Development of a framework to perform longitudinal micro-computed tomography monitoring on ex vivo embryonic chick femur cultures

Abstract

In the field of bone tissue engineering and regenerative medicine, ex vivo embryonic chick femur culture models have demonstrated their experimental advantages. The work reported in this thesis was dedicated to the development of a framework through a bioreactor approach in combination with the technology of micro-computed tomography (?CT) to conduct longitudinal studies on ex vivo embryonic chick femur cultures. The bioreactor chamber was designed to allow isolated embryonic chick femurs to be positioned at an air/liquid interface under a basic organotypic culture condition for ?CT monitoring. By time-lapsed monitoring of the bone tissue, ?CT evaluation provided the information on temporal and spatial changes of the chick femur model in a three-dimensional scheme. Different experimental groups were examined with respect to the frequency of ?CT scans and the lengths of the period under organotypic culture. It was found that, after 10 days of culture, the femurs scanned every other day exhibited similar bone growth and bone dynamic morphometry as the femurs scanned only at the beginning and the end of culture. This demonstrated the multiple experimental manipulations and irradiation did not have a significant influence on the quantified bone parameters. However, considering transient bone biology, the registration method of superimposing two measurements from the interval of two days showed much more dynamic bone activity than the ones of the same femur registered from the corresponding two time points at the beginning and the end of the culture period of 10 days. Furthermore, for the femurs cultured for a longer period of 4 weeks, more bone formation and less bone resorption was shown during the first two weeks than during the second two weeks. The results indicated the importance of choosing the suitable length of culture periods and scan time points in order to study dynamic bone activity. It is therefore recommended that, in the future, a ?CT monitoring scheme should be taken into consideration in a longitudinal study. In conclusion, by taking the bioreactor approach, a feasible model for longitudinal studies on ex vivo embryonic chick femur cultures could be successfully established.