Browsing by Author "Albritton, Jacob L."

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    3D bioprinting: improving in vitro models of metastasis with heterogeneous tumor microenvironments
    (The Company of Biologists, 2017) Albritton, Jacob L.; Miller, Jordan S.; Bioengineering
    Even with many advances in treatment over the past decades, cancer still remains a leading cause of death worldwide. Despite the recognized relationship between metastasis and increased mortality rate, surprisingly little is known about the exact mechanism of metastatic progression. Currently available in vitro models cannot replicate the three-dimensionality and heterogeneity of the tumor microenvironment sufficiently to recapitulate many of the known characteristics of tumors in vivo. Our understanding of metastatic progression would thus be boosted by the development of in vitro models that could more completely capture the salient features of cancer biology. Bioengineering groups have been working for over two decades to create in vitro microenvironments for application in regenerative medicine and tissue engineering. Over this time, advances in 3D printing technology and biomaterials research have jointly led to the creation of 3D bioprinting, which has improved our ability to develop in vitro models with complexity approaching that of the in vivo tumor microenvironment. In this Review, we give an overview of 3D bioprinting methods developed for tissue engineering, which can be directly applied to constructing in vitro models of heterogeneous tumor microenvironments. We discuss considerations and limitations associated with 3D printing and highlight how these advances could be harnessed to better model metastasis and potentially guide the development of anti-cancer strategies.
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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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    A novel ex vivo tumor system identifies Src-mediated invasion and metastasis in mesenchymal tumor cells in non-small cell lung cancer
    (Springer Nature, 2019) Padhye, Aparna; Ungewiss, Christin; Fradette, Jared J.; Rodriguez, B. Leticia; Albritton, Jacob L.; Miller, Jordan S.; Gibbons, Don L.; Bioengineering
    Lung cancer is the foremost cause of cancer related deaths in the U.S. It is a heterogeneous disease composed of genetically and phenotypically distinct tumor cells surrounded by heterotypic cells and extracellular matrix dynamically interacting with the tumor cells. Research in lung cancer is often restricted to patient-derived tumor specimens, in vitro cell cultures and limited animal models, which fail to capture the cellular or microenvironment heterogeneity of the tumor. Therefore, our knowledge is primarily focused on cancer-cell autonomous aberrations. For a fundamental understanding of lung cancer progression and an exploration of therapeutic options, we focused our efforts to develop an Ex Vivo Tumor platform to culture tumors in 3D matrices, which retains tumor cell heterogeneity arising due to in vivo selection pressure and environmental influences and recapitulate responses of tumor cells to external manipulations. To establish this model, implanted syngeneic murine tumors from a mutant KRAS/p53 model were harvested to yield multicellular tumor aggregates followed by culture in 3D extracellular matrices. Using this system, we identified Src signaling as an important driver of invasion and metastasis in lung cancer and demonstrate that EVTs are a robust experimental tool bridging the gap between conventional in vitro and in vivo models.
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    Ultrahigh-throughput generation and characterization of cellular aggregates in laser-ablated microwells of poly(dimethylsiloxane)
    (Royal Society of Chemistry, 2016) Albritton, Jacob L.; Roybal, Jonathon D.; Paulsen, Samantha J.; Calafat, Nick; Flores-Zaher, Jose A.; Farach-Carson, Mary C.; Gibbons, Don L.; Miller, Jordan S.; Bioengineering; Biosciences
    Aggregates of cells, also known as multicellular aggregates (MCAs), have been used as microscale tissues in the fields of cancer biology, regenerative medicine, and developmental biology for many decades. However, small MCAs (fewer than 100 cells per aggregate) have remained challenging to manufacture in large quantities at high uniformity. Forced aggregation into microwells offers a promising solution for forming consistent aggregates, but commercial sources of microwells are expensive, complicated to manufacture, or lack the surface packing densities that would significantly improve MCA production. To address these concerns, we custom-modified a commercial laser cutter to provide complete control over laser ablation and directly generate microwells in a poly(dimethylsiloxane) (PDMS) substrate. We achieved ultra rapid microwell production speeds (>50000 microwells per h) at high areal packing densities (1800 microwells per cm2) and over large surface areas for cell culture (60 cm2). Variation of the PDMS substrate distance from the laser focal plane during ablation allowed for the generation of microwells with a variety of sizes, contours, and aspect ratios. Casting of high-fidelity microneedle masters in polyurethane allowed for non-ablative microwell reproduction through replica molding. MCAs of human bone marrow derived mesenchymal stem cells (hMSCs), murine 344SQ metastatic adenocarcinoma cells, and human C4-2 prostate cancer cells were generated in our system with high uniformity within 24 hours, and computer vision software aided in the ultra-high-throughput analysis of harvested aggregates. Moreover, MCAs maintained invasive capabilities in 3D migration assays. In particular, 344SQ MCAs demonstrated epithelial lumen formation on Matrigel, and underwent EMT and invasion in the presence of TGF-β. We expect this technique to find broad utility in the generation and cultivation of cancer cell aggregates, primary cell aggregates, and embryoid bodies.