This proposal describes the development of tools that will be applied to robustly investigate the role of
circadian rhythms in tissue engineering for the first time by: synchronizing rhythms in vitro; reinstating absent
rhythms locally in regenerating sites in vivo; and aligning therapeutic delivery to distinct circadian phases. Our
lab focuses on timing as a tool in tissue engineering, whereby we use therapeutic signals to co-ordinate
various phases of repair over the time scale of days. But, 24 hr circadian rhythms – which play critical roles in
biological systems (e.g., tissue formation, cell signaling, cell activity) – are ignored in tissue engineering studies
and product development. For example, in current tissue engineering cell cultures individual cells have a
circadian rhythm, but they rapidly fall out of synch with other cells in the culture, eliminating rhythmic processes
that would occur in the natural system. Indeed, patient populations with disrupted circadian rhythms (e.g.,
diabetes, obesity) also have poor tissue regeneration and they are the target of many tissue engineering
strategies. Yet, nobody has considered this lack of rhythmicity in developing tissue engineering strategies.
From the therapeutic timing perspective, there is strong evidence in many diseases that the efficacy of
systemically delivered drugs is strongly affected by the time of day. In local tissue regenerating sites, it is highly
probable that there are also optimum circadian times for therapeutic delivery, which needs to be investigated.
In the next five years we will begin to fill these gaps in tissue engineering research laying the groundwork for
an unexplored approach that can be harnessed to optimize tissue regeneration. First, this work will impart the
currently absent circadian rhythms into in vitro tissue engineering studies of skin, bone, and vascularization.
This will be accomplished using a robotics device that interfaces with standard tissue culture setups to provide
synchronizing signals (e.g., glucocorticoids, temperature) at precise timepoints. Interestingly, glucocorticoid
rhythms are altered in patient populations with poor regeneration (e.g., obesity, diabetes) but synthetic
glucocorticoids given systemically can reinstate circadian rhythms. In a first-of-its-kind approach, we will test
the ability to drive local circadian rhythms at a regenerating site via glucocorticoid signaling. To do this we will
develop circadian drug delivery systems based on ultrasound- or light-triggered release that are capable of
precisely timed daily local delivery of glucocorticoids. The automated tools and circadian drug delivery system
will additionally be modified and used to demonstrate the effect of growth factor alignment with circadian
phases on tissue repair. This proposal will rigorously investigate the interplay between circadian rhythms and
tissue engineering, provide the tools to research and test these rhythms, and demonstrate how these rhythms
can be used to enhance regeneration. With this foundation, our labs’ vision is to lead exploration of this new
facet of tissue engineering, undertaking future work that manipulates these rhythms for regeneration of multiple
tissues, more deeply explores the mechanisms, and translates these new tools and findings to the clinic.