Tissue engineered allograft total disc transplantation using exogenous nucleus pulposus cells: an experimental study in a beagle model

English Keywords:Intervertebral disc degeneration  Intervertebral disc transplantation  Human telomerase reverse transcriptase  Viral transfection  Nucleus Pulposus cells  Beagle dogs

English Abstract:

  【Abstract】 Objectives: To investigate in vivo rehepitation of the transplanted tissue engineered allograft total disc and to explore the biological effect of nucleus pulposus(NP) cells or hTERT gene transfected NP cells on allograft total disc transplantation. Methods: Eighteen canine lumbar intervertebral discs were obtained from 5 canines and cryopreserved in liquid nitrogen. Canine nucleus pulposus cells were isolated and transduced with rAAV-hTERT. The cells were injected into the discs to construct a "tissue-engineered" allograft disc(group A). NP cells and DMEM/F12 were used for positive control(group B) and blank control(group C) respectively. 18 beagle dogs received the 3 groups of allograft IVD composites implantation respectively. Radiographic examination was performed at 4, 8 and 12 weeks after implantation. At 12 weeks after operation, all dogs were sacrificed and the lumbar spines were harvested for the biomechanical test and histological analysis, ectogenic NP cell tracing and hTERT mRNA analysis. Results: Bony fusion between intervertebral disc allograft and adjacent host intervertebral body was observed in all animals. The disc height and T2 signal intensity preservation in group A and B were better than group C. MRI showed typical degenerative changes in group C. In group A, the normalized grayscale of the transplanted disc in MRI image was significant higher than that of the controls at 12 weeks. Biomechanical test showed a poor stability preservation in group C compared with group A and B. PKH-26 positive cells were identified within the allograft discs in group A at 12 weeks, which provided matrix for cell survival. Histological analysis showed the NP cell morphology, cell number and distribution of the allograft discs were better preserved in group A and B than group C at 12 weeks of follow-up. Conclusions: NP cells or hTERT loaded NP cells intervention can effectively resist the degeneration of the allogenic transplanted intervertebral discs in beagle model. The hTERT loaded NP cells show better anti-degeneration effect than NP cells. This modified disc regeneration technique through NP cell injection may preserve the disc function better, which can ensure the long-term outcome of allograft disc transplantation.