Aim:  Decidual endothelial cells are able to synthesize C1q and express surface-bound C1q under physiological conditions. Since decidua is a site of active angiogenesis, we sought to ascertain whether C1q could play a role in this process.

Material and Methods:  To confirm our hypothesis we used different approaches such as permeability, cell migration and proliferation assay, besides wound healing and aortic ring assay.

Results:  C1q acts as a permeabilizing factor inducing the FITC-BSA leakage through a monolayer of endothelial cells (ECs). Next, we found that C1q was able to promote motility of ECs in a wound healing assay, and to recruit ECs acting as a chemotactic factor, furthermore C1q was also found to have an additional effect on EC inducing cell proliferation. To confirm and extend these data, we used the rat aortic ring assay to evaluate the ex vivo effect of C1q.

Conclusion:  Based on our findings, we propose that C1q exerts unexpected proangiogenic effects.