It is followed by the dedifferentiation of the cells. This process produces only a minimal concentration of the cells. Hence the use of micro carrier cultures is done for the well-mixed bioreactor systems. The defects in the skeleton system are a big impediment to the normal functioning of the human system. The autogenous bone transplantation is practiced for the bone replacement so far. (Schieker, 2006).This method has increased risk of surgery and post operative morbidality to the patients. This method also has the disadvantage of limited quantity and the secondary operational procedure costs. The calcium phosphate ceramics is widely used for the production of the bone supplement. The hydroxyapatites of the calcium phosphate ceramics have considerable clinical use because of their chemical and relvant crystallographic structures to bone. The cell based therapy aims at developing the 3D biohybrid structure of a scaffold and cultured cells. The bioreactors that are established for the microbes and mammalian cultures are not suitable for the 3D structure constructs. Hence the need for a tissue specific bioreactor design arose. To restore back the skeleton function, the bone tissue engineering is used. The production of tissue engineered piece of spongy bone is one of the challenging fields in bone tissue engineering. The three key elements of bone tissue engineering are osteogenic progenitor cells, osteoinductive growth factors and osteoconductive matrices.
Osteoblasts are the differentiated cells that arise from the osteoprogenitor cells. These cells are very mobile and they change the shape and size according to the matrix of the bone. These cells appear with in the vascular tissue. These cells are responsible for the synthesis and the secretion of the organic matrix of the bone. Bone remodeling and the bone reformation are the two types of the tissue engineering processes that can are possible with the osteoblast cells.