Intracellular label-free detection of mesenchymal stem cell metabolism within a perivascular niche-on-a-chip

Abstract

The stem cell niche at the perivascular space in human tissue plays a pivotal role in dictating the overall fate of stem cells within it. Mesenchymal stem cells (MSCs), in particular, experience influential microenvironmental conditions, which induce specific metabolic profiles that affect processes such as cell differentiation and dysregulation of the immunomodulatory funtion. Reports focusing specifically on the metabolic status of MSCs under the effect of pathophysiological stimuli - in terms of flow velocities, shear stresses or oxygen tension - do not model heterogenous gradients, highlighting the need of more advanced models reproducing the metabolic niche. Organ-on-a-chip technology offers the most advanced tools for stem cell niche modelling thus allowing for controlled dynamic culture conditions while profiling tunable oxygen tension gradients. However, current systems for live cell detection of metabolic activity inside microfluidic devices require the integration of microsensors that allow for extracellular measurments only, giving innacurate and indirect information about the metabolic state of cells. Here, we present a metabolic toolbox coupling a miniatuirzed in vitro system for human-MSCs dynamic culture, that mimics microenvironmental conditions of the perivascular niche, with high-resolution imaging of intracellular metabolism. Using Fluorescence Lifetime Imaging Microscopy (FLIM) we monitor the spatial metabolic machinery and correlate it with experimentally validated intracellular oxygen concentration after designing the oxygen tension decay along the fluidic chamber by in silico models prediction. Our platform allows for the subjection of a metabolic profile to MSCs, mimicking the physiological niche in space and time, and its real-time monitoring representing a functional tool for modelling perivascular niches, relevant diseases and metabolic-related uptake of pharmaceuticals.