Homocysteine Facilitates Prominent Polygonal Angiogenetic Networks of a Choroidal Capillary Sprouting Model.

PURPOSE

To investigate the effects of homocysteine on choroidal angiogenesis, we established an ex vivo choroidal sprouting explant model and examined the potential growth factors for angiogenesis.

METHODS

Choroid fragments with retinal pigment epithelium were isolated from mouse and embedded in Matrigel. Homocysteine at different concentrations were added to the culture mediums. The choroidal explants were observed at different time points, and the total area of choroidal sprouting was measured and analyzed.

RESULTS

Homocysteine evoked choroidal capillary sprouting by inducing capillary endothelial cell proliferation with pericyte formation and by facilitating polygonal angiogenetic networks. In some cases, vascular lumens were observed in the newly forming capillaries facilitated by homocysteine. The choroidal sprouting effect of homocysteine can only be observed at a certain range of homocysteine concentration, with 1-mM homocysteine exhibiting the most significantly increased choroidal sprouting areas. Isolectin overexpression was noted in the homocysteine-treated group. Possible growth factors for angiogenesis were detected through immunofluorescent staining, which demonstrated the overexpression of platelet-derived growth factor C and angiopoietin 1 in the homocysteine-treated preparations only. In these preparations, platelet-derived growth factor C was highly expressed in the tip cells of sprouting capillaries.

CONCLUSIONS

We therefore conclude that platelet-derived growth factor C and angiopoietin 1 may play key roles in the choroid angiogenesis evoked by homocysteine.