Direct Cartilage Repair Using 3D Bioprinting Technology

INTRODUCTION: Articular cartilage is commonly injured and current tissue engineering strategies cannot as yet fabricate new tissue that is indistinguishable from native cartilage with respect to zonal organization, ECM composition, and mechanical properties. Almost all current strategies of cartilage repair involve a procedure of removing healthy cartilage tissue around the lesion to create artificial defects for further treatment or implantation. This procedure in fact causes additional necrosis to the existing cartilage and it is believed to lead to ultimate cartilage degeneration and failure of implanted tissue. Direct cartilage repair with engineered tissue closely mimicking native cartilage to the lesion site without any additional damages to the existing healthy tissue is therefore very attractive. The ideal implanted tissue is expected to integrate with existing native cartilage and to repair lesions of different sizes and thicknesses. The multifaceted nature of this challenge requires a technique adaptable to variable physical dimensions and properties for tissue repair; we believe that bioprinting, based on inkjet printing technology, provides the necessary capabilities. Inkjet printing is a non-contact printing technique that reproduces digital pattern onto a substrate with tiny ink drops. Functional human microvasculature was successfully bioprinted with an average cell viability of 90%. We reasoned that a cell-based approach using a matrix that could be polymerized in place might provide a way to generate a mechanically strong system with mechanical properties matched to native tissue, and this would be advantageous for direct cartilage repair. We describe here the first successful realization of this approach.