Continuous monitoring of tissue growth inside a perfusion bioreactor by optical coherence tomography

Tissue engineering aims to create in vitro functional tissues that could ultimately be used as autologous implants. Considering the large number of parameters that have to be tested to optimize the tissue growth and to achieve a better understanding of tissue formation, relevant biological in vitro models are needed which can be monitored and characterized all along the different stages of tissue engineering: cell seeding, cell growth, extra-cellular matrix (ECM) deposition, matrix turn-over and tissue organization. We developed porous chitosan scaffolds (phi 1.5mm) that enclose a 300um microchannel to encourage fluid shear-stress stimulation and more specifically to support bundle formation for the specific case of tendon tissue engineering. These scaffolds were loaded in perfusion bioreactors and monitored during several days by optical coherence tomography (OCT). The fiber based time domain OCT employed a 1300nm superluminescent diode with a bandwith of 52 nm and a xyz resolution of 16*16*14 in free space. This set up allowed us to assess the volume fraction of cell seeded in the microchannels, and thus to optimize the seeding procedure. The cell growth and ECM deposition were successfully monitored at different time point as the channels were filled by newly formed material. Different scattering behaviors have been observed during cell growth and ECM production. The possibility to monitor continuously the scaffolds under perfusion will allow an easy discrimination of the parameters affecting the pre-tissue formation rate growth.