Percutaneous Transplantation Of Nucleus Pulposus Cells Cultured In Vitro To The Intervertebral Discs: A Potential Therapeutic Strategy For Disc Degeneration

Background: Intervertebral disc degeneration is one of the major causes of low back pain, to which there has no cure so far. Investagations on to biologically repair degenerated intervertebral disc have achieved significant progress recently. Since the disc cell's proliferative ability is poor when cultured in vitro, to establish an appropriate culture technique is still a keystone for current researches.Objectives: Nucleus pulpous (NP) cells isolated from New Zealand rabbits were cultured in monolayer and simple three-dimensional culture system respectively to assess their ability to maintain morphology and to synthesize proteoglycan. And to evaluate the potential of the percutaneous transplantation of the nucleus pulpous cells cultured in vitro to retard the intervertebral disc degeneration. Methods: Nucleus pulposus cells were isolated from New Zealand rabbits by Trypsin plus collagenase â…£ digestion. Some of the isolated rabbits' nucleus pulposus cells were cultured in monolayers, the rest were centrifuged at low speeds to aggregate and allowed to form pellets in 15ml polypropylene conical tubes. At different culturing time, the intakes of [35S]sulfate, reflecting the ability of synthesizing proteolycan in cells cultured under either condition, was assessed, meanwhile the cells were analyzed histologically. Based on the results of above, the cells having a higher intake rate of [35S]sulfate were percutaneously transplanted to the rabbits' L2/L3, L3/L4 and L4/L5 intervertebral discs of whose nucleus pulposus were previously removed, while those were injected with the culture medium were allocated into sham group. MRI scanning and histological examination (as for disc degeneration, Nishimura grading system was adopted) were carried out on 14th day after transplantation to evaluate these discs. Results: The morphology kept stable and the intake of 35S increased in the cells cultured either in monolayers or in pellets. However, the intake rate of 35S was higher in those cultured in pellets than in monolayers(P<0.05). MRI scanning and histologically examining suggested that intervertebral discs degenerated more severely in the rabbits underging nucleus pulposus aspiration than in those only punctured. Transplantation of NP cells could retard intervertebral discs to degenerate further after NP aspiration.Conclusions: The ability of the NP cells to synthesize proteoglycan is higher when cultured in three-dimensional pellets than in monolayers. Percutaneous aspiration of the NP can induce the degeneration of the rabbits' intervertebral discs, while transplantation of NP cells can retard these discs to degenerate further.