Design and performance of an optically accessible, low-volume, mechanobioreactor for long-term study of living constructs.

Currently available bioreactor systems used by tissue engineers permit either direct, high-magnification observation of cell behavior or application of mechanical loads to growing tissue constructs, but not both simultaneously. Further, in most loading bioreactors, the volume of the dead space is not minimized to reduce the cost associated with perfusion media, exogenous stimulatory/inhibitory agents, proteases, and label. We have designed, developed, and tested a bioreactor that simultaneously satisfies the combined requirements of providing (i) controlled tensile mechanical stimulation, (ii) direct high-magnification imaging capability, and (iii) low dead-space volume. This novel mechanostimulatory (uniaxial tensile loading) bioreactor operates on an inverted microscope and permits continuous optical access (up to 600×) to a loaded, growing construct for extended periods of time (weeks). The reactor employs an adjustable reaction chamber in which the dead space can be reduced to <2 mL. The device has been used to cultivate our human primary corneal fibroblast-derived, tissue-engineered system for up to 14 days. Using the instrument we have successfully recorded (i) the process of fibroblasts populating, growing to confluence, and stratifying on different substrates; (ii) recorded complex and organized cell sheet motions; and (iii) recorded the behavior of a subpopulation of what appear to be degradative/catabolic cells within our fibroblast culture. The device is capable of providing detailed, long-term, dynamic images of mechanically stimulated cell/matrix interaction that have not been observed previously.