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.
Bone Marrow Cells Cell Communication