Background and objectives: Tenocytes change their structure, composition and mechanical properties to adapt to mechanical loading. Voltage gated and mecha-nosensitive ion channels may play a key role in human tenocytes to regulate some or all initial responses to mechanical stimulation. To date, there has been no direct investigation of ion channel expression by human tenocytes.

Methods: Human tenocytes were cultured from patellar tendon samples harvested from five patients undergoing routine total knee replacement surgery (mean age: 66 years; range 63-73 years). RT-PCR, Western Blotting and whole cell electrophysiological studies were performed to investigate the expression of different classes of ion channels within tenocytes.

Results: Human tenocytes express mRNA and protein encoding voltage operated calcium channel (VOCCs) sub-units (Ca alpha 1A, Ca alpha 1C, Ca alpha 1D, Ca alpha2 delta1) and the mechanosensitive tandem pore domain potassium channel (2PK+) TREK-1. They exhibit whole cell currents consistent with the functional expression of these channels. In addition, other ionic currents were detected within these tenocytes consistent with the expression of voltage gated potassium channels, voltage gated sodium channels, and other outwardly rectifying leak currents.

Discussion and conclusions: Human tendon cells show increased levels of intracellular calcium when stress is applied to them. One of the mechanisms by which this occurs is by the influx of extracellular calcium into the cell via ion channels. VOCCs and TREK channels have been implicated in mechanotransduction signalling pathways in numerous connective tissue cell types. This study suggests that these mechanisms may be present in human tenocytes. In addition, human tenocytes may express other channel currents. Ion channels may represent potential targets for the pharmacological management of chronic tendinopathies.