Migration of Mesenchymal Stem Cells Through Cerebrospinal Fluid into Injured Spinal Cord Tissue

Study Design: Experimental spinal cord injury using a rat model.

Objective: To investigate the potential for survival and migration of transplanted mesenchymal stem cells through the subarachnoid space into injured thoracic spinal cord tissue following injection into the more caudal lumbar spine.

Methods: A total of 70 adult Lewis rats were used with 64 having a partial and complete thoracic spinal cord injury (SCI) performed by the weight drop method at T9-T10 using the NYU Impactor. Six rats received only laminectomy for sham control. Mesenchymal stem cells (MSCs) were harvested from the femur of these rats and labeled by transduction of ANOVA virus containing green fluorescent protein (GFP) gene (Adv-GFP). At day 3, 5, and 7 after thoracic SCI, the rats received an injection into the subarachnoid space. The injections including: GFP-MSC, B-Gal-MSC, and PBS only. Injured rat spinal cords where harvested at day 7, 14, or 28, prepared for frozen sectioning, staining, and immunostaining.

Results: Adv-GFP transduced MSCs demonstrated strong green fluorescence both in the nucleus and in the cell body. Green fluorescent cells proven to be genuine GFP-positive cells were observed on the surface of the injured spinal cord parenchyma. The rate of the GFP-positive cells gathered into the central lesion within 10 mm was significantly higher than sham control. Also, GFP-positive cells were observed in the deeper area of the perivascular spaces, and some of them had integrated into the parenchyma. Immunostaining against Nestin demonstrated that some GFP-positive cells differentiated into neural stem cells and mature neurons or glial cells.

Conclusions: Transplanted MSCs injected into the subarachnoid space of the lumbar spine can migrate to injured thoracic spinal cord tissue. The ratio of MSCs observed at the injury site was significantly higher than in the intact spinal cord, and also infiltrated into the deeper spinal cord parenchyma by the perivascular spaces. Lastly, some MSCs differentiated into Nestin-positive, immature neurons or glial cells.