Mette Slot Nielsen

Post-translationally modified residues of native human osteopontin are located in clusters: identification of 36 phosphorylation and five O-glycosylation sites and their biological implications

OPN (osteopontin) is an integrin-binding highly phosphorylated glycoprotein, recognized as a key molecule in a multitude of biological processes such as bone mineralization, cancer metastasis, cell-mediated immune response, inflammation and cell survival. A significant regulation of OPN function is mediated through PTM (post-translational modification). Using a combination of Edman degradation and MS analyses, we have characterized the complete phosphorylation and glycosylation pattern of native human OPN. A total of 36 phosphoresidues have been localized in the sequence of OPN. There are 29 phosphorylations (Ser8, Ser10, Ser11, Ser46, Ser47, Thr50, Ser60, Ser62, Ser65, Ser83, Ser86, Ser89, Ser92, Ser104, Ser110, Ser113, Thr169, Ser179, Ser208, Ser218, Ser238, Ser247, Ser254, Ser259, Ser264, Ser275, Ser287, Ser292 and Ser294) located in the target sequence of MGCK (mammary gland casein kinase) also known as the Golgi kinase (S/T-X-E/S(P)/D). Six phosphorylations (Ser101, Ser107, Ser175, Ser199, Ser212 and Ser251) are located in the target sequence of CKII (casein kinase II) [S-X-X-E/S(P)/D] and a single phosphorylation, Ser203, is not positioned in the motif of either MGCK or CKII. The 36 phosphoresidues represent the maximal degree of modification since variability at many sites was seen. Five threonine residues are O-glycosylated (Thr118, Thr122, Thr127, Thr131 and Thr136) and two potential sites for N-glycosylation (Asn63 and Asn90) are not occupied in human milk OPN. The phosphorylations are arranged in clusters of three to five phosphoresidues and the regions containing the glycosylations and the RGD (Arg-Gly-Asp) integrin-binding sequence are devoid of phosphorylations. Knowledge about the positions and nature of PTMs in OPN will allow a rational experimental design of functional studies aimed at understanding the structural and functional interdependences in diverse biological processes in which OPN is a key molecule.

Chronic subthalamic high-frequency deep brain stimulation in Parkinson's disease – a histopathological study

This study describes the pathological findings in the brain of a patient with Parkinsons disease (PD) treated with bilateral subthalamic high‐frequency deep brain stimulation (STN DBS) for 29u2003months prior to death. After routine neuropathological examination, tissue blocks containing the electrode tracts, the subthalamic nucleus (STN), the substantia nigra and the pre‐frontal cortex were paraffin embedded and cut into 5‐μm‐thick serial sections and stained with several conventional staining methods and immunohistochemistry. Bilateral nigral depigmentation, cell loss and Lewy body formation confirmed the diagnosis of PD. Microscopic evaluation furthermore confirmed the location of the electrodes in the STN. The electrode tracts were surrounded by a 150‐μm‐wide glial fibrillary acidic protein (GFAP)‐positive capsule consisting of a thin collagen layer lining the lumen of the tract, whilst an area with few cells and axons constituted the capsule wall towards the surrounding normal brain tissue. The brain tissue appeared normal outside the capsule boundaries with no difference in areas of stimulation compared with areas of no stimulation. Our results correspond with previous studies performed after fewer months of STN DBS and indicate mild histopathological changes in the vicinity of the electrode tract, appearing to result from the electrode placement and not from the electrical stimulation.

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 Alzheimers 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.

The substantia nigra pars compacta of the Göttingen minipig: an anatomical and stereological study.

Parkinson disease (PD) is a neurodegenerative disorder resulting from progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNc). Despite advances in medical and surgical therapies, many PD patients experience progression of their symptoms and medical side effects over time. To explore new treatments, new animal models mimicking the progressive PD nature are needed. The pig is well suited for this purpose with its large gyrated brain, sensitive to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The objective of this study was to provide the anatomical foundation for such a model, describing in detail the SNc in normal Göttingen minipigs and estimating the volume and total number of tyrosine hydroxylase (TH)-positive neurons. The brain stems of 6 Göttingen minipigs were paraffin embedded and serially cut before Nissl staining and immunohistochemical visualization of TH. The volume of the SNc and the total number of TH-positive neurons were estimated by design-based stereology. The substantia nigra was located at the dorsal rim of the crus cerebri extending throughout the mesencephalon. A dorsal pars compacta and a ventral pars reticulata were demonstrated. The SNc merged with the ventral tegmental area medially and the retro-rubral field dorsocaudolaterally. The total number of TH-positive neurons in the SNc unilaterally was estimated to 80,700 [74,100;87,300], and the volume estimate was 26.4xa0mm3 [25.0;27.8]. We conclude that the anatomy of the SNc in the Göttingen minipig corresponds well with that of higher primates, and is well suited for further studies aimed at optimizing this non-primate large animal model for PD.

Neuromodulation in a minipig MPTP model of Parkinson disease

Large animal neuroscience enables the use of conventional clinical brain imagers and the direct use and testing of surgical procedures and equipment from the human clinic. The greater complexity of the large animal brain additionally enables a more direct translation to human brain function in health and disease. Economical, ethical, scientific and practical issues may on the other hand hamper large animal neuroscience. Large animal neuroscience should therefore either be performed in order to examine large animal species dependent problems or to complement promising small animal basic studies by constituting an intermediate research system, bridging small animal CNS research to the human CNS. We have, accordingly, during the last ten years used the Göttingen minipig to examine neuromodulatory treatment modalities such as stem cell transplantation and deep brain stimulation directed towards Parkinson disease. This has been accomplished by the development of a MPTP-based large animal model of Parkinson disease in the Göttingen minipig and the development of stereotaxic and surgical approaches needed to manipulate the Göttingen minipig CNS. The instituted changes in the CNS can be evaluated in the live animal by brain imaging (PET and MR), cystometry, gait analysis, neurological evaluation and by post mortem examination based on histology and stereological analysis.

Safety and Function of a New Clinical Intracerebral Microinjection Instrument for Stem Cells and Therapeutics Examined in the Göttingen Minipig

Background: A new intracerebral microinjection instrument (IMI) allowing multiple electrophysiologically guided microvolume injections from a single proximal injection path in rats has been adapted to clinical use by coupling the IMI to an FHC microTargeting Manual Drive, designed to be used with standard stereotactic frame-based systems and FHC frameless microTargeting Platforms. Methods: The function and safety of the device was tested by conducting bilateral electrophysiologically guided microinjections of fluorescent microspheres in the substantia nigra of 4 Göttingen minipigs. Results: The device was easy to handle and enabled accurate electrophysiologically guided targeting of the substantia nigra with minimal local tissue damage. Conclusion: The IMI is suitable for clinical use and may prove useful for various stereotactic procedures that require high levels of precision and/or three-dimensional distribution of therapeutics within the brain.

MRI protocol for in vivo visualization of the Göttingen minipig brain improves targeting in experimental functional neurosurgery

BACKGROUNDnThe Göttingen minipig is increasingly used as an animal model in experimental neuroscience as a much needed alternative to non-human primates. Accurate spatial targeting in this species in vivo is challenging, and most clinically available magnetic resonance imaging (MRI) protocols do not provide sufficient spatial resolution for this purpose. Thus, the aim of this study was to develop an in vivo pre-operative MRI protocol allowing direct visualization of individual nuclei of major interest in the minipig brain.nnnMATERIALS AND METHODSnThree Göttingen minipigs underwent MRI using an inversion-recovery fast spin-echo sequence that was optimized with regards to the following parameters: inversion time, relaxation time, echo time and spatial and temporal resolution, giving a scan duration acceptable for the tight schedule usually employed in a neurosurgical procedure. The most optimal pulse sequence was applied in 8 Göttingen minipigs and the anatomical structures were identified.nnnRESULTS AND CONCLUSIONnHigh-resolution images with excellent contrast were acquired, presenting negligible geometric distortions. Minor flow artifacts from the large neck vessels generated the most prominent artifact. Determination of coordinates necessary in experimental neurosurgery in the Göttingen minipig was considerably improved with this MRI protocol.