Transforming growth factor-beta renders ageing microglia inhibitory to oligodendrocyte generation by CNS progenitors.

It is now well-established that the macrophage and microglial response to CNS demyelination influences remyelination by removing myelin debris and secreting a variety of signaling molecules that influence the behaviour of oligodendrocyte progenitor cells (OPCs). Previous studies have shown that changes in microglia contribute to the age-related decline in the efficiency of remyelination. In this study, we show that microglia increase their expression of the proteoglycan NG2 with age, and that this is associated with an altered micro-niche generated by aged, but not young, microglia that can divert the differentiation OPCs from oligodendrocytes into astrocytes in vitro. We further show that these changes in ageing microglia are generated by exposure to high levels of TGFß. Thus, our findings suggest that the rising levels of circulating TGFß known to occur with ageing contribute to the age-related decline in remyelination by impairing the ability of microglia to promote oligodendrocyte differentiation from OPCs, and therefore could be a potential therapeutic target to promote remyelination.

Metformin Restores CNS Remyelination Capacity by Rejuvenating Aged Stem Cells.

The age-related failure to produce oligodendrocytes from oligodendrocyte progenitor cells (OPCs) is associated with irreversible neurodegeneration in multiple sclerosis (MS). Consequently, regenerative approaches have significant potential for treating chronic demyelinating diseases. Here, we show that the differentiation potential of adult rodent OPCs decreases with age. Aged OPCs become unresponsive to pro-differentiation signals, suggesting intrinsic constraints on therapeutic approaches aimed at enhancing OPC differentiation. This decline in functional capacity is associated with hallmarks of cellular aging, including decreased metabolic function and increased DNA damage. Fasting or treatment with metformin can reverse these changes and restore the regenerative capacity of aged OPCs, improving remyelination in aged animals following focal demyelination. Aged OPCs treated with metformin regain responsiveness to pro-differentiation signals, suggesting synergistic effects of rejuvenation and pro-differentiation therapies. These findings provide insight into aging-associated remyelination failure and suggest therapeutic interventions for reversing such declines in chronic disease.

Therapeutic Noninvasive Brain Stimulation in Alzheimer's Disease.

Alzheimer's disease (AD) is a looming public health crisis that currently lacks an effective treatment. Noninvasive Brain Stimulation (NBS), particularly transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), offers a promising alternative approach to pharmacological interventions for an increasing number of neurological and psychiatric conditions. The aim of this review is summarize data from therapeutic trials of NBS in AD and other dementing illnesses. Despite the potential of NBS, there is limited theoretical framework and a lack of guidelines for its applications to AD. Several published clinical trials failed to report key parameters of the interventions thus limiting the utility of the study to assess efficacy and safety. Our review concludes with some suggestions for future studies aimed to advance research into NBS as a potential treatment for the symptoms and disabilities caused by AD and to enable comparison of results across trials. Ultimately, appropriately powered, and controlled, multi-site randomized clinical trials will be needed to evaluate the therapeutic potential of NBS in AD.