Influence on Chondrogenesis of Human Osteoarthritic Chondrocytes in Co-Culture with Donor-Matched Mesenchymal Stem Cells from Infrapatellar Fat Pad and Subcutaneous Adipose Tissue

Co-culture of mesenchymal stem cells (MSCs) and articular chondrocytes (ACs) has been proposed for autologous cartilage cell-based therapies, to overcome the issues associated to limited availability of articular chondrocytes (ACs). To evaluate the potentiality of a co-culture approach in aged osteoarthritic patients, MSCs from infrapatellar fat pad (IFP-MSCs) and knee subcutaneous adipose tissue (ASCs) were co-cultured with donor-matched osteoarthritic, expanded and cryopreserved, ACs in a 75%/25% ratio. Co-cultures were prepared also from nasal chondrocytes (NCs) to evaluate their possible use as an alternative to ACs. Pellets were differentiated for 14 days, using mono-cultures of each cell type as reference. Chondrogenic genes SOX9, COL2A1, ACAN were less expressed in co-cultures compared to ACs and NCs. Total GAGs content in co-cultures did not differ significantly from values predicted as the sum of each cell type contribution corrected for the co-culture ratio, as confirmed by histology. No significant differences were observed for GAGs/DNA in mono-cultures, demonstrating a reduced chondrogenic potential of ACs and NCs. In conclusion, a small percentage of expanded and cryopreserved ACs and NCs did not lead to IFP-MSCs and ASCs chondro-induction. Our results suggest that chondrogenic potential and origin of chondrocytes may play a relevant role in the outcome of co-cultures, indicating a need for further investigations to demonstrate their clinical relevance in the treatment of aged osteoarthritic patients.