Astrocytes display regional differences in their physiological responses to pro-inflammatory stimulation.
O’Sullivan J, Imiolek, MD, Murphy RD, Jimenez-Mateos E, Caldwell MA.
Discipline of Physiology and Trinity College Institute for Neuroscience, Trinity College, Dublin 2.
Introduction: Astrocytes play integral roles in maintaining homeostasis and surveying the micro-environment in the healthy CNS. Under pathological conditions, such as Alzheimer’s and Parkinson’s disease, astrocytes become activated and contribute to disease progression. The reactive astrocyte phenotype arises from a range of pathological scenarios where astrogliosis leads to further pro-inflammatory cytokine production and thus, neuronal damage and death. Although astrocytes are historically viewed as a uniform glial population, in recent years they have been recognised as highly diverse at molecular, morphological and functional levels. Transcriptomic and proteomic studies revealed pronounced astrocyte heterogeneity across brain regions, suggesting that this heterogeneity is shaped by developmental patterning cues, intra- and extracellular signals and neuronal interactions. Induced pluripotent stem cell (iPSC)-derived astrocytes provide an excellent system for studying region-specific astrocytes. When guided by appropriate patterning cues, iPSC can be differentiated into neural progenitors with forebrain, midbrain, hindbrain or spinal identities, which then can be further differentiated into regionally distinct astrocyte progenitors.
Aims: Our research has focused on cortical and ventral midbrain differentiation in line with our interest in Alzheimer’s disease and Parkinson’s disease. It is the aim of this work to directly compare cortical (CTX) and ventral midbrain (VM) astrocytes from the same iPSC line to identify differences in morphology, gene expression, protein level and functionality.
Methods: For this we have differentiated the same parental iPSC line into cortical and ventral midbrain neural astrocytes. With these astrocytes we explored changes across morphology (ICC), gene and protein expression (qPCR, ELISA, Bulk RNA sequencing) and functionality (Seahorse and calcium imaging) at baseline and in response to inflammatory stimulation.
Results: We have observed clear morphological, transcriptomic and functional differences in these regional iPSC-derived astrocytes both at baseline and in response to pro-inflammatory stimulus (n=3 differentiations into astrocytes from IPSCs, with three technical replicates per experiment). This indicates that these cells may play very different roles in the different regions of the brain and highlighting the critical importance of selecting the appropriate region for the study being conducted.