modulators of FGF signaling in the developing, adult, and stressed nervous system

Members of the fibroblast growth factor (FGF) family are involved in a variety of cellular processes. In the nervous system, they affect the differentiation and migration of neurons, the formation and maturation of synapses, and the repair of neuronal circuits following insults. Because of the varied yet critical functions of FGF ligands, their availability and activity must be tightly regulated for the nervous system, as well as other tissues, to properly develop and function in adulthood. In this regard, FGF binding proteins (FGFBPs) have emerged as strong candidates for modulating the actions of secreted FGFs in neural and non-neural tissues. Here, we will review the roles of FGFBPs in the peripheral and central nervous systems.

Muscle Fibers Secrete FGFBP1 to Slow Degeneration of Neuromuscular Synapses during Aging and Progression of ALS

The identity of muscle secreted factors critical for the development and maintenance of neuromuscular junctions (NMJs) remains largely unknown. Here, we show that muscle fibers secrete and concentrate the fibroblast growth factor binding protein 1 (FGFBP1) at NMJs. Although FGFBP1 expression increases during development, its expression decreases before NMJ degeneration during aging and in SOD1^G93A mice, a mouse model for amyotrophic lateral sclerosis (ALS). Based on these findings, we examined the impact of deleting FGFBP1 on NMJs. In the absence of FGFBP1, NMJs exhibit structural abnormalities in developing and middle age mice. Deletion of FGFBP1 from SOD1^G93A mice also accelerates NMJ degeneration and death. Based on these findings, we sought to identify the mechanism responsible for decreased FGFBP1 in stressed skeletal muscles. We show that FGFBP1 expression is inhibited by increased accumulation of the transforming growth factor-β1 (TGF-β1) in skeletal muscles and at their NMJs. These findings suggest that targeting the FGFBP1 and TGF-β1 signaling axis holds promise for slowing age- and disease-related degeneration of NMJs.

SIGNIFICANCE STATEMENT

The neuromuscular junction (NMJ) is critical for all voluntary movement. Its malformation during development and degeneration in adulthood impairs motor function. Therefore, it is important to identify factors that function to maintain the structural integrity of NMJs. We show that muscle fibers secrete and concentrate the fibroblast growth factor binding protein 1 (FGFBP1) at NMJs. However, FGFBP1 expression decreases in skeletal muscles during aging and before NMJ degeneration in SOD1^G93A mice, a mouse model for amyotrophic lateral sclerosis. We show that transforming growth factor-β1 is responsible for the decreased levels of FGFBP1. Importantly, we demonstrate critical roles for FGFBP1 at NMJs in developing, aging and SOD1^G93A mice.

Temporospatial expression of fibulin-1 after acute spinal cord injury in rats

OBJECTIVE

Fibulin-1 is a matricellular protein that plays important roles in motility inhibition in a variety of cells and blocks the proliferation of cultured neural stem cells. The biological function of fibulin-1 in the spinal cord has not been fully elucidated.

METHODS

To clarify the expressions and possible functions of fibulin-1 in spinal cord injury (SCI), we performed an acute spinal cord contusion injury model in adult rats. Our work studied the temporospatial expression patterns of fibulin-1.

RESULTS

Western blot analysis revealed that fibulin-1 levels significantly increased 5 days after spinal cord contusion. Immunohistochemistry confirmed an increased number of fibulin-1 immunopositive cells about 2 mm from the lesion site. Moreover, double immunofluorescence labeling suggested that these changes were especially prominent in neurons and microglia.

CONCLUSION

These findings suggest that fibulin-1 may be involved in neuronal apoptosis and microglial activation after SCI.

Floor plate-derived sonic hedgehog regulates glial and ependymal cell fates in the developing spinal cord

Cell fate specification in the CNS is controlled by the secreted morphogen sonic hedgehog (Shh). At spinal cord levels, Shh produced by both the notochord and floor plate (FP) diffuses dorsally to organize patterned gene expression in dividing neural and glial progenitors. Despite the fact that two discrete sources of Shh are involved in this process, the individual contribution of the FP, the only intrinsic source of Shh throughout both neurogenesis and gliogenesis, has not been clearly defined. Here, we have used conditional mutagenesis approaches in mice to selectively inactivate Shh in the FP (Shh(FP)) while allowing expression to persist in the notochord, which underlies the neural tube during neurogenesis but not gliogenesis. We also inactivated Smo, the common Hh receptor, in neural tube progenitors. Our findings confirm and extend prior studies suggesting an important requirement for Shh(FP) in specifying oligodendrocyte cell fates via repression of Gli3 in progenitors. Our studies also uncover a connection between embryonic Shh signaling and astrocyte-mediated reactive gliosis in adults, raising the possibility that this pathway is involved in the development of the most common cell type in the CNS. Finally, we find that intrinsic spinal cord Shh signaling is required for the proper formation of the ependymal zone, the epithelial cell lining of the central canal that is also an adult stem cell niche. Together, our studies identify a crucial late embryonic role for Shh(FP) in regulating the specification and differentiation of glial and epithelial cells in the mouse spinal cord.

Neurotrophic effects of magnesium fructose 1, 6-diphosphate on cortical neurons

In this study, we evaluated the neurotrophic effects of magnesium fructose 1, 6-diphosphate (FDP-Mg) on cortical neurons. The results demonstrated that FDP-Mg promoted dendrite outgrowth and neuronal survival in a dose-dependent manner. In order to investigate the associated mechanisms, we determined adenosine triphosphate (ATP) levels and brain-derived neurotrophic factor (BDNF) mRNA expression in cortical neurons. Treatment with FDP-Mg significantly increased ATP levels and BDNF mRNA expression in cortical neurons. These data suggest that FDP-Mg can exert neurotrophic effects on cortical neurons. The increases in BDNF mRNA expression and cellular ATP levels are involved in the neurotrophic effects produced by FDP-Mg.

Anti-tumor effects of fibroblast growth factor-binding protein (FGF-BP) knockdown in colon carcinoma

Background

Fibroblast growth factors FGF-1 and FGF-2 are often upregulated in tumors, but tightly bound to heparan sulphate proteoglycans of the extracellular matrix (ECM). One mechanism of their bioactivation relies on the FGF-binding protein (FGF-BP) which, upon reversible binding to FGF-1 or -2, leads to their release from the ECM. FGF-BP increases tumorigenicity and is highly expressed in tumors like colon carcinoma. In this paper, we analyse cellular and molecular consequences of RNAi-mediated FGF-BP knockdown in colon carcinoma, and explore the therapeutic effects of the nanoparticle-mediated delivery of small interfering RNAs (siRNAs) for FGF-BP targeting.

Results

Employing stable RNAi cells, we establish a dose-dependence of cell proliferation on FGF-BP expression levels. Decreased proliferation is mirrored by alterations in cell cycle distribution and upregulation of p21, which is relevant for mediating FGF-BP effects. While inhibition of proliferation is mainly associated with reduced Akt and increased GSK3β activation, antibody array-based analyses also reveal other alterations in MAPK signalling. Additionally, we demonstrate induction of apoptosis, mediated through caspase-3/7 activation, and alterations in redox status upon FGF-BP knockdown. These effects are based on the upregulation of Bad, Bax and HIF-1α, and the downregulation of catalase. In a therapeutic FGF-BP knockdown approach based on RNAi, we employ polymer-based nanoparticles for the in vivo delivery of siRNAs into established wildtype colon carcinoma xenografts. We show that the systemic treatment of mice leads to the inhibition of tumor growth based on FGF-BP knockdown.

Conclusions

FGF-BP is integrated in a complex network of cytoprotective effects, and represents a promising therapeutic target for RNAi-based knockdown approaches.

Impact of fibroblast growth factor-binding protein-1 expression on angiogenesis and wound healing

Fibroblast growth factors (FGFs) participate in embryonic development, in maintenance of tissue homeostasis in the adult, and in various diseases. FGF-binding proteins (FGFBP) are secreted proteins that chaperone FGFs stored in the extracellular matrix to their receptor, and can thus modulate FGF signaling. FGFBP1 (alias BP1, FGF-BP1, or HBp17) expression is required for embryonic survival, can modulate FGF-dependent vascular permeability in embryos, and is an angiogenic switch in human cancers. To determine the function of BP1 in vivo, we generated tetracycline-regulated conditional BP1 transgenic mice. BP1-expressing adult mice are viable, fertile, and phenotypically indistinguishable from their littermates. Induction of BP1 expression increased mouse primary fibroblast motility in vitro, increased angiogenic sprouting into subcutaneous matrigel plugs in animals and accelerated the healing of excisional skin wounds. FGF-receptor kinase inhibitors blocked these effects. Healing skin wounds showed increased macrophage invasion as well as cell proliferation after BP1 expression. Also, BP1 expression increased angiogenesis during the healing of skin wounds as well as after ischemic injury to hindlimb skeletal muscles. We conclude that BP1 can enhance FGF effects that are required for the healing and repair of injured tissues in adult animals.

Chemical priming for spinal cord injury: a review of the literature part II-potential therapeutics

INTRODUCTION

Spinal cord injury is a complex cascade of reactions secondary to the initial mechanical trauma that puts into action the innate properties of the injured cells, the circulatory, inflammatory, and chemical status around them, into a non-permissive and destructive environment for neuronal function and regeneration. Priming means putting a cell, in a state of "arousal" towards better function. Priming can be mechanical as trauma is known to enhance activity in cells.

MATERIALS AND METHODS

A comprehensive review of the literature was performed to better understand the possible chemical primers used for spinal cord injuries.

CONCLUSIONS

Taken together, many studies have shown various promising results using the substances outlined herein for treating SCI.

A distinct role for secreted fibroblast growth factor-binding proteins in development

FGFs modulate diverse biological processes including embryonic development. Secreted FGF-binding proteins (BPs) can release FGFs from their local extracellular matrix storage, chaperone them to their cognate receptors, and thus modulate FGF signaling. Here we describe 2 chicken BP homologs (chBP) that show distinct expression peaks at embryonic days E7.5 (chBP2) and E11.5 (chBP1), although their tissue distribution is similar (skin = intestine>lung>heart, liver). Embryos were grown ex ovo to monitor the phenotypic impact of a timed in vivo knockdown of expression peaks by microinjection of specific siRNAs targeted to either of the chBPs. Knockdown of peak expression of chBP2 caused embryonic lethality within <5 days. Surviving embryos showed defective ventral wall closure indicative of altered dorsoventral patterning. This defect coincided with reduced expression of HoxB7 but not HoxB8 that are involved in the control of thoracic/abdominal segment morphology. Also, MAPK phosphatase 3, a negative regulator of FGF signaling, and sonic hedgehog that can participate in feedback control of the FGF pathway were reduced, reflecting altered FGF signaling. Knockdown of the chBP1 expression peak caused embryonic lethality within <3 days although no distinct morphologic phenotype or pathways alterations were apparent. We conclude that BPs play a significant role in fine-tuning the complex FGF signaling network during distinct phases of embryonic development.

Effect of FGF-binding protein 3 on vascular permeability

Fibroblast growth factor-binding protein 1 (FGF-BP1 is BP1) is involved in the regulation of embryonic development, tumor growth, and angiogenesis by mobilizing endogenous FGFs from their extracellular matrix storage. Here we describe a new member of the FGF-BP family, human BP3. We show that the hBP3 protein is secreted from cells, binds to FGF2 in vitro and in intact cells, and inhibits FGF2 binding to heparin. To determine the function of hBP3 in vivo, hBP3 was transiently expressed in chicken embryos and resulted in > 50% lethality within 24 h because of vascular leakage. The onset of vascular permeability was monitored by recording the extravasation kinetics of FITC-labeled 40-kDa dextran microperfused into the vitelline vein of 3-day-old embryos. Vascular permeability increased as early as 8 h after expression of hBP3. The increased vascular permeability caused by hBP3 was prevented by treatment of embryos with PD173074, a selective FGFR kinase inhibitor. Interestingly, a C-terminal 66-amino acid fragment (C66) of hBP3, which contains the predicted FGF binding domain, still inhibited binding of FGF2 to heparin similar to full-length hBP3. However, expression of the C66 fragment did not increase vascular permeability on its own, but required the administration of exogenous FGF2 protein. We conclude that the FGF binding domain and the heparin binding domain are necessary for the hBP3 interaction with endogenous FGF and the activation of FGFR signaling in vivo.

Chronic antidepressant treatments increase basic fibroblast growth factor and fibroblast growth factor-binding protein in neurons

One of the mechanisms proposed for antidepressant drugs is the enhancement of synaptic connections and plasticity in the hippocampus and cerebral cortex. Fibroblast growth factor 2 (FGF2) is a growth factor essential for the proper formation of synaptic connections in the cerebral cortex, maturation and survival of catecholamine neurons, and neurogenesis. In this report, we attempted to establish a correlation between antidepressant treatments and FGF2 expression in the cerebral cortex and hippocampus, two brain areas relevant for depression. Desipramine (DMI, 10mg/kg) or fluoxetine (FLU, 5mg/kg) was injected acutely (single injection) or chronically (daily injection for two weeks) in adult rats. Chronic, but not acute, antidepressant treatments increase FGF2 immunoreactivity in neurons of the cerebral cortex and in both astrocytes and neurons of the hippocampus. FGF2 immunoreactivity in the cortex was increased mainly in the cytoplasm of neurons of layer V. Western blot analyses of nuclear and cytosolic extracts from the cortex revealed that both antidepressants increase FGF2 isoforms in the cytosolic extracts and decrease accumulation of FGF2 immunoreactivity in the nucleus. To characterize the anatomical and cellular specificity of antidepressants, we examined FGF-binding protein (FBP), a secreted protein that acts as an extracellular chaperone for FGF2 and enhances its activity. DMI and FLU increased FBP immunoreactivity in both cortical and hippocampal neurons. Our data suggest that FGF2 and FBP may participate in the plastic responses underlying the clinical efficacy of antidepressants.