Fabrication of a Gelatin-Based Microdevice for Vascular Cell Culture

Injury-on-a-chip for modelling microvascular trauma-induced coagulation

Blood coagulation is a highly regulated injury response that features polymerization of fibrin fibers to prevent the passage of blood from a damaged vascular endothelium. A growing body of research seeks to monitor coagulation in microfluidic systems but fails to capture coagulation as a response to disruption of the vascular endothelium. Here we present a device that allows compression injury of a defined segment of a microfluidic vascular endothelium and the assessment of coagulation at the injury site. This pressure injury-on-a-chip (PINCH) device allows visualization of coagulation as the accumulation of fluorescent fibrin at injury sites. Quantification of fluorescent fibrin levels upstream of and at injury sites confirm that pre-treating vascular endothelium with fluid shear stress helps capture coagulation as an injury response. We leverage the PINCH devices to demonstrate the limited coagulation response of type A hemophiliacs and evaluate the performance of hemostatic microparticles and fibrinolytic nanoparticles. Our findings and the straightforward fabrication of the PINCH devices make it a promising choice for additional screening of hemostatic therapeutics.

Open Microfluidic Cell Culture in Hydrogels Enabled by 3D-Printed Molds

Cell culture models with tissue-mimicking architecture enable thein vitro investigation of cellular behavior and cell-cell interactions. These models can recapitulate the structure and function of physiological systems and can be leveraged to elucidate mechanisms of disease. In this work, we developed a method to create open microfluidic cell cultures in vitro using 3D-printed molds. The method improves sample accessibility, is simpler to manufacture than traditional closed microfluidic cell culture systems and requires minimal specialized equipment, making it an attractive method for cell culture applications. Further, these molds can generate multiple tissue-mimicking structures in various hydrogels, including blood vessel mimics using endothelial cells (HUVECs). Various geometries were patterned into agarose, gelatin, and collagen type I hydrogels, including star-shaped wells, square wells, round wells, and open channels, to demonstrate the versatility of the approach. Open channels were created in collagen with diameters ranging from 400 µm to 4 mm and in multiple collagen densities ranging from 2 mg/mL to 4 mg/mL. To demonstrate the applicability of our approach for tissue modeling, blood vessel mimics were generated in open channels with diameters of 800 µm and 2 mm, with high cell viability (>89%) for both dimensions. The vessel mimics were used to study the effects of hypoxia on cell viability and CD31 expression by subjecting them to a reduced-O2 environment (∼16% O2). As compared to normoxia conditions, vessel mimics under hypoxia had a reduction in cell viability by 8.3% and CD31 surface expression by 7.4%. Overall, our method enables the generation of different geometries in hydrogels and the development of in vitro tissue mimics for biological applications.

Protocol for quantum dot-based cell counting and immunostaining of pulmonary arterial cells from patients with pulmonary arterial hypertension

Currently, there is no protocol for growing and culturing primary pulmonary arterial cells (PACs) available from the Pulmonary Hypertension Breakthrough Initiative (PHBI). Here, we present a protocol for cultivating and maintaining three major PACs collected from patients with pulmonary arterial hypertension (PAH): endothelial (PAH-ECs), smooth muscle (PAH-SMCs), and adventitial cells (PAH-ADCs). We describe steps for obtaining PACs from PHBI, evaluating the growth of cells labeled with quantum dots (QDs), and staining endothelial cell (EC) markers for immunofluorescence imaging. For complete details on the use and execution of this protocol, please refer to Al-Hilal et al.1.

Gelatin-based cell culture device for construction and X-ray irradiation of a three-dimensional oral cancer model

Bioassays using three-dimensional (3D) tissue models offer several advantages over 2D culture assays because they can reproduce the structure and function of native tissues. In this study, we used our newly designed gelatin device to generate a miniature 3D model of human oral squamous cell carcinoma with stroma and blood vessels. To enable air-liquid interface culture, we conceived a new device structure in which three wells were lined up and separated by a dividing thread; the wells could be connected by removing the dividing thread. Cells were seeded in the center well with the dividing thread to form a multilayer, followed by the supply of media from the side wells after thread removal. Human oral squamous cell carcinoma (HSC-4) cells, human umbilical vein endothelial cells (HUVECs), and normal human dermal fibroblasts (NHDFs) were successfully cocultured, resulting in structures that mimicked 3D-cancer tissues. This 3D-cancer model was subjected to an X-ray sensitivity assay, followed by the evaluation of DNA damage using confocal microscopy and section-scanning electron microscopy.