The effect of Wharton′s jelly-derived mesenchymal stem cells in a xenograft canine model for intervertebral disc degeneration

English Keywords:Wharton′s jelly-derived mesenchymal stem cells  Cell transplantation  Intervertebral disc degeneration  Animal experiment

English Abstract:

  【Abstract】 Objectives: To assess the effect of human umbilical cord Wharton′s jelly-derived mesenchymal stem cells(WJMSCs) in a xenograft canine model for intervertebral disc degeneration. Methods: WJMSCs were isolated from human umbilical cords and labeled with rAAV2-EGFP. Twenty healthy adult Beagle dogs were used for animal experiment. Degenerative models were established in L4/5, L5/6, L6/7 intervertebral discs by aspiration of the nucleus pulposus. For each canine, L4/5 was used as degenerative segments(group B), L5/6 was injected with 0.9% saline 4 weeks after first operation(group C), L6/7 was injected with EGFP-labbled WJMSCs 4 weeks after first operation(group D), and the intact disc L3/4 served as an un-injured control (group A). The animals were followed up for 24 weeks after the initial operation. Spinal image was evaluated at 0, 4, 8, 12 and 24 weeks after operation respectively. Histologic analyses were performed at 24 weeks. Gene expression analysis for aggrecan, type Ⅱ collagen, SOX-9 and type Ⅰ collagen was performed. Results: The WJMSCs in vitro were adherent growth and exhibited fibroblast-like morphology. GFP expression was confirmed using fluorescence microscope 3 days after rAAV2-EGFP infection. Disc height and T2-weighted signal intensity were higher in group D than group B and C at 8, 12 and 24 weeks(P<0.05), and didn′t show significantly changes in all groups at 0 and 4 weeks. GFP-positive WJMSCs were detected in the nucleus pulposus of the canine in group D 24 weeks after first operation. Histological assay showed better preserved in group D as compared to the operated degenerated control discs(group B and C). Safranin O staining showed higher aggrecan content in group D. Disc regeneration was also confirmed at the gene expression level by using real-time polymerase chain reaction. The relative gene expressions of matrix-related genes(aggrecan and type Ⅱ collagens) were significantly increased in group D when compared to those of group B and group C(P<0.05). Conclusions: The transplanted WJMSCs can survive in the disc of canine. The increased amount of aggrecan and type Ⅱ collagen in the nucleus pulposus suggests that WJMSCs may serve as a new valuable resource in cell transplantation therapy for degenerative disc disease.