Bone and Cartilage from Stem Cells: Growth Optimalization and Stabilization of Cell Phenotypes

Engineered cells replacing tissues should mimic the three-dimensional (3D) structure and reflect the different cell phenotypes exhibited by the lost or damaged tissue (Raimondi 2006; Keung, Healy et al. 2010). The engineered cells should also demonstrate a certain plasticity, i.e. an ability to adapt to the environment, in which they are deposited, reflecting the minute differences in features necessary to rebuild a functional tissue, which is able to renew itself over time (Grad and Salzmann 2009; Ohishi, Chiusaroli et al. 2009; Tare, Kanczler et al. 2010). Osteoblastic cells in bone need to be able to involve themselves in a remodelling cycle with osteoclasts (Hanada, Hanada et al. 2010; Trouvin and Goeb 2010), which may be recruited from surrounding bone structures, and/or may be furnished as preosteoclasts within the population of osteoblasts. Furthermore, the osteoblasts should be able to undergo a distinct alteration in terms of life-span defined characteristics (Lian and Stein 2003; Lian, Stein et al. 2006; Gordeladze, Reseland et al. 2009), including the transition to osteocytes. Finally, the newly formed engineered tissue does not survive unless it develops a vascular network (Matsumoto, Kuroda et al. 2008; Grellier, Bordenave et al. 2009) furnishing the bone tissue with oxygen, growth factors and nutrients. Chondrocytes in engineered cartilage should be able to produce an extracellular matrix reflecting the composition, water-binding capacity and mechanical characteristics of true