The Investigation of a TIMP-1-modulated Glial-Derived Factor Affecting Neuroblastoma Cell Death

The original role of astrocytes was believed to have been as a neuronal-supportive cell in the brain. It has now been discovered that they play imperative roles, from reuptake of neurotransmitters from the extracelluar space to signal propagation and developmental control by the release of factors into the extracellular space. SH-SY5Y and IMR-32 cells are common neuroblastoma cell lines which model cancerous brain cells when left undifferentiated. In recent studies tissue inhibitors of metalloproteinases (TIMPs) have been implicated in neurodegenerative diseases, but their exact role in cell death is unknown. A double-blind cell culture experiment was conducted using astrocytes from wild type and TIMP-1 knockout mice to evaluate the role of TIMP-1 in neuronal cell death. Undifferentiated and differentiated SH-SY5Y cells, as well as undifferentiated IMR-32 cells, were treated with either wild type glial cell media (WT-GCM) or TIMP-1 knockout glial cell media (KO-GCM) for 24 hours and cell viability was evaluated. Undifferentiated SH-SY5Y and IMR-32 cells exposed to WT-GCM showed a significant increase in cell death when compared to cells exposed to KO-GCM. The glial conditioned media had no effect on SH-SY5Y cells differentiated using retinoic acid. Supplementation of the KO-GCM with recombinant TIMP-1 to physiological levels had no impact on cell death in SH-SY5Y undifferentiated cells, while supplementation of WT-GCM with recombinant TIMP-1 completely blocked the cell death seen following WT-GCM treatment alone. Heating of the WT-GCM completely eliminated the increased cell death produced by the WT-GCM. These results suggest that TIMP-1 may be modulating a temperature-dependent, cell media-soluble factor that is released by astrocytes and influences cell death mechanisms of undifferentiated neuroblastoma cells

The neural stem cell secretome and its role in brain repair.

Compelling evidence from experimental animal disease models and early-phase clinical trials identifies the transplantation of neural progenitor/stem cells (NSCs) as a viable path towards the development of clinically applicable exogenous stem cell therapies. Building from current advances in the field of NSC biology and following the positive outcomes of NSC transplantation studies, the contemporary view is that transplanted NSCs act as local 'factories' capable of producing and secreting a wide array of immune and neurotrophic factors. This has launched a 'stem cell race' to identify the mechanisms behind stem-cell mediated repair in what has been labeled the paracrine hypothesis. This hypothesis proposes that NSC grafts act as a natural source of potent biologics capable of modulating and promoting the restoration of several key functions in the central nervous system (CNS) tissue following acute or chronic tissue damage. Investigators have been inspired to examine novel ways to harness and utilize the pro-regenerative properties of NSC therapies as an alternative approach to a more classical (small molecule based) treatment of CNS diseases. In this review, we will discuss the most recent findings of human NSC (hNSCs) transplants in experimental animal models of CNS diseases that identify of hNSC-secreted factors, including those trafficked within extracellular membrane vesicles (EVs), and the outcomes of recent clinical trials utilizing hNSC therapeutics in CNS diseases

Stem Cells of the Aging Brain.

The adult central nervous system (CNS) contains resident stem cells within specific niches that maintain a self-renewal and proliferative capacity to generate new neurons, astrocytes, and oligodendrocytes throughout adulthood. Physiological aging is associated with a progressive loss of function and a decline in the self-renewal and regenerative capacities of CNS stem cells. Also, the biggest risk factor for neurodegenerative diseases is age, and current in vivo and in vitro models of neurodegenerative diseases rarely consider this. Therefore, combining both aging research and appropriate interrogation of animal disease models towards the understanding of the disease and age-related stem cell failure is imperative to the discovery of new therapies. This review article will highlight the main intrinsic and extrinsic regulators of neural stem cell (NSC) aging and discuss how these factors impact normal homeostatic functions within the adult brain. We will consider established in vivo animal and in vitro human disease model systems, and then discuss the current and future trajectories of novel senotherapeutics that target aging NSCs to ameliorate brain disease

Harnessing the Neural Stem Cell Secretome for Regenerative Neuroimmunology.

Increasing evidence foresees the secretome of neural stem cells (NSCs) to confer superimposable beneficial properties as exogenous NSC transplants in experimental treatments of traumas and diseases of the central nervous system (CNS). Naturally produced secretome biologics include membrane-free signaling molecules and extracellular membrane vesicles (EVs) capable of regulating broad functional responses. The development of high-throughput screening pipelines for the identification and validation of NSC secretome targets is still in early development. Encouraging results from pre-clinical animal models of disease have highlighted secretome-based (acellular) therapeutics as providing significant improvements in biochemical and behavioral measurements. Most of these responses are being hypothesized to be the result of modulating and promoting the restoration of key inflammatory and regenerative programs in the CNS. Here, we will review the most recent findings regarding the identification of NSC-secreted factors capable of modulating the immune response to promote the regeneration of the CNS in animal models of CNS trauma and inflammatory disease and discuss the increased interest to refine the pro-regenerative features of the NSC secretome into a clinically available therapy in the emerging field of Regenerative Neuroimmunology

Stem Cell Therapies for Progressive Multiple Sclerosis.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by demyelination and axonal degeneration. MS patients typically present with a relapsing-remitting (RR) disease course, manifesting as sporadic attacks of neurological symptoms including ataxia, fatigue, and sensory impairment. While there are several effective disease-modifying therapies able to address the inflammatory relapses associated with RRMS, most patients will inevitably advance to a progressive disease course marked by a gradual and irreversible accrual of disabilities. Therapeutic intervention in progressive MS (PMS) suffers from a lack of well-characterized biological targets and, hence, a dearth of successful drugs. The few medications approved for the treatment of PMS are typically limited in their efficacy to active forms of the disease, have little impact on slowing degeneration, and fail to promote repair. In looking to address these unmet needs, the multifactorial therapeutic benefits of stem cell therapies are particularly compelling. Ostensibly providing neurotrophic support, immunomodulation and cell replacement, stem cell transplantation holds substantial promise in combatting the complex pathology of chronic neuroinflammation. Herein, we explore the current state of preclinical and clinical evidence supporting the use of stem cells in treating PMS and we discuss prospective hurdles impeding their translation into revolutionary regenerative medicines

Astrocyte Support for Oligodendrocyte Differentiation can be Conveyed via Extracellular Vesicles but Diminishes with Age.

The aging brain is associated with significant changes in physiology that alter the tissue microenvironment of the central nervous system (CNS). In the aged CNS, increased demyelination has been associated with astrocyte hypertrophy and aging has been implicated as a basis for these pathological changes. Aging tissues accumulate chronic cellular stress, which can lead to the development of a pro-inflammatory phenotype that can be associated with cellular senescence. Herein, we provide evidence that astrocytes aged in culture develop a spontaneous pro-inflammatory and senescence-like phenotype. We found that extracellular vesicles (EVs) from young astrocyte were sufficient to convey support for oligodendrocyte differentiation while this support was lost by EVs from aged astrocytes. Importantly, the negative influence of culture age on astrocytes, and their cognate EVs, could be countered by treatment with rapamycin. Comparative proteomic analysis of EVs from young and aged astrocytes revealed peptide repertoires unique to each age. Taken together, these findings provide new information on the contribution of EVs as potent mediators by which astrocytes can extert changing influence in either the disease or aged brain

Cellular senescence in progenitor cells contributes to diminished remyelination potential in progressive multiple sclerosis

Cellular senescence is a form of adaptive cellular physiology associated with aging. Cellular senescence causes a proinflammatory cellular phenotype that impairs tissue regeneration, has been linked to stress, and is implicated in several human neurodegenerative diseases. We had previously determined that neural progenitor cells (NPCs) derived from induced pluripotent stem cell (iPSC) lines from patients with primary progressive multiple sclerosis (PPMS) failed to promote oligodendrocyte progenitor cell (OPC) maturation, whereas NPCs from age-matched control cell lines did so efficiently. Herein, we report that expression of hallmarks of cellular senescence were identified in SOX2+ progenitor cells within white matter lesions of human progressive MS (PMS) autopsy brain tissues and iPS-derived NPCs from patients with PPMS. Expression of cellular senescence genes in PPMS NPCs was found to be reversible by treatment with rapamycin, which then enhanced PPMS NPC support for oligodendrocyte (OL) differentiation. A proteomic analysis of the PPMS NPC secretome identified high-mobility group box-1 (HMGB1), which was found to be a senescence-associated inhibitor of OL differentiation. Transcriptome analysis of OPCs revealed that senescent NPCs induced expression of epigenetic regulators mediated by extracellular HMGB1. Lastly, we determined that progenitor cells are a source of elevated HMGB1 in human white matter lesions. Based on these data, we conclude that cellular senescence contributes to altered progenitor cell functions in demyelinated lesions in MS. Moreover, these data implicate cellular aging and senescence as a process that contributes to remyelination failure in PMS, which may impact how this disease is modeled and inform development of future myelin regeneration strategies

Astrocyte Support for Oligodendrocyte Differentiation can be Conveyed via Extracellular Vesicles but Diminishes with Age

Abstract: The aging brain is associated with significant changes in physiology that alter the tissue microenvironment of the central nervous system (CNS). In the aged CNS, increased demyelination has been associated with astrocyte hypertrophy and aging has been implicated as a basis for these pathological changes. Aging tissues accumulate chronic cellular stress, which can lead to the development of a pro-inflammatory phenotype that can be associated with cellular senescence. Herein, we provide evidence that astrocytes aged in culture develop a spontaneous pro-inflammatory and senescence-like phenotype. We found that extracellular vesicles (EVs) from young astrocyte were sufficient to convey support for oligodendrocyte differentiation while this support was lost by EVs from aged astrocytes. Importantly, the negative influence of culture age on astrocytes, and their cognate EVs, could be countered by treatment with rapamycin. Comparative proteomic analysis of EVs from young and aged astrocytes revealed peptide repertoires unique to each age. Taken together, these findings provide new information on the contribution of EVs as potent mediators by which astrocytes can extert changing influence in either the disease or aged brain