Effects of Oxygen Transport on 3-D Human Mesenchymal Stem Cell Metabolic Activity in Perfusion and Static Cultures: Experiments and Mathematical Model

Abstract

Human mesenchymal stem cells (hMSCs) have unique potential to develop into functional tissue constructs to replace a wide range of tissues damaged by disease or injury. While recent studies have highlighted the necessity for 3-D culture systems to facilitate the proper biological, physiological, and developmental processes of the cells, the effects of the physiological environment on the intrinsic tissue development characteristics in the 3-D scaffolds have not been fully investigated. In this study, experimental results from a 3-D perfusion bioreactor system and the static culture are combined with a mathematical model to assess the effects of oxygen transport on hMSC metabolism and proliferation in 3-D constructs grown in static and perfusion conditions. Cells grown in the perfusion culture had order of magnitude higher metabolic rates, and the perfusion culture supports higher cell density at the end of cultivation. The specific oxygen consumption rate for the constructs in the perfusion bioreactor was found to decrease from 0.012 to 0.0017 micromol/10(6) cells/h as cell density increases, suggesting intrinsic physiological change at high cell density. BrdU staining revealed the noneven spatial distribution of the proliferating cells in the constructs grown under static culture conditions compared to the cells that were grown in the perfusion system. The hypothesis that the constructs in static culture grow under oxygen limitation is supported by higher Y(L/G) in static culture. Modeling results show that the oxygen tension in the static culture is lower than that of the perfusion unit, where the cell density was 4 times higher. The experimental and modeling results show the dependence of cell metabolism and spatial growth patterns on the culture environment and highlight the need to optimize the culture parameters in hMSC tissue engineering.

Transport and shear in a microfluidic membrane bilayer device for cell culture

“…Michaelis-Menten parameters have been reported for oxygen consumption by a wide variety of cell types including mesenchymal stem cells. 33,45,35,36 A particular application focus for the device design described herein is culture of MSCs under very low oxygen tensions, such as those that might obtain during embryonic development 37 or in the marrow or a wound environment. In response to a low oxygen tension, MSCs upregulate hypoxiainduced factors that then control cell behaviors such as proliferation and differentiation ͑e.g., into osteoblasts or chondrocytes͒.…”

“…[33][34][35][36][37][38][39] Very low oxygen concentrations are often reported to foster greater retention of desirable stem cell behaviors, for instance, proliferation. However, culturing cells at low oxygen concentrations exacerbates the rapid depletion from flowing culture medium.…”

Fluid Dynamics and Mass Transfer in a Perfusion Bioreactor with a Porous Wall

“…It was found [3] that the shear stress in this bioreactor was significantly lower than others, which made their bioreactor suitable for cell cultures sensitive to shear stress. A model was developed [4], [5] for mass transport in the perfusion channel partially filled with a porous layer, in which the flow convection in the porous layer has been neglected. The model was improved [3] by applying Brinkman's model in the porous layer.…”

Tracking Hypoxic Signaling in Encapsulated Stem Cells

“…Several techniques have been applied to measure the spatial distribution of oxygen within tissues using bloodgas analyzers, dissolved oxygen probes, and fluorescent/ luminescent particles. [48][49][50]60,61 These systems offer high levels of sensitivity and specificity, but do not show how the cells respond to their local oxygen environment. The marker system described here can complement such techniques and offers great potential as a tool to track biological responses in tissue engineering studies.…”