Mesenchymal Stromal Cells and Neural Stem Cells Potential for Neural Repair in Spinal Cord Injury and Human Neurodegenerative Disorders

Abstract

Spinal cord injury represents a serious neurodegenerative condition mostly characterized by inflammation, demyelination, loss of neurons and glial cells. Patients who suffer from spinal cord trauma show limited functional recovery, which frequently leads to deficit of multiple sensory, motor and autonomic systems resulting to clinical signs of partial or complete paralysis with prominent spasticity and rigidity (Cizkova et al. 2007). Because of the limited regenerative capacity of the adult CNS due to the inhibitory molecules, decrease of trophic factor support and scar tissue formation, the current functional treatments for SCI are not successful (Rowland et al. 2008). However, emerging research evidences on regenerative medicine involving adult and neural stem cells has put much attention on the development of cell based therapies which could promote regeneration of lesioned CNS (Barnabe-Heider & Frisen, 2008; Goldman, 2005). One of the most important factors for the stem cells candidates that are being used in transplantation strategies, is their compatibility with the host tissue. Therefore, preferential criteria for stem cells transplantation in clinical trials are their ability to be used as autologous transplant to avoid moral and ethical dilemma as well as immunosuppressive therapy. Mesenchymal stem cells (MSCs) fulfill all these criteria and can be easily isolated from patient’s bone marrow or adipose tissue. However, in many cases their beneficial effect in regard to the treatment of neurodegenerative disorders is most likely due to paracrine (Zacharek et al. 2007) or immunomodulatory effects (Djouad et al. 2003), rather than by direct cell replacement (Jorgensen, 2009). Therefore, other sources of autologous stem cells, such as „Schwann cells” derived from peripheral nerve, „Olfactory ensheating cells” (OECs) (Papastefanaki et al. 2007; Raisman et al. 2011) from olfactory bulb, or even allogenic