The direction of human mesenchymal stem cells into the chondrogenic lineage is influenced by the features of hydrogel carriers.

Low back pain is a major public health issue in the Western world, one main cause is believed to be intervertebral disc (IVD) degeneration. To halt/diminish IVD degeneration, cell therapy using different biomaterials e.g. hydrogels as cell carriers has been suggested. In this study, two different hydrogels were examined (in vitro) as potential cell carriers for human mesenchymal stem cells (hMSCs) intended for IVD transplantation. The aim was to investigate cell-survival and chondrogenic differentiation of hMSCs when cultured in hydrogels Puramatrix® or Hydromatrix® and potential effects of stimulation with growth hormone (GH). hMSCs/hydrogel cultures were investigated for cell-viability, attachment, gene expression of chondrogenic markers SOX9, COL2A1, ACAN and accumulation of extracellular matrix (ECM). In both hydrogel types, hMSCs were viable for 28days, expressed integrin ß1 which indicates adhesion of hMSCs. Differentiation was observed into chondrocyte-like cells, in a higher extent in hMSCs/Hydromatrix® cultures when compared to hMSCs/Puramatrix® hydrogel cultures. Gene expression analyses of chondrogenic markers verified results. hMSCs/hydrogel cultures stimulated with GH displayed no significant effects on chondrogenesis. In conclusion, both hydrogels, especially Hydromatrix® was demonstrated as a promising cell carrier in vitro for hMSCs, when directed into chondrogenesis. This knowledge could be useful in biological approaches for regeneration of degenerated human IVDs.

Indications of that migration of stem cells is influenced by the extra cellular matrix architecture in the mammalian intervertebral disk region.

Disk-degeneration is believed a major cause for lumbar pain. Previously, potential stem cell niches in the intervertebral disk (IVD) region, located adjacent to epiphyseal plate, was reported. The aim of the study was to examine migration of mesenchymal stem cells (MSCs), extracellular matrix (ECM) architecture in a potential cellular migration route (CMR; area located between the niche and IVD) and in the IVD in non-degenerated lapine- and in human degenerated IVD tissues. Human MSCs (n=3), human degenerated IVD tissues (n=10) and lapine IVDs (n=10) were collected. The samples were examined by immunohistochemistry for stem cell markers; CD90, OCT3/4, pre-chondrocytic marker; GDF5, catabolic markers; MMP9, MMP13, inflammatory marker; IL1R, cellular migration markers; SNAI1, SNAI2, adhesion markers; ß1-INTEGRIN and DDR2. In addition, gene-expression analyses (Real time PCR) were performed on additional samples. Further, time lapse studies were performed with hMSCs cultured on aligned COLL-I-fibers-coated glass-slides in DMEM-LG, 10% human serum containing fibroblast growth factor (bFGF). Presence of stem cells (CD90+, OCT3/4+), pre-chondocytic cells (GDF5+) and cells positive for migration markers (SNAI1+, SNAI2+), catabolic markers (MMP9+, MMP13+), inflammatory marker (IL1R+), adhesion markers (DDR2+, B1-INTEGRIN+) were detected (gene- and protein level) in investigated CMR and IVD regions. In the time lapse studies, MSCs alignment and protrusions were observed orientated in the same direction as collagen fibers. Results display influence of ECM collagen architecture and collagen fiber spatial direction on migration of stem cells. The results can be useful when developing tissue-engineering strategies for disk-degeneration.

Human disk cells from degenerated disks and mesenchymal stem cells in co-culture result in increased matrix production.

Transplantation of mesenchymal stem cells (MSCs) has been suggested for disk degeneration, which is characterized by dysfunctional cells and low proteoglycan production. The aim of this study was to examine the effects of a 3D co-culture system using human disk cells (DCs) and MSCs on collagen and proteoglycan production. DCs and MSCs were expanded in monolayer and grown in pellet cultures for 7, 14 and 28 days and analyzed for hydroxyproline (HP), reflecting total collagen production, and glycosaminoglycan (GAG) accumulation. DCs and MSCs co-cultured at different ratios (25/75, 50/50 and 75%/25%) were examined for GAG accumulation. Collagen type II expression was analyzed immunohistochemically. In a second series, conditioned media were added to pellet cultures of degenerated DCs or MSCs. DCs from degenerated disks and MSCs demonstrated lower total collagen production than non-degenerated DC pellets. GAG production was comparable in DCs and MSCs, except in the youngest donor, with MSC producing about 10 times higher GAG/DNA. Co-cultures resulted in approximately 1.5 times higher GAG/DNA production than DCs. Increased collagen type II expression was seen in co-cultures compared to DC or MSC culture alone, except in the case with highly active MSCs. No positive effect of conditioned media was seen. In conclusion, co-culture of MSCs with degenerated DCs increased proteoglycan and collagen-type ceII production, indicating that in future clinical therapy MSCs can be transplanted without pre-differentiation in vitro. The lack of effect of conditioned media suggests that the positive effect of co-culture on matrix production is not due to soluble factors.