Because the neural differentiation capacity of bone marrow stromal cells (BMSCs) 
is still a matter of controversial debate, we performed a thorough investigation 
into the differentiation capacity of human BMSCs and examined their therapeutic 
potency. BMSCs were isolated from the femur and kept in cell cultures with 
various cultivation protocols being applied. In standard culture conditions 
using a fetal calf serum-enriched medium, while not exhibiting a neural 
phenotype, the majority of cells expressed a variety of neuronal marker proteins 
as well as the astrocyte marker GFAP. Only a minority of stem cells expressed 
nestin, a marker for neural precursor cells. Cultivation in serum-free medium 
supplemented with specific growth factors resulted in a markedly higher 
percentage of nestin-positive cells. To establish the therapeutic potency of 
bone marrow-derived cells, the synthesis of neurotrophic factors such as NGF, 
BDNF and GDNF was analyzed under non-stimulating standard culture conditions as 
well as after a neural selection procedure. The therapeutic potency of BMSCs was 
further examined with regard to their migratory potential in vitro and after 
transplantation in vivo. After stereotactic engraftment into the lateral 
ventricle of adult rats, mesenchymal stem cells were seen to adhere to the 
ependymocytes and cells of the choroids plexus. Afterwards grafted cells passed 
through the ependymal barrier, locating in the subventricular space. Their BMSCs 
took up a close host graft interaction without any degenerative influence on the 
host cells. Furthermore, there was morphological as well as immunohistochemical 
evidence for a transdifferentiation within the host tissue. In addition, BMSCs 
could be efficiently transduced using a third-generation adenoviral vector, 
indicating their potential feasibility for a gene-therapeutic option.