Despite Imatinib (IM), a selective inhibitor of Bcr-Abl, having led to improved prognosis in Chronic Myeloid Leukemia (CML) patients, acquired resistance and long-term adverse effects is still being encountered. There is, therefore, urgent need to develop alternative strategies to overcome drug resistance.

Although historically, the traditional bidimensional in vitro cell system has been widely used in research, providing much fundamental information regarding cellular functions and signaling pathways as well as nuclear activities, the simplicity of this system does not fully reflect the heterogeneity and complexity of the in vivo systems. From this arises the need to use animals for experimental research and in vivo testing. Nevertheless, animal use in experimentation presents various aspects of complexity, such as ethical issues, which led Russell and Burch in 1959 to formulate the 3R (Replacement, Reduction, and Refinement) principle, underlying the urgent need to introduce non-animal-based methods in research. Considering this, three-dimensional (3D) models emerged in the scientific community as a bridge between in vitro and in vivo models, allowing for the achievement of cell differentiation and complexity while avoiding the use of animals in experimental research. The purpose of this review is to provide a general overview of the most common methods to establish 3D cell culture and to discuss their promising applications. Three-dimensional cell cultures have been employed as models to study both organ physiology and diseases; moreover, they represent a valuable tool for studying many aspects of cancer. Finally, the possibility of using 3D models for drug screening and regenerative medicine paves the way for the development of new therapeutic opportunities for many diseases.

The objective of this article was to investigate the safety and regenerative potential of a newly developed biomimetic scaffold when applied to osteochondral defects in an animal model. A new multilayer gradient nano‐composite scaffold was obtained by nucleating collagen fibrils with hydroxyapatite nanoparticles. In the femoral condyles of 12 sheep, 24 osteochondral lesions were created. Animals were randomized into three treatment groups: scaffold alone, scaffold colonized in vitro with autologous chondrocytes and empty defects. Six months after surgery, the animals were sacrificed and the lesions were histologically evaluated. Histologic and gross evaluation of specimens showed good integration of the chondral surface in all groups except for the control group. Significantly better bone regeneration was observed both in the group receiving the scaffold alone and in the group with scaffold loaded with autologous chondrocytes. No difference in cartilage surface reconstruction and osteochondral defect filling was noted between cell‐seeded and cell‐free groups. In the control group, no bone or cartilage defect healing occurred, and the defects were filled with fibrous tissue. Quantitative macroscopic and histological score evaluations confirmed the qualitative trends observed. The results of the present study showed that this novel osteochondral scaffold is safe and easy to use, and may represent a suitable matrix to direct and coordinate the process of bone and hyaline‐like cartilage regeneration. The comparable regeneration process observed with or without autologous chondrocytes suggests that the main mode of action of the scaffold is based on the recruitment of local cells. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:116–124, 2010