Cardiogenic Genes Expressed in Cardiac Fibroblasts Contribute to Heart Development and Repair

Abstract

Rationale Cardiac fibroblasts are critical to proper heart function through multiple interactions with the myocardial compartment but appreciation of their contribution has suffered from incomplete characterization and lack of cell-specific markers. Objective To generate an unbiased comparative gene expression profile of the cardiac fibroblast pool, identify and characterize the role of key genes in cardiac fibroblast function, and determine their contribution to myocardial development and regeneration. Methods and Results High-throughput cell surface and intracellular profiling of cardiac and tail fibroblasts identified canonical MSC and a surprising number of cardiogenic genes, some expressed at higher levels than in whole heart. Whilst genetically marked fibroblasts contributed heterogeneously to interstitial but not cardiomyocyte compartments in infarcted hearts, fibroblast-restricted depletion of one highly expressed cardiogenic marker, Tbx20, caused marked myocardial dysmorphology and perturbations in scar formation upon myocardial infarction. Conclusions The surprising transcriptional identity of cardiac fibroblasts, the adoption of cardiogenic gene programs and direct contribution to cardiac development and repair provokes alternative interpretations for studies on more specialized cardiac progenitors, offering a novel perspective for reinterpreting cardiac regenerative therapies.

Developmental origin and lineage plasticity of endogenous cardiac stem cells

“…A systematic dissection of the nature, roles and origins of cardiac SCA1 + cells remains to be performed. Recent single-cell expression profiling confirmed that the SCA1 + /PDGFRα + fraction of cardiac interstitial cells, probably derived from the epicardium (Chong et al, 2011;Furtado et al, 2014), is enriched in clonogenicity and multi-lineage differentiation after in vivo engraftment . However, cell retention after engraftment was low and it remains to be determined whether heterogeneity per se in the total SCA1…”

“…Colonies and the larger stromal cell population also express some cardiac developmental transcription factors, including GATA4, TBX5, HAND1 and MEF2C, suggesting a cardiac identity and/or lineagecommitted state (Furtado et al, 2014;Noseda et al, 2015). Cultured cCFU-F show long-term growth through serial passage, reflecting their ability to self-renew, and display multipotency in vitro and in surrogate in vivo assays, including co-culture with ESCs to form teratomas and after injection into infarcted hearts (Chong et al, 2011;Noseda et al, 2015).…”

View from the heart: cardiac fibroblasts in development, scarring and regeneration

“…However, fibroblasts have recently reached centre stage in regenerative medicine due to their capacity to be reprogrammed into alternative cell lineages Ieda et al, 2010Ieda et al, , 2009Nam et al, 2014Nam et al, , 2013aQian et al, 2013Qian et al, , 2012Takahashi et al, 2007;Takahashi and Yamanaka, 2006), their capacity to interact with other cell types in their microenvironment , and their ability to modulate disease processes (Furtado et al, 2014a;Takeda et al, 2010). As cardiac fibroblasts play a prominent role in heart scarring, it is essential to understand and control the activity of these cells in order to develop efficient treatments for heart failure.…”

Probing chromatin landscape reveals roles of endocardial TBX20 in septation

“…Our analysis of genomic regions that were available for TF interaction through ATAC-seq in endocardial lineages and bound by TBX20 in embryonic heart revealed overrepresentation of specific TF motifs. Several of these TFs, including NKX2-5, GATA4, MEF2, and TEAD, have been previously associated with TBX20 in adult cardiomyocytes and cardiac fibroblasts (31,34). Interestingly, motifs highly enriched near TBX20-binding sites within endocardial lineages included those recognized by the AP1 family, which contains JUN, FOS, ATF, and MAF proteins.…”

“…In addition, we found overrepresentation of motifs for GATA family TFs MAFA, a member of the bZIP family of TFs that includes AP1 factors MEF2C, homeodomain TFs NKX2-1 and NKX2-5, and TEAD TF-binding motifs ( Figure 5B and Supplemental Table 2). NKX2-5, GATA, MEF2, and TEAD TFs have been previously identified as cofactors of TBX20 in cell lines and adult heart, indicating a high level of functional conservation (3,30,31,33,34).…”