Transmural Flow Upregulates PD-L1 Expression in Microvascular Networks.

Endothelial programmed death-ligand 1 (PD-L1) expression is higher in tumors than in normal tissues. Also, tumoral vasculatures tend to be leakier than normal vessels leading to a higher trans-endothelial or transmural fluid flow. However, it is not clear whether such elevated transmural flow can control endothelial PD-L1 expression. Here, a new microfluidic device is developed to investigate the relationship between transmural flow and PD-L1 expression in microvascular networks (MVNs). After treating the MVNs with transmural flow for 24 h, the expression of PD-L1 in endothelial cells is upregulated. Additionally, CD8 T cell activation by phytohemagglutinin (PHA) is suppressed when cultured in the MVNs pre-conditioned with transmural flow. Moreover, transmural flow is able to further increase PD-L1 expression in the vessels formed in the tumor microenvironment. Finally, by utilizing blocking antibodies and knock-out assays, it is found that transmural flow-driven PD-L1 upregulation is controlled by integrin αVß3. Overall, this study provides a new biophysical explanation for high PD-L1 expression in tumoral vasculatures.

BRCA1 the Versatile Defender: Molecular to Environmental Perspectives.

The evolving history of BRCA1 research demonstrates the profound interconnectedness of a single protein within the web of crucial functions in human cells. Mutations in BRCA1, a tumor suppressor gene, have been linked to heightened breast and ovarian cancer risks. However, despite decades of extensive research, the mechanisms underlying BRCA1's contribution to tissue-specific tumor development remain elusive. Nevertheless, much of the BRCA1 protein's structure, function, and interactions has been elucidated. Individual regions of BRCA1 interact with numerous proteins to play roles in ubiquitination, transcription, cell checkpoints, and DNA damage repair. At a cellular scale, these BRCA1 functions coordinate tumor suppression, R-loop prevention, and cellular differentiation, all of which may contribute to BRCA1's role in cancer tissue specificity. As research on BRCA1 and breast cancer continues to evolve, it will become increasingly evident that modern materials such as Bisphenol A should be examined for their relationship with DNA stability, cancer incidence, and chemotherapy. Overall, this review offers a comprehensive understanding of BRCA1's many roles at a molecular, cellular, organismal, and environmental scale. We hope that the knowledge gathered here highlights both the necessity of BRCA1 research and the potential for novel strategies to prevent and treat cancer in individuals carrying BRCA1 mutations.

New Strategy for Promoting Vascularization in Tumor Spheroids in a Microfluidic Assay.

Previous studies have developed vascularized tumor spheroid models to demonstrate the impact of intravascular flow on tumor progression and treatment. However, these models have not been widely adopted so the vascularization of tumor spheroids in vitro is generally lower than vascularized tumor tissues in vivo. To improve the tumor vascularization level, a new strategy is introduced to form tumor spheroids by adding fibroblasts (FBs) sequentially to a pre-formed tumor spheroid and demonstrate this method with tumor cell lines from kidney, lung, and ovary cancer. Tumor spheroids made with the new strategy have higher FB densities on the periphery of the tumor spheroid, which tend to enhance vascularization. The vessels close to the tumor spheroid made with this new strategy are more perfusable than the ones made with other methods. Finally, chimeric antigen receptor (CAR) T cells are perfused under continuous flow into vascularized tumor spheroids to demonstrate immunotherapy evaluation using vascularized tumor-on-a-chip model. This new strategy for establishing tumor spheroids leads to increased vascularization in vitro, allowing for the examination of immune, endothelial, stromal, and tumor cell responses under static or flow conditions.

Interstitial flow promotes the formation of functional microvascular networks in vitro through upregulation of matrix metalloproteinase-2.

Self-organized microvascular networks (MVNs) have become key to the development of many microphysiological models. However, the self-organizing nature of this process combined with variations between types or batches of endothelial cells (ECs) often lead to inconsistency or failure to form functional MVNs. Since interstitial flow (IF) has been reported to play a beneficial role in angiogenesis, vasculogenesis, and 3D capillary morphogenesis, we systematically investigated the role IF plays during neovessel formation in a customized single channel microfluidic chip for which IF has been fully characterized. Compared to static conditions, MVNs formed under IF have higher vessel density and diameters and greater network perfusability. Through a series of inhibitory experiments, we demonstrated that IF treatment improves vasculogenesis by ECs through upregulation of matrix metalloproteinase-2 (MMP-2). We then successfully implemented a novel strategy involving the interplay between IF and MMP-2 inhibitor to regulate morphological parameters of the self-organized MVNs, with vascular permeability and perfusability well maintained. The revealed mechanism and proposed methodology were further validated with a brain MVN model. Our findings and methods have the potential to be widely utilized to boost the development of various organotypic MVNs and could be incorporated into related bioengineering applications where perfusable vasculature is desired.

A Robust Method for Perfusable Microvascular Network Formation In Vitro.

Micropost-based microfluidic devices are widely used for microvascular network (MVN) formation in diverse research fields. However, consistently generating perfusable MVNs of physiological morphology and dimension has proven to be challenging. Here, how initial seeding parameters determine key characteristics of MVN formation is investigated and a robust two-step seeding strategy to generate perfusable physiological MVNs in microfluidic devices is established.

A robust vasculogenic microfluidic model using human immortalized endothelial cells and Thy1 positive fibroblasts.

Human umbilical vein endothelial cells (HUVECs) and stromal cells, such as human lung fibroblasts (FBs), have been widely used to generate functional microvascular networks (µVNs) in vitro. However, primary cells derived from different donors have batch-to-batch variations and limited lifespans when cultured in vitro, which hampers the reproducibility of µVN formation. Here, we immortalize HUVECs and FBs by exogenously expressing human telomerase reverse transcriptase (hTERT) to obtain stable endothelial cell and FB sources for µVN formation in vitro. Interestingly, we find that immortalized HUVECs can only form functional µVNs with immortalized FBs from earlier passages but not from later passages. Mechanistically, we show that Thy1 expression decreases in FBs from later passages. Compared to Thy1 negative FBs, Thy1 positive FBs express higher IGFBP2, IGFBP7, and SPARC, which are important for angiogenesis and lumen formation during vasculogenesis in 3D. Moreover, Thy1 negative FBs physically block microvessel openings, reducing the perfusability of µVNs. Finally, by culturing immortalized FBs on gelatin-coated surfaces in serum-free medium, we are able to maintain the majority of Thy1 positive immortalized FBs to support perfusable µVN formation. Overall, we establish stable cell sources for µVN formation and characterize the functions of Thy1 positive and negative FBs in vasculogenesis in vitro.