Abstract
In this study, we investigated interactions among microglia (MG), bone marrow mesenchymal stem cells (BMSCs) and neurons in cerebral ischemia and the potential mechanisms using an in vitro oxygen-glucose deprivation (OGD) model. Rat BMSCs were incubated with conditioned medium (CM) from in vitro cultures of OGD-activated rat MG and murine BV2 MG cells. Effects of glial cell-derived neurotrophic factor (GDNF) on rat neuron viability, apoptosis, lactate dehydrogenase (LDH) leakage and mitochondrial membrane potential (MMP) were analyzed in this model. OGD-activated MG promoted GDNF production by BMSCs (P < 0.01). Tumor necrosis factor-α (TNFα), but not interleukin-6 (IL6) or interleukin 1β (IL1β), promoted GDNF production by BMSCs (P < 0.001). GDNF or CM pre-treated BMSCs elevated neuronal viability and suppressed apoptosis (P < 0.05 or P < 0.01); these effects were inhibited by the RET antibody. GDNF activated MEK/ERK and phosphoinositide-3-kinase (PI3K)/AKT signaling but not JNK/c-JUN. Furthermore, GDNF upregulated B cell lymphoma 2 (BCL2) and heat shock 60 kDa protein 1 (HSP60) levels, suppressed LDH leakage, and promoted MMP. Thus, activated MG produce TNFα to stimulate GDNF production by BMSCs, which prevents and repairs OGD-induced neuronal injury, possibly via regulating MEK/ERK and PI3K/AKT signaling. These findings will facilitate the prevention and treatment of neuronal injury by cerebral ischemia.