Intravenous Transplantation of Mesenchymal Stem Cells Reduces the Number of Infiltrated Ly6C⁺ Cells but Enhances the Proportions Positive for BDNF, TNF-1α, and IL-1β in the Infarct Cortices of dMCAO Rats

Abstract

The resident microglial and infiltrating cells from peripheral circulation are involved in the pathological processes of ischemia stroke and may be regulated by mesenchymal stem/stromal cell (MSC) transplantation. The present study is aimed at differentiating the neurotrophic and inflammatory roles played by microglial vs. infiltrating circulation-derived cells in the acute phase in rat ischemic brains and explore the influences of intravenously infused allogeneic MSCs. The ischemic brain injury was induced by distal middle cerebral artery occlusion (dMCAO) in SD rats, with or without MSC infusion in the same day following dMCAO. Circulation-derived infiltrating cells in the brain were identified by Ly6C, a majority of which were monocytes/macrophages. Without MSC transplantation, among the infiltrated Ly6C+ cells, some were positive for BDNF, IL-1β, or TNF-α. Following MSC infusion, the overall number of Ly6C+ infiltrated cells was reduced by 50%. In contrast, the proportions of infiltrated Ly6C+ cells coexpressing BDNF, IL-1β, or TNF-α were significantly enhanced. Interestingly, Ly6C+ cells in the infarct area could produce either neurotrophic factor BDNF or inflammatory cytokines (IL-1β or TNF-α), but not both. This suggests that the Ly6C+ cells may constitute heterogeneous populations which react differentially to the microenvironments in the infarct area. The changes in cellular composition in the infarct area may have contributed to the beneficial effect of MSC transplantation.

Neurogenin-1 Overexpression Increases the Therapeutic Effects of Mesenchymal Stem Cells through Enhanced Engraftment in an Ischemic Rat Brain

“…For these reasons, MSCs are the first stem cells to have been tested in clinical studies for the treatment of stroke. Preclinical studies demonstrated that administration of MSCs via intracerebral (10,11), intravenous (12)(13)(14), intra-arterial (15,16), and intraventricular/intrathecal routes (17) showed therapeutic benefits of MSCs in animal models of acute stroke (18). Although intravenous administration of autologous MSCs from bone marrow was found to be safe and well tolerated in ischemic stroke patients (19)(20)(21)(22), no significant improvement was observed in neurological outcomes following intravenous administration of allogeneic MSCs (23).…”

Peripheral Circulation and Astrocytes Contribute to the MSC-Mediated Increase in IGF-1 Levels in the Infarct Cortex in a dMCAO Rat Model

“…The activated microglia stain positive for CD68 ( Figure 1 ), and both activated and resting stage microglia are positive for Iba-1. In our previous studies, we reported that CD68+ microglia express IGF-1 in the brain of a stroke model [ 15 , 19 ]. In the present study, we continued to look into a wider range of microglia population—Iba-1+ cells, with regard to IGF-1 expression.…”

“…The performance of allogeneic bone marrow MSC (BMSC) culture, infusion, dMCAO model establishment, and behavioral tests have been described in our previous study [ 19 ].…”

“…In brief, primary cultures of bone marrow stromal cells were obtained from donor young adult male rats, and BMSCs were isolated as previously described [ 15 , 19 ]. Animals were anesthetized with 3.5% isoflurane and then maintained with 1.0–2.0% isoflurane in N 2 O : O 2 (2 : 1).…”

“…As described in our previous study [ 15 , 19 ], the selection of sections for each rat and the demarcation of the counting area in the infarct cortex were in accordance with the work published by Gelosa et al [ 21 ]. In brief, we outlined the counting area in the dorsal infarct cortex which was 2 mm adjacent to the boundary line between the normal and infarct areas (Supplementary Figure 1 ).…”