['The objective of this systematic review was to assess cell/biomaterial treatments of degenerative disc disease in controlled animal trails. The primary endpoints were restoration of disc height and T2 signal intensity.', "PubMed, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), and Cochrane Database of Systematic Reviews (CDSR) were searched for studies reporting on the use of tissue engineering treatments (cells/biomaterials/cells and biomaterials) for degenerative disc disease treatments in a controlled trial. Publication bias was assessed graphically using funnel plots and Egger's regression. Data were grouped by follow-up duration - early (<4 weeks), intermediate (4-12 weeks) and late (>12 weeks), and weighted mean differences (WMD) were calculated using DerSimonian-Laird Random Effect models.", 'Thirteen papers, published between 2004 and 2011, were included in this study. In comparison with the injured disc, all three treatments showed a positive effect in disc height, but none of the treatments restored disc height compared to the healthy disc. Overall, there seemed to be a better effect on disc height restoration for the treatment with cells and biomaterials. None of the treatments could achieve the same T2 signal intensity as the healthy disc, and compared to the injured disc, only the treatment with cells and biomaterials showed consistently better results.'] Does tissue engineering approach to degenerative disc disease -- a meta-analysis of controlled animal trials?