Building Better Experimental Bone Grafts

In science, as in life, there is no need to reinvent the wheel. Sometimes the better strategy is to think creatively about what exists and build a more robust wheel. Or, in the case of tissue engineers working in the laboratory, build better experimental bone grafts. In the February 23 issue of the Proceedings of the National Academy of Sciences (Volume 107, Num­ber 8), National In­stitute of Dental and Cranio­facial Re­search (NIDCR) gran­tee Gor­dana Vunjak-Nova­ko­vic, PhD, and her Columbia Uni­versity colleagues report taking an important step forward in learning to integrate existing tissue engineering concepts into a more efficient production process. In the study, the scientists used this streamlined process to engineer a human stem cell-de­rived bone condyle for the temporomandibular joint (TMJ). According to the scientists, the technological im­provements in fabricating the scaffold, the mold that forms the 3-dimensional shape of the replacement tissue, allowed for greater precision in capturing the unique geometry of the TMJ condyle. The group also designed a radically novel “anatomical” bioreactor with the aid of computation to culture a graft as complex as the TMJ. The bioreactor—5 cm high and 7.5 cm in external diameter—continuously perfuses the interstitial pores of the scaffold with growth medium to transport nutrients and oxygen to the multipotent hu­man mesenchymal stem cells (hMSCs) throughout the cultured TMJ construct and re­move their waste products. The modifications allowed bet­ter induction of the hMSCs, allowing them to differentiate, lay down bone tissue matrix, and grow into a fully viable TMJ condyle.  
“The engineered graft does not replicate the entire joint anatomy inclusive of the cartilage layer and the TMJ disc that are often damaged in TMJ disorders,” they noted. “However, this ap­proach could impact developmental biology (where high-fidelity tissue models can be used to study bone formation) and bioengineering and clinical translation (by providing surgeons with large and via­ble anatomically shaped bone grafts for treating craniofa­cial or orthopedic wounds.” 

(Source: NIDCR, Sci­ence News in Brief, March 24, 2010.)
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