Comparative analysis of astrocytes in the prefrontal cortex of primates: Insights into the evolution of human brain energetics. Issue 18 (20th July 2022)

• Record Type: Journal Article
• Authors: Munger, Emily L.; Edler, Melissa K.; Hopkins, William D.; Hof, Patrick R.; Sherwood, Chet C.; Raghanti, Mary Ann
• Is Part Of: Journal of comparative neurology. Volume 530:Issue 18(2022)
• Page Start: 3106
• Page End: 3125
• Publication Date: 2022-07-20
• Subjects: astrocyte -- EAAT2 -- GFAP -- glia -- GLUT1 -- human -- prefrontal cortex -- primate; Comparative neurobiology -- Periodicals; Neurology -- Periodicals; 616
• DOI: 10.1002/cne.25387
• Languages: English
• ISSNs: 0021-9967

Abstract

Abstract: Astrocytes are the main homeostatic cell of the brain involved in many processes related to cognition, immune response, and energy expenditure. It has been suggested that the distribution of astrocytes is associated with brain size, and that they are specialized in humans. To evaluate these, we quantified astrocyte density, soma volume, and total glia density in layer I and white matter in Brodmann's area 9 of humans, chimpanzees, baboons, and macaques. We found that layer I astrocyte density, soma volume, and ratio of astrocytes to total glia cells were highest in humans and increased with brain size. Overall glia density in layer I and white matter were relatively invariant across brain sizes, potentially due to their important metabolic functions on a per volume basis. We also quantified two transporters involved in metabolism through the astrocyte‐neuron lactate shuttle, excitatory amino acid transporter 2 (EAAT2) and glucose transporter 1 (GLUT1). We expected these transporters would be increased in human brains due to their high rate of metabolic consumption and associated gene activity. While humans have higher EAAT2 cell density, GLUT1 vessel volume, and GLUT1 area fraction compared to baboons and chimpanzees, they did not differ from macaques. Therefore, EAAT2 and GLUT1 are not related to increased energetic demands of the human brain. Taken together, these data provide evidence that astrocytes play a unique role in both brain expansion and evolution among primates, with an emphasis on layer I astrocytes having a potentially significant role in human‐specific metabolic processing and cognition. Abstract : We quantified astrocytes expressing glial fibrillary acidic protein in human and nonhuman primates. We report that astrocyte density, soma volume, and ratio of astrocytes to total glia cells in layer I of Brodmann.s area 9 increased significantly with brain size enlargement and was greatest in humans. Roman numerals denote cortical layer. Scale bars = 25 µm.