Lucia Verrillo1, Eleonora Mangano2, Denise Drongitis3, Ivan Merelli2, Francesca Pischedda4, Giovanni Piccoli4, Clarissa Consolandi2, Roberta Bordoni2, Maria Giuseppina Miano5. 1. Institute of Genetics and Biophysics "Adriano Buzzati-Traverso", National Research Council, Naples, Italy; University of Campania "Luigi Vanvitelli", Caserta, Italy. 2. Institute of Biomedical Technologies, National Research Council, Segrate, Milan, Italy. 3. Institute of Genetics and Biophysics "Adriano Buzzati-Traverso", National Research Council, Naples, Italy. Electronic address: denise.drongitis@igb.cnr.it. 4. University of Trento, CIBIO & Dulbecco Telethon Institute, Trento, Italy. 5. Institute of Genetics and Biophysics "Adriano Buzzati-Traverso", National Research Council, Naples, Italy. Electronic address: mariag.miano@igb.cnr.it.
Abstract
BACKGROUND: The application of single-cell RNA sequencing (scRNASeq) represents a unique approach to identify hundreds to millions of cells in mammalian cortical multilayers at different stages of embryogenesis. ScRNASeq technology applied to neurological studies requires the use of fresh starting materials because standard cryopreservation methods do not guarantee high viability of cortical primary cells derived from dissected brain areas. NEW METHOD: Here we set up and validate an innovative strategy to perform scRNASeq studies in cryopreserved primary cortical cells isolated from E15.5 mouse embryo. In order to freeze cortical primary cells, we have employed Neurostore, a medium able to guarantee high viability and cell composition of embryonic cortex after thawing. COMPARISON WITH EXISTING METHODS: We showed for the first time the possibility to run scRNASeq experiments on primary cortical cells in an off-line set-up, ensuring cellular integrity and diversity. RESULTS: By trypan blue assay and flow cytometry analysis, we found that Neurostore-cryopreserved cortical cells showed approximately 95 % of viability. Satisfactory RNA recovery and cDNA libraries were achieved. Transcriptome sequencing of 35,763 cryoconserved single cells yielded a robust data-set, identifying 25 cell clusters in three biological samples. Prevalence of peculiar neural populations before and after the cryopreservation-resuscitation procedure was verified by marker gene expression and immunofluorescence analysis. CONCLUSIONS: Our findings support the evidence that frozen primary cortical cells can be successfully employed in scRNASeq experiments allowing an unprecedented flexibility in experimental procedures, such as sample preparation and subsequent processing steps performed in different locations.
BACKGROUND: The application of single-cell RNA sequencing (scRNASeq) represents a unique approach to identify hundreds to millions of cells in mammalian cortical multilayers at different stages of embryogenesis. ScRNASeq technology applied to neurological studies requires the use of fresh starting materials because standard cryopreservation methods do not guarantee high viability of cortical primary cells derived from dissected brain areas. NEW METHOD: Here we set up and validate an innovative strategy to perform scRNASeq studies in cryopreserved primary cortical cells isolated from E15.5 mouse embryo. In order to freeze cortical primary cells, we have employed Neurostore, a medium able to guarantee high viability and cell composition of embryonic cortex after thawing. COMPARISON WITH EXISTING METHODS: We showed for the first time the possibility to run scRNASeq experiments on primary cortical cells in an off-line set-up, ensuring cellular integrity and diversity. RESULTS: By trypan blue assay and flow cytometry analysis, we found that Neurostore-cryopreserved cortical cells showed approximately 95 % of viability. Satisfactory RNA recovery and cDNA libraries were achieved. Transcriptome sequencing of 35,763 cryoconserved single cells yielded a robust data-set, identifying 25 cell clusters in three biological samples. Prevalence of peculiar neural populations before and after the cryopreservation-resuscitation procedure was verified by marker gene expression and immunofluorescence analysis. CONCLUSIONS: Our findings support the evidence that frozen primary cortical cells can be successfully employed in scRNASeq experiments allowing an unprecedented flexibility in experimental procedures, such as sample preparation and subsequent processing steps performed in different locations.