(158k) Engineering Vascular Cells and Macro-Fluidic Platforms for Physiological Organ and Tissue Culture

The vasculature plays a critical role during embryogenesis. After birth, the vasculature continues to have a strong footprint in many essential biological processes of organs and tissues. For example, the vasculature delivers nutrients and gases to maintain tissue survival, transports biological wastes to the appropriate organs for further processing, and enables trafficking of immune cells to the injured tissues. In pathological tumors, the maladaptive vasculature invades the tumor tissues to fuel the tumor growth and metastasis. In addition, the vasculature remains an essential component in tissue engineering and translational medicine. The tissue engineering field has made significant progress to create in vitro organ-on-chip models to better mimic several biological organs such as skin, pancreas, lung, and brain (1,2). Despite these efforts, there are setbacks in current models of organ-on-chip. For instance, to incorporate the vasculature, efforts have been made to generate microfluidic platforms with embedded mature adult endothelial cells to generate some network of blood vessels in these organ-on-chip models. However, these mature endothelial cells lose their intrinsic capability in vitro to generate a robust blood vessel network and lose their ability to interact and adapt to different cell types in co-culture. As a result, the blood vessels in organ-on-chip models are poorly functional. In addition, the micro-fluidic organ-on-chips are miniaturized versions of organs, where simple diffusion of nutrients and gases is sufficiently enough to feed the cells whereas organ and tissues in the body heavily rely on blood flow carrying nutrients and gases through dedicated vascular conduits (3). Thus, the small-scale organ-on-chips render the blood vessels and fluid perfusion unnecessary. They also make it challenging to address how transported nutrients, and gases by blood vessels alter cellular behavior in organs or tissues in the body.

To address the first limitation of organ-on-chip models where mature endothelial cells do not form robust vascular network in vitro, we first engineered adaptive vascular endothelial cells by introducing vasculogenic transcriptional factor into mature endothelial cells. The engineered endothelial cells upregulated several genes involved in angiogenesis and vasculogenesis. Consequently, in 3D hydrogel culture, these engineered endothelial cells formed a robust and functional network of vasculature. Moreover, when placed in co-culture with several other cell types such as normal colon organoids, tumor colon organoids, and pancreatic islets, they not only survive, and adapt to the culture environment of other cell types, they also avidly interact with the organoids and islets. To overcome the limitation of dimension in traditional micro-fluidic organ-on-chips, we engineer macro-fluidic devices where dimensions of the devices are extended up to 2cm in length and width. After seeding these engineered-endothelial cells into the macro-fluidic devices and incorporating fluidic pump, we successfully generated a large scale robust and functional vasculature network in macro-fluidic devices. The vascular network in macro-fluidic device is fully functional as they support perfusion of medium and even human whole blood without clotting. To further extend the study, we investigate the function of the vascularized macro-fluidic organ-on-chip by embedding human pancreatic islets inside the organ-on-chip. Upon glucose stimulation, pancreatic islets in the vascularized macro-fluidic organ-on-chip sense glucose and release insulin similar to in vivo physiological glucose response of human pancreatic islets (4). Our efforts continue to investigate and expand the vascularized macro-fluidic organ-on-chips into different organotypic models such as colon, and liver organ-on-chips.

[1] Nguyen, D.H.T., Stapleton, S.C., Yang, M.T., Cha, S.S., Choi, C.K., Galie, P.A., Chen, C.S. (2013). Biomimetic model to reconstitute angiogenic sprouting morphogenesis in vitro. Proceedings of the National Academy of Sciences. 110(17): 6712-6717.

[2] Nguyen, D.H.T., Esak, L., Alimperti, S., Norgard. R.J., Wong, A., Lee, J.J.K., Eyckmans, J., Stanger, B.Z., Chen, C.S. (2019). A biomimetic pancreatic cancer on-ship reveals endothelial ablation via ALK7 signaling. Science Advances. 5(8): eaav6789.

[3] Galie, P.A., Nguyen, D.H.T., Choi, C.K., Cohen, D.M., Janmey, P.A., Chen, C.S. (2014). “Fluid shear stress threshold regulates angiogenic sprouting”. Proceedings of the National Academy of Sciences. 111(22): 7968-7973.

[4] Palikuqi, B., Nguyen, D.H.T., Li, G., Schreiner, R., Pellegata, A.F., Liu, Y., Redmond, D., Geng, F., Lin, Y., Gómez-Salinero, J.M., Yokoyama, M., Zumbo, P., Zhang, T., Kunar, B., Witherspoon, M., Han, T., Tedeschi, A.M., Scottoni, F., Lipkin, S., Dow, L., Elemento, O., Xiang, J.Z., Shido, K., Spence, J., Zhou, J.Q., Schwartz, R.E., DeCoppi, P., Rabbany, S.Y., Rafii, S. (2020). “Adaptable human endothelial cells for hemodynamic vascularization of normal and malignant organoids”. Nature. Accepted.