https://www.selleckchem.com/products/tween-80.html (2020), published in this issue.Alzheimer's disease, obesity-related metabolic syndrome, and cancer are the leading causes of death and among the most costly medical conditions in the Western world. In all three cases, recent discoveries establish the TREM2 receptor as a major pathology-induced immune signaling hub that senses tissue damage and activates robust immune remodeling in response to it. In this review, we summarize and question what is known and remains to be discovered about TREM2 signaling pathway, track the consequences of its activation in physiological niches and pathological contexts, and highlight the promising potential of therapeutic manipulation of TREM2 signaling.Intravenous infusion of mesenchymal stromal cells (MSCs) is thought to be a viable treatment for numerous disorders. Although the intrinsic immunosuppressive ability of MSCs has been credited for this therapeutic effect, their exact impact on endogenous tissue-resident cells following delivery has not been clearly characterized. Moreover, multiple studies have reported pulmonary sequestration of MSCs upon intravenous delivery. Despite substantial efforts to improve MSC homing, it remains unclear whether MSC migration to the site of injury is necessary to achieve a therapeutic effect. Using a murine excisional wound healing model, we offer an explanation of how sequestered MSCs improve healing through their systemic impact on macrophage subpopulations. We demonstrate that infusion of MSCs leads to pulmonary entrapment followed by rapid clearance, but also significantly accelerates wound closure. Using single-cell RNA sequencing of the wound, we show that following MSC delivery, innate immune cells, particularly macrophages, exhibit distinctive transcriptional changes. We identify the appearance of a pro-angiogenic CD9+ macrophage subpopulation, whose induction is mediated by several proteins secreted by MSCs, including COL6A1, PRG4, and