Blood flow influences vascular growth during tumour angiogenesis

Many factors play a role in tumour angiogenesis. We observed growing tumour Vessels in vivo to study the relationship between blood flow and Vascular enlargement. Mammary adenocarcinoma was implanted into Fisher-344 rat with dorsal skin-fold transparent chambers. Vascular growth was observed and rec orded on videotape through a microscope for 6 h. Vascular networks were pho tographed and traced every 30 min to identify changes over time. Tumour sec tions were stained with Masson's trichrome and anti-factor VIII-related ant igen. Tumour growth was rapid enough for differences to be seen each hour. Vessels with a high blood flow showed an increase in diameter within a few hours and new branches formed from these vessels. in contrast, vessels with out an increase in blood flow showed no change in diameter. Vessels within the interstitium surrounding the tumour were lined by endothelium that was positive for anti-factor VIII-related antigen staining. Vessels in the tumo ur had extremely rare endothelial cells detectable by Masson's trichrome or anti-factor VIII-related antigen staining. In conclusion, increased blood flow may cause vascular enlargement and some primitive Vessels seem to lack endothelium.