Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The present study proposed to graft mesenchymal stem cells (MSCs), which continuously produce BDNF, into the spinal cord ventral horn, after ventral root avulsion. Neurotrophin expression was naturally achieved by culturing MSCs in an undifferentiated state for at least 10 weeks. Lewis rats were subjected to cells injected through the lateral funiculus. unilateral avulsion of lumbar ventral roots, receiving 3 x 10(5) Two weeks after surgery, the animals were sacrificed and neuronal survival, astroglial reaction and synaptic inputs within the motor nucleus analyzed. The results indicated that the MSCs treatment significantly rescued avulsed motoneurons. Such neuronal survival was related to in vivo mRNA up regulation as well as expression of BDNF and GDNF. Such increase was correlated to the preservation of synaptophysin- positive nerve terminals. Thus it was proposed that when maintained undifferentiated for a period of 10 weeks, MSCs may be used as a continuous source of BDNF, positively influencing neuronal survival and synaptic plasticity. (C) 2008 Elsevier Inc. All rights reserved.332290300Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [24/2005]