A system for engineering an osteochondral construct in the shape of an articular surface: Preliminary results

A tissue-engineered articular condyle could provide a new alternative approach to joint replacement. This study describes progress made towards engineering an articular condyle in vitro using human bone marrow stromal cells (hBMSCs) in a biphasic matrix. hBMSCs were transferred to a rat collagen-I hydrogel which was then pressed onto a bovine cancellous bone matrix. The gel/cell suspensions, each at a density of approximately 5×10⁵ cells/ml containing fourth passage cells pressed into an adult human tibial condyle form using CT scan based moulds. The osteochondral constructs fabricated in vitro were stimulated in a bioreactor using cyclic compression and continuous perfusion. Penetration and cell distribution were demonstrated as homogeneous and cells were found to be viable after gel compression. The filamentous structure of the collagen fibres was more dense and homogeneous using compression. Mechanical tests showed a significant enhancement of primary matrix stability after initial compression. Stiffness was not observed to increase significantly over 7 days under loading in a bioreactor. The successful integration of mechanical stimulation in the tissue engineering process leads to an improvement in the structural and biomechanical properties of these tissues and offers new possibilities in the management of joint injuries and degenerative diseases. Remarkably, the stiffness was enhanced in our setting after initial compression of the construct in the glass cylinder without observing a negative influence on cell viability. Further studies need to clarify the influence of compression and various mechanical and hydrostatic stress patterns over different periods of time.