Scaffolds Derived from ECM Produced by Chondrogenically Induced Human MSC Condensates Support Human MSC Chondrogenesis

Osteoarthritis is a leading cause of disability affecting an increasing number of individuals. However, cartilage replacement therapies are inadequate, and better cartilage regeneration products must be developed. In this work, we describe a human mesenchymal stem cell (hMSC)-based approach for fabricating extracellular matrix (ECM) scaffolds from tissue-engineered cartilage sheets and then for inducing chondrogenesis of reseeded hMSCs within the ECM scaffolds. Two types of ECM scaffolds were fabricated: one from high-density hMSC sheets cultured with media-supplemented transforming growth factor beta-1 (TGF-β1; -MS) and the other from high-density hMSC sheets incorporated with TGF-β1-laden gelatin microspheres (+MS), which significantly enhance chondrogenesis within the sheet system. Interestingly, when scaffolds were reseeded with hMSCs, -MS scaffolds lead to significantly more glycosaminoglycan (GAG) accumulation than +MS scaffolds. Importantly, ECM scaffolds could be soak loaded with TGF-β1 to produce cartilage of similar quality as that of constructs cultured with TGF-β1 in the media, thereby removing the need for supplementing the media with the growth factor. Lastly, tissues formed with the scaffolds were larger with more uniform cartilage matrix elaboration compared to scaffold-free groups making this strategy a clinically promising auto- or allogeneic therapy.