New insights into acute ischemic stroke from the perspective of spatial omics

Abstract

Acute ischemic stroke (AIS) is a common cerebrovascular disease characterized by high incidence and disability rates, placing a significant burden on global healthcare systems. Various cell types, including microglia, astrocytes, oligodendrocytes, and peripheral immune cells, interact in the pathological process of AIS, profoundly influencing the disease's prognosis. This review, for the first time, summarizes the biological functions and interaction mechanisms of microglia, astrocytes, oligodendrocytes, their subgroups, and infiltrating peripheral immune cells at different time points and spatial distributions following AIS, from the perspective of spatial single-cell omics. Spatial transcriptomics technology combines high-resolution gene expression information with tissue spatial architecture, enabling researchers to precisely identify the spatial distribution and dynamic crosstalk between CNS-resident cells and peripheral immune cell subsets. Intervening in the interactions between cell subgroups or different cell types and effectively targeting specific subgroups in the target area, may help minimize the negative effects of harmful subsets while enhancing the functions of beneficial ones. The application of spatial single-cell transcriptomics provides an unprecedented perspective for understanding the complex intercellular interactions following stroke, laying the foundation for precision interventions and targeted therapies.

Keywords: acute ischemic stroke; immune inflammation.; microglia; peripheral immune cells; spatial omics.

Figure 1

Overview. The use of single-cell sequencing and spatial transcriptomics to investigate the gene expression profiles and biological functions of cell subpopulations with different spatial distributions in AIS.

Figure 2

Microglial subpopulations at different spatial locations. Following AIS, the activation of microglia and the infiltration of immune cells contribute to what is referred to as an "inflammatory storm." During this process, the ICAM microglial subpopulation located in the ischemic core region and the IPAM microglial subpopulation in the penumbra play crucial roles. These subpopulations express entirely different marker genes and perform distinct biological functions. In the PIA_P region, the MG4 subpopulation, as well as the MG3 and MG5 subpopulations in the PIA_D region, also express specific marker genes, each reflecting their unique biological functions. The entire process represents a complex interplay between "damage" and "repair," highlighting the dynamic and intricate nature of immune responses and repair mechanisms following a stroke.

Figure 3

Specific mechanisms by which microglia participate in the pathological process of AIS. M1 microglia primarily exert pro-inflammatory effects, leading to the infiltration of peripheral immune cells and the death of astrocytes and oligodendrocytes, which in turn affects myelin regeneration, disrupts the BBB, and causes neurological dysfunction. On the other hand, M2 microglia can partially reverse the harmful effects of M1. Different microglial subpopulations, refined from a single-cell perspective, also perform distinct roles. The ICAM subpopulation primarily exerts pro-inflammatory effects, whereas the IPAM subpopulation plays a key role in anti-inflammation, tissue repair, and improvement of neurological function.

Figure 4

The role of astrocytes at different spatial locations in AIS. Based on the distance from the infarct core, astrocyte subpopulations in AIS can be categorized into proximal and distal subpopulations. These subpopulations express distinct characteristic genes and perform different biological functions. Furthermore, the ischemic core region and its surrounding areas are divided into four distinct regions (A, B, C, and D), each characterized by unique gene signatures and playing different roles. The functions of these regions and subpopulations highlight the spatial heterogeneity of astrocytes in tissue repair and damage response following stroke.

Figure 5

Biological functions of oligodendrocytes in AIS. Oligodendrocytes play a crucial role in myelination and neuronal regeneration. However, environmental changes, such as calcium overload and oxidative stress, not only hinder the differentiation of OPCs into mature oligodendrocytes but also increase the likelihood of oligodendrocyte apoptosis or necrosis. These factors collectively impact the survival and function of oligodendrocytes, further exacerbating neural damage and impairing myelin regeneration and neurological recovery.

Figure 6

Functional roles of oligodendrocytes at different spatial locations in AIS. The disease-associated mature oligodendrocytes 1 subpopulation expresses high levels of Serpina3n and Klk6. The disease-associated mature oligodendrocytes 2 subpopulation is primarily localized near the lateral ventricles and expresses genes such as Cd63, Eif1, Cct5, Ctsd, Ddit3, and Cdkn1a. The disease-associated mature oligodendrocytes IFN subpopulation is mainly found in the core of the lesion. Each subpopulation contributes to the injury repair process following AIS through its unique gene expression patterns and biological functions.

Figure 7

Role of peripheral immune cells in AIS. During the pathogenesis of AIS, peripheral immune cells play complex and multifaceted roles in the pathophysiological process. Monocytes and neutrophils, as the first peripheral immune cells to infiltrate the CNS, contribute to disease progression through the following mechanisms: (1) directly exacerbating structural and functional disruption of the BBB; (2) secreting large quantities of pro-inflammatory cytokines, establishing a positive feedback loop that continuously recruits additional peripheral immune cells to the ischemic lesion; and (3) initiating and sustaining a neuroinflammatory cascade, which has been demonstrated to significantly aggravate secondary brain injury. In contrast, lymphocytes exhibit a distinct response pattern: their activation is relatively delayed during the acute phase, but they may play a crucial role in later stages by modulating the immune microenvironment to facilitate tissue repair.

Figure 8

Temporal dynamics of crosstalk between peripheral immune cells and CNS glial cells. During the acute phase of AIS, activated microglia release inflammatory mediators that recruit peripheral immune cells, particularly monocytes and neutrophils, to migrate and accumulate in the ischemic lesion area, leading to a significant early increase in these cell populations. This process establishes a vicious cycle: infiltrating peripheral immune cells exacerbate BBB disruption and vasogenic brain edema through the release of reactive oxygen species, while the compromised BBB integrity further promotes the infiltration of peripheral immune cells and perpetuates the inflammatory response. It should be noted that a moderate inflammatory response plays a crucial physiological role in clearing necrotic cells and damaged tissue. As the disease progresses into the subacute or chronic phase, the immune microenvironment in the CNS undergoes a significant shift, transitioning from a pro-inflammatory state to an anti-inflammatory and reparative state. Key features of this transition include:1.Activated microglia undergo phenotypic switching and begin secreting anti-inflammatory factors such as IL-10 and TGF-β to suppress excessive inflammation, while collaborating with astrocytes to establish an inflammatory barrier.2.Astrocytes not only form glial scars to contain inflammatory spread but also secrete various neurotrophic factors, including brain-derived neurotrophic factor, to promote neuronal survival and synaptic remodeling.3.Oligodendrocyte precursor cells proliferate and differentiate to participate in myelin regeneration, facilitating the restoration of neural conduction.4.Emerging evidence suggests that specific lymphocyte subsets may contribute to late-stage tissue repair by modulating immune responses, while the extent of peripheral immune cell infiltration is markedly reduced during this phase.

Figure 9

Activation of microglia and infiltration of peripheral immune cells. Following AIS, the activation of microglia and the subsequent infiltration of peripheral immune cells lead to vascular dysfunction and disruption of the BBB. This process further facilitates the infiltration of peripheral immune cells into the CNS, creating a vicious cycle that ultimately exacerbates neurological dysfunction.

Figure 10

Interactions between various glial cells and immune cells after AIS. Different subpopulations of microglia, astrocytes, oligodendrocytes, and peripheral immune cells together form the complex immune microenvironment in AIS. Within this microenvironment, the interplay between various "beneficial" and "detrimental" factors ultimately determines the outcome of AIS. The dynamic interactions among these glial cells and immune cells not only influence the inflammatory response but also play a crucial role in injury repair and neurological recovery.