Role of toll-like receptors 2 and 4 in the neuroprotective effects of bone marrow�derived mesenchymal stem cells in an experimental model of ischemic stroke

Objective: Ischemic stroke is a major cause of death and prolonged disability worldwide. Inflammation plays an important role in post-ischemic injury. Mesenchymal stem cells (MSCs) have protective effects in stroke treatment due to their anti-inflammatory properties. Toll-like receptors (TLRs) 2 and 4 are two innate immune receptors that trigger inflammatory processes. Here, we investigated the association of these receptors with the protective effect of MSCs after middle cerebral artery occlusion (MCAO) in rats. Methods: MSCs were isolated from the bone marrow of young rats and expanded in vitro. A model of ischemic stroke was performed by transient MCAO with 24 or 72 hours of reperfusion. Two hours after ischemia/reperfusion (I/R), the rats received MSCs or saline via tail vein and the sham group underwent surgery without MCAO. The relative gene expressions of TLR2, TLR4, and MyD88 were evaluated in the ischemic penumbra by the real-time PCR technique. Active astrocyte and microglia and TLR-expressing cells were detected by immunohistochemistry (IHC). Results: MSCs significantly decreased the genes expression of TLR2 (P = 0.006), TLR4 (P = 0.038), and MyD88 (P = 0.009) after their upregulation by I/R. Moreover, the IHC results indicated that glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (Iba-1) positive cells were significantly increased by I/R (P < 0.001), and MSCs significantly decreased the number of GFAP (P = 0.003), Iba-1 (P = 0.001), TLR2 (P = 0.004), and TLR4 (P = 0.007) positive cells 72 hours after I/R. Conclusion: The neuroprotective effect of MSCs in brain ischemic injury is associated with its anti-inflammatory effects and modulation of the activity of immune cells. Inhibition of TLR2 and TLR4 expression is one of the possible mechanisms of this protective effect. © 2018 Wiley Periodicals, Inc