Co-culture of infrapatellar fat pad-derived mesenchymal stromal cells and articular chondrocytes in plasma clot for cartilage tissue engineering

Background. Cell source plays a deterministic role in defining the outcome of a cell-based cartilage regenerative therapy and its clinical translational ability. Recent efforts in the direction of co-culture of two or more cell types attempt to combine the advantages of constituent cell types and negate their demerits. Methods. We examined the potential of co-culture of infrapatellar fat pad derived mesenchymal stromal cells (IFP MS Cs) and articular chondrocytes (ACs) in plasma clots in terms of their ratios and culture formats for cartilage tissue engineering. Results and discussion. It was observed that IFP MSCs and ACs interact positively to produce a better quality hyaline cartilage-like matrix. While a supra-additive deposition of sulfated Glycosaminoglycans (sGAG), collagen type II, aggrecan and link protein was observed, deposition of collagen type I and X was sub-additive. (Immuno)-histologically similar cartilage was generated in vitro in IFP MSC:AC ratio of 50:50 and pure AC groups thus yielding a hyaline cartilage with 50% reduced requirement of ACs. Subsequently, we investigated if this response could be improved further by enabling better cell-cell interactions using scaffold-free systems such as self-assembled cartilage or by encapsulating cellular micro-aggregates in plasma clot. However, it was inferred that while self-assembly may have enabled better cell-cell interaction, poor cell survival negated its overall beneficial role, whereas the micro-aggregate group demonstrated highly heterogeneous matrix deposition within the construct, thus diminishing its translational utility. Overall, it was concluded that co-culture of IFP MSCs and ACs at a ratio of 50:50 within plasma clots demonstrated potential for cell-based cartilage regenerative therapy.