Effects of induced neural stem cells on immune cells following traumatic brain injury

Objective To study the effects of grafted induced neural stem cells (iNSCs) on microglia activation states and reactive astrogliosis following traumatic brain injury (TBI). Methods TBI models were established using a standardized weight-drop device. At 12 h after TBI, a total of 1×106 iNSCs were transplanted into the brains of TBI mice. On day 7 after TBI, animals were sacrificed for morphological analysis. Double-labeling experiments were utilized to determine the effects of iNSC grafts on ED1-and Iba1-positive microglia, GFAP-positive astrocytes and NeuN-positive neurons in the brains of TBI mice. Results Following TBI, we observed dramatic increases in the numbers of ED1- and Iba1-positive microglia and GFAP-positive astrocytes in the brains of TBI mice. However, grafted iNSCs significantly suppressed the numbers of ED1- and Iba1-positive microglia and GFAP-positive astrocytes in the brains of TBI mice. Additionally, iNSC grafts substantially reduced the levels of apoptotic NeuN-positive neurons in the brains of TBI mice. Conclusion INSC grafts can modulate microglia activation states and inhibit reactive astrogliosis to promote neuronal survival post-TBI. Key words: Induced neural stem cell; Microglia; Astrocyte; Traumatic brain injury; Transplantation