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Tissue engineering has markedly matured since its early beginnings in the 1980s. In addition to the original goal to regenerate damaged organs, the field has started to explore modeling of human physiology “in a dish”. Induced pluripotent stem cell (iPSC) technologies now enable studies of organ regeneration and disease modeling in a patient-specific context. We discuss the potential of “organ-on-a-chip” systems to study regenerative therapies with focus on three distinct organ systems: cardiac, respiratory, and hematopoietic. We propose that the combinatorial studies of human tissues at these two scales would help realize the translational potential of tissue engineering.

Traditional drug screening models are often unable to faithfully recapitulate human physiology in health and disease, motivating the development of microfluidic organs-on-a-chip (OOC) platforms that can mimic many aspects of human physiology and in the process alleviate many of the discrepancies between preclinical studies and clinical trials outcomes. Linsitinib, a novel anti-cancer drug, showed promising results in pre-clinical models of Ewing Sarcoma (ES), where it suppressed tumor growth. However, a Phase II clinical trial in several European centers with patients showed relapsed and/or refractory ES. We report an integrated, open setting, imaging and sampling accessible, polysulfone-based platform, featuring minimal hydrophobic compound binding. Two bioengineered human tissues – bone ES tumor and heart muscle – were cultured either in isolation or in the integrated platform and subjected to a clinically used linsitinib dosage. The measured anti-tumor efficacy and cardiotoxicity were compared with the results observed in the clinical trial. Only the engineered tumor tissues, and not monolayers, recapitulated the bone microenvironment pathways targeted by linsitinib, and the clinically-relevant differences in drug responses between non-metastatic and metastatic ES tumors. The responses of non-metastatic ES tumor tissues and heart muscle to linsitinib were much closer to those observed in the clinical trial for tissues cultured in an integrated setting than for tissues cultured in isolation. Drug treatment of isolated tissues resulted in significant decreases in tumor viability and cardiac function. Meanwhile, drug treatment in an integrated setting showed poor tumor response and less cardiotoxicity, which matched the results of the clinical trial. Overall, the integration of engineered human tumor and cardiac tissues in the integrated platform improved the predictive accuracy for both the direct and off-target effects of linsitinib. The proposed approach could be readily extended to other drugs and tissue systems.

OBJECTIVE: Oxygen is essential to wound healing; therefore, accurate monitoring can guide clinical decisions. Clinical wound assessment is often subjective, and tools to monitor wound oxygen are typically expensive, indirect, and highly variable. This study demonstrates the utility of a novel, low-cost oxygen-sensing thin film for serial assessment of wound oxygenation. DESIGN: Dual-layer films were fabricated with boron oxygen-sensing nanoparticles (BNPs) impregnated into a chitosan-polycaprolactone (CS-PCL) layer for direct wound bed contact with a relatively oxygen impermeable calcium alginate surface layer. The BNPs are a dual emissive difluoroboron β-diketonate dye incorporated into poly(lactic acid) nanoparticles (BF(2)nbm(I)PLA). Under UV excitation, the BNPs emit fluorescence based on concentration and oxygen sensitive phosphorescence. The fluorescence/phosphorescence (F/P) ratio is directly proportional to oxygen concentration. METHODS: A series of in vitro oxygen challenges and in vivo murine and porcine wound healing models were used to validate the utility of the film in sensing wound oxygenation. MAIN RESULTS: In vitro testing demonstrated the oxygen-sensing capability of the BNP film and ability to shield ambient oxygen to isolate wound oxygen. In vivo testing demonstrated the ability of the film to accurately monitor relative oxygen changes in a murine wound over time, measuring a 22% F/P increase during acute healing. CONCLUSIONS: This study presents a low-cost, noninvasive, direct, and serial oxygen mapping technology to detect spatial differences in wound oxygenation. Clinical use of the films has the potential to monitor wound healing trajectories and guide wound care decisions.

Microvascular endothelial cell heterogeneity and its relationship to hemodynamics remains poorly understood due to a lack of sufficient methods to examine these parameters in vivo at high resolution throughout an angiogenic network. The availability of surrogate markers for functional vascular proteins, such as green fluorescent protein, enables expression in individual cells to be followed over time using confocal microscopy, while photoacoustic microscopy enables dynamic measurement of blood flow across the network with capillary-level resolution. We combined these two non-invasive imaging modalities in order to spatially and temporally analyze biochemical and biomechanical drivers of angiogenesis in murine corneal neovessels. By stimulating corneal angiogenesis with an alkali burn in Tie2-GFP fluorescent-reporter mice, we evaluated how onset of blood flow and surgically-altered blood flow affects Tie2-GFP expression. Our study establishes a novel platform for analyzing heterogeneous blood flow and fluorescent reporter protein expression across a dynamic microvascular network in an adult mammal.

Summary Most cancer deaths are due to tumor metastasis rather than the primary tumor. Metastasis is a highly complex and dynamic process that requires orchestration of signaling between the tumor, its local environment, distant tissue sites, and immune system. Animal models of cancer metastasis provide the necessary systemic environment but lack control over factors that regulate cancer progression and often do not recapitulate the properties of human cancers. Bioengineered “organs-on-a-chip” that incorporate the primary tumor, metastatic tissue targets, and microfluidic perfusion are now emerging as quantitative human models of tumor metastasis. The ability of these systems to model tumor metastasis in individualized, patient-specific settings makes them uniquely suitable for studies of cancer biology and developmental testing of new treatments. In this review, we focus on human multi-organ platforms that incorporate circulating and tissue-resident immune cells in studies of tumor metastasis., Graphical abstract, Components of the immune system; bioengineering; cancer; biochemical assay

In the Undergraduate School of Engineering and Applied Sciences (SEAS) at the University of Virginia (UVa), there are few opportunities for undergraduate students to teach, let alone develop, an introductory course for their major. As two undergraduate engineering students (D. N. Tavakol and C. J. Broshkevitch), we were among the first students to take advantage of a new initiative at UVa SEAS to offer student-led courses. As part of this new program, we designed a 1000-level, 1-credit, pass-fail course entitled Introduction to Research in Regenerative Medicine. During a student’s first year at the University, opportunities to build research skills and gain exposure to topics within the field of the biomedical sciences are relatively rare, so, to fill this gap, we focused our course on teaching primarily freshman undergraduate students how to synthesize and contextualize scientific literature, covering both basic science and clinical applications. At the end of the course, students self-reported increased confidence in reading and discussing scientific papers and review articles. The critical impact of this course lies not only in an early introduction to the popularized field of regenerative medicine, but also encouragement for younger students to participate in research early on and to appreciate the value of interdisciplinary interactions. The teaching model can be extended for implementation of student-taught introductory courses across diverse undergraduate major tracks at an institution.

Modeling the interaction between the supportive stroma and the hematopoietic stem and progenitor cells (HSPC) is of high interest in the regeneration of the bone marrow niche in blood disorders. In this work, we present an injectable co-culture system to study this interaction in a coherent in vitro culture and in vivo transplantation model. We assemble a 3D hematopoietic niche in vitro by co-culture of supportive OP9 mesenchymal cells and HSPCs in porous, chemically defined collagen-coated carboxymethylcellulose microscaffolds (CCMs). Flow cytometry and hematopoietic colony forming assays demonstrate the stromal supportive capacity for in vitro hematopoiesis in the absence of exogenous cytokines. After in vitro culture, we recover a paste-like living injectable niche biomaterial from CCM co-cultures by controlled, partial dehydration. Cell viability and the association between stroma and HSPCs are maintained in this process. After subcutaneous injection of this living artificial niche in vivo, we find maintenance of stromal and hematopoietic populations over 12 weeks in immunodeficient mice. Indeed, vascularization is enhanced in the presence of HSPCs. Our approach provides a minimalistic, scalable, biomimetic in vitro model of hematopoiesis in a microcarrier format that preserves the HSPC progenitor function, while being injectable in-vivo without disrupting the cell-cell interactions established in vitro.