Bioreactor based engineering of large-scale human cartilage grafts for joint resurfacing.

Apart from partial or total joint replacement, no surgical procedure is currently available to treat large and deep cartilage defects associated with advanced diseases such as osteoarthritis. In this work, we developed a perfusion bioreactor system to engineer human cartilage grafts in a size with clinical relevance for unicompartmental resurfacing of human knee joints (50 mm diameter × 3 mm thick). Computational fluid dynamics models were developed to optimize the flow profile when designing the perfusion chamber. Using the developed system, human chondrocytes could be seeded throughout large 50 mm diameter scaffolds with a uniform distribution. Following two weeks culture, tissues grown in the bioreactor were viable and homogeneously cartilaginous, with biomechanical properties approaching those of native cartilage. In contrast, tissues generated by conventional manual production procedures were highly inhomogeneous and contained large necrotic regions. The unprecedented engineering of human cartilage tissues in this large-scale opens the practical perspective of grafting functional biological substitutes for the clinical treatment for extensive cartilage defects, possibly in combination with surgical or pharmacological therapies to support durability of the implant. Ongoing efforts are aimed at integrating the up-scaled bioreactor based processes within a fully automated and closed manufacturing system for safe, standardized, and GMP compliant production of large-scale cartilage grafts.

The use of flow perfusion culture and subcutaneous implantation with fibroblast-seeded PLLA-collagen 3D scaffolds for abdominal wall repair.

Highly cellularised 3D-tissue constructs designed to repair large, complex abdominal wall defects were prepared using poly (lactic acid) (PLLA)-collagen scaffolds in vitro using a flow perfusion bioreactor. The PLLA-collagen scaffolds had a unique structure consisting of a collagen sponge formed within the pores of a mechanically stable knitted mesh of PLLA. The effect of the flow perfusion bioreactor culturing conditions was investigated in vitro for 0, 7, 14 and 28 days on scaffolds seeded with dermal fibroblasts. The cultured constructs were subsequently studied subcutaneously (SC) in an in vivo animal model. The results of in vitro studies demonstrated that the perfusion system facilitated increased cell proliferation and homogenous distribution in the PLLA-collagen scaffolds compared to static conditions. A highly cellularised 3D-tissue construct was formed by 7 days incubation under perfusion conditions, with increased cellularity by the 28 day time point. The in vivo model demonstrated that implanting constructs with high cellularity resulted in exceptional cell stabilisation, with the survival of implanted cells and expression of the phenotypically-relevant extracellular matrix proteins collagen types I and III, studied by fluorescence in situ hybridisation (FISH) and immunohistochemistry. The implantation of this porous PPLA-collagen scaffold seeded with dermal fibroblasts following in vitro maturation using a flow perfusion bioreactor system suggests a significant advance over current state-of-the-art procedures for the reconstruction of large, complex abdominal wall tissue defects.