O-37: Suppression of p75 Expression Improves Functionality of Bone Marrow Stromal Cells After Transplantation into Injured Spinal Cord Model of Rats
Objective: Bone marrow stromal cells (BMSCs) have been successfully employed for cell therapy of neurodegenerative disorders, e.g. spinal cord injury (SCI). One of the major problems in cell transplantation, specifically after in vivo neural differentiation, is the high rate of cell death. p75 receptor promotes neuronal apoptosis after binding to neurotrophines (NGF, BDNF, NT3). Our previous studies have shown that p75 gene expression and apoptosis would simultaneously happen in rat BMSCs in a time window of 6-12 hours after induction of neural differentiation in culture. Therefore, the aim of our study was to investigate the in vitro effects of p75 suppression on apoptosis rate of BMSC-derived neural-like cells, and to evaluate the in vivo functional effects of transplantation of p75 suppressed BMSCs in spinal cord injured rats. Materials and Methods: Specific p75 siRNA was designed and cloned into pRNA-U6.1/Hygro plasmid. Then, BMSCs were transfected with p75 shRNA and differentiated into neural-like cells. Flow cytometry was applied to determine their rate of apoptosis. Spinal cord contusion injury was performed at L1 vertebrae level using weight <font><font>drop</font></font> method. Animals were divided into four groups: 1. PBS treated SCI rats; 2. BMSC treated SCI rats; 3. SCI rats treated with p75 shRNA transfected BMSCs and 4. sham-operated group. Cells were labeled with DiI and grafted into the lesion site. The BBB test was carried out weekly for 5 weeks to determine functional recovery of animals. Animals were sacrificed after 5 weeks for histological examination. Results: Flow cytometry analysis revealed a 3.5 fold reductions in apoptosis. Furthermore, there was a significant difference (p≤0.05) between all the examined groups with the most significant difference between groups one and three. Conclusion: These results demonstrate that genetically modified BMSCs in which p75 gene expression is suppressed could be a better candidate for cell therapy of SCI.