Monitoring Steady Flow Effects on Cell Distribution in Engineered Valve Tissues by Magnetic Resonance Imaging

Abstract

In heart valve tissue engineering, assessment of cell migration under dynamic states can provide insights on the evolving tissue structure. We labeled human vascular smooth muscle (SMCs), endothelial (ECs), and bone marrow-derived mesenchymal stem cells (BMSCs) with superparamagnetic iron oxide (SPIO) microparticles and visualized them using magnetic resonance imaging (MRI) under steady flow. We determined that vascular cells were able to remain reasonably viable and proliferate well after being labeled with SPIO microparticles (200 μg/mL) for 48 hours. SPIO-labeled cells were successfully visualized using T2* contrast. When physiologically representative shear stresses (5-6 dynes/cm2) were applied to SMC-EC coculture-seeded scaffolds, hypointense regions seemed to have decreased after 2 weeks in some locations, whereas others revealed sustained levels of T2* contrast; similar observations were seen in the case of BMSC-seeded scaffolds. This could be attributable to increased out-of-plane cell migratory activity, which occurred from the fluid-induced mechanical cues received, which was not previously evidenced in static culture. Vascular cells and BMSCs were labeled with remarkably high concentrations of SPIO. Moreover, steady fluid flow enhanced intrascaffold cell migration of vascular SMCs and ECs as well as BMSCs, which, in turn, significantly improved construct cellularity and extracellular collagen content.

Differentiation and Distribution of Marrow Stem Cells in Flex-Flow Environments Demonstrate Support of the Valvular Phenotype

“…We interpret that BMSC to endothelial cell differentiation and intra-scaffold BMSC migration patterns are enhanced under flow states and is not strongly flow magnitude-dependent. Indeed, we previously visualized and monitored the increase in cell scaffold migratory patterns via magnetic resonance imaging, which was found to be augmented under steady flow-alone conditions compared to no flow controls [ 52 ]. On the other hand, the link between the mechanical environments and α-SMA expressing cells within the de novo valvular tissues is not as straightforward.…”

Iron Oxide Nanoparticles in Regenerative Medicine and Tissue Engineering

“…Functional tissue engineering of heart valves is a major challenge. To observe cell migration into the developing tissue structure under dynamic conditions, human vascular SMCs, ECs and BM-MSCs were labeled with IONPs and then seeded onto a nonwoven scaffold of a mixture of polyglycolic acid (PGA) and PLA in a hybridization tube [ 285 ]. Mechanical conditioning under dynamic flow conditions was performed in a flow chamber of an MRI-compatible bioreactor and enhanced cell migration of SMCs, ECs and BM-MSCs within the scaffold and significantly increased extracellular collagen content.…”

Bioreactor Synergy with 3D Scaffolds: New Era for Stem Cells Culture

“…Wong labeled cells on fiber and in collagen with green and red fluorescent protein expressing hUVECs, respectively, to visualize and monitor the formation of capillary networks. Martinez uses superparamagnetic iron oxide (SPIO) particles to label cells and perform magnetic resonance imaging (MRI) observations. − These techniques, both in some cases, can be used to assess the growth state of cells but not necessarily applicable to all bioreactors, which require further study.…”