Intervertebral disc regeneration. Studies on stem cell niches and cell transplantation

Abstract: Abstract Intervertebral disc regeneration Studies on stem cell niches and cell transplantation Helena Barreto Henriksson Gothenburg 2010 Low back pain is a common condition in the Western world and disc degeneration (DD) is considered a major cause. DD is characterized by dysfunctional cells and decreased matrix production. The aim of this thesis was to explore normal growth and regeneration in the intervertebral disc (IVD). Further, to test possibilities of cell therapy treatment for D... merDs. The methods used include in vitro- and in vivo experiments. In vitro methods were: monolayer, 3D cell cultures and explants models with human mesenchymal stem cells (hMSCs), articular chondrocytes and IVD cells. Cells/ tissues were analyzed for cell proliferation markers; BrdU, KI67, migration markers: β1-INTEGRIN, SNAIL-homolog-1 (SNAI1), SNAIL-homolog-2 (SLUG), progenitor/stem cell markers: STRO1, C-KIT, Notch1, CD105 and chondrogenic lineage markers: GDF5 and SOX9, matrix markers: COLLAGEN I and II, glycosaminoglycans, AGGRECAN by biochemical methods, flowcytometry, Real-time PCR and microscopy. Disc appearance was evaluated with MRI. Results from normal regeneration studies: a potential stem cell niche was identified in the IVD region lateral to the epihyseal plate and in the annulus fibrosus outer region, based on findings of label-retaining cells and presence of cells expressing stem cell/progenitor markers, in young and mature animals. Migrating cells expressing SNAI1, SLUG, β1-integrin and GDF5 and SOX9 around niches were observed. Results from the cell therapy experiments; In vitro analyses; 3D co-culture system of hMSC and IVD cells showed an increased COLLAGEN II production. In vivo: Xenotransplanted cells survived in vivo 6 months (porcine IVDs) and produced matrix in hydrogel/MSCs injected IVDs. Taken together, these findings illustrate a normal slow regeneration of the IVD, and that growth and regeneration is presumably supported by progenitor cells deriving from niches adjacent to the IVD. Further, that human IVD cells and MSCs interact positively on matrix production when co-cultured and the survival of transplanted cells in vivo support the possibility for cell therapy treatment of DD. These results encourage further studies to arrest IVD degeneration, by stimulation of regenerative mechanisms in situ or by cell therapy.