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

The stem cell niche at the perivascular space in human tissue plays a pivotal role in dictating the overallfate of stem cells within it. Mesenchymal stem cells (MSCs) in particular, experience influentialmicroenvironmental conditions, which induce specific metabolic profiles that affect processes of celldifferentiation and dysregulation of the immunomodulatory function. Reports focusing specifically on themetabolic status of MSCs under the effect of pathophysiological stimuli–in terms of flow velocities, shearstresses or oxygen tension–do not model heterogeneous gradients, highlighting the need for moreadvanced models reproducing the metabolic niche. Organ-on-a-chip technology offers the mostadvanced tools for stem cell niche modelling thus allowing for controlled dynamic culture conditions whileprofiling tuneable oxygen tension gradients. However, current systems for live cell detection of metabolicactivity inside microfluidic devices require the integration of microsensors. The presence of suchmicrosensors poses the potential to alter microfluidics and their resolution does not enable intracellularmeasurements but rather a global representation concerning cellular metabolism. Here, we present ametabolic toolbox coupling a miniaturisedin vitrosystem for human-MSCs dynamic culture, which mimicsmicroenvironmental conditions of the perivascular niche, with high-resolution imaging of cell metabolism.Using fluorescence lifetime imaging microscopy (FLIM) we monitor the spatial metabolic machinery andcorrelate it with experimentally validated intracellular oxygen concentration after designing the oxygentension decay along the fluidic chamber byin silicomodels prediction. Our platform allows the metabolicregulation of MSCs, mimicking the physiological niche in space and time, and its real-time monitoringrepresenting a functional tool for modelling perivascular niches, relevant diseases and metabolic-relateduptake of pharmaceuticals.