Oxygen consumption in human, tissue-engineered myobundles during basal and electrical stimulation conditions.

Brittany N Davis,Varun Prasad,Ringo Yen,George A Truskey

doi:10.1063/1.5093417

Abstract

During three-dimensional culture of skeletal muscle in vitro, electrical stimulation provides an important cue to enhance skeletal muscle mimicry of the in vivo structure and function. However, increased respiration can cause oxygen transport limitations in these avascular three-dimensional constructs, leading to a hypoxic, necrotic core, or nonuniform cell distributions in larger constructs. To enhance oxygen transport with convection, oxygen concentrations were measured using an optical sensor at the inlet and outlet of an 80 μl fluid volume microphysiological system (MPS) flow chamber containing three-dimensional human skeletal muscle myobundles. Finite element model simulations of convection around myobundles and oxygen metabolism by the myobundles in the 80 μl MPS flow chamber agreed well with the oxygen consumption rate (OCR) at different flow rates, suggesting that under basal conditions, mass transfer limitations were negligible for flow rates above 1.5 μl s-1. To accommodate electrodes for electrical stimulation, a modified 450 μl chamber was constructed. Electrical stimulation for 30 min increased the measured rate of oxygen consumption by the myobundles to slightly over 2 times the basal OCR. Model simulations indicate that mass transfer limitations were significant during electrical stimulation and, in the absence of mass transfer limitations, electrical stimulation induced about a 20-fold increase in the maximum rate of oxygen consumption. The results indicate that simulated exercise conditions increase respiration of skeletal muscle and mass transfer limitations reduce the measured levels of oxygen uptake, which may affect previous studies that model exercise with engineered muscle.

Highlights

Skeletal muscle tissue engineering holds great promise for drug screening,[1,2] regenerative medicine,[3,4] soft robotic devices,[5] and the study of muscle development, disease, growth, and metabolism.[6,7,8,9,10] current skeletal muscle tissue engineered constructs lack the complex cellular and molecular organization, mature muscle protein expression, and adequate functional output characteristic of native muscle.[11]
Oxygen consumption rates in myobundles under resting conditions were measured in an 80 ll microphysiological system (MPS) flow chamber (Figs. 1 and S1A) at varying flow rates in the absence of electrical stimulation
The myobundle was attached to a porous nylon frame to maintain tension and rests slightly above the bottom of the 80 ll chamber to enable flow around the myobundle

Summary

Introduction

Skeletal muscle tissue engineering holds great promise for drug screening,[1,2] regenerative medicine,[3,4] soft robotic devices,[5] and the study of muscle development, disease, growth, and metabolism.[6,7,8,9,10] current skeletal muscle tissue engineered constructs lack the complex cellular and molecular organization, mature muscle protein expression, and adequate functional output characteristic of native muscle.[11]. We measured the myobundle oxygen consumption rate (OCR) using the OROBOROS O2k system,[19] providing the first results for oxygen consumption by engineered human skeletal muscle. The O2K system is highly accurate but is not well-suited for studies of skeletal muscle that is electrically stimulated. Measurements in the O2K system break sterility and cannot be used for repeated long-term studies with the same engineered myobundles. Flow of media around the myobundles in a microphysiological system (MPS) flow chamber enables the realtime, nondestructive measurement of oxygen metabolism with and without electrical stimulation. These added advantages enable the APL Bioeng.

Methods

Results

Discussion

Conclusion