Targeted delivery of nerve growth factor to the cholinergic basal forebrain of Alzheimer's disease patients: application of a second-generation encapsulated cell biodelivery device.

BACKGROUND: Targeted delivery of nerve growth factor (NGF) has emerged as a potential therapy for Alzheimer's disease (AD) due to its regenerative effects on basal forebrain cholinergic neurons. This hypothesis has been tested in patients with AD using encapsulated cell biodelivery of NGF (NGF-ECB) in a first-in-human study. We report our results from a third-dose cohort of patients receiving second-generation NGF-ECB implants with improved NGF secretion. METHODS: Four patients with mild to moderate AD were recruited to participate in an open-label, phase Ib dose escalation study with a 6-month duration. Each patient underwent stereotactic implant surgery with four NGF-ECB implants targeted at the cholinergic basal forebrain. The NGF secretion of the second-generation implants was improved by using the Sleeping Beauty transposon gene expression technology and an improved three-dimensional internal scaffolding, resulting in production of about 10 ng NGF/device/day. RESULTS: All patients underwent successful implant procedures without complications, and all patients completed the study, including implant removal after 6 months. Upon removal, 13 of 16 implants released NGF, 8 implants released NGF at the same rate or higher than before the implant procedure, and 3 implants failed to release detectable amounts of NGF. Of 16 adverse events, none was NGF-, or implant-related. Changes from baseline values of cholinergic markers in cerebrospinal fluid (CSF) correlated with cortical nicotinic receptor expression and Mini Mental State Examination score. Levels of neurofilament light chain (NFL) protein increased in CSF after NGF-ECB implant, while glial fibrillary acidic protein (GFAP) remained stable. CONCLUSIONS: The data derived from this patient cohort demonstrate the safety and tolerability of sustained NGF release by a second-generation NGF-ECB implant to the basal forebrain, with uneventful surgical implant and removal of NGF-ECB implants in a new dosing cohort of four patients with AD. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01163825 . Registered on 14 Jul 2010.

Encapsulated galanin-producing cells attenuate focal epileptic seizures in the hippocampus.

PURPOSE: Encapsulated cell biodelivery (ECB) is a relatively safe approach, since the devices can be removed in the event of adverse effects. The main objectives of the present study were to evaluate whether ECB could be a viable alternative of cell therapy for epilepsy. We therefore developed a human cell line producing galanin, a neuropeptide that has been shown to exert inhibitory effects on seizures, most likely acting via decreasing glutamate release from excitatory synapses. To explore whether ECB of genetically modified galanin-producing human cell line could provide seizure-suppressant effects, and test possible translational prospect for clinical application, we implanted ECB devices bilaterally into the hippocampus of rats subjected to rapid kindling, a model for recurrent temporal lobe seizures. METHODS: Two clones from a genetically modified human cell line secreting different levels of galanin were tested. Electroencephalography (EEG) recordings and stimulations were performed by electrodes implanted into the hippocampus at the same surgical session as ECB devices. One week after the surgery, rapid kindling stimulations were initiated. KEY FINDINGS: Enzyme-linked immunosorbent assay (ELISA) measurements prior to device implantation showed a release of galanin on average of 8.3 ng/mL/24 h per device for the low-releasing clone and 12.6 ng/mL/24 h per device for the high-releasing clone. High-releasing galanin-producing ECB devices moderately decreased stimulation-induced focal afterdischarge duration, whereas low-releasing ECB devices had no significant effect. SIGNIFICANCE: Our study shows that galanin-releasing ECB devices moderately suppress focal stimulation-induced recurrent seizures. Despite this moderate effect, the study provides conceptual proof that ECB could be a viable alternative approach to cell therapy in humans, with the advantage that the treatment could be terminated by removing these devices from the brain. Thereby, this strategy provides a higher level of safety for future therapeutic applications, in which genetically modified human cell lines that are optimized to produce and release antiepileptic compounds could be clinically evaluated for their seizure-suppressant effects.

Targeted delivery of nerve growth factor via encapsulated cell biodelivery in Alzheimer disease: a technology platform for restorative neurosurgery.

OBJECT: The authors describe the first clinical trial with encapsulated cell biodelivery (ECB) implants that deliver nerve growth factor (NGF) to the cholinergic basal forebrain with the intention of halting the degeneration of cholinergic neurons and the associated cognitive decline in patients with Alzheimer disease (AD). The NsG0202 implant (NsGene A/S) consists of an NGF-producing, genetically engineered human cell line encapsulated behind a semipermeable hollow fiber membrane that allows the influx of nutrients and the efflux of NGF. The centimeter-long capsule is attached to an inert polymer tether that is used to guide the capsule to the target via stereotactic techniques and is anchored to the skull at the bur hole. METHODS: Six patients with mild to moderate AD were included in this Phase Ib open-label safety study and were divided into 2 dose cohorts. The first cohort of 3 patients received single implants targeting the basal nucleus of Meynert (Ch4 region) bilaterally (2 implants per patient), and after a safety evaluation, a second cohort of 3 patients received bilateral implants (a total of 4 implants per patient) targeting both the Ch4 region and the vertical limb of the diagonal band of Broca (Ch2 region). Stereotactic implantation of the devices was successfully accomplished in all patients. Despite extensive brain atrophy, all targets could be reached without traversing sulci, the insula, or lateral ventricles. RESULTS: Postoperative CT scans allowed visualization of the barium-impregnated tethers, and fusion of the scans with stereotactic MR images scan was used to verify the intended positions of the implants. Follow-up MRI at 3 and 12 months postimplantation showed no evidence of inflammation or device displacement. At 12 months, implants were successfully retrieved, and low but persistent NGF secretion was detected in half of the patients. CONCLUSIONS: With refinement, the ECB technology is positioned to become an important therapeutic platform in restorative neurosurgery and, in combination with other therapeutic factors, may be relevant for the treatment of a variety of neurological disorders. Clinical trial registration no.: NCT01163825.

Long-term delivery of nerve growth factor by encapsulated cell biodelivery in the Göttingen minipig basal forebrain.

Nerve growth factor (NGF) prevents cholinergic degeneration in Alzheimer's disease (AD) and improves memory in AD animal models. In humans, the safe delivery of therapeutic doses of NGF is challenging. For clinical use, we have therefore developed an encapsulated cell (EC) biodelivery device, capable of local delivery of NGF. The clinical device, named NsG0202, houses an NGF-secreting cell line (NGC-0295), which is derived from a human retinal pigment epithelial (RPE) cell line, stably genetically modified to secrete NGF. Bioactivity and correct processing of NGF was confirmed in vitro. NsG0202 devices were implanted in the basal forebrain of Göttingen minipigs and the function and retrievability were evaluated after 7 weeks, 6 and 12 months. All devices were implanted and retrieved without associated complications. They were physically intact and contained a high number of viable and NGF-producing NGC-0295 cells after explantation. Increased NGF levels were detected in tissue surrounding the devices. The implants were well tolerated as determined by histopathological brain tissue analysis, blood analysis, and general health status of the pigs. The NsG0202 device represents a promising approach for treating the cognitive decline in AD patients.

Generation and properties of a new human ventral mesencephalic neural stem cell line.

Neural stem cells (NSCs) are powerful research tools for the design and discovery of new approaches to cell therapy in neurodegenerative diseases like Parkinson's disease. Several epigenetic and genetic strategies have been tested for long-term maintenance and expansion of these cells in vitro. Here we report the generation of a new stable cell line of human neural stem cells derived from ventral mesencephalon (hVM1) based on v-myc immortalization. The cells expressed neural stem cell and radial glia markers like nestin, vimentin and 3CB2 under proliferation conditions. After withdrawal of growth factors, proliferation and expression of v-myc were dramatically reduced and the cells differentiated into astrocytes, oligodendrocytes and neurons. hVM1 cells yield a large number of dopaminergic neurons (about 12% of total cells are TH+) after differentiation, which also produce dopamine. In addition to proneural genes (NGN2, MASH1), differentiated cells show expression of several genuine mesencephalic dopaminergic markers such as: LMX1A, LMX1B, GIRK2, ADH2, NURR1, PITX3, VMAT2 and DAT, indicating that they retain their regional identity. Our data indicate that this cell line and its clonal derivatives may constitute good candidates for the study of development and physiology of human dopaminergic neurons in vitro, and to develop tools for Parkinson's disease cell replacement preclinical research and drug testing.

GDNF released from encapsulated cells suppresses seizure activity in the epileptic hippocampus.

To date, a variety of pharmacological treatments exists for patients suffering epilepsy, but systemically administered drugs offer only symptomatic relief and often cause unwanted side effects. Moreover, available drugs are not effective in one third of the patients. Thus, more local and more effective treatment strategies need to be developed. Gene therapy-based expression of endogenous anti-epileptic agents represents a novel approach that could interfere with the disease process and result in stable and long-term suppression of seizures in epilepsy patients. We have reported earlier that direct in vivo viral vector-mediated overexpression of the glial cell line-derived neurotrophic factor (GDNF) in the rat hippocampus suppressed seizures in different animal models of epilepsy. Here we explored whether transplantation of encapsulated cells that release GDNF in the hippocampus could also exert a seizure-suppressant effect. Such ex vivo gene therapy approach represents a novel, more clinically safe approach, since the treatment could be terminated by retrieving the transplants from the brain. We demonstrate here that encapsulated cells, which are genetically modified to produce and release GDNF, can suppress recurrent generalized seizures when implanted into the hippocampus of kindled rats.

Efficient in vivo protection of nigral dopaminergic neurons by lentiviral gene transfer of a modified Neurturin construct.

Protein injection studies of the glial cell line derived neurotrophic factor (GDNF) family member Neurturin (NTN) have demonstrated neuroprotective effects on dopaminergic (DA) neurons, which are selectively lost during Parkinson's disease (PD). However, unlike GDNF, NTN has not previously been applied in PD models using an in vivo gene therapy approach. Difficulties with lentiviral gene delivery of wild type (wt) NTN led us to examine the role of the pre-pro-sequence, and to evaluate different NTN constructs in order to optimize gene therapy with NTN. Results from transfected cultured cells showed that wt NTN was poorly processed, and secreted as a pro-form. A similarly poor processing was found with a chimeric protein consisting of the pre-pro-part from GDNF and mature NTN. Moreover, we found that the biological activity of pro-NTN differs from mature NTN, as pro-NTN did not form a signaling complex with the tyrosine kinase receptor Ret and GFRalpha2 or GFRalpha1. Deletion of the pro-region resulted in significantly higher secretion of active NTN, which was further increased when substituting the wt NTN signal peptide with the immunoglobulin heavy-chain signal peptide (IgSP). The enhanced secretion of active mature NTN using the IgSP-NTN construct was reproduced in vivo in lentiviral-transduced rat striatal cells and, unlike wt NTN, enabled efficient neuroprotection of lesioned nigral DA neurons, similar to GDNF. An in vivo gene therapy approach with a modified NTN construct is therefore a possible treatment option for Parkinson's disease that should be further explored.

A new versatile and compact lentiviral vector.

During the past decade, lentiviral vectors based on the HIV-1 genome have been developed to become highly useful tools for efficient and stable delivery of transgenes to dividing and nondividing cells in a variety of experimental protocols. The vector system has been progressively and substantially improved,mainly to meet growing concerns over safety issues. However, the actual design and size of the lentiviral transfer vector often makes transgene cloning and DNA preparation a troublesome task. In this study, the pHR transfer vector used for lentivirus production in many laboratories was modified to contain a more versatile polylinker than the one present in the original pHR vector. In addition, the vector was significantly reduced in size from 12 to 7 kb, by replacing the original vector backbone with sequence from the multipurpose pUC18 vector. These modifications allowed for easier cloning and higher DNA yields without compromising the fundamental ability of this vector system to transduce cells in vitro and in vivo. Finally, the trimmed vector sequence was fully characterized by sequencing the vector in its entirety. In both cultured cells and directly into the rat striatum, transduction with this lentivirus, based on the modified pHsCXW vector, was as efficient and durable as with the pHR vector-based virus. In conclusion, the modified lentiviral transfer vector pHsCXW holds promise as a new valuable tool for the research community in the field of gene transfer.

Serum osteoprotegerin (OPG) and the A163G polymorphism in the OPG promoter region are related to peripheral measures of bone mass and fracture odds ratios.

The purpose of this study is to investigate the association of serum osteoprotegerin (OPG) and the A163G polymorphism in the OPG promoter with peripheral measures of bone mass and with odds ratios for wrist and hip fracture in a case-control study of postmenopausal Danish women. The study included 66 women with lower forearm fracture, 41 women with hip fracture, and 206 age-matched controls. All had broadband ultrasound attenuation (BUA) and speed of sound (SOS) measured at the heel as well as bone mineral density (BMD) measured by DXA at the distal forearm. S-OPG was measured by ELISA. The A163G genotypes were determined by PCR-RFLP analysis. S-OPG levels correlated positively with age ( r = 0.45; P << 0.0001) and negatively with distal forearm BMD ( r = -0.31; P << 0.0001), heel BUA ( r = -0.23; P << 0.0001), and heel SOS ( r = -0.22; P << 0.0001). Comparing the highest quartile of S-OPG to the lowest, the odds ratio for osteoporotic fracture was 2.5 (95% CI, 1.3-4.7; P = 0.006). The G allele of the A163G was associated with significantly lower t-scores of both lower forearm BMD, heel BUA, and heel SOS as well as being significantly more frequent in the fracture patients compared to the controls. Patients with a combination of the highest quartile of S-OPG and presence of the G allele ( n = 23) had a significantly elevated fracture odds ratio, 4.0 (95% CI, 1.7-9.9). A significant negative association between S-OPG with peripheral measures of bone mass and with increased fracture odds ratios was found. Furthermore, the A163G mutation in the OPG promoter had a significant influence on bone mass and fracture status independently of S-OPG level.

Generation of a synthetic mammalian promoter library by modification of sequences spacing transcription factor binding sites.

The development of a set of synthetic mammalian promoters with different specific activities is described. The library is based on a synthetic promoter, JeT, constructed as a 200 bp chimeric promoter built from fragments of the viral SV40 early promoter and the human beta-actin and ubiquitin C promoters. The JeT promoter was made by separating the included consensus boxes by the same distances in base pairs as found in the wild-type promoters, thus preserving transcription factor interaction. The resulting promoter was shown to drive reporter expression to high levels in enhanced green fluorescent protein and secreted alkaline phosphatase reporter assays. By replacing sequences separating the transcription factor binding sites with randomized sequences of the same length, sets of new promoters with different strengths, spanning a 10-fold range of transcriptional activity in cell culture, was obtained. The measured activity of each promoter in the library was highly specific and reproducible when tested in HiB5 and ARPE-19 cell culture.