Search

Brain tumors are dynamic complex ecosystems with multiple cell types. To model the brain tumor microenvironment in a reproducible and scalable system, we developed a rapid three-dimensional (3D) bioprinting method to construct clinically relevant biomimetic tissue models. In recurrent glioblastoma, macrophages/microglia prominently contribute to the tumor mass. To parse the function of macrophages in 3D, we compared the growth of glioblastoma stem cells (GSCs) alone or with astrocytes and neural precursor cells in a hyaluronic acid-rich hydrogel, with or without macrophage. Bioprinted constructs integrating macrophage recapitulate patient-derived transcriptional profiles predictive of patient survival, maintenance of stemness, invasion, and drug resistance. Whole-genome CRISPR screening with bioprinted complex systems identified unique molecular dependencies in GSCs, relative to sphere culture. Multicellular bioprinted models serve as a scalable and physiologic platform to interrogate drug sensitivity, cellular crosstalk, invasion, context-specific functional dependencies, as well as immunologic interactions in a species-matched neural environment.

Growth factors (GFs) are critical components in governing cell fate during tissue regeneration. Their controlled delivery is challenging due to rapid turnover rates in vivo. Functionalized hydrogels, such as heparin-based hydrogels, have demonstrated great potential in regulating GF release. While the retention effects of various concentrations and molecular weights of heparin have been investigated, the role of geometry is unknown. In this work, 3D printing is used to fabricate GF-embedded heparin-based hydrogels with arbitrarily complex geometry (i.e., teabag, flower shapes). Simplified cylindrical core–shell structures with varied shell thickness are printed, and the rates of GF release are measured over the course of 28 days. Increasing the shell layers’ thickness decreases the rate of GF release. Additionally, a mathematical model is developed, which is found capable of accurately predicting GF release kinetics in hydrogels with shell layers greater than 0.5 mm thick (R(2) > 0.96). Finally, the sequential release is demonstrated by printing two GFs in alternating radial layers. By switching the spatial order, the delivery sequence of the GFs can be modulated. This study demonstrates how 3D printing can be utilized to fabricate user-defined structures with unique geometry in order to control the rate of GF release in hydrogels.