Hematogenous Macrophages: A New Therapeutic Target for Spinal Cord Injury.

Yuanzhe Ding,Jingquan Yang,Sheng Wang,Xiaolei Zhang,Di Zhang

doi:10.3389/fcell.2021.767888

Abstract

Spinal cord injury (SCI) is a devastating disease leading to loss of sensory and motor functions, whose pathological process includes mechanical primary injury and secondary injury. Macrophages play an important role in SCI pathology. According to its origin, it can be divided into resident microglia and peripheral monocyte-derived macrophages (hematogenous Mφ). And it can also be divided into M1-type macrophages and M2-type macrophages on the basis of its functional characteristics. Hematogenous macrophages may contribute to the SCI process through infiltrating, scar forming, phagocytizing debris, and inducing inflammatory response. Although some of the activities of hematogenous macrophages are shown to be beneficial, the role of hematogenous macrophages in SCI remains controversial. In this review, following a brief introduction of hematogenous macrophages, we mainly focus on the function and the controversial role of hematogenous macrophages in SCI, and we propose that hematogenous macrophages may be a new therapeutic target for SCI.

Highlights

Spinal cord injury (SCI) used to be considered a traumatic disease that mostly occurs in the youth (Pickett et al, 2006; Niemeyer et al, 2020)
In this review, following a brief introduction of hematogenous macrophages, we mainly focus on the function and the controversial role of hematogenous macrophages in SCI, and we propose that hematogenous macrophages may be a new therapeutic target for SCI
Microglia and hematogenous macrophages have similar morphology and are both involved in serial pathological processes of SCI such as inflammation phagocytosis and ischemic reperfusion injury (Nakajima et al, 2020)

Summary

BACKGROUND

Spinal cord injury (SCI) used to be considered a traumatic disease that mostly occurs in the youth (Pickett et al, 2006; Niemeyer et al, 2020). In the SCI, pro-inflammatory cytokines such as IL-β, TNF-α, and IL-6, which are released by activated microglia cells (Jeong 2010), may promote the infiltration of hematogenous macrophages to the injury site. Microglia and hematogenous macrophages have similar morphology and are both involved in serial pathological processes of SCI such as inflammation phagocytosis and ischemic reperfusion injury (Nakajima et al, 2020) They have many differences in origin, biological markers, and functions (Daneman 2018; Watanabe et al, 2019). Popovich intravenously injected clodronate liposome to deplete hematogenous macrophages, which led to a reduction of infiltrating macrophages at the damaged edge As a result, it decreased the tissue cavity in lesion and promoted the recovery of motor function (Popovich 1999).

Result

Findings

SUMMARY AND PERSPECTIVES