Mimicking Natural Bone Development to Produce Tissue for Bone Grafts

Objective: Repair of large bone defects caused by trauma, disease or congenital defects remain clinically challenging. Autologous bone transplantation, the current gold standard, can have drawbacks such as long-term post operative pain at the donor tissue site and hip instability, also the amount of bone which can be harvested is limited, especially in young children. Therefore there is a need for a new technology to provide bone tissue for transplantation. Tissue-engineered hypertrophic cartilage grafts have potential to address this demand as, unlike bone grafts, they can withstand lower oxygen levels and contain factors to induce angiogenesis and osteogenesis in vivo. The objective of this research was to investigate the potential of nasal septal cartilage to produce a hypertrophic cartilage graft for use in bone repair. 

Method: Chondrocytes were isolated from the nasal septa of 6 week-old Wistar rats. The cell number was expanded by monolayer culture and then the chondrocytes were seeded on to polyglycolic acid (PGA) scaffolds and cultured for 42 days in hypertrophic differentiation media. The differentiation state of the tissue was followed by measuring gene expression during the culture period using quantitative polymerase chain reaction (qPCR). Histological and immunohistochemical techniques were also used to assess the extent of hypertrophic differentiation.

Result: Differentiated hypertrophic cartilage tissues were produced during the culture period. These contained typical, morphologically large cells and expressed both collagen type X and alkaline phosphatase (markers of hypertrophic chondrocytes). Gene expression studies showed that with increasing time in culture a decrease in markers of hyaline chondrocyte phenotype was seen, with a related increase in hypertrophic chondrocyte gene expression.

Conclusion: Chondrocytes isolated from the nasal septum are an attractive source for cartilage cells which can be used to form a hypertrophic cartilage tissue in the laboratory, which has potential for implantation in vivo for bone defect repair.