Micro-engineered devices for assessing cellular responses to mechanical stimulation of ex vivo tissues

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The soft tissue of lower-limb prosthetic users encounters unique biomechanical challenges. Although not intended to tolerate high loads and deformation, it becomes a weight-bearing structure within the residuum-prosthesis-complex. Consequently, deep soft tissue layers may be damaged, resulting in Deep Tissue Injury (DTI). Whilst considerable effort has gone into DTI research on immobilised individuals, only little is known about the aetiology and population-specific risk factors in amputees. There is a clear gap in understanding what mechanisms contribute to a biologically safe and biomechanically sound prosthetic fit. Therefore, new information is necessary to advance future body-device interface designs and management of symptoms. Considering this, it is fundamental to understand what is happening at the cellular and tissue-level in response to forces resulting from prosthetic use. Research problem To address this lack of understanding at the tissue and cellular level, new tools are required. Organ-on-a-chip (OOC) is an emerging area that builds upon technological advances in micro-engineering methods for biological applications (lab-on-a-chip, microfluidics, cell engineering) to develop in vitro systems that recapitulate the in vivo functions and physiochemical environment of tissues. However, whilst a diverse range of cell-culture based OOC models have been developed, they cannot fully replicate the complexity of tissues in vivo and there are few reports of on-chip tissue-based models (where intact tissue samples are maintained). Given the benefits of OOC technologies (precisely controlled fluid flows, ability to multiplex, control over the local cellular environment etc.), exciting opportunities exist to develop new microsystems for maintaining and analysing ex vivo tissue whose cellular and extracellular matrix architecture is preserved. Such systems would be well suited to novel investigations into monitoring tissue damage and remodelling in response to mechanical forces, both in the short-term (hours) and long-term (weeks). The elastomer-based soft lithography approaches widely used to create OOC devices are well suited to the application of mechanical stimuli. Methods for applying stretch have been widely reported, though primarily for mono- and multi- layer cell culture systems (e.g. the seminal "lung-on-a-chip"). However, compression-based biomechanical stimuli have been little explored. Therefore, the aim of this project is to develop the first example of an ex vivo tissue-based OOC system optimised for maintaining skeletal muscle in vitro whilst applying controlled loading conditions. The system will be designed to enable live-cell microscopy of the tissue and to be adaptable for use other tissue types (e.g. skin, vascular).