Human Bone Marrow-Derived Mesenchymal Stromal Cells Injected Intrathecally in NOD/SCID Mice Preclinical Study of Biosafety and Biodistribution

Objective: Mesenchymal stromal cells (MSCs) have potent immunomodulatory and neuroprotective properties, and have been tested in neurodegenerative diseases resulting in meaningful clinical improvements. Regulatory guidelines specify the need to perform preclinical studies prior any clinical trial, including bio-distribution assays and tumourigenesis exclusion. We conducted a preclinical study of human bone marrow MSCs (hBM-MSCs) injected by intrathecal route in immunosuppressed NOD/SCID mice, to explore cellular bio-distribution and toxicity, as a privileged administration method for cell therapy in Friedreich´s Ataxia (FRDA). Methods: For this purpose, hBM-MSCs have been characterized according to the ISCT standards and 3 × 105 cells were injected by intrathecal route in 12 animals (experimental group) and the same volume of culture media in 6 animals (control group). Blood samples were collected at 24 hours (n=9) or 4 months (n=9) to assess toxicity, and eight organs were harvested for histology studies. Genomic DNA was isolated from all tissues, and mouse GAPDH and human β2M and β-actin genes were amplified by qPCR to analyze hBMMSCs biodistribution. Results: There were no deaths or acute or chronic toxicity. Hematology, biochemistry and body weight were in the range of normal values in all groups. At 24 hours hBM-MSCs were detected in 4/6 spinal cords and 1/6 hearts, and at 4 months in 3/6 hearts and 1/6 brains of transplanted mice. No tumours were found. Conclusion: This study demonstrated that intrathecal injection of hBM-MSCs is safe, non-toxic and do not produce tumors. These results provide further evidence that hBM-MSCs might be used in a clinical trial in patients with FRDA.