Simultaneous Flow Cytometric Characterization of Multiple Cell Types Retrieved from Mouse Brain/Spinal Cord Through Different Homogenization Methods

Summary

We present a flow cytometry method to identify simultaneously different cell types retrieved from mouse brain or spinal cord. This method could be exploited to isolate or characterize pure cell populations in neurodegenerative diseases or to quantify the extent of cell targeting upon in vivo administration of viral vectors or nanoparticles.

Abstract

Recent advances in viral vector and nanomaterial sciences have opened the way for new cutting-edge approaches to investigate or manipulate the central nervous system (CNS). However, further optimization of these technologies would benefit from methods allowing rapid and streamline determination of the extent of CNS and cell-specific targeting upon administration of viral vectors or nanoparticles in the body. Here, we present a protocol that takes advantage of the high throughput and multiplexing capabilities of flow cytometry to allow a straightforward quantification of different cell subtypes isolated from mouse brain or spinal cord, namely microglia/macrophages, lymphocytes, astrocytes, oligodendrocytes, neurons and endothelial cells. We apply this approach to highlight critical differences between two tissue homogenization methods in terms of cell yield, viability and composition. This could instruct the user to choose the best method depending on the cell type(s) of interest and the specific application. This method is not suited for analysis of anatomical distribution, since the tissue is homogenized to generate a single-cell suspension. However, it allows to work with viable cells and it can be combined with cell-sorting, opening the way for several applications that could expand the repertoire of tools in the hands of the neuroscientist, ranging from establishment of primary cultures derived from pure cell populations, to gene-expression analyses and biochemical or functional assays on well-defined cell subtypes in the context of neurodegenerative diseases, upon pharmacological treatment or gene therapy.

Introduction

Gene and drug delivery technologies (such as viral vectors and nanoparticles) have become a powerful tool that can be applied to gain better insights on specific molecular pathways altered in neurodegenerative diseases and for development of innovative therapeutic approaches^1,2,3. Optimization of these tools relies on quantification of: (1) the extent of penetration in the CNS upon different routes of administration and (2) targeting of specific cell populations. Histological analyses are usually applied to visualize fluorescent reporter genes or fluorescently-tagged nanopart....

Protocol

All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Dana Farber Cancer Institute (protocol number 16-024).

1. Preparation of solutions needed for the experiment

1. Prepare 1x Hank’s balanced salt solution (HBSS) by diluting 10x HBSS with sterile water. Pre-chill the solution on ice. At least 25 mL of solution are needed for each sample.
2. Prepare isotonic Percoll solution (IPS) by mixing 10x sterile HBSS 1:10 with density gradient medium (i.e., Percoll). Pre-chill on ice.
   NOTE: IPS can be stored for up to 30 days at 4 °C.
3. Prepare flow cytome....

Results

We compared two different homogenization methods (DH versus PD) applied to mouse brain and spinal cord, to test the efficiency in retrieving different viable cell types suitable for downstream applications. To do so, we exploited a 9-color flow cytometry panel designed to characterize, in the same sample, different CNS cell types including microglia, lymphocytes, neurons, astrocytes, oligodendrocytes and endothelium.

Brain and spinal cord tissues were retrieved from different mice (n ≥ 6), spl.......

Discussion

Herein we describe a protocol for the co-purification and concurrent flow cytometric analysis of some of the most relevant CNS cells from mouse brain and spinal cord. Traditionally, histological analyses have been applied to describe the distribution of nanoparticles or the transduction efficiency of viral vectors in the CNS^5,13, or to provide insights on morphological and molecular changes occurring in specific cell types during a pathology or upon pharmacologic.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
10X HBSS (Calcium, Magnesium chloride, and Magnesium Sulfate-free)	Gibco	14185-052
70 mm Cell Strainer	Corning	431751
ACSA/ACSA2 anti-mouse antibody	Miltenyi Biotec	130-117-535	APC conjugated
Bovine Serum Albumin	Sigma Aldrich	A9647-1KG
CD11b rat anti-mouse antibody	Invitrogen	47-0112-82	APC-eFluor 780 conjugated
CD31 rat anti-mouse antibody	BD Bioscience	562939	BV421 conjugated
CD45 rat anti-mouse antibody	Biolegend	103138	Brilliant Violet 510 conjugated
CD90.1/Thy1.1 rat anti-mouse antibody	Biolegend	202518	PE/Cy7 conjugated
CD90.2/Thy1.2 rat anti-mouse antibody	Biolegend	1005325	PE/Cy7 conjugated
Conical Tubes (15 mL)	CellTreat	229411
Conical Tubes (50 mL)	CellTreat	229422
Dounce Tissue Grinder set (Includes Mortar as well as Pestles A and B)	Sigma-Aldrich	D9063-1SET
Fc (CD16/CD32) Block rat anti-mouse antibody	BD Pharmingen	553142
Fetal Bovine Serum	Benchmark	100-106
Neural Tissue Dissociation Kit (P)	Miltenyi Biotec	130-092-628
O4 anti mouse/rat/human antibody	Miltenyi Biotec	130-095-895	Biotin conjugated
Percoll	GE Healthcare	10266569	sold as not sterile reagent
Percoll	Sigma	65455529	sterile reagent (to be used for applications requiring sterility)
Percoll PLUS	Sigma	GE17-5445-01	reagent containing very low traces of endotoxin
Streptavidin	Invitrogen	S3258	Alexa Fluor 680 conjugated