Chapter 5 Cell Based Therapies: What Do We Learn from Periosteal Osteochondrogenesis?

摘要

Unraveling isolation, cultivation and transplantation protocols is often difficult and time consuming but essential to exploit the full potential of cell based therapies. Studying periosteal callus formation, may give novel insights how this tissue can be used to repair cartilage and bone defects and thus bypass optimization of the protocols mentioned above. Periosteal callus can be induced in vivo without breaking the bone. During periosteal callus formation, osteochondrogenic progenitor cells which reside in the cambium cambium layer, differentiate via the sequential steps of endochondral bone formation; chondrogenesis is initiated then chondrocytes differentiate into hypertrophic cells. These hypertrophic chondrocytes release pro-angiogenic factors, mineralize and bone is deposited. Grafts can be harvested during the chondrogenic phase. Compared to isolated undifferentiated periosteal cells, cells in these grafts survive the transplantation into an osteochondral defect much better. By injecting a gel between bone and periosteum, the micro-environment can be manipulated. Per example inhibition of vascularization and induction of hypoxia enhances periosteal chondrogenesis both in vitro and in vivo. Taken together, studying repair processes of the body in detail may not only give essential information for different cell based therapies, but can even lead to a complete other approach in which the body its own regenerative capacity is used.