3D Microstructure Inhibits Mesenchymal Stem Cells Homing to the Site of Liver Cancer Cells on a Microchip

Recent research advances of the biomimetic tumor microenvironment and regulatory factors on microfluidic devices: A systematic review

Tumor microenvironment is a multicomponent system consisting of tumor cells, noncancer cells, extracellular matrix, and signaling molecules, which hosts tumor cells with integrated biophysical and biochemical elements. Because of its critical involvement in tumor genesis, invasion, metastasis, and resistance, the tumor microenvironment is emerging as a hot topic of tumor biology and a prospective therapeutic target. Unfortunately, the complex of microenvironment modeling in vitro is technically challenging and does not effectively generalize the local tumor tissue milieu. Recently, significant advances in microfluidic technologies have provided us with an approach to imitate physiological systems that can be utilized to mimic the characterization of tumor responses with pathophysiological relevance in vitro. In this review, we highlight the recent progress and innovations in microfluidic technology that facilitates the tumor microenvironment study. We also discuss the progress and future perspective of microfluidic bionic approaches with high efficiency for the study of tumor microenvironment and the challenges encountered in cancer research, drug discovery, and personalized therapy.

Investigating the Regulation of Neural Differentiation and Injury in PC12 Cells Using Microstructure Topographic Cues

In this study, we designed and manufactured a series of different microstructure topographical cues for inducing neuronal differentiation of cells in vitro, with different topography, sizes, and structural complexities. We cultured PC12 cells in these microstructure cues and then induced neural differentiation using nerve growth factor (NGF). The pheochromocytoma cell line PC12 is a validated neuronal cell model that is widely used to study neuronal differentiation. Relevant markers of neural differentiation and cytoskeletal F-actin were characterized. Cellular immunofluorescence detection and axon length analysis showed that the differentiation of PC12 cells was significantly different under different isotropic and anisotropic topographic cues. The expression differences of the growth cone marker growth-associated protein 43 (GAP-43) and sympathetic nerve marker tyrosine hydroxylase (TH) genes were also studied in different topographic cues. Our results revealed that the physical environment has an important influence on the differentiation of neuronal cells, and 3D constraints could be used to guide axon extension. In addition, the neurotoxin 6-hydroxydopamine (6-OHDA) was used to detect the differentiation and injury of PC12 cells under different topographic cues. Finally, we discussed the feasibility of combining the topographic cues and the microfluidic chip for neural differentiation research.

Mesenchymal Stem Cells as a Promising Cell Source for Integration in Novel In Vitro Models

The human-relevance of an in vitro model is dependent on two main factors-(i) an appropriate human cell source and (ii) a modeling platform that recapitulates human in vivo conditions. Recent years have brought substantial advancements in both these aspects. In particular, mesenchymal stem cells (MSCs) have emerged as a promising cell source, as these cells can differentiate into multiple cell types, yet do not raise the ethical and practical concerns associated with other types of stem cells. In turn, advanced bioengineered in vitro models such as microfluidics, Organs-on-a-Chip, scaffolds, bioprinting and organoids are bringing researchers ever closer to mimicking complex in vivo environments, thereby overcoming some of the limitations of traditional 2D cell cultures. This review covers each of these advancements separately and discusses how the integration of MSCs into novel in vitro platforms may contribute enormously to clinical and fundamental research.

Recent advances in microfluidics for drug screening

With ever increasing drug resistance and emergence of new diseases, demand for new drug development is at an unprecedented urgency. This fact has led to extensive recent efforts to develop new drugs and novel techniques for efficient drug screening. However, new drug development is commonly hindered by cost and time span. Thus, developing more accessible, cost-effective methods for drug screening is necessary. Compared with conventional drug screening methods, a microfluidic-based system has superior advantages in sample consumption, reaction time, and cost of the operation. In this paper, the advantages of microfluidic technology in drug screening as well as the critical factors for device design are described. The strategies and applications of microfluidics for drug screening are reviewed. Moreover, current limitations and future prospects for a drug screening microdevice are also discussed.

Probing tumor microtissue formation and epithelial-mesenchymal transition on a well-mesh microchip

Three-dimensional cultures of tumor microtissues and biomimetic simulation of tumor microenvironments are of great significance in the study of tumorigenesis and development processes. In this study, a well-mesh microchip was developed to realize the formation and culture of tumor microtissues in vitro. Human lung adenocarcinoma HCC827 cells and large-cell lung cancer NCI-H460 cells were used. The size and morphology of the microtissues have been observed. In addition, we constructed an in situ three-dimensional co-culture model with tumor cell microtissues (HCC827 or NCI-H460 cells), extracellular matrix (Matrigel), and human umbilical vein endothelial cells. HCC827 microtissue epithelial-mesenchymal transition (EMT) in the established well-mesh microchip also was investigated, and the results showed that recombinant transforming growth factor could activate the Snail and Akt gene and promote migration and EMT with the decrease of E-cadherin expression for HCC827. This well-mesh microchip features simple operation and easy observation, and could provide a new method for the study of tumor cells and tumor microenvironments in vitro. Therefore, this model has potential application value in organ-on-chip technology, tissue engineering, and drug evaluation.

Integrin α9 Suppresses Hepatocellular Carcinoma Metastasis by Rho GTPase Signaling

Integrin subunit alpha 9 (ITGA9) mediates cell-cell and cell-matrix adhesion, cell migration, and invasion through binding different kinds of extracellular matrix (ECM) components. However, its potential role and underlying molecular mechanisms remain unclear in hepatocellular carcinoma (HCC). Here, we found that ITGA9 expression was obviously decreased in patients with HCC, which was negatively correlated with HCC growth and metastasis. ITGA9 overexpression significantly inhibited cell proliferation and migration in vitro as well as tumor growth and metastasis in vivo. Our data demonstrated that the inhibitory effect of ITGA9 on HCC cell motility was associated with reduced phosphorylation of focal adhesion kinase (FAK) and c-Src tyrosine kinase (Src), disrupted focal adhesion reorganization, and decreased Rac1 and RhoA activity. Our data suggest ITGA9, as a suppressor of HCC, prevents tumor cell migration and invasiveness through FAK/Src-Rac1/RhoA signaling.

Nanofiber membrane supported lung-on-a-chip microdevice for anti-cancer drug testing

Organ-on-a-chip technology can simulate the physiological and pathological microenvironment of tissues and organs in vitro, thus offering the potential of dispensing with animal models to predict the toxicity and efficacy of therapies. In this study, taking the alveolar microenvironment as a model, we developed a lung-on-a-chip with a poly(lactic-co-glycolic acid) (PLGA) electrospinning nanofiber membrane as the chip substrate and cell scaffold. The PLGA nanofiber membrane, with a controlled thickness of ∼3 μm, is porous and permeable to molecules, has good biocompatibility, and offers a means to simulate the alveolar respiratory membrane. On the chip, we carried out cell culture and co-culture of human non-small cell lung cancer cells (A549) and human fetal lung fibroblasts (HFL1), and evaluated gefitinib, an epidermal growth factor receptor (EGFR)-targeted anti-tumor drug. We further probed the possible sources of A549 cell drug resistance in the presence of HFL1 cells. In addition, we co-cultured A549, HFL1, and human umbilical vein endothelial cells (HUVECs), and found that A549 cells could lead to endothelial cell apoptosis or death, and then the occurrence of tumor invasion. This established lung-on-a-chip is simple, effective, and easy to operate. It is expected to have important applications in personalized treatment of lung tumors and to play a potential role in other clinical treatments and tissue engineering.