Correlation between Contrast-Enhanced Ultrasound and Microvessel Density via CD31 and CD34 in the rabbit VX2 lung peripheral tumor model

Aim: To evaluate the tumor angiogenesis in lung peripheral VX2 tumor model by contrast-enhanced ultrasound (CEUS) and to determine the correlation between CEUS parameters and microvessel density (MVD) calculated via CD31 and CD34 expression. Materials and methods: VX2 pulmonary tumors were created in eight Japanese white rabbits by implanting a VX2 sarcoma into the lower portion of the right lung through ultrasound guidance. Tumors were allowed to grow for 14-21 days to achieve a diameter of 7-15 mm, and were examined by CEUS using a SonoVue contrast agent. The results were recorded as digital video images, and the time-intensity curves and hemodynamic parameters were analyzed. Pathological tumor specimens were immediately obtained after the ultrasound examinations. Tumor specimens were stained with hematoxylin and eosin (H&E) and expressed as CD31 and CD34. The different endothelial cell markers were determined by immunohistochemical staining. MVD was calculated via CD 31 and CD34, and the relationship between CEUS parameters and MVDs was analyzed. Results: Two distinct types of microvessels were identified in lung peripheral VX2 tumors: differentiated (CD34+) and undifferentiated (CD31+) vessels. A significant correlation was found between CEUS parameters and undifferentiated MVD (CD31+ vessels) in lung peripheral VX2 tumors (p<0.05). A reverse correlation was observed between different MVDs. Conclusions: Two different degrees of differentiation of vascular endothelial cells (CD31 and CD34) exist in the rabbit lung peripheral VX2 tumor model. CD31 MVD can more effectively evaluate tumor angiogenesis compared with CD34 MVD. CEUS, as a non-invasive imaging method, can effectively evaluate tumor angiogenesis in rabbit peripheral lung cancer.