Browsing by Author "Sazer, Daniel W."

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    Contextual cues from cancer cells govern cancer-associated fibroblast heterogeneity
    (Cell Press, 2021) Bota-Rabassedas, Neus; Banerjee, Priyam; Niu, Yichi; Cao, Wenjian; Luo, Jiayi; Xi, Yuanxin; Tan, Xiaochao; Sheng, Kuanwei; Ahn, Young-Ho; Lee, Sieun; Parra, Edwin Roger; Rodriguez-Canales, Jaime; Albritton, Jacob; Weiger, Michael; Liu, Xin; Guo, Hou-Fu; Yu, Jiang; Rodriguez, B. Leticia; Firestone, Joshua J.A.; Mino, Barbara; Creighton, Chad J.; Solis, Luisa M.; Villalobos, Pamela; Raso, Maria Gabriela; Sazer, Daniel W.; Gibbons, Don L.; Russell, William K.; Longmore, Gregory D.; Wistuba, Ignacio I.; Wang, Jing; Chapman, Harold A.; Miller, Jordan S.; Zong, Chenghang; Kurie, Jonathan M.; Bioengineering
    Cancer cells function as primary architects of the tumor microenvironment. However, the molecular features of cancer cells that govern stromal cell phenotypes remain unclear. Here, we show that cancer-associated fibroblast (CAF) heterogeneity is driven by lung adenocarcinoma (LUAD) cells at either end of the epithelial-to-mesenchymal transition (EMT) spectrum. LUAD cells that have high expression of the EMT-activating transcription factor ZEB1 reprogram CAFs through a ZEB1-dependent secretory program and direct CAFs to the tips of invasive projections through a ZEB1-driven CAF repulsion process. The EMT, in turn, sensitizes LUAD cells to pro-metastatic signals from CAFs. Thus, CAFs respond to contextual cues from LUAD cells to promote metastasis.
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    Development, characterization, and applications of multi-material stereolithography bioprinting
    (Springer Nature, 2021) Grigoryan, Bagrat; Sazer, Daniel W.; Avila, Amanda; Albritton, Jacob L.; Padhye, Aparna; Ta, Anderson H.; Greenfield, Paul T.; Gibbons, Don L.; Miller, Jordan S.; Bioengineering
    As a 3D bioprinting technique, hydrogel stereolithography has historically been limited in its ability to capture the spatial heterogeneity that permeates mammalian tissues and dictates structure–function relationships. This limitation stems directly from the difficulty of preventing unwanted material mixing when switching between different liquid bioinks. Accordingly, we present the development, characterization, and application of a multi-material stereolithography bioprinter that provides controlled material selection, yields precise regional feature alignment, and minimizes bioink mixing. Fluorescent tracers were first used to highlight the broad design freedoms afforded by this fabrication strategy, complemented by morphometric image analysis to validate architectural fidelity. To evaluate the bioactivity of printed gels, 344SQ lung adenocarcinoma cells were printed in a 3D core/shell architecture. These cells exhibited native phenotypic behavior as evidenced by apparent proliferation and formation of spherical multicellular aggregates. Cells were also printed as pre-formed multicellular aggregates, which appropriately developed invasive protrusions in response to hTGF-β1. Finally, we constructed a simplified model of intratumoral heterogeneity with two separate sub-populations of 344SQ cells, which together grew over 14 days to form a dense regional interface. Together, these studies highlight the potential of multi-material stereolithography to probe heterotypic interactions between distinct cell types in tissue-specific microenvironments.
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    Perfusable cell-laden matrices to guide patterning of vascularization in vivo
    (Royal Society of Chemistry, 2023) Parkhideh, Siavash; Calderon, Gisele A.; Janson, Kevin D.; Mukherjee, Sudip; Mai, A. Kristen; Doerfert, Michael D.; Yao, Zhuoran; Sazer, Daniel W.; Veiseh, Omid; Bioengineering
    The survival and function of transplanted tissue engineered constructs and organs require a functional vascular network. In the body, blood vessels are organized into distinct patterns that enable optimal nutrient delivery and oxygen exchange. Mimicking these same patterns in engineered tissue matrices is a critical challenge for cell and tissue transplantation. Here, we leverage bioprinting to assemble endothelial cells in to organized networks of large (>100 μm) diameter blood vessel grafts to enable spatial control of vessel formation in vivo. Acellular PEG/GelMA matrices with perfusable channels were bioprinted and laminar flow was confirmed within patterned channels, beneficial for channel endothelialization and consistent wall shear stress for endothelial maturation. Next, human umbilical vein endothelial cells (HUVECs) were seeded within the patterned channel and maintained under perfusion culture for multiple days, leading to cell–cell coordination within the construct in vitro. HUVEC and human mesenchymal stromal cells (hMSCs) were additionally added to bulk matrix to further stimulate anastomosis of our bioprinted vascular grafts in vivo. Among multiple candidate matrix designs, the greatest degree of biomaterial vascularization in vivo was seen within matrices fabricated with HUVECs and hMSCs encapsulated within the bulk matrix and HUVECs lining the walls of the patterned channels, dubbed design M-C_E. For this lead design, vasculature was detected within the endothelialized, perfusable matrix channels as early as two weeks and αSMA+ CD31+ vessels greater than 100 μm in diameter had formed by eight weeks, resulting in durable and mature vasculature. Notably, vascularization occurred within the endothelialized, bioprinted channels of the matrix, demonstrating the ability of bioprinted perfusable structures to guide vascularization patterns in vivo. The ability to influence vascular patterning in vivo can contribute to the future development of vascularized tissues and organs.
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    Projection-based stereolithography for direct 3D printing of heterogeneous ultrasound phantoms
    (Public Library of Science, 2021) Paulsen, Samantha J.; Mitcham, Trevor M.; Pan, Charlene S.; Long, James; Grigoryan, Bagrat; Sazer, Daniel W.; Harlan, Collin J.; Janson, Kevin D.; Pagel, Mark D.; Miller, Jordan S.; Bouchard, Richard R.; Bioengineering
    Modern ultrasound (US) imaging is increasing its clinical impact, particularly with the introduction of US-based quantitative imaging biomarkers. Continued development and validation of such novel imaging approaches requires imaging phantoms that recapitulate the underlying anatomy and pathology of interest. However, current US phantom designs are generally too simplistic to emulate the structure and variability of the human body. Therefore, there is a need to create a platform that is capable of generating well-characterized phantoms that can mimic the basic anatomical, functional, and mechanical properties of native tissues and pathologies. Using a 3D-printing technique based on stereolithography, we fabricated US phantoms using soft materials in a single fabrication session, without the need for material casting or back-filling. With this technique, we induced variable levels of stable US backscatter in our printed materials in anatomically relevant 3D patterns. Additionally, we controlled phantom stiffness from 7 to >120 kPa at the voxel level to generate isotropic and anisotropic phantoms for elasticity imaging. Lastly, we demonstrated the fabrication of channels with diameters as small as 60 micrometers and with complex geometry (e.g., tortuosity) capable of supporting blood-mimicking fluid flow. Collectively, these results show that projection-based stereolithography allows for customizable fabrication of complex US phantoms.