Aim: To evaluate, whether scintigraphic studies with radiolabeled erythrocytes may be used to demonstrate the formation of new vessels during angiogenesis and if an effect on antiangiogenetic therapy could be detected.
Methods: As an angiogenesis model we used the ingrowth of blood vessels in matrigel, subcutaneously injected into mice. In order to measure the relative blood volume in the matrigel non-invasively, mouse erythrocytes were labeled with Technetium-99m DTPA. The amount of activity in the matrigel was measured 30 minutes after injection of the radiolabeled erythrocytes with a gammacamera (in-vivo) and a gammacounter (ex-vivo). These results were correlated with the concentration of hemoglobin in the matrigel and the immunhistochemically evaluated density of blood vessels. The influence of the angiogenesis stimulating growth factor (bFGF) and the antiangiogenetic effect of the cyclooxigenase type 2 inhibitor (COX-2) NS398 were tested.
Results: There was a close correlation between the activity concentration in the matrigel and the hemoglobin content. Treatment with bFGF significantly increased the activity concentration from 1.74% +/- ID/g to 4.06% +/- 0.36 (p < 0.01), whereas treatment with NS398 significantly inhibited tracer uptake from 2.83% ID/g +/- 0.33 to 0.87% ID/g +/- 0.12 (p < 0.01).
Conclusion: These results demonstrate the feasibility of using (99m)Tc labelled erythrocytes for scintigraphic imaging to assess the effects of angiogenesis stimulating and inhibiting interventions non-invasively.