Effect of the mixture of bone marrow mesenchymal stromal cells and annulus fibrosus cells in repairing the degenerative discs of rabbits.

Abstract

The aims of this study were to investigate the effect of a mixture of bone marrow mesenchymal stem cells (BMSCs) and annulus fibrosus cells (AFCs) in repairing the degenerative discs of rabbits, and to provide an experimental basis for its clinical application. BMSCs from rabbits were cultured in vitro and mixed with AFCs. The animal model of degenerative intervertebral disc was built by aspirating the nucleus pulposus (L3-4, L4-5, L5-6, and L6-7) through a posterolateral approach. Mixtures of BMSCs and AFCs (group A), BMSCs alone (B), or saline (C) were injected into test discs, and changes evaluated by plain radiographs, magnetic resonance imaging, and histology. After two weeks, each group showed typical internal disc disruption; stenosis of the intervertebral space, weakening T2 disc signal, decreased disc height and expression of type II collagen and glycosaminoglycan, and fibrosis of the nucleus pulposus. After cell transplantation, the disc heights in groups A and B were regained; however, they continued to decrease in group C. The transplanted cells survived in the discs, proliferated after transplantation, and produced copious matrix. Macroscopic and histological evaluations confirmed structural and nuclear preservation in cell-transplanted discs. The secretions and expressions of Type Ⅱ collagen and glycosaminoglycan in group A were statistically significant higher than those in group B (Type Ⅱ collagen, group A 141.6 ± 5.87, group B 139.8 ± 8.65, P = 0.004; glycosaminoglycan, group A 3.008 ± 0.35, group B 2.94 ± 0.29, P = 0.003). Expression of type II collagen and glycosaminoglycan was significantly greater in group A than group B. Therefore, co-transplantation of BMSCs and AFCs can restore the extracellular matrix, making this approach superior to transplantation of BMSCs alone, which may be beneficial for the therapy of intervertebral disc degeneration.