Intervertebral disc cell- and hydrogel-supported and spontaneous intervertebral disc repair in nucleotomized sheep

PURPOSE: Regenerative repair is a promising new approach in treating damaged intervertebral discs. An experimental scheme was established for autologous and/or allogenic repair after massive disc injury. METHODS: Disc healing was promoted in 11 animals by injecting in vitro expanded autologous/homologous disc cells 2 weeks after stab injury of lumbar discs L1-2. The following control discs were used in our sheep injury model: L2-3, vehicle only; L3-4, injury only; L4-5, undamaged; and lumbar discs from four non-experimental animals. Disc cells were suspended in a biologically supportive albumin/hyaluronan two-component hydrogel solution that polymerizes when inserted in order to anchor cells at the injection site. The parameters studied were MRI, DNA, glycosaminoglycan, collagen content, histology, immunohistology for collagens type I, II and aggrecan, and mRNA expression of GAPDH, β-actin, collagen type I, II, X, aggrecan, lubricin, and IL-1β. RESULTS: All parameters demonstrated almost complete healing of the injured discs after 6 months, when compared with data from both the endogenous non-injured controls as well as from the healthy animals. CONCLUSION: Sheep experience spontaneous recovery from disc injury. The process of endogenous repair can be enhanced by means of hydrogel-supported cells.