Browsing by Subject "GDNF"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Characterization of dendritic morphology and neurotransmitter phenotype of thoracic descending propriospinal neurons after complete spinal cord transection and GDNF treatment
    (Elsevier, 2016-03) Deng, Lingxiao; Ruan, Yiwen; Chen, Chen; Frye, Christian Corbin; Xiong, Wenhui; Jin, Xiaoming; Jones, Kathryn; Sengelaub, Dale; Xu, Xiao-Ming; Department of Anatomy & Cell Biology, IU School of Medicine
    After spinal cord injury (SCI), poor regeneration of damaged axons of the central nervous system (CNS) causes limited functional recovery. This limited spontaneous functional recovery has been attributed, to a large extent, to the plasticity of propriospinal neurons, especially the descending propriospinal neurons (dPSNs). Compared with the supraspinal counterparts, dPSNs have displayed significantly greater regenerative capacity, which can be further enhanced by glial cell line-derived neurotrophic factor (GDNF). In the present study, we applied a G-mutated rabies virus (G-Rabies) co-expressing green fluorescence protein (GFP) to reveal Golgi-like dendritic morphology of dPSNs. We also investigated the neurotransmitters expressed by dPSNs after labeling with a retrograde tracer Fluoro-Gold (FG). dPSNs were examined in animals with sham injuries or complete spinal transections with or without GDNF treatment. Bilateral injections of G-Rabies and FG were made into the 2nd lumbar (L2) spinal cord at 3 days prior to a spinal cord transection performed at the 11th thoracic level (T11). The lesion gap was filled with Gelfoam containing either saline or GDNF in the injury groups. Four days post-injury, the rats were sacrificed for analysis. For those animals receiving G-rabies injection, the GFP signal in the T7-9 spinal cord was visualized via 2-photon microscopy. Dendritic morphology from stack images was traced and analyzed using a Neurolucida software. We found that dPSNs in sham injured animals had a predominantly dorsal-ventral distribution of dendrites. Transection injury resulted in alterations in the dendritic distribution with dorsal-ventral retraction and lateral-medial extension. Treatment with GDNF significantly increased the terminal dendritic length of dPSNs. The density of spine-like structures was increased after injury, and treatment with GDNF enhanced this effect. For the group receiving FG injections, immunohistochemistry for glutamate, choline acetyltransferase (ChAT), glycine, and GABA was performed in the T7-9 spinal cord. We show that the majority of FG retrogradely-labeled dPSNs were located in the Rexed Lamina VII. Over 90% of FG-labeled neurons were glutamatergic, with the other three neurotransmitters contributing less than 10% of the total. To our knowledge this is the first report describing the morphologic characteristics of dPSNs and their neurotransmitter expressions, as well as the dendritic response of dPSNs after transection injury and GDNF treatment.
  • Thumbnail Image
    Item
    Combinational treatment approach for traumatic spinal cord injury
    (2016-03-02) Walker, Melissa J.; Xu, Xiao-Ming
    Spinal cord injury (SCI) is devastating and debilitating, and currently no effective treatments exist. Approximately, 12,000 new cases of SCI occur annually in the United States alone. The central nervous system has very low repair capability after injury, due to the toxic environment in the injured tissue. After spinal cord trauma, ruptured blood vessels cause neighboring cells and tissues to be deprived of oxygen and nutrients, and result in the accumulation of carbon dioxide and waste. New blood vessels form spontaneously after SCI, but then retract as the injured tissue forms a cavity. Thus, the newly formed vasculature likely retracts because it lacks a structural support matrix to extend across the lesion. Currently, in the field of spinal cord injury, combinational treatment approaches appear to hold the greatest therapeutic potential. Therefore, the aim of these studies was to transplant a novel, non-immunogenic, bioengineered hydrogel, into the injured spinal cord to serve as both a structural scaffold (for blood vessels, axons, and astrocytic processes), as well as a functional matrix with a time-controlled release of growth factors (Vascular endothelial growth factor, VEGF; Glial cell line-derived neurotrophic factor, GDNF). The benefit of this hydrogel is that it remains liquid at cooler temperatures, gels to conform to the space surrounding it at body temperature, and was designed to have a similar tensile strength as spinal cord tissue. This is advantageous due to the non-uniformity of lesion cavities following contusive spinal cord injury. Hydrogel alone and combinational treatment groups significantly improved several measures of functional recovery and showed modest histological improvements, yet did not provoke any increased sensitivity to a thermal stimulus. Collectively, these findings suggest that with further investigation, hydrogel along with a combination of growth factors might be a useful therapeutic approach for repairing the injured spinal cord.
  • Thumbnail Image
    Item
    GDNF secreted from adipose-derived stem cells stimulates VEGF-independent angiogenesis
    (Impact Journals, LLC, 2016-06-14) Zhong, Zhaohui; Gu, Huiying; Peng, Jirun; Wang, Wenzheng; Johnstone, Brian H.; March, Keith L.; Farlow, Martin R.; Du, Yansheng; Department of Neurology, School of Medicine
    Adipose tissue stroma contains a population of mesenchymal stem cells (MSC) promote new blood vessel formation and stabilization. These adipose-derived stem cells (ASC) promote de novo formation of vascular structures in vitro. We investigated the angiogenic factors secreted by ASC and discovered that glial-derived neurotrophic factor (GDNF) is a key mediator for endothelial cell network formation. It was found that both GDNF alone or present in ASC-conditioned medium (ASC-CM) stimulated capillary network formation by using human umbilical vein endothelial cells (HUVECs) and such an effect was totally independent of vascular endothelial growth factor (VEGF) activity. Additionally, we showed stimulation of capillary network formation by GDNF, but not VEGF, could be blocked by the Ret (rearranged during transfection) receptor antagonist RPI-1, a GDNF signaling inhibitor. Furthermore, GDNF were found to be overexpressed in cancer cells that were resistant to the anti-angiogenic treatment using the VEGF antibody. Cancer cells in the liver hepatocellular carcinoma (HCC), a non-nervous related cancer, highly overexpressed GDNF as compared to normal liver cells. Our data strongly suggest that, in addition to VEGF, GDNF secreted by ASC and HCC cells, may be another important factor promoting pathological neovascularization. Thus, GDNF may be a potential therapeutic target for HCC and obesity treatments.
  • Thumbnail Image
    Item
    Plasma membrane localization of the GFL receptor components: a nexus for receptor crosstalk
    (Springer, 2020-08-07) Donnelly, Christopher R.; Pierchala, Brian A.; Anatomy and Cell Biology, School of Medicine
    The glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) comprise a group of four homologous and potent growth factors that includes GDNF, neurturin (NRTN), artemin (ARTN), and persephin (PSPN). The survival, growth, and mitotic activities of the GFLs are conveyed by a single receptor tyrosine kinase, Ret. The GFLs do not bind directly to Ret in order to activate it, and instead bind with high affinity to glycerophosphatidylinositol (GPI)-anchored coreceptors called the GDNF family receptor-αs (GFRαs). Several mechanisms have recently been identified that influence the trafficking of Ret and GFRαs in and out of the plasma membrane, thereby affecting their availability for ligand binding, as well as their levels by targeting to degradative pathways. This review describes these mechanisms and their powerful effects on GFL signaling and function. We also describe the recent discovery that p75 and Ret form a signaling complex, also regulated by plasma membrane shuttling, that either enhances GFL survival signals or p75 pro-apoptotic signals, dependent on the cellular context.
  • Thumbnail Image
    Item
    RET-DEPENDENT AND RET-INDEPENDENT MECHANISMS OF GFL-INDUCED ENHANCEMENT IN THE CAPSAICIN STIMULATED-RELEASE OF iCGRP FROM SENSORY NEURONS
    (2010-02-02T22:18:31Z) Schmutzler, Brian S.; Hingtgen, Cynthia M., 1966-; Cummins, Theodore R.; Vasko, Michael R.; Broustovetski, Nikolai; Hudmon, Andy
    The glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) are peptides implicated in the inflammatory response. They are released in increased amounts during inflammation and induce thermal hyperalgesia. Whether these molecules directly affect the sensitivity of primary nociceptive sensory neurons is unknown. This information could provide a link between increased inflammation-induced release of GFLs and their ability to promote inflammatory hyperalgesia. These molecules bind to one of four GFRα receptor subtypes, and this GFL-GFRα complex often translocates to the receptor tyrosine kinase, Ret. The focus of this dissertation was to determine whether GFLs modulate the stimulated-release of calcitonin gene-related peptide (CGRP). Isolated sensory neurons and freshly dissociated spinal cord tissue were used to examine the enhancement in stimulated-release of CGRP, a measure of sensitization. Exposure of isolated sensory neurons to GDNF, neurturin, and artemin, enhanced the capsaicin stimulated-release of immunoreactive CGRP (iCGRP). Sensitization by GFLs occurred in freshly dissociated spinal cord tissue. Persephin, another member of the GFL family, did not enhance stimulated-release of iCGRP. These results demonstrate that specific GFLs are mediators of neuronal sensitivity. The intracellular signaling pathways responsible for this sensitization were also evaluated. Inhibition of the mitogen activated protein kinase (MAPK)/extracellular signal-related kinase 1/2 (Erk 1/2) pathway selectively abolished the enhancement of CGRP release by GDNF. NTN-induced sensitization was abolished by inhibition of the phosphatidylinositol-3-kinase (PI-3K) pathway. Reduction in Ret abolished the GDNF-induced sensitization, but did not fully inhibit NTN or ART-induced sensitization. Inhibition of other cell surface receptors (neural cell adhesion molecule (NCAM), and Integrin β-1) had distinct effects on the sensitization capability of each of the GFLs. Ret and NCAM inhibition in combination abolished ART-induced sensitization. It was necessary to inhibit Ret, NCAM, and Integrin β-1 to prevent the NTN-induced sensitization. These data demonstrate that the GFLs use distinct signaling mechanisms to induce the sensitization of nociceptive sensory neurons. The work presented in this thesis provides the first evidence for these novel and distinct Ret-independent pathways for GFL-induced actions and provides insight into the mechanism of sensory neuronal sensitization in general.