A novel in vitro loading system for high frequency loading of cultured tendon fascicles

Tendons are known to adapt to their mechanical environment, however high frequency low magnitude (HFLM) loading regimes (10-50Hz), which are effective in promoting bone anabolic effects, have not been investigated in controlled conditions in tendon. In vitro loading systems (IVLS) enable precise characterisation of the link between their controlled mechanical environment and cultured tissue biological response. We report a novel IVLS design using an applied magnetic field to produce time varying loading in cultured rat tail tendon fascicles (RTTF). The design was validated through magnetic flux, load cell and viability measurements, and we report the results of preliminary experiments testing the hypothesis that an HFLM loading regime will maintain the biochemical and mechanical properties of fresh RTTF in culture over 7 days. Tissue viability was maintained for 7 days under all loading conditions, and the average peak load applied to RTTFs using the IVLS at 20Hz was 0.125N. RTTFs cultured for 7 days with HFLM loading showed a trend for a higher tangent modulus than fresh tissue, and significantly higher modulus than unloaded RTTFs. GAG content of HFLM cultured RTTFs was not significantly changed from that of fresh RTTFs. This novel, validated IVLS will provide new knowledge of tendon mechanobiology and has already shown the potential of clinically relevant HFLM loading for influencing tendon biology.