Bioprinting Cartilage Scaffolds

Knee replacement is common and joint degeneration occurs when cartilage deteriorates. However, donor cartilage and synthetic alternatives are scarce. Lee et al . created poly-e-caprolactone (PCL) scaffolds by three-dimensionally (3D) printing using anatomically correct dimensions of the meniscus and then loading the PCL scaffolds at specific locations with polymeric microspheres containing one of two growth factors, which were released sequentially. Connective tissue growth factor (CTGF) was released first, followed by transforming growth factor–β3 (TGF-β3). Sequential exposure of mesenchymal stem cells (MSCs) in culture to these two growth factors stimulated their differentiation into fibrochondrocytes cells that produced procollagens. When the growth factor–embedded scaffolds were placed over human MSCs in culture, the scaffolds induced zone-specific matrix development: Type I collagen was produced in the outer zone and type II collagen in the inner zone, similar to the distribution in the native meniscus. Implantation of the PCL scaffolds in sheep with partial meniscectomy, designed on the basis of the sheep meniscus anatomy, either embedded with the growth factors or lacking the growth factors resulted in tissue regeneration with the desired mechanical properties only when the PCL scaffolds containing the growth factors were used. This study suggested that this acellular biomaterial combined with 3D printing and embedded with the appropriate growth factors could provide a mechanism for repairing deteriorated cartilage in not only the knees, but also tendon-bone junctions, the intervertebral discs of the spine, and the temporomandibular joint. C. H. Lee, S. A. Rodeo, L. A. Fortier, C. Lu, C. Erisken, J. J. Mao, Protein-releasing polymeric scaffolds induce fibrochondrocytic differentiation of endogenous cells for knee meniscus regeneration in sheep.  Sci. Transl. Med . 6 , 266ra171 (2014). [Abstract]