CHAPTER 7: CONCLUSIONS AND FUTURE WORK
7.3 Future Work
Most of our future work for the project will focus on further elucidating the role of afterload in the context of sunitinib cardiotoxicity. Future experiments will utilize human cardiac microtissues. We would like to expand our metrics for evaluating the effects of sunitinib under varying degrees of afterload. Specifically we would like to include experiments that measure force under varying degrees of afterload, in the presence or absence of sunitinib. This will require us to be able to make force measurements at a fixed tissue length, to account for any resting sarcomere length changes that may be occurring. We are actively working to develop methods to control tissue length by inserting iron particles in pillar caps and controlling pillar displacement with a magnet (Fig 7.1 panel A). Additionally, we would like to be able to induce secondary increases in afterload in our CMT model. We believe that this attribute would make our work more clinically relevant as a secondary change in afterload is a better mimic of the secondary
development of hypertension in patients. Furthermore, if secondary increases in afterload can be reversed, it would give us the opportunity to begin answering the question whether sunitinib induced cardiotoxicity could be reversed by decreasing the amount of afterload on the heart. To accomplish this, we plan on using magnetic particles, except in this case the particles would be embedded in a very soft layer of PDMS at the bottom of the well. The application of a magnetic field would cause the iron particle to align, resulting in the hardening of the bottom layer, effectively shortening the pillars, thus increasing their spring constants (Fig 7.1 panel B).
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Figure 7.1: Modifying the cardiac microtissue platform to study the effect of afterload on cardiac function in the context of sunitinib. A) Making force
measurements at fixed tissue lengths by controlling pillar displacement with embedded iron particles and magnetics. One pillar will be pulled with a magnet to control tissue length by being, while the other pillar will report resulting forces. B) Secondary changes in afterload are accomplished by embedding iron particles into a soft layer of PDMS on the bottom of the wells. Under a magnetic field this bottom layer will harden
significantly, effectively shortening pillar length, thus increasing spring constant. Figure credit: Elise A. Corbin, PhD.
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Another area for future work would be to study sunitinib in human CMTs created from iPS lines from patients with different histories of cardiotoxicity from sunitinib. Penn’s Cardiovascular Institute has access to blood samples from patients undergoing chemotherapy, which could be used to generate iPSC lines (See section 2.3.2.2 for a discussion on patient specific iPS-CMs). Specifically, we would like to test weather iPSC-CM CMTs from patients who have experienced sunitinib cardiotoxicity have greater in vitro susceptibility than iPSC-CM CMTs from patients without cardiotoxicity despite higher exposures. If we are successful in those studies, than we would examine whether gene editing can mitigate sunitinib cardiotoxicity (see section 2.3.2.2 for a discussion on gene editing).
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