Neuroregeneration

1. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neuroregeneration Bear M. F., Connors B. W. Paradiso M. A. Neuroscience. Exploring the brain. 2007, 3d ed. Lippincott Williams and Wilkins

2. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neuroregeneration • Terminology • Axon regeneration • Molecular and cellular mechanisms limiting axon • regeneration in CNS • Therapeutic strategies to promote axon regeneration • Neural stem cells • Stem cell therapy

3. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neuroregeneration • Terminology • Axon regeneration • Molecular and cellular mechanisms limiting axon • regeneration in CNS • Therapeutic strategies to promote axon regeneration • Neural stem cells • Stem cell therapy

4. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Terminology • NEURODEGENERATION The loss of neuronal processes (axons and dendrites) and death of nerve cells • NEURODEGENERATIVE DISORDER A type of neurological disease marked by the loss of nerve cells: e.g. Alzheimer’s disease (AD), Parkinson’s disease PD), Huntington’s disease (HD) • REGENERATION • Growth anew of lost tissue or destroyed parts or organs • NEUROREGENERATION • Regeneration of the nervous tissue manifested by • Nerve (axon) regeneration • Neural stem-cell proliferation, migration and differentiation

5. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neuroregeneration • Terminology • Axon regeneration • Molecular and cellular mechanisms limiting axon • regeneration in CNS • Therapeutic strategies to promote axon regeneration • Neural stem cells • Stem cell therapy

6. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Axon regeneration • Traumatic injury of the spinal cord that transects axon processes • results in permanent functional impairment, even when the neuronal • cell bodies that are located away from the injury site remain alive. • At present there are no clinical treatments available to stimulate • regeneration of cut axons within the CNS. • Although many CNS neurons can survive for years after axotomy, the • severed axons ultimately fail to regenerate beyond the lesion site, in • contrast to those in the PNS or embryonic nervous system. • Spinal cord injured patients receive high doses of the steroid • methylprednisolone immediately following injury to suppress an • unfavorable inflammatory reaction. This drug, however, does not • restore functions that are lost when axons are cut.

7. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Changes in CNS environment after maturation and injury

8. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Plastic mechanisms potentially contributing to recovery after spinal cord injury

9. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Methods • In vivo: animal models • In vitro: cell cultures Left: neurons were grown on control fibroblasts Right: neurons were grown on fibroblasts genetically engineered to express CAM

10. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neuroregeneration • Terminology • Axon regeneration • Molecular and cellular mechanisms limiting axon • regeneration in CNS • Therapeutic strategies to promote axon regeneration • Neural stem cells • Stem cell therapy

11. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Inhibitors of axon regeneration Growth inhibitory activity associated with myelin • Myelin-associated glycoprotein (MAG) • Growth inhibitory protein Nogo • Oligodendrocyte-myelin glycoprotein (OMgp) • Oligodendrocyte-proteoglycan NG2 Growth inhibitory activity present at the glial scar • Chondroitin sulfate proteoglycans (CSPG): • - versican • - phosphocan • - neurocan Other factors limiting axon-regrowth • Inflammatory response • Alterations in the ECM • Upregulation of semaphorins, ephrins, tenascin-C

12. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Glial inhibitors

13. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neuroregeneration • Terminology • Axon regeneration • Molecular and cellular mechanisms limiting axon • regeneration in CNS • Therapeutic strategies to promote axon regeneration • Neural stem cells • Stem cell therapy

14. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Strategies to promote axon regeneration 1. Neutralization of the inhibitory factors in the injured CNS - Ab infusion (MonAb, IN-1, against Nogo-A ) - A therapeutic vaccine approach - Passive immunization at the time of lesion - Antagonist peptide (Nogo-66 NEP1-40 peptide) - Inhibition of Rho signaling (Y-27632, an inhibitor of p160ROCK) - Inhibiting CSPG (Chondroitinase ABC) - Anti-scarring treatment (inhibition of fibroblast proliferation) 2. Stimulation of axon regeneration by modulating the neuronal signaling responses: - Treatment with neurotrophic factors (NGF, BDNF, NT-3, GDNF, LIF, FGF-2) 3. Cell transplantation: e.g. Schwann cells, fibroblasts modified to express trophic factors, fetal spinal cord transplants, embryonic stem cells etc.

15. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neuroregeneration • Terminology • Axon regeneration • Molecular and cellular mechanisms limiting axon • regeneration in CNS • Therapeutic strategies to promote axon regeneration • Neural stem cells • Stem cell therapy

16. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neural stem cells Neurodegenerative disorders (AD, PD and HD) are characterized by continuous loss of neurons that are not replaced. It is postulated that a primary deficit in neural cell proliferation, migration and differentiation might contribute to net cell loss and neuronal circuit disruption in these disorders.

17. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neural stem cells Ventricular and subventricular zones in the wall of the lateral ventricle adjacent to the caudate-putamen Subgranular zone of the hippocampus NSC Migration of NSC Olfactory bulb Differentiation Integration NSC Neurons Dentate gyrus NPC Differentiation Local interneurons

18. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neural stem cell niches The SVZ niche, cell types and stem cell lineage The DG neurogenic niche, cell types and lineage SVZ, subventricular zone; DG, dentate gyrus; LV, lateral ventricle; BL, specialized basal lamina; BV, blood vessels; A (red), neuroblasts; B (blue), neural stem cells (SVZ astrocytes); C (green), transit rapidly amplifying cells; D (yellow), precursors; G (red), neurons

19. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Stem and progenitor cells in the adult human brain The human temporal lobe: it includes periventricular neural stem cells (red) that generate at least three populations of potentially neurogenic transit amplifying progenitors of both neuronal and glial lineages (yellow). These include the neuronal progenitor cells of the ventricular subependyma, those of the SGZ of the dentate gyrus, and the glial progenitor cells of the subcortical white matter. Each transit amplifying pool may then give rise to differentiated progeny appropriate to their locations, including neurons (purple), oligodendrocytes (green), and parenchymal astrocytes (blue).

20. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Neuroregeneration • Terminology • Axon regeneration • Molecular and cellular mechanisms limiting axon • regeneration in CNS • Therapeutic strategies to promote axon regeneration • Neural stem cells • Stem cell therapy

21. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Thalamus Nigrostriatal pathway Substantia nigra pars compacta Dopaminergic neurons Parkinson’s disease (degenerative disorder of the CNS that often impairs the sufferer's motor skills and speech) PD patient (sketch, 1886) Muscle rigidity, tremor (bradykinesia) Treatment: L-DOPA ( dyskinesia: involuntary movements) PET scan, dopamine activity in basal ganglia, putamen and caudate

22. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Developmental pathway of dopamine neurons

23. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Alternative sources of stem cells for transplantation in PD

24. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Present limitations in the development of the hESC-based therapy for PD

25. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Generation of dopamine neurons from autologous human mesenchimal stem cells (MSCs)

26. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Main points Neural degeneration in the central nervous system is manifested by the loss of neuronal processes (axons and dendrites) and death of nerve cells resulting in dysfunctional plasticity and cognitive impairment. Traumatic injury of the spinal cord that transects neuronal processes results in permanent functional impairment, even when the neuronal cell bodies that allocated away from the injury site remain alive. The glial environment in the adult CNS, which includes inhibitory molecules in CNS myelin as well as proteoglycans associated with astroglial scaring, might present a major hurdle for successful axon regeneration. Therefore, targeting the inhibitory components of the adult glial environment might not only promote the regeneration of the damaged nerve fibers but also enhance axon sprouting and plasticity after CNS injury. Neural stem cells, able to self renew and give rise to both neurons and glia, line the cerebral ventricles of the adult human brain. These various stem and progenitor cell types may provide targets for pharmacotherapy for a variety of disorders of the central nervous system. Each resident progenitor type may be immortalized and induced to differentiate in vivo by the actions of both exogenous factors and small molecule, modulators of progenitor selective signaling pathways. Stem cell transplantation to replace the degenerated neurons may be a promising therapy for PD. There are three sources of stem cells currently in testing: embryonic stem cell, neural stem cells and mesenchymal stem cells. Future stem cell research should focus not only on ameliorating the symptoms of PD, but also on neuroprotection or neural rescue that can favorably modify the natural course and slow the progression of the disease.

27. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Helpful reading • Blesch A and Tuzhynski MH (2009) Spinal cord injury: plasticity, regeneration and the challenge of translational drug development. TINS 32:41-47. • Li J-Y et al. (2008) Lewy bodies in grafted neurons in subjects with Parkinson’s disease suggest host-to-graft disease propagation. Nat Medicine 14:501-503. • Goldman SA (2007) Disease targets and strategies for the therapeutic modulation of endogenous neural stem and progenitor cells. Clin Pharm Therapeutics. 82:453-460. • Ma QH et al. (2007) Physiological role of neurite outgrowth inhibitors in myelinated axons of the central nervous system – implications for the therapeutic neutralization on neurite outgrowth inhibitors. Curr Pharm Des. 13:2529-2537. • Trzaska KA et al. (2007) Current advances in the treatment of Parkinson's disease with stem cells. Curr Neurovasc Res. 4:99-109. • Yiu G et al. (2006) Glial inhibition of CNS axon regeneration. Nat Rev Neurosci. 7:617-627. • Correia AS et al. (2005) Stem cell-based therapy for Parkinson's disease. Ann Med. 37:487-498. • Wang Y et al. (2007) Stem cell transplantation: A promising therapy for Parkinson’s disease. J Neuroimmune Pharmacol. 2:243-250.

28. DEPARTMENT OF NEUROSCIENCE AND PHARMACOLOGY Presentation http://plab.ku.dk Professors Vladimir Berezin Neuroregeneration