GSE111853
Screening in Human Cardiac Organoids Identifies a Requirement for the Mevalonate Pathway in Cardiomyocyte Proliferation
Purpose: Induction of endogenous proliferation is a promising strategy for cardiac regeneration. We find that GSK3 inhibition activates a cell cycle network whereas MST1 inhibition drives the mevalonate pathway, with synergistic activation of proliferation. However, all GSK3 inhibitors tested also reduce contractile force in hCO. We screened for small molecule activators of cardiomyocyte proliferation that did not alter contractile force in hCOs. This was overcome by screening of a boutique compound library, identifying a p38 inhibitor, which activated a cell cycle network without reducing force. The screen also identified a TGFBR inhibitor that induces the mevalonate pathway and can also synergise to activate proliferation.  RNA sequencing was performed to investigate underlying mechanisms of action. Methods: RNA samples were processed with Illumina TruSeq Stranded mRNA Library prep kit selecting for poly(A) taled RNA following the manufacturer's recommendations. Libraries were quantified with Qubit HS (ThermoFisher) and Fragment Analyzer (Advances Analytical Technologies) adjusted to the appropriate concentration for sequencing. Indexed libraries were pooled and sequenced at a final concentration of 1.8 pM on an Illumina NextSeq 500 high-output run using paired-end chemistry with 75 bp read length. The sequencing data was demultiplexed using Illumina bcl2fastq2-v2.17. The quality of the reads was assessed thanks to FastQC. The reads were then processed and mapped to the human genome hg38 using the Bcbio-nextgen framework version 1.0.3. The aligner used was HISAT2 2.0.5.  Raw counts were normalised and analysed with DESeq2. Results: Analysis of RNAseq data lead to the understanding that compound 3 regulated the cell cycle network, which was similar to GSK3 inhibitors, whereas compound 65 regulated the mevalonate network, which was similarly to MST1 inhibitors. Conclusions: The current study adds to a growing body of evidence that alterations in cardiomyocyte metabolism may be a cause rather than a consequence of cardiomyocyte cell cycle arrest. Controlling cellular metabolism is emerging as a key strategy in the fight against cancer but the same pathways may conversely be required for the development of cardiac regenerative therapies. Overall design: mRNA profiles of hCO samples (control and treated with three compounds selected from screen) were generated on an Illumina NextSeq 500 high-output run.