Astrocytes

Human primary astrocytes (ScienCell Research Laboratories, Catalog number: 1800) and Quick-Glia - Astrocyte SeV kit cultures, harvested at either 28 days or 42 days post SeV infection, were plated at 7,800 cells/cm2 in a Geltrex-coated 96-well plate (Corning, Catalog number: 353072) and grown in ScienCell Astrocyte medium (ScienCell Research Laboratories, without FBS, Catalog number: 1801) for 14 days. As a negative control, human iPSCs were plated in StemFit Basic04 medium (Ajinomoto, Catalog number: ASB04-C) two days before assay measurement using the plating density stated above. 30 minutes prior to assay execution, culture medium was replaced with Hanks' Balanced Salt Solution (HBSS) without phenol red (Fisher Scientific, Catalog number: 14025092). Subsequently, cells were exposed to 100µM L-glutamate (Tocris, Catalog number: 0218) in HBSS for 60 minutes. Immediately after the assay, solution was collected and cells were dislodged using a 1:1 mixture of TrypLE Select Enzyme (Fisher Scientific, Catalog number: 12563029) and 0.02% EDTA (Lonza, Catalog number: 17-711E). The numbers of live cells were determined using a NucleoCounter NC-200 (Chemometec, Catalog number: 900-0200) cell counter. Glutamate concentration was measured by a bioluminescence-based Glutamate-Glo assay kit (Promega, Catalog number: J7021) and a SPECTRAFluor Plus microplate reader (Tecan). To determine the amount of glutamate cleared, all values were first background signal-subtracted using a HBSS only sample and concentrations were thereafter acquired from the glutamate titration curve according to manufacturer’s instructions.