A Microfluidics-Based Screening Tool to Assess the Impact of Blood Plasma Factors on Microvascular Integrity

Vascular dysfunction in hemorrhagic viral fevers: opportunities for organotypic modeling

The hemorrhagic fever viruses (HFVs) cause severe or fatal infections in humans. Named after their common symptom hemorrhage, these viruses induce significant vascular dysfunction by affecting endothelial cells, altering immunity, and disrupting the clotting system. Despite advances in treatments, such as cytokine blocking therapies, disease modifying treatment for this class of pathogen remains elusive. Improved understanding of the pathogenesis of these infections could provide new avenues to treatment. While animal models and traditional 2D cell cultures have contributed insight into the mechanisms by which these pathogens affect the vasculature, these models fall short in replicatingin vivohuman vascular dynamics. The emergence of microphysiological systems (MPSs) offers promising avenues for modeling these complex interactions. These MPS or 'organ-on-chip' models present opportunities to better mimic human vascular responses and thus aid in treatment development. In this review, we explore the impact of HFV on the vasculature by causing endothelial dysfunction, blood clotting irregularities, and immune dysregulation. We highlight how existing MPS have elucidated features of HFV pathogenesis as well as discuss existing knowledge gaps and the challenges in modeling these interactions using MPS. Understanding the intricate mechanisms of vascular dysfunction caused by HFV is crucial in developing therapies not only for these infections, but also for other vasculotropic conditions like sepsis.

Donor-Derived Engineered Microvessels for Cardiovascular Risk Stratification of Patients with Kidney Failure

Cardiovascular disease is the cause of death in ≈50% of hemodialysis patients. Accumulation of uremic solutes in systemic circulation is thought to be a key driver of the endothelial dysfunction that underlies elevated cardiovascular events. A challenge in understanding the mechanisms relating chronic kidney disease to cardiovascular disease is the lack of in vitro models that allow screening of the effects of the uremic environment on the endothelium. Here, a method is described for microfabrication of human blood vessels from donor cells and perfused with donor serum. The resulting donor-derived microvessels are used to quantify vascular permeability, a hallmark of endothelial dysfunction, in response to serum spiked with pathophysiological levels of indoxyl sulfate, and in response to serum from patients with chronic kidney disease and from uremic pigs. The uremic environment has pronounced effects on microvascular integrity as demonstrated by irregular cell-cell junctions and increased permeability in comparison to cell culture media and healthy serum. Moreover, the engineered microvessels demonstrate an increase in sensitivity compared to traditional 2D assays. Thus, the devices and the methods presented here have the potential to be utilized to risk stratify and to direct personalized treatments for patients with chronic kidney disease.

Development of a cancer metastasis-on-chip assay for high throughput drug screening

Metastasis is the cause of most triple-negative breast cancer deaths, yet anti-metastatic therapeutics remain limited. To develop new therapeutics to prevent metastasis, pathophysiologically relevant assays that recapitulate tumor microenvironment is essential for disease modeling and drug discovery. Here, we have developed a microfluidic metastasis-on-chip assay of the early stages of cancer metastasis integrated with the triple-negative breast cancer cell line (MDA-MB-231), stromal fibroblasts and a perfused microvessel. High-content imaging with automated quantification methods was optimized to assess the tumor cell invasion and intravasation within the model. Cell invasion and intravasation were enhanced when fibroblasts co-cultured with a breast cancer cell line (MDA-MB-231). However, the non-invasive breast cancer cell line, MCF7, remained non-invasive in our model, even in the presence of fibroblasts. High-content screening of a targeted anti-cancer therapy drug library was conducted to evaluate the drug response sensitivity of the optimized model. Through this screening, we identified 30 compounds that reduced the tumor intravasation by 60% compared to controls. Multi-parametric phenotypic analysis was applied by combining the data from the metastasis-on-chip, cell proliferation and 2D cell migration screens, revealing that the drug library was clustered into eight distinct groups with similar drug responses. Notably, MEK inhibitors were enriched in cluster cell invasion and intravasation. In contrast, drugs with molecular targets: ABL, KIT, PDGF, SRC, and VEGFR were enriched in the drug clusters showing a strong effect on tumor cell intravasation with less impact on cell invasion or cell proliferation, of which, Imatinib, a multi-kinase inhibitor targeting BCR-ABL/PDGFR/KIT. Further experimental analysis showed that Imatinib enhanced endothelial barrier stability as measured by trans-endothelial electrical resistance and significantly reduced the trans-endothelial invasion activity of tumor cells. Our findings demonstrate the potential of our metastasis-on-chip assay as a powerful tool for studying cancer metastasis biology, drug discovery aims, and assessing drug responses, offering prospects for personalized anti-metastatic therapies for triple-negative breast cancer patients.

Engineered Vasculature for Cancer Research and Regenerative Medicine

Engineered human tissues created by three-dimensional cell culture of human cells in a hydrogel are becoming emerging model systems for cancer drug discovery and regenerative medicine. Complex functional engineered tissues can also assist in the regeneration, repair, or replacement of human tissues. However, one of the main hurdles for tissue engineering, three-dimensional cell culture, and regenerative medicine is the capability of delivering nutrients and oxygen to cells through the vasculatures. Several studies have investigated different strategies to create a functional vascular system in engineered tissues and organ-on-a-chips. Engineered vasculatures have been used for the studies of angiogenesis, vasculogenesis, as well as drug and cell transports across the endothelium. Moreover, vascular engineering allows the creation of large functional vascular conduits for regenerative medicine purposes. However, there are still many challenges in the creation of vascularized tissue constructs and their biological applications. This review will summarize the latest efforts to create vasculatures and vascularized tissues for cancer research and regenerative medicine.

Quantify permeability using on-a-chip models in high-throughput applications

Traditionally, to quantify permeability of a biological barrier, the initial slope is used, based on the assumption of sink condition (concentration of the donor is constant, and the receiver increases less than 10%). With on-a-chip barrier models, this assumption fails in cell-free or leaky conditions, which requires the use of the exact solution. To encounter a time delay from performing the assay and acquiring the data, we present a protocol with the exact equation modified to incorporate a time offset.

ZNF185 prevents stress fiber formation through the inhibition of RhoA in endothelial cells

Signaling through cAMP/protein kinase A (PKA) promotes endothelial barrier function to prevent plasma leakage induced by inflammatory mediators. The discovery of PKA substrates in endothelial cells increases our understanding of the molecular mechanisms involved in vessel maturation. In this study, we evaluate a cAMP inducer, forskolin, and a phospho-PKA substrate antibody to identify ZNF185 as a PKA substrate. ZNF185 interacts with PKA and colocalizes with F-actin in endothelial cells. Both ZNF185 and F-actin accumulate in the plasma membrane region in response to forskolin to stabilize the cortical actin structure. By contrast, ZNF185 knockdown disrupts actin filaments and promotes stress fiber formation without inflammatory mediators. Constitutive activation of RhoA is induced by ZNF185 knockdown, which results in forskolin-resistant endothelial barrier dysfunction. Knockout of mouse Zfp185 which is an orthologous gene of human ZNF185 increases vascular leakage in response to inflammatory stimuli in vivo. Thrombin protease is used as a positive control to assemble stress fibers via RhoA activation. Unexpectedly, ZNF185 is cleaved by thrombin, resulting in an N-terminal actin-targeting domain and a C-terminal PKA-interacting domain. Irreversible dysfunction of ZNF185 protein potentially causes RhoA-dependent stress fiber formation by thrombin.