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[Cultivation, screening, identification and transplantation of Muse cell from human umbilical cord-derived for spinal cord injury in rats].

OBJECTIVE
To investigate multilineage-differentiating stress-enduring (Muse) by immunomagnetic bead screening from Wharton's jelly mesenchymal stromal cells(WJ-MSCs), and explore transplantation of Muse cell for safety and effectivensess of sub acute cord injury in rats.


METHODS
Donated Wharton's Jelly-mesenchymal stromal cells (WJ-MSCs) were successfully derived from a human umbilical cord by a series of procedures namely physical isolation of Wharton's Jelly from cord membrane, collagenase and trypsin treatment and density gradient centrifugation. Magnetic activated cell sorting was performed to specifically select SSEA3+ Muse cells, and flow cytometry and immunocytochemistry were used to identify further. In vivo, spinal cord contusion injury model in rats was induced by NYU-III impactor, and were randomly divided and equally into four groups, namely group A (sham), group B (control), group C (Non-Muse cells transplantation) and group D (Muse cells transplantation). Laminectomy was conducted in group A but no spinal cord contusion injury. Laminectomy and cord injury were performed in group B, C and D, 10 g trip rod was freely falling down from 12.5 mm. Two weeks later, group B, C and D were received PBS injection, Non-Muse cells transplantation and Muse cells transplantation respectively, four-point injection were performed in each cord with totally 4×10⁵ cells. BBB scores were evaluated on 1 day, 1, 2, 3, 4, 5 and 6 week after injury. Four weeks after cell transplantation, the rats were sacrificed, and immunohistochemistry were carried out to observe survival, migration and differentiation of the injected cells.


RESULTS
The expression of CD105, CD90 and CD73 were over 99.5% in the derived WJ-MSCs population, but CD45 and CD14 were lower than 0.5%, positive rate of SSEA3+ was 1.46% under flow cytometer, However, after MACS sorting, the percentage of 92.0% Muse cells expressed SSEA3 and CD105, and immunohistochemistry results of SSEA3 showed typically membrane morphology with special processes. In vivo, BBB scores was 21 in group A at different time points. One-way ANOVA and LSD analysis showed that BBB scores in group C and D were significantly higher than that in group B (P=0.004, 0.002), but there was no significantly difference between group C and D. Further intra-group paired t test showed that BBB score was significantly higher at 4 weeks than that 3 weeks in group C (P=0.005). However, in group D, BBB scores were significantly higher at 4 and 6 week than those at 3 and 5 weeks, P values were 0.005 and 0.016 respectively. Immunohistochemistry results showed that both Muse cells and Non-Muse cells could survive for 4 weeks in rats and they migrated from the four-point injection to injury site. But there showed more Muse cells survival than Non-Muse cells in the cord.


CONCLUSIONS
Immunomagnetic bead screening is efficient to select large number of purified SSEA3+ Muse cells. Muse cells could survive and target-migrate in injured cord to improve BBB scores continuously. Muse cells are a novel kind of seed cells in the spinal cord injury treatment.