Preparation of a Non-Cardiomyocyte Cell Suspension for Single-Cell RNA Sequencing from a Post-Myocardial Infarction Adult Mouse Heart

Summary

Here, we describe a protocol to isolate a sufficient amount of single non-cardiomyocytes with high viability from a post-myocardial infarction (MI) mouse heart. This can be used for subsequent single-cell sequencing, flow cytometry analysis, and primary cell culture.

Abstract

Myocardial infarction (MI) is one of the most common cardiovascular diseases, with increasing mortality worldwide. Non-cardiomyocytes account for more than half of the total cardiac cell population, and they contribute to adaptive compensations upon myocardial injury, including inflammatory responses, tissue repair, and scar formation. To study the post-MI cardiac microenvironment, single-cell RNA sequencing (scRNA-seq) is widely used to identify different cardiac cell types and intercellular communications. Among the procedures of scRNA-seq sample preparation, preparing the cell suspension is one of the most critical steps, because the cell viability can affect the quality of the scRNA-seq results. Therefore, we designed an experimental protocol for preparing a non-cardiomyocyte cell suspension from post-MI mouse hearts with an extra focus on improving the cell viability by choosing mild digestive enzymes, controlling the digestion time, and applying fluorescence-activated cell sorting (FACS). Finally, we isolated CD45⁺ cells from the non-cardiomyocyte cell suspension obtained through this protocol, and then we performed scRNA-seq.

Introduction

Myocardial infarction (MI) is one of the most common cardiovascular diseases, and its mortality increasing throughout the world¹. MI is caused by an insufficient blood supply to the surrounding myocardium, which can be a result of a coronary artery blockage that occurs with atherosclerotic plaque rupture. Although percutaneous coronary intervention (PCI) has reduced the mortality rates of acute MI patients, the high prevalence of heart failure post MI remains a problem². The key pathophysiology underlying post-MI heart failure is the body's compensatory response to cardiac injuries, which involves replacing the dead ....

Protocol

All the experiments were conducted in accordance with the guidelines for the care and use of laboratory animals at Zhejiang University and were approved by the Animal Advisory Committee at Zhejiang University.

1. Left anterior descending coronary artery ligation (LAD ligation) surgery

NOTE: Eight week old male C57BL/6J mice were used as models. The hearts were harvested 2 weeks after MI. Left anterior descending coronary artery ligation surgery was carried out as previously described and demonstrated¹¹.

1. Disinfect the surgical instruments with 70% ethanol before....

Results

A single-cell suspension with high vitality was obtained by implementing section 2 of this protocol. However, cell fragments could still be observed (Figure 1A); hence, fluorescence-activated cell sorting (FACS) was performed to further improve the quality¹⁶.After FACS, the average cell size reduces from 9.6 µm to 9.1 µm (Table 1), which suggests that the proportion of cell fragments can be effectively reduced in the cell suspension by FACS (<.......

Discussion

This article aimed to describe a protocol to isolate single non-cardiomyocytes from mouse hearts post MI. The protocol can be applied to isolate different types of cells in the post-MI microenvironment with high quality, including immune cells, endothelial cells, and fibroblasts. Three essential factors are crucial for obtaining a high-quality cell suspension for single-cell sequencing. The first one is the setting of the enzymatic digestion. It is important to control the time of digestion and the volume and concentrati.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Acridine Orange / Propidium Iodide Stain	Logos biosystems	F23001
Automated Cell Counter	Logos biosystems	L20001
Bovine Serum Albumin	Servicebio	G5001	Cytoprotective effect
Cell Counting Slides	Logos biosystems	L12001
Collagenase Type IV	Gibco	17104019	Digestive enzymes
Dispase II	Sigma	D4693	Digestive enzymes
Dnase I	Roche	11284932001	Prevent cell clumping
Falcon 40μm Cell Strainer	Falcon	352340	Remove cell clumps
Falcon 70μm Cell Strainer	Falcon	352350	Remove undigested tissue and clumps
Flow Cell Sorter	Beckman Coulter	B25982
Iodophor	OU QING SI	10054963976859
Needle Holder	FST	12061-01
Ophthalmic Forceps	RWD	F14012-10
Ophthalmic Scissors	RWD	S11036-08
Phosphate Buffered Saline	Servicebio	G4202-500ML
RBC Lysis Buffer	Beyotime	C3702-120ml	Remove red blood cells
Rib Retractor	FST	17005-04
Rodent Ventilator	Harvard	730043
RPMI 1640 Medium	Gibco	11875093	Solvent solution of enzyme
Sterile Scissor	RWD	S14014-10