Intellectual Merit: One of the major challenges in tissue engineering is the inability to grow thick tissues due to lack of vascular perfusion. In addition, a key feature of many adult stem cell niches is their proximity to the vasculature in vivo. Vascular cells not only form conduits to deliver nutrient and oxygen, but also provide cues to control the cellular phenotype in the surrounding tissues. Therefore, building a functional vascular network with physiological perfusion is critical to both fields of stem cells and tissue engineering. The objective of this proposal is to create a perfused, functional perivascular niche with controllable components and physiological parameters. Our approach is to build a 3-D perfused functional vascular channel within hydrogels using a new bio-fabrication technology developed in our lab. These fabricated vascular channels provide a realistic in vitro model system to investigate capillary morphogenesis around the perfused vascular channel within the 3-D matrix. Meanwhile, the imaging modalities to assess the 3-D structures and functions of the vascular channels and to observe the outgrowth of vascular networks is lacking for such thick 3-D matrices (2~3mm). To overcome this problem, we are also developing and improving a new imaging technique called Laminar Optical Tomography (LOT). LOT is able to obtain depth-resolved 3-D quantitative images to depths of several millimeters with high sensitivity. To achieve the full potential of LOT in imaging thick tissue and promote its application in tissue engineering research, we propose to merge these two disciplines (3-D imaging & 3-D tissue printing) in a new platform to study the vasculature formation in thick matrix: Specific Aim 1: Create a perfused, interconnected vasculature within 3-D matrix utilizing a novel cell printing technology. Specific Aim 2: Integrate a high-resolution, multi-spectral molecular laminar optical tomography platform for thick tissue imaging. Specific Aim 3: Validate the LOT in multi-color imaging of vascular structures and fluid flow; Study the maturation process and functionalities of the synthesized structure with regard to matrix properties and culture parameters. The proposed research will generate significant intellectual merits in the fields of stem cells, tissue engineering and biomedical optics: (1) By integrating a novel cell printing technology into the vasculature formation process, this research will lead to a new method to recapitulate and study perivascular niches ex vivo. Through studying its patterning and maturation process under a 3-D perfused environment, this research will define critical factors for the 3-D vasculature to achieve its functions. (2) This research will integrate a new CCD based LOT system and will develop specialized reconstruction algorithm for large data sets. This will establish a new high-resolution mesoscopic fluorescence imaging technique, which will provide a new method to perform functional and molecular imaging of 3-D tissue engineered construct. (3) More generally, this work will identify a set of design principles for the printed structures to support the growth of the surrounding tissues in vitro, and thereby lay the foundation to biofabricate thicker tissues in the future.
Broader Impacts: This research has broad impacts in research, society, and education: (1) The proposed research activities will generate fundamental knowledge related to 3-D vascular tissue formation as well as new technologies to obtain functional molecular imaging of the tissues. Both of these advancements will be critical for engineering thick tissue construct and understanding the complex biology of cell interactions within 3-D matrix, which has become increasingly important to the whole field. (2) The proposed educational components will educate undergraduate/graduate students with up-to-date technologies, experimental skills, and creative thinking that are indispensable in the growing field of biomedical engineering. (3) The proposed research and education activities will also have a broad impact on K-12 education through several proposed programs for underrepresented groups in science and engineering, as well as extensive outreach programs targeting students from throughout New York's Tech Valley region. Through activities demonstrating how engineers can solve societal challenges, our students will be more likely to pursue career in science and engineering.
