Objectives: Squamous cell carcinoma (SCC) and salivary gland adenoid cystic carcinoma (ACC) are two common malignancies in the oral and maxilla-facial region[1,2].It has been proved that angiogenesis promotes growth,invasion and metastasis of SCC and ACC[3].Traditional in vitro angiogenesis models are usually developed using cell culture plates,which are high consumption and low throughput[4,5].In addition,the cells are completely different from the complex tissue microenvironment in vivo.Microfluidic technology has been proved to be an ideal platform to operate mammal cells with low consumption and high throughput[6].Thus,the purpose of this study is to develop an in vitro tumor-induced angiogenesis model based on microfluidic technology.Then,the processes of SCC and ACC-induced angiogenesis will be investigated using this model.Materials and methods: Soft lithography technique was used to fabricate the SU8 master.The Polydimethylsiloxane (PDMS) layer was molded by the master and bonded to a glass substrate irreversibly.Three cell lines,including Human umbilical vein endothelial cell line (HUVEC),a high metastatic ACC cell line ACC-M and a tongue squamous cell carcinoma cell line SCC-6,were used in our study.Primary normal fibroblasts (NF) were prepared from the sample of normal gingival.Cultrex Basement Membrane Extract (BME) was used as substitute of extracellular matrix (ECM) in our study.HUVEC were co-cultured with SCC-6,ACC-M or NF on the microfluidic model.The differentiation,migration and tube formation of HUVEC were quantified.Results: The microfluidic model developed in this study is composed of two parallel endothelial cell culture channels and six separate angiogenesis units.Each angiogenesis unit contains one opening cell culture chamber and two angiogenesis channels,which locate on the lateral sides of cell culture chamber and connect with two endothelial cell culture channels respectively.The height of endothelial cell culture channels was designed to be higher than that of the angiogenesis channels to generate stop-flow junctions at the interface between these two kinds of channels.These junctions assist in the prevention of BME from leakage during BME loading.BME was loaded into angiogenesis channels through cell culture chambers to mimic ECM between blood vessels and tumor.HUVEC cells were seeded on the surface of endothelial cell culture channels to mimic blood vessels.SCC-6 and ACC-M cells were seeded into different cell culture chambers to mimic primary tumors.NF was used as a normal control.It was found that HUVEC cells migrated into BME containing in the angiogenesis channels in all three groups.At the migration front,tip cells with long filopodia were observed.Some tip cells contacted with the following HUVEC,termed as stable tip cells.Some are detached from the following HUVEC,termed as unstable tip cells.The number of unstable tip cells was significantly higher in SCC-6 and ACC-M groups than that in NF group.Regarding the direction,HUVEC cells in SCC-6 group presented more definite directional migration towards tumor cells.The migrating distance and area of HUVEC increased significantly in ACC-M and SCC-6 groups than that in NF group.Tube formation was observed in both ACC-M and SCC-6 groups after 48h stimulation,but no obvious tube was observed in NF group.Conclusions: In this study,we developed a microfluidic-based model,which can mimic tumor-induced angiogenesis in vitro.ACC-M and SCC-6-induced angiogenesis were studied on this model.Both tumor cells presented stronger angiogenetic inducibility than NF.The microfluidic-based angiogenesis model is simple to operate and has good reproducibility.We hope the model would be a useful platform for the study of cancer-induced angiogenesis.