Stem cells and their differentiated off-springs are often used in the field of regenerative medicine
and bone tissue engineering. As sufficient vascularization of bone grafts remains a main bottleneck,
knowledge about angiogenic properties of these cell types is a prerequisite for choosing the best approach.
The chorioallantoic membrane (CAM) assay was used to study the impact of three primary human cell
types (adipose-derived stem cells, osteoblasts and endothelial cells) and three differentiated cells (adiposederived
stem cells differentiated towards osteoblasts or endothelial cells or a 1:1 co-culture of both); the
control consisted of no cell seeding. Angiogenic properties were quantified after one week by imaging the CAM surface and
analyzing vessel length, diameter, end points, sprouting, density and cross points with CapImage® software program.
While primary osteoblasts clearly enhanced angiogenesis with respect to vessel length, diameter and sprouting, primary
endothelial cells did not support this process compared to the control. Primary adipose-derived stem cells behaved rather
neutral. As for the differentiated cells, differentiated osteoblasts behaved similar as primary osteoblasts and differentiated
endothelial cells similar as primary endothelial cells. The co-culture of differentiated cells did not enhance angiogenesis
significantly. There were some inter-individual differences in angiogenic properties among different donors of stem cells
related to their gene expression.
For the stimulation of angiogenesis in tissue engineered bone constructs, the use of primary cells is suggested because the
differentiation towards osteoblasts as well as endothelial cells is not only time-consuming, but goes along with lower angiogenic
activity compared to primary cells.