Islet Preconditioning via Multimodal Microfluidic Modulation of Intermittent Hypoxia

Abstract

Simultaneous stimulation of ex vivo pancreatic islets with dynamic oxygen and glucose is a critical technique for studying how hypoxia alters glucose-stimulated response, especially in transplant environments. Standard techniques using a hypoxic chamber cannot provide both oxygen and glucose modulations while monitoring stimulus-secretion coupling factors in real-time. Using novel microfluidic device with integrated glucose and oxygen modulations, we quantified hypoxic impairment of islet response by calcium influx, mitochondrial potentials, and insulin secretion. Glucose-induced calcium response magnitude and phase were suppressed by hypoxia, while mitochondrial hyperpolarization and insulin secretion decreased in coordination. More importantly, hypoxic response was improved by preconditioning islets to intermittent hypoxia (IH, 1min/1min 5%–21% cycling for 1 hour), translating to improved insulin secretion. Moreover, blocking mitochondrial KATP channels removed preconditioning benefits of IH, similar to mechanisms in preconditioned cardiomyocytes. Additionally, the multimodal device can be applied to a variety of dynamic oxygen-metabolic studies in other ex vivo tissues.

A microfluidic device to study cancer metastasis under chronic and intermittent hypoxia

“…Since the vascular channel also contained flowing medium, some cells emerging into the vascular channel may have been swept away before cell fixing, staining and enumeration. These results demonstrate that the device can indeed be used to generate an oxygen gradient similar to that in the studies of Lo et al, 26 and Adler et al 28 However, in this device, a gradient is applied across an ECM matrix providing an in situ invasion assay and mimics the process of both tumor cell invasion and intravasation. None of these earlier devices have this capability.…”

“…Placing microdevices inside environment chambers with controlled gas flow can achieve chronic hypoxia 20,21 or cycles to model ischemia/reperfusion injury. 22 Temporal control of oxygen concentration also has been achieved with the inclusion of gas channels either overlying, 23,24 or underneath 25,26 the cell culture channels. Similarly, spatial control of oxygen concentration has been achieved with the inclusion of gas channels adjacent to [27][28][29] and overlying 30 the cell culture channels.…”

“…33 Furthermore, spatial gradients have been achieved by chemical control 34 and electrolytic control of oxygen concentration. 35 Lo et al, 26 demonstrated oxygen control to study calcium signaling and insulin kinetics of islet cells with intermittent hypoxia cycles of 1 min.…”

Microfluidic cell culture system with on-chip hypoxic conditioning

“…Recent studies reveal that microfluidic platforms are powerful tools to manipulate the oxygen condition in microenvironment [4][5][6][7]. Many microfluidic devices producing hypoxic conditions to date [4][5][6][7], however, mainly focused on precise and micro-scaled control of oxygen tension intended for generation of oxygen gradients on-chip, while portability of the entire system including gas supply and concentration control has received little attention.…”

“…Many microfluidic devices producing hypoxic conditions to date [4][5][6][7], however, mainly focused on precise and micro-scaled control of oxygen tension intended for generation of oxygen gradients on-chip, while portability of the entire system including gas supply and concentration control has received little attention. These devices would often require large apparatus such as gas tanks/regulators, and frequent calibration processes to ensure desired concentration profiles for actual use.…”