Angiogenesis-on-a-chip coupled with single-cell RNA sequencing reveals spatially differential activations of autophagy along angiogenic sprouts

Towards advanced regenerative therapeutics to tackle cardio-cerebrovascular diseases

The development of vascularized organoids as novel modelling tools of the human cardio-cerebrovascular system for preclinical research has become an essential platform for studying human vascularized tissues/organs for development of personalized therapeutics during recent decades. Organ-on-chip technology is promising for investigating physiological in vitro responses in drug screening development and advanced disease models. Vascularized tissue/organ-on-a-chip benefits every step of drug discovery pipeline as a screening tool with close human genome relevance to investigate human systems biology. Simultaneously, cardio-cerebrovascular-on-chip-integrated microfluidic system serves as an alternative to preclinical animal research for studying (patho-)physiological processes of human blood vessels during embryonic development and cardio-cerebrovascular disease. Integrated with next-generation techniques, such as three-dimensional bioprinting of both cells and matrix, may enable vascularized organoid-on-chip-based novel drug development as personalized therapeutics.

Type III sodium-dependent inorganic phosphate transporters are required for the phenotypes in human brain microvascular endothelial cells

Inorganic phosphate (Pi) homeostasis in the brain is critical for the development of primary brain calcification (PBC). In the brains of patients with PBC, calcification occurs in the cerebral small vessels, and it is primarily caused by mutated SLC20A2, a gene that encodes a type III Pi transporter. A previous study founded that the SLC20 family, which includes SLC20A1 and SLC20A2, contributes to Pi homeostasis in the central nervous system. However, the impact of these Pi transporters on the brain vessel phenotype remains unknown. Thus, in this study, we aimed to investigate the effect of SLC20A1 or SLC20A2 depletion on the phenotype of human brain microvascular endothelial cells (hBMECs). We assessed the primary phenotypes of vascular endothelial cells, such as proliferation, tube formation, and VE-cadherin expression. The results showed that hBMECs silenced for SLC20A1 or SLC20A2 had decreased proliferative and angiogenic ability, as well as VE-cadherin expression. The intracellular Pi concentration ([Pi]i) remained constant in SLC20A1-silenced hBMECs whereas it increased in SLC20A2-silenced cells. Tube formation ability was no change even at 3 mM, a concentration higher than [Pi]i which was increased in SLC20A2-silenced hBMECs. Thus, increased [Pi]i in SLC20A2-silenced hBMECs may have a small impact on phenotypic changes. In conclusion, abnormalities in Pi homeostasis caused by SLC20A2 depletion were suggested to play a minor role in PBC endothelial pathology.

Intussusceptive angiogenesis-on-a-chip: Evidence for transluminal vascular bridging by endothelial delamination

Intussusceptive angiogenesis is an increasingly recognized vessel duplication process that generates and reshapes microvascular beds. However, the mechanism by which a vessel splits into two is poorly understood. Particularly vexing is formation of the hallmark transluminal endothelial cell bridge. How an endothelial cell comes to cross a flowing lumen rather than line it is enigmatic. To elucidate this, we used a microvessel-on-a-chip strategy, creating a microconduit coherently lined with flow-sensitive endothelial cells but in which transluminal bridges also formed. Bridge morphologies ranged from filamentous strand to multicellular columns with a central extracellular matrix-containing core. These bridge architectures were found to recapitulate those in microvessels in embryos, tumors, diseased organs, and the dermis of patients with limb-threatening ischemia. Time-lapse, multiplane, three-dimensional (3D) microscopy of the microphysiologic conduit revealed that bridges arose from endothelial cells oriented orthogonal to flow that partially released from the wall while retaining attachments at the ends. This delamination process was blocked by hyperactivation of Rho and augmented by interventions that weaken cell-substrate interactions, including inhibiting nonmuscle myosin II and blocking α5ß1 integrin. Thus, endothelial cells can leave their monolayer and transect a flowing lumen through controlled delamination. This previously unrecognized lumen entry program could explain the launch of intussusceptive angiogenesis and opens a framework for intervening.

GelMA@LNP/AST Promotes eNOS-Dependent Angiogenesis Through Autophagy Activation for the Treatment of Hind Limb Ischemia

Purpose

Limb ischemia is a refractory disease characterized by insufficient angiogenesis and tissue necrosis. Currently, the primary clinical treatment method is surgical intervention; however, the prognosis for patients with severe limb ischemia remains unsatisfactory. Although some studies have evaluated the effects of using bioactive factors to promote neovascularization and tissue repair, the clinical outcomes have not met expectations, possibly due to the difficulties in maintaining biological activity and avoiding potential side effects. Traditional Chinese medicine, specifically astilbin (AST), is a potential therapeutic agent in promoting tissue regeneration. However, there have been no reports on its efficacy in treating limb ischemia through promoting angiogenesis.

Materials and Methods

In this study, we prepared AST-loaded lignin nanoparticles (LNP/AST) with sustained-release functionality, which were mixed with GelMA hydrogel (GelMA@LNP/AST). The angiogenic effects were evaluated in a mouse model of hind limb ischemia. To further investigate the mechanism of angiogenesis, human endothelial cell line EA.hy926 was exposed to different concentrations of AST. The effects of AST on cell migration and angiogenesis were studied using wound healing assays and angiogenesis assays. The changes in angiogenesis markers, autophagy markers, and eNOS levels were detected using qPCR and Western blotting. 3-MA was used to assess the role of autophagy in the activation of eNOS mediated by AST and its subsequent angiogenic effects.

Results

GelMA@LNP/AST significantly promoted blood flow recovery in mice with hind limb ischemia. This effect was mainly attributed to the enhanced migration and angiogenic capabilities of endothelial cells mediated by AST. A potential underlying mechanism could be that the autophagy induced by AST increases eNOS activity.

Conclusion

GelMA@LNP/AST enables complete revascularization in female mice after hind limb ischemia, thereby achieving limb preservation and restoring motor function. Given the good therapeutic potential of the GelMA@LNP/AST in revascularization, it may become an effective strategy for successfully salvaging limbs in cases of limb ischemia.

Integrating Vascular Phenotypic and Proteomic Analysis in an Open Microfluidic Platform

This research introduces a vascular phenotypic and proteomic analysis (VPT) platform designed to perform high-throughput experiments on vascular development. The VPT platform utilizes an open-channel configuration that facilitates angiogenesis by precise alignment of endothelial cells, allowing for a 3D morphological examination and protein analysis. We study the effects of antiangiogenic agents─bevacizumab, ramucirumab, cabozantinib, regorafenib, wortmannin, chloroquine, and paclitaxel─on cytoskeletal integrity and angiogenic sprouting, observing an approximately 50% reduction in sprouting at higher drug concentrations. Precise LC-MS/MS analyses reveal global protein expression changes in response to four of these drugs, providing insights into the signaling pathways related to the cell cycle, cytoskeleton, cellular senescence, and angiogenesis. Our findings emphasize the intricate relationship between cytoskeletal alterations and angiogenic responses, underlining the significance of integrating morphological and proteomic data for a comprehensive understanding of angiogenesis. The VPT platform not only advances our understanding of drug impacts on vascular biology but also offers a versatile tool for analyzing proteome and morphological features across various models beyond blood vessels.

Standardizing designed and emergent quantitative features in microphysiological systems

Microphysiological systems (MPSs) are cellular models that replicate aspects of organ and tissue functions in vitro. In contrast with conventional cell cultures, MPSs often provide physiological mechanical cues to cells, include fluid flow and can be interlinked (hence, they are often referred to as microfluidic tissue chips or organs-on-chips). Here, by means of examples of MPSs of the vascular system, intestine, brain and heart, we advocate for the development of standards that allow for comparisons of quantitative physiological features in MPSs and humans. Such standards should ensure that the in vivo relevance and predictive value of MPSs can be properly assessed as fit-for-purpose in specific applications, such as the assessment of drug toxicity, the identification of therapeutics or the understanding of human physiology or disease. Specifically, we distinguish designed features, which can be controlled via the design of the MPS, from emergent features, which describe cellular function, and propose methods for improving MPSs with readouts and sensors for the quantitative monitoring of complex physiology towards enabling wider end-user adoption and regulatory acceptance.

The Edifice of Vasculature-On-Chips: A Focused Review on the Key Elements and Assembly of Angiogenesis Models

The conception of vascularized organ-on-a-chip models provides researchers with the ability to supply controlled biological and physical cues that simulate the in vivo dynamic microphysiological environment of native blood vessels. The intention of this niche research area is to improve our understanding of the role of the vasculature in health or disease progression in vitro by allowing researchers to monitor angiogenic responses and cell-cell or cell-matrix interactions in real time. This review offers a comprehensive overview of the essential elements, including cells, biomaterials, microenvironmental factors, microfluidic chip design, and standard validation procedures that currently govern angiogenesis-on-a-chip assemblies. In addition, we emphasize the importance of incorporating a microvasculature component into organ-on-chip devices in critical biomedical research areas, such as tissue engineering, drug discovery, and disease modeling. Ultimately, advances in this area of research could provide innovative solutions and a personalized approach to ongoing medical challenges.

Modeling of intravenous caspofungin administration using an intestine-on-chip reveals altered Candida albicans microcolonies and pathogenicity

Candida albicans is a commensal yeast of the human intestinal microbiota that, under predisposing conditions, can become pathogenic and cause life-threatening systemic infections (candidiasis). Fungal-host interactions during candidiasis are commonly studied using conventional 2D in vitro models, which have provided critical insights into the pathogenicity. However, microphysiological models with a higher biological complexity may be more suitable to mimic in vivo-like infection processes and antifungal drug efficacy. Therefore, a 3D intestine-on-chip model was used to investigate fungal-host interactions during the onset of invasive candidiasis and evaluate antifungal treatment under clinically relevant conditions. By combining microbiological and image-based analyses we quantified infection processes such as invasiveness and fungal translocation across the epithelial barrier. Additionally, we obtained novel insights into fungal microcolony morphology and association with the tissue. Our results demonstrate that C. albicans microcolonies induce injury to the epithelial tissue by disrupting apical cell-cell contacts and causing inflammation. Caspofungin treatment effectively reduced the fungal biomass and induced substantial alterations in microcolony morphology during infection with a wild-type strain. However, caspofungin showed limited effects after infection with an echinocandin-resistant clinical isolate. Collectively, this organ-on-chip model can be leveraged for in-depth characterization of pathogen-host interactions and alterations due to antimicrobial treatment.