In the adult brain, new neurons are continuously generated in the subventricular zone and dentate gyrus, but it is unknown whether these neurons can replace those lost following damage or disease. Here we show that stroke, caused by transient middle cerebral artery occlusion in adult rats, leads to a marked increase of cell proliferation in the subventricular zone. Stroke-generated new neurons, as well as neuroblasts probably already formed before the insult, migrate into the severely damaged area of the striatum, where they express markers of developing and mature, striatal medium-sized spiny neurons. Thus, stroke induces differentiation of new neurons into the phenotype of most of the neurons destroyed by the ischemic lesion. Here we show that the adult brain has the capacity for self-repair after insults causing extensive neuronal death. If the new neurons are functional and their formation can be stimulated, a novel therapeutic strategy might be developed for stroke in humans.

/pdf/neuronal-replacement-from-endogenous-precursors-in-the-adult-4ghf3i2h7x.pdf

Neuronal replacement from endogenous precursors in the adult brain after stroke

Malignant brain tumors strike deep into the psyche of those receiving and those delivering the diagnosis. Malignant gliomas, the most common subtype of primary brain tumors, are aggressive, highly invasive, and neurologically destructive tumors considered to be among the deadliest of human cancers. In its most aggressive manifestation, glioblastoma (GBM), median survival ranges from 9 to 12 months, despite maximum treatment efforts—a statistical fact that has changed little over several decades of technological advances in neurosurgery, radiation therapy, and clinical trials of conventional and novel therapeutics. Over the same time period, there has been an explosion of knowledge in cancer biology and basic science discovery that has fueled meaningful progress in the treatment of many common human cancers, including those of the breast, lung, and prostate. It is perplexing that therapies used effectively in the treatment of these solid tumors are overwhelmingly ineffective in the treatment of GBM, perhaps reflecting the eccentric biology and cellular origin of this neoplasm. To date, only one new agent has been documented to have modest activity against intermediate-grade gliomas, whereas no effective agents have emerged for the treatment of GBM, despite 20 years of enrolling patients in clinical trials. It is ironic that although a comprehensive view of the genetic lesions encountered in malignant gliomas has been compiled, substantive conceptual and practical barriers remain in assigning functional significance to these genetic changes and in harnessing this basic information into the development of drugs that make a difference in patient care. The history of treating malignant gliomas dates back to the middle of the 19th century and parallels landmark advances in modern surgical technique and the clinical discipline of neurology. The first brain tumor surgery of the modern era was performed in 1884 by Rickman

/pdf/malignant-glioma-genetics-and-biology-of-a-grave-matter-5dxbdiape8.pdf

Malignant glioma: Genetics and biology of a grave matter

The Evolving Concept of a Stem Cell: Entity or Function?

Widespread demyelination and axonal loss are the pathological hallmarks of multiple sclerosis. The multifocal nature of this chronic inflammatory disease of the central nervous system complicates cellular therapy and puts emphasis on both the donor cell origin and the route of cell transplantation. We established syngenic adult neural stem cell cultures and injected them into an animal model of multiple sclerosis--experimental autoimmune encephalomyelitis (EAE) in the mouse--either intravenously or intracerebroventricularly. In both cases, significant numbers of donor cells entered into demyelinating areas of the central nervous system and differentiated into mature brain cells. Within these areas, oligodendrocyte progenitors markedly increased, with many of them being of donor origin and actively remyelinating axons. Furthermore, a significant reduction of astrogliosis and a marked decrease in the extent of demyelination and axonal loss were observed in transplanted animals. The functional impairment caused by EAE was almost abolished in transplanted mice, both clinically and neurophysiologically. Thus, adult neural precursor cells promote multifocal remyelination and functional recovery after intravenous or intrathecal injection in a chronic model of multiple sclerosis.

Injection of adult neurospheres induces recovery in a chronic model of multiple sclerosis

Because neurogenesis persists in the adult mammalian brain and can be regulated by physiological and pathological events, we investigated its possible involvement in the brain's response to focal cerebral ischemia. Ischemia was induced by occlusion of the middle cerebral artery in the rat for 90 min, and proliferating cells were labeled with 5-bromo-2'-deoxyuridine-5'-monophosphate (BrdUrd) over 2-day periods before sacrificing animals 1, 2 or 3 weeks after ischemia. Ischemia increased the incorporation of BrdUrd into cells in two neuroproliferative regions-the subgranular zone of the dentate gyrus and the rostral subventricular zone. Both effects were bilateral, but that in the subgranular zone was more prominent on the ischemic side. Cells labeled with BrdUrd coexpressed the immature neuronal markers doublecortin and proliferating cell nuclear antigen but did not express the more mature cell markers NeuN and Hu, suggesting that they were nascent neurons. These results support a role for ischemia-induced neurogenesis in what may be adaptive processes that contribute to recovery after stroke.

https://www.pnas.org/content/pnas/98/8/4710.full.pdf

Neurogenesis in dentate subgranular zone and rostral subventricular zone after focal cerebral ischemia in the rat

One of the impediments to the treatment of brain tumors (e.g., gliomas) has been the degree to which they expand, infiltrate surrounding tissue, and migrate widely into normal brain, usually rendering them “elusive” to effective resection, irradiation, chemotherapy, or gene therapy. We demonstrate that neural stem cells (NSCs), when implanted into experimental intracranial gliomas in vivo in adult rodents, distribute themselves quickly and extensively throughout the tumor bed and migrate uniquely in juxtaposition to widely expanding and aggressively advancing tumor cells, while continuing to stably express a foreign gene. The NSCs “surround” the invading tumor border while “chasing down” infiltrating tumor cells. When implanted intracranially at distant sites from the tumor (e.g., into normal tissue, into the contralateral hemisphere, or into the cerebral ventricles), the donor cells migrate through normal tissue targeting the tumor cells (including human glioblastomas). When implanted outside the CNS intravascularly, NSCs will target an intracranial tumor. NSCs can deliver a therapeutically relevant molecule—cytosine deaminase—such that quantifiable reduction in tumor burden results. These data suggest the adjunctive use of inherently migratory NSCs as a delivery vehicle for targeting therapeutic genes and vectors to refractory, migratory, invasive brain tumors. More broadly, they suggest that NSC migration can be extensive, even in the adult brain and along nonstereotypical routes, if pathology (as modeled here by tumor) is present.

https://www.pnas.org/content/pnas/97/23/12846.full.pdf

Neural stem cells display extensive tropism for pathology in adult brain: evidence from intracranial gliomas.

The remarkable migratory and tumor-tropic capacities of neural stem cells (NSCs and/or neuroprogenitor cells) represent a potentially powerful approach to the treatment of invasive brain tumors, such as malignant gliomas. We have previously shown that whether implanted directly into or at distant sites from an experimental intracranial glioma, NSCs distributed efficiently throughout the main tumor mass and also tracked advancing tumor cells, while stably expressing a reporter transgene. As therapeutic proof-of-concept, NSCs genetically modified to produce the prodrug activating enzyme cytosine deaminase (CD), effected an 80% reduction in the resultant tumor mass, when tumor animals were treated with the systemic prodrug, 5-fluorocytosine. We now extend our findings of the tumor-tropic properties of NSCs (using a well-characterized, clonal NSC line C17.2), by investigating their capacity to target both intracranial and extracranial tumors, when administered into the peripheral vasculature. We furthermore d...

Intravascular Delivery of Neural Stem Cell Lines to Target Intracranial and Extracranial Tumors of Neural and Non-Neural Origin

The present invention relates to the field of cellular and molecular therapy with modified (genetically or growth factor engineered) and unmodified stem cells (SCs). More particularly, the invention relates to a method of systemic treatment of central nervous system (CNS) and other tumors in both intracranial/intraspinal and extracranial/extraspinal sites, using neural stem cells (NSCs), a prototype for solid organ, non-hematopoietic stem cells.

Systemic gene delivery vehicles for the treatment of tumors

Methods for Gene Delivery to Neural Tissue

Tuberous sclerosis (TSC) is an autosomal dominant genetic disorder characterized by abnormalities in cellular migration, proliferation, and differentiation in many tissues. Benign hamartomas develop in multiple organs, believed to be caused by somatic mutation in addition to germ line mutation to cause loss of both alleles of either the TSC1 or TSC2 tumor suppressor gene, with resultant dysregulated growth due to loss of hamartin or tuberin function, respectively. This study focuses on detecting spontaneous lesions in a knockout mouse model of TSC2 by magnetic resonance imaging (MRI) and exploring the efficiency of introducing gene products into lesions, using transduced endothelial cells as gene vehicles. MRI was shown to be effective in detecting spontaneous lesions in multiple tissues as a means of assessing the prevalence of tumors. Tsc(2+/) heterozygous mice were screened at 12-24 months of age. MRI detected 100% of the renal lesions (cystadenomas, renal cell carcinomas) and 75% of the hepatic lesions (hemangiosarcomas), later identified by histology. Cell-mediated gene delivery was evaluated by immunohistochemical analysis of renal, hepatic, and lung lesions after intravenous delivery of MS1 mouse endothelial cells, transduced to express an enhanced form of green fluorescent protein (EGFP). Preliminary immunohistochemical analysis, using a polyclonal antibody to EGFP and a horseradish peroxidase-diaminobenzidine detection system, revealed these cells throughout liver, kidney, and lung sections from injected animals, organs that are frequently affected in TSC2 patients, as well as within the lesions themselves.

Magnetic resonance imaging and characterization of spontaneous lesions in a transgenic mouse model of tuberous sclerosis as a model for endothelial cell-based transgene delivery.

Alice B. Brown

Papers

Neural stem cells display extensive tropism for pathology in adult brain: evidence from intracranial gliomas.

Intravascular Delivery of Neural Stem Cell Lines to Target Intracranial and Extracranial Tumors of Neural and Non-Neural Origin

Systemic gene delivery vehicles for the treatment of tumors

Methods for Gene Delivery to Neural Tissue

Magnetic resonance imaging and characterization of spontaneous lesions in a transgenic mouse model of tuberous sclerosis as a model for endothelial cell-based transgene delivery.