Earth’s rotation generates the basic circadian rhythm of day and night to which all living organisms must adapt to survive. In mammals, this happens thanks to a central clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus and to peripheral clock genes at the cellular level. The main environmental cue capable of synchronizing such clocks is light sensed by retinal ganglion cells signaling through a complex nervous pathway to the pineal gland which ultimately regulates melatonin synthesis that occurs during the night, darkness hours in all mammals. The central clock synchronized by melatonin drives the circadian oscillation of the sympathetic nervous system (SNS) adrenergic activity which in turn controls glucocorticoid production in the adrenal glands. These oscillations are integrated with peripheral cellular clocks by still not completely understood mechanisms and drive the homeostatic control of activity-rest (sleep) cycles, cardiovascular activity, body temperature, and immune-hematopoietic functions. The neuronal and hormonal mechanisms governing the circadian oscillation of hematopoiesis and immunity will be addressed in this review focusing on those offering therapeutic perspectives.

Globally, the incidence of Parkinson’s disease (PD) is increasing faster than other neurodegenerative disorders. Neuropathologically, PD is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta due to the accumulation of aggregates of misfolded α-synuclein (α-Syn) in the cytoplasm of these neurons, forming Lewy bodies. Extracellular vesicles (EVs) are associated with the spread of α-Syn to different brain areas. However, at the same time that these EVs contribute to the pathophysiology of PD, they can also be explored as therapeutic, serving as a vehicle to deliver specific molecules, since these vesicles can easily cross the blood-brain barrier. Thus, this review summarizes the recent progress in EVs as a therapeutic strategy for PD, focusing on their delivery to the brain, and discusses the potential challenges and future directions in this field.

For more than a decade now, research studies, proof of concept work, and clinical trials have endeavored to understand how mesenchymal stem cells might be used to help protect, repair, and/or regenerate damaged brain tissue following stroke. To date, the majority of studies have not demonstrated significant improvements in either morbidity or medium-long-term outcome, although safety has been relatively well proven. Limitations are likely to be linked to the pathobiological complexity and seriousness of stroke tissue damage, low efficacy of treatment, and short half-life of bio-active proteins released by stem cells. This article will highlight the heterogeneity and limitation of completed studies and the current status of ongoing work. At the same time, the potential of other combinational type treatments, such as drug-loading and targeting, and the use of hydrogels is discussed.