Signaling within the pineal gland: A parallelism with the central nervous system

Microglia in Circumventricular Organs: The Pineal Gland Example

The circumventricular organs (CVOs) are unique areas within the central nervous system. They serve as a portal for the rest of the body and, as such, lack a blood-brain barrier. Microglia are the primary resident immune cells of the brain parenchyma. Within the CVOs, microglial cells find themselves continuously challenged and stimulated by local and systemic stimuli, even under steady-state conditions. Therefore, CVO microglia in their typical state often resemble the activated microglial forms found elsewhere in the brain as they are responding to pathological conditions or other stressors. In this review, I focus on the dynamics of CVO microglia, using the pineal gland as a specific CVO example. Data related to microglia heterogeneity in both homeostatic and unhealthy environments are presented and discussed, including those recently generated by using advanced single-cell and single-nucleus technology. Finally, perspectives in the CVO microglia field are also included.Summary StatementMicroglia in circumventricular organs (CVOs) continuously adapt to react differentially to the diverse challenges they face. Herein, I discuss microglia heterogeneity in CVOs, including pineal gland. Further studies are needed to better understand microglia dynamics in these unique brain areas. .

Melatonin protects gingival mesenchymal stem cells and promotes differentiation into osteoblasts

Melatonin (MEL) has antioxidant properties and participates in osteogenic differentiation. In periodontitis, in which increased oxidative stress and bone resorption are involved, mesenchymal stem cells derived from the gingiva (GMSCs) combined with MEL could be relevant for osteogenic regeneration. In this study, we studied the antioxidant and differentiating effect of MEL on an in vitro system of GMSCs. Primary culture of GMSCs from Wistar rats was developed to evaluate differentiation into osteoblasts with an appropriate medium with or without MEL. Marker genes of mesenchymal stem cells by real time-polymerase chain reaction, clonogenic capacity, and cell migration after wound assay were used to characterize GMSCs as mesenchymal stem cells. Alkaline phosphatase activity and the alizarin red technique were used to evaluate osteogenic activity and differentiation. MEL increased alkaline phosphatase activity and alizarin red values, promoting osteogenic differentiation. Besides this, MEL protected GMSCs in a model of cellular damage related to oxidative stress, returning viability to baseline. MEL was more effective in promoting and protecting GMSCs by the production of osteogenic cells when oxidative stress is present. This evidence supports the use of MEL as a novel bone-regenerative therapy in periodontal diseases.