[Repair of spinal cord injury with rats' umbilical cord MSCs]

To study the growth characteristics of umbilical cord MSCs (UCMSCs) in vitro and its effect on the nerve regeneration after spinal cord injury (SCI).

UCMSCs isolated from pregnant rats umbilical cord were cultured and purified in vitro. Sixty female Wistar rats weighing (300 +/- 10) g were randomized into three groups (n=20 per group). UCMSCs group (group A) in which UCMSCs suspension injection was conducted; DMEM control group (group B) in which 10% DMEM injection was conducted; sham group (group C) in which the animal received laminectomy only. Establish acute SCI model (T10) by Impactor model-II device in group A and group B. The recovery of the lower extremity was observed using BBB locomotor scoring system, neurofilament 200 (NF-200) immunofluorescence staining was performed to detect the neural regeneration, and then the corticospinal tract (CST) was observed using the biotinylated dextran amine (BDA) tracing.

Cultured UCMSCs were spindle-shaped fibrocyte-like adherent growth, swirling or parallelly. The USMSCs expressed CD29, but not CD31, CD45, and HLA-DR. The BBB score was higher in group A than group B 4, 5, and 6 weeks after operation, and there was a significant difference between two groups (P < 0.05). The BBB scores at different time points were significantly lower in groups A and B than that in group C (P < 0.05). UCMSCs was proved to survive and assemble around the injured place by frozen section of the cords 6 weeks after injury. NF-200 positive response area in groups A, B, and C was (11,943 +/- 856), (7,986 +/- 627), and (13,117 +/- 945) pixels, respectively, suggesting there was a significant difference between groups A, C and group B (P < 0.05), and no significant difference was evident between group A and group C (P > 0.05). BDA anterograde tracing 10 weeks after operation demonstrated that more regenerated nerve fibers went through injured area in group A, but just quite few nerve fibers in group B went through the injuried cavity. The ratios of regenerative axons amount to T5 axons in group A and group B were smaller than that of group C (P < 0.05).

UCMSCs can proliferate rapidly in vitro, survive and differentiate to neurons after being grafted into injured spinal cord. The transplantation of UCMSCs is effective in promoting functional recovery and axonal regeneration after SCI.