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Introduction:There is an urgent need for a reliable in vitrosystem to accurately replicate the cardiac physiological and pathological environment for drug testing. The limited availability of human heart tissue culture systems has led to inaccurate interpretations of cardiac-related drug effects. Our group developed a culture system for pig/human heart slices that enables functional and structural viability for 6 days using continuous electrical stimulation and enriched media. This culture system can more reliably detect cardiotoxic effects compared to hiPSC-CMs. However, by day 10, the slices undergo cardiomyocyte dedifferentiation and fibrotic remodeling making them inadequate for long-term drug testing.Hypothesis:To determine whether incorporating physiological mechanical, and humoral cues within the culture system can fully emulate cardiac physiology and pathophysiology in culture.Methods and results:We have developed a novel cardiac tissue culture model (CTCM) that can electro-mechanically stimulate heart slices with physiological (0 to 80 mmHg) preload and afterload during each cardiac cycle. After 12 days in culture, this approach alone partially improved the viability of heart slices but did not maintain the structural integrity. Therefore, following a small molecule screening, we found that incorporating 100 nM tri-iodothyronine (T3) and 1 μM dexamethasone (Dex) into our culture media preserved the structural integrity of the slices for 12 days. When combined with T3/Dex, the CTCM system fully maintained the transcriptional profile, viability, metabolic activity, and structural integrity for 12 days at the same levels as fresh heart tissue. Furthermore, to test the ability of the CTCM to emulate cardiac hypertrophy, increasing the peak pressure to 140 mmHg resulted in induced cardiac hypertrophy within 6 days in culture as indicated by a 3-fold increase in NT-ProBNP release, increased NFATC4 and P-ERK expression, and increased cardiomyocyte cross-sectional area.Conclusions:This new CTCM heart slice culture system incorporating physiological electromechanical and humoral cues can emulate cardiac physiology and pathophysiology in culture, which could be used for drug screening for new therapeutics and cardiotoxins.

Introduction:Drug induced cardiotoxicity is a major cause of market withdrawal. The limited availability of human heart tissue has led to inaccurate interpretations of cardiac related drug effects. Our group had developed a culture system for pig/human heart slices that is functionally and structurally viable 6 days under electric stimulation and enriched media and could reliably demonstrate the subacute toxic effect of anti-cancer therapeutics. However, by day 10, the slices underwent cardiomyocyte dedifferentiation and fibrotic remodeling, making them inadequate for long-term cardiotoxicity testing.Aims:Including physiological mechanical and humoral cues within the culture system can prolong the viability of the human heart tissue in culture.Methods and Results:Following small molecule screening, we found that incorporation of 100 nM Tri-iodo-thyronine (T3) and 1 μM Dexamethasone (Dex) into our culture media preserved microscopic structure for 12 days in pig and human slices. However, RNA sequencing revealed a significant down regulation in cardiac contractile genes as early as day 8 in culture. To address this, we developed a novel bioengineered Cardiac Tissue Culture Model (CTCM) that can electro-mechanically stimulate heart slices with physiological preload and afterload during each cardiac cycle (Figure 1). Transcriptionally, combining CTCM with T3/Dex treatment, CTCM system was able to maintain the cardiac contractile gene expression at the same levels as the fresh hear tissue. Functionally, heart slices cultured in our CTCM with T3/Dex treatment, completely preserved structural viability and metabolic activity for 12 days.Conclusion:This study demonstrates a new physiological culture system for human heart slices that provides physiological mechanical and humoral cues for maintaining viability and functionality of the heart slices. CTCM may be an ideal platform for chronic cardiotoxicity testing.