Effect of human mesenchymal stem cells on neuronal death and memory deficits induced by trimethyltin in the rat hippocampus

Trimethyltin (TMT) is a potent toxicant which selectively kills cells in the central nervous system (CNS) and immune system. Within the CNS, TMT selectively destroyed neurons in the neocortex, amygdala, and olfactory tubercle, however its most striking effects were observed in the hippocampal formation. In the present study, we examined the effects of human umbilical cord blood (hUCB)-derived mesenchymal stem cells (MSCs) on TMTinduced hippocampal cell death and the impairments of learning and memory in Morris water maze in rats. The hUCB-MSCs were grafted into the hippocampus 1 week after TMT (6.0 mg/kg, i.p.)-induced neurodegeneration. We identified that hUCB-MSCs survived and were differentiated in TMT-induced rat brain by the hoechst dye analysis, bromodeoxyuridine and neuronal marker NeuN immunofluorescence. In rats exposed to TMT, the hUCBMSCs grafts improved spatial learning and memory in the water maze, suggesting that grafts can in some circumstances reduce spatial deficits on the CNS after TMT-induced neurodegeneration. The present results suggest that hUCB-MSCs grafted into the TMT-induced rat brain are capable of differentiation into neurons as well as improving spatial recognition.