Comparative study of GDNF delivery systems for the CNS: polymer rods, encapsulated cells, and lentiviral vectors
Introduction
Neurodegenerative disorders of the central nervous system (CNS) are characterized by a selective and progressive degeneration of neuronal subpopulations leading to severe debilitating clinical symptoms. Current treatments consist mainly in symptomatic therapies with no effect on the onset or disease progression. Efforts are thus being made to develop neuroprotection or even neuroregenerative strategies. Neurotrophic factors hold the greatest promise to achieve this goal.
Neurotrophic factors (NTFs) are polypeptides known to promote growth, survival and differentiation of neurons during development, as well as plasticity and structural integrity of the adult nervous system. These proteins have demonstrated potent neuroprotective effects on various neuronal populations in experimental models of neurodegenerative diseases, such as nerve growth factor (NGF) for Alzheimer’s disease (AD), glial cell line-derived neurotrophic factor (GDNF) for Parkinson’s disease (PD), or ciliary neurotrophic factor (CNTF) for Huntington’s disease (HD) [1], [2]. Several clinical trials have been conducted with each of these factors, so far, however, without success. Part of the problems may be related to inefficient delivery technique.
The CNS delivery of NTFs is limited by factors such as (i) their inability to cross the blood–brain-barrier, (ii) their poor stability in a fluid environment, (iii) their limited diffusion through brain parenchyma, and (iv) the side-effects associated with binding to extra-target receptors [3], [4]. Intracerebroventricular (ICV) administration eliminates the need to bypass the blood–brain-barrier. Poor diffusion within the brain parenchyma [5], [6] and occurrence of severe side-effects limit, however, its applicability. Excruciating pain was indeed described with the ICV administration of NGF in AD patients [7], [8]; weight loss, nausea and abnormal sexual behavior was reported with the ICV administration of GDNF in PD patients [9]. In contrast, animal experiments have shown that direct parenchymal administration dramatically reduces the occurrence of side-effects reported with ICV application [5], [10]. These observations emphasize the need for localized, sustained delivery of these molecules in specific nuclei of the CNS.
Direct localized CNS delivery is achievable either by mechanical means, or by cell or gene therapy. In the context of this work, we have chosen to compare a representative of each of the three approaches for the intrastriatal delivery of GDNF, a promising trophic factor for the treatment of PD, and deduct the relative advantages/disadvantages of the three delivery techniques.
Section snippets
GDNF-releasing polymer rods
Ethylene-vinyl acetate copolymer (EVA; Elvax, Dupont, Wilmington, USA) was cleaned by 20 washes in absolute ethanol followed by 20 washes in sterile distilled water, and finally dried under a mild vacuum. Bovine serum albumin (BSA; Sigma, Buchs, Switzerland) was sieved to a size <37 μm using scrynel PET33HC meshes (PolyLabo). A 10% (w/v) solution of purified EVA in methylene chloride solvent was prepared with 23% BSA (w/w total) and 1% recombinant human GDNF (Amgen) (w/w total), vortexed and
Diffusion pattern of GDNF in the striatum
One and 4 weeks following the implantation of polymer rods or hollow fibers, and the injection of lentiviral vectors into the rat striatum, immunohistochemical detection of hGDNF was performed to characterize the diffusion of the NTF throughout this structure (Fig. 1). One week post-surgery, GDNF staining was present over a maximal distance of 4 mm in the three groups, which almost corresponds to the entire striatum volume according to the rat brain atlas of Paxinos and Watson [16] (Fig. 1A–C).
Discussion
In the present study, we have compared the efficiency of three different methods for delivery of the neurotrophic factor GDNF in the brain parenchyma of adult rats. Polymer rods, encapsulated cells and lentiviral vectors enable the continuous and localized expression of significant amounts of GDNF in the striatum. Although the diffusion pattern of GDNF was approximately identical with the three approaches at 1 week post-surgery, results of the 4-week time point suggest that polymer rods are
Conclusion
The present work reveals the efficiency of three different delivery methods in providing a significant amount of GDNF in the rat striatum. These data open interesting perspectives for the treatment of neurodegenerative diseases. The dose and the time during which GDNF needs to be administered, i.e. more detailed pharmacokinetics for the administration of this trophic factor in the CNS will require further investigations to determine which one of these approaches would be particularly relevant
Acknowledgements
The authors thank Vivianne Padrun, Fabienne Pidoux, Maria Rey, Laurence Winkel and Christel Sadeghi for expert technical assistance. This work was partially supported by the Swiss National Science Foundation and the 5th European Framework Program “Neuroget”.
References (33)
- et al.
The role of neuronal growth factors in neurodegenerative disorders of the human brain
Brain Res. Rev.
(1998) - et al.
Recombinant proteins for neurodegenerative diseases: the delivery issue
Trends Neurosci.
(2001) - et al.
Distribution of intracerebral ventricularly administered neurotrophins in rat brain and its correlation with trk receptor expression
Exp. Neurol.
(1994) - et al.
NGF released from a polymer matrix prevents loss of ChAT expression in basal forebrain neurons following a fimbria–fornix lesion
Exp. Neurol.
(1990) - et al.
Implantation of bioactive growth factor-secreting rods enhances fetal dopaminergic graft survival, outgrowth density, and functional recovery in a rat model of Parkinson’s disease
Exp. Neurol.
(2000) - et al.
Implants of polymer-encapsulated genetically modified cells releasing glial cell line-derived neurotrophic factor improve survival, growth, and function of fetal dopaminergic grafts
Exp. Neurol.
(1998) - et al.
Cellular delivery of CNTF but not NT-4/5 prevents degeneration of striatal neurons in a rodent model of Huntington’s disease
Cell Transplant.
(1998) Lentiviruses as gene transfer agents for delivery to non-dividing cells
Curr. Opin. Biotechnol.
(1998)- et al.
Lentiviral vectors as a gene delivery system in the mouse midbrain: cellular and behavioural improvements in a 6-OHDA model of Parkinson’s disease using GDNF
Exp. Neurol.
(2000) - et al.
Lentiviral vectors: regulated gene expression
Mol. Ther.
(2000)
Pharmacology of neurotrophic factors
Annu. Rev. Pharmacol. Toxicol.
Localized delivery of proteins in the brain: can transport be customized?
Pharm. Res.
Brain-derived neurotrophic factor (BDNF) prevents the degeneration of medial septal cholinergic neurons following fimbria transection
J. Neurosci.
Nerve growth factor affects 11C-nicotine binding, blood flow, EEG, and verbal episodic memory in an Alzheimer patient (case report)
J. Neural Transm. Park. Dis. Dement. Sect.
Intracerebroventricular infusion of nerve growth factor in three patients with Alzheimer’s disease
Dement. Geriatr. Cogn. Disord.
Clinicopathological findings following intraventricular glial-derived neurotrophic factor treatment in a patient with Parkinson’s disease
Ann. Neurol.
Cited by (41)
Sustainable green synthesized nanoparticles for neurodegenerative diseases diagnosis and treatment
2023, Materials Today: ProceedingsCitation Excerpt :“Neurodegenerative disorders” (NDs) are a class of chronic or perhaps hereditary illnesses defined by a loss of neuronal subtypes over time. ( PD) Parkinson's disease and (AD) Alzheimer's disease are two of the conditions that have had the largest influence on society in the twenty-first century [1–4]Fig. 1. The public and health sectors are heavily burdened by neurodegenerative illnesses due to the subsequent immunological activation of (CNS) central nervous system.
2.21 Xenogenic tissues and biomaterials for the skeletal system
2017, Comprehensive Biomaterials IILevetiracetam-loaded biodegradable polymer implants in the tetanus toxin model of temporal lobe epilepsy in rats
2013, Journal of Clinical NeuroscienceCitation Excerpt :In rats this distance is 4 mm to 5 mm. Previous investigations have shown that substances released from intraparenchymally implanted polymers are able to penetrate around 3 mm,10–14 suggesting that LEV released from the implants in our study would not have reached the seizure focus in the hippocampus in high concentrations. High concentrations of LEV in the motor and somatosensory cortices may have been able to slow or interrupt seizure propagation, leading to the observed reduction in seizure duration; however, the inadequate concentration in the hippocampus would have had no effect on seizure initiation and therefore on seizure frequency.
Neurotrophic Factors and Neurodegenerative Diseases. A Delivery Issue.
2012, International Review of NeurobiologyCitation Excerpt :The majority of the papers dealing with NTF delivery by means of implants is relating to GDNF and its application in neurodegenerative disorders, mainly PD. In particular, a comparative work on GDNF delivery by EVAc polymer rods, encapsulated cells, and lentiviral vectors was performed in rats (Bensadoun et al., 2003). The outputs demonstrated that GDNF-loaded EVAc implants stereotaxically placed into rat striatum are the most suitable for short-term protocols, while lentiviral vectors and encapsulated cells are more adapted for long-term application.
Nanotechnological applications for the treatment of neurodegenerative disorders
2009, Progress in NeurobiologyTowards controlled release of BDNF - Manufacturing strategies for protein-loaded lipid implants and biocompatibility evaluation in the brain
2007, Journal of Controlled Release
- 1
These authors contributed equally to this work.