Single-Cell Analysis: A Method for In-Depth Phenotyping of Cells Involved in Asthma

Abstract

Asthma is a chronic inflammatory lung disease with high prevalence, making it one of the most common chronic conditions worldwide. Its pathophysiology is influenced by a range of genetic and environmental factors, resulting in a complex and heterogeneous disease profile. Asthma is primarily associated with a type 2 (T2) immune response, though non-T2 endotypes also contribute to disease pathology. Generally, asthma is characterized by the infiltration and activation of various cell types, including dendritic cells, eosinophils, innate lymphoid cells, lymphocytes, mast cells, and neutrophils, which participate in T1, T2, and T17 immune responses. Despite advances in understanding, many questions remain unresolved. Therefore, emerging omic techniques, such as single-cell RNA sequencing (scRNA-seq), offer novel insights into the underlying mechanisms of asthma and the roles of these immune cells. Recent scRNA-seq studies in asthma have identified multiple novel immune cell subtypes and clusters, suggesting their potential functions in disease pathology. The rapid advancement of scRNA-seq technology now enables in-depth investigation of individual cells within tissues, allowing for precise cell-type classification and detailed molecular profiling. Nonetheless, certain limitations persist, which require further refinement in future studies.

Keywords: allergic diseases; asthma; immune cells; single-cell RNA-seq.

Figure 1

Steps of single-cell RNA-seq technique and analysis. In general, the workflow of single-cell sequencing includes the following steps: (A) Sample collection and preparation: initial collection and processing of the sample. (B) Isolation of single cells and cDNA synthesis: single cells can be isolated using various methods, such as plate-based sample preparation or bead-based single-cell capture. (C) Library preparation, sequencing, and data Analysis: construction of libraries, followed by sequencing and subsequent data analysis using bioinformatics tools.

Figure 2

Single-cell analysis of key cell types involved in asthma pathogenesis. Single-cell RNA sequencing (scRNA-seq) studies have been performed on various cell types implicated in asthma pathogenesis, including T and B lymphocytes, dendritic cells, eosinophils, epithelial cells, type 2 innate lymphoid cells (ILC2), and macrophages. These studies have identified previously unknown genes that may play an important role in asthma development, and their analysis has led to the establishment of several new subtypes or clusters of these cells, contributing to the understanding of the underlying mechanisms of asthma. Human genes are written in italics and uppercase, whereas mouse genes are written in italics and lowercase, in accordance with international nomenclature standards. Additionally, each gene is color-coded based on the cell and origin source: red for blood, blue for airway and lung tissue, and green for other sources (e.g., intestine, spleen, bone marrow, etc.).