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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: The influence of direct current electrical stimulation on chondrocytes in a 3D model system

Author: AKANJI, Oto-Ola O

Year: 2008

Supervisor(s): Dan Bader, David Lee

The present work examined the influence of an applied direct current on chondrocyte viability, ECM synthesis and Ca2+ signalling with the aim to further understand chondrocyte metabolic mechanisms.

A robust stimulation chamber, which incorporated the well established chondrocyte-agarose 3D culture model was developed. A cell viability profiling protocol was used to assess the effect of varying current densities on the model system. In addition, biochemical and molecular techniques were used to assess alterations in ECM synthesis and cell proliferation induced by the stimulation regimes. Furthermore, an investigation of real-time Ca2+ signalling within electrical stimulated chondrocyte-agarose constructs was performed.

The current density magnitude and duration of exposure were observed to influence cell viability within the constructs. The study revealed that the mean cell viability is maintained at greater than 90% following exposure to a current density of 4 mA/cm2 for 6 hours. The applied current density of 4 mA/cm2 did not significantly alter ECM synthesis and chrondrocyte proliferation rates. There were also no systematic influences of the current on aggrecan and collagen II mRNA expression levels. However, it was evident that the applied current altered the mechanism of response at a sub-molecular level. In the absence of direct current (dc), the observed Ca2+ signalling response was markedly reduced by verapamil. However, during the application of dc, verapamil did not affect the response. These data would suggest that the influence of the applied current is dependent on the sensitivity of the cell population employed and independent of voltage-gated Ca2+ entry into the cytoplasm. Future work would involve the manipulation of the existing protocol and an investigation of the Ca2+ independent mechanisms associated with chondrocyte metabolism.